2001 Vol. 19, No. 1
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Display Method:
2001, 19(1): 1-6.
Abstract:
Based on the petroleum and gas resources production significant scientific fields which are faced by our Chinese and the development planning in early 21st eenturv of China,the petroleum geoehemieal studies and researches have been discussed in this paper. These subjects include petroleum studies and researches in regions of northwest and east China and even the areas out of China,natural gas, reservoir immature oils and oil derived from coals hiomarker and marine petroleum generation and laeustrine black shale and digital petroleum geochemistry and so on.And the development of this field has been prospected here.
Based on the petroleum and gas resources production significant scientific fields which are faced by our Chinese and the development planning in early 21st eenturv of China,the petroleum geoehemieal studies and researches have been discussed in this paper. These subjects include petroleum studies and researches in regions of northwest and east China and even the areas out of China,natural gas, reservoir immature oils and oil derived from coals hiomarker and marine petroleum generation and laeustrine black shale and digital petroleum geochemistry and so on.And the development of this field has been prospected here.
2001, 19(1): 20-27.
Abstract:
Middle Jurassi。-Earlv Cretaceous Qiangtang foreland basin is located between Jinshajiang suture belt and Bangong-Nu-jing suture belt.It is an important petroliferous basin in the north of Qinghai-Xizang Plateau.This had been basin elongates in E-Wdirection with 800 km long and 200 km to 300 km wide.Both of the northern and southern margins of the basin are largemsuture belt and linked to thrusting of large suture helt,so the Qiangtang foreland basin belongs to composite foreland basin according to Jordan's classification of the foreland hasin(1988).~ The foreland basin had been filled with 3 000-6 000 m thick marine sediments of Middle Jurassic to Earlv Creta-ceous.The spacial changes of the stratigraphy indicate that the basin texture looks like a symmetric boody and it can he subdivided into three tectonic paleogeomorphic units from north to south e.g. northern hasin center uplift and southern basin.The sedimentary thickness in the north varies from 3 000 to 6 000 m, and from zero to 1 000 m in center uplift and from 3 000 to 5 000 m in the south. The thickness changes of filled show that the occurrence of the Mesozoic filling stratig-raphy is in the north and the south of the basin thicker than in the center uplift of the basin.There are two centers of suhsi-dence of the basin the front of suture belt. Both of them are located in the front of the suture belt of the south and north foredeep belt.The basin is one of common foreland basins between suture belt and belongs to typical symmetric foreland basin.This kind of basin geometry is related to basement uplifts and thrusts in the cratonic edge of the mountain helt wihich allows huge svnsedimentarv molasse sediments to he preserved. Middle Jurassic to Early Cretaceous tectonic sequence is bounded by unconformitv and composed of the Quemocuo for-mation Buqu formation Xiali formation Suowa formation and Xueshan formation which is more than 3 000 m in depth.A tectonic sequence is a body of genetically-related strata isolated by unconformitvy and it had been deposited in a basin-formed stage responding to a thrusting episode.The provenance and constituent of the clasts in sandstone and conglomerate indicate that there are three provenances in the foreland hasin including Jinshajiang suture helt Bangong-Nujiang suture belt and the center uplift of the later was formed in the late Triassic.There are three marginal fades belts in the basin rec- ognized two of them distribute in the front of suture helt one of them distributes in the both side of center uplift.The sedi-mentarv fades can he symmetrically subdivided into four fades belt from center uplift to north or to south namely center up-lift foreland slope fore-deep and the foothill of thrust belt.The statistic measured data of cross-bedding,rippled mark and flute mold indicate that there are two palaeocurrents systems and one drainage distribution pattern in the hasin the cen-to uplift was drainage division. The uplifting amplitudes of the center uplift can provide information on the thrusting strength of both suture belt.The highland of the center uplift characterised by fan,fan delta conglomerate mark that Jingshajiang tectonic belt or Bangong-Nujiang tectonic belt were thrustcd scvcrclv to produce lots of tectonic load which led to rise the center uplift severely whereas the topography of underwater uplift in the center uplift characterised by carbonate hank and ramp mark that the Jingshajiang tectonic belt or Bangong-Nujiang tectonic belt was in the course of static times.So the evolution of the basin can he divide in to five stages by the emplacement of large thrust sheets on both side of the basin by Bangong-Nujiang suture belt Jingshajiang suture belt.
Middle Jurassi。-Earlv Cretaceous Qiangtang foreland basin is located between Jinshajiang suture belt and Bangong-Nu-jing suture belt.It is an important petroliferous basin in the north of Qinghai-Xizang Plateau.This had been basin elongates in E-Wdirection with 800 km long and 200 km to 300 km wide.Both of the northern and southern margins of the basin are largemsuture belt and linked to thrusting of large suture helt,so the Qiangtang foreland basin belongs to composite foreland basin according to Jordan's classification of the foreland hasin(1988).~ The foreland basin had been filled with 3 000-6 000 m thick marine sediments of Middle Jurassic to Earlv Creta-ceous.The spacial changes of the stratigraphy indicate that the basin texture looks like a symmetric boody and it can he subdivided into three tectonic paleogeomorphic units from north to south e.g. northern hasin center uplift and southern basin.The sedimentary thickness in the north varies from 3 000 to 6 000 m, and from zero to 1 000 m in center uplift and from 3 000 to 5 000 m in the south. The thickness changes of filled show that the occurrence of the Mesozoic filling stratig-raphy is in the north and the south of the basin thicker than in the center uplift of the basin.There are two centers of suhsi-dence of the basin the front of suture belt. Both of them are located in the front of the suture belt of the south and north foredeep belt.The basin is one of common foreland basins between suture belt and belongs to typical symmetric foreland basin.This kind of basin geometry is related to basement uplifts and thrusts in the cratonic edge of the mountain helt wihich allows huge svnsedimentarv molasse sediments to he preserved. Middle Jurassic to Early Cretaceous tectonic sequence is bounded by unconformitv and composed of the Quemocuo for-mation Buqu formation Xiali formation Suowa formation and Xueshan formation which is more than 3 000 m in depth.A tectonic sequence is a body of genetically-related strata isolated by unconformitvy and it had been deposited in a basin-formed stage responding to a thrusting episode.The provenance and constituent of the clasts in sandstone and conglomerate indicate that there are three provenances in the foreland hasin including Jinshajiang suture helt Bangong-Nujiang suture belt and the center uplift of the later was formed in the late Triassic.There are three marginal fades belts in the basin rec- ognized two of them distribute in the front of suture helt one of them distributes in the both side of center uplift.The sedi-mentarv fades can he symmetrically subdivided into four fades belt from center uplift to north or to south namely center up-lift foreland slope fore-deep and the foothill of thrust belt.The statistic measured data of cross-bedding,rippled mark and flute mold indicate that there are two palaeocurrents systems and one drainage distribution pattern in the hasin the cen-to uplift was drainage division. The uplifting amplitudes of the center uplift can provide information on the thrusting strength of both suture belt.The highland of the center uplift characterised by fan,fan delta conglomerate mark that Jingshajiang tectonic belt or Bangong-Nujiang tectonic belt were thrustcd scvcrclv to produce lots of tectonic load which led to rise the center uplift severely whereas the topography of underwater uplift in the center uplift characterised by carbonate hank and ramp mark that the Jingshajiang tectonic belt or Bangong-Nujiang tectonic belt was in the course of static times.So the evolution of the basin can he divide in to five stages by the emplacement of large thrust sheets on both side of the basin by Bangong-Nujiang suture belt Jingshajiang suture belt.
2001, 19(1): 43-47.
Abstract:
Hvdrothermal activity is widely occurring along the active plate boundaries and intraplate volcanic centers which is exchanging heat and material between the lithosphere and the oceans.Okinawa Trough is an important part of Rvukv T-A-ha system汕ich is in the collision and suhduction zone between a oceanic block and continental block and is reported to he in the early stage of back-arc spreading with a rift structure and an embryonic marginal hasin} its origin and evolution may he one of the most interseting problems in geophysics and geology today.Hvdrothermal activity as a window and clue of studying the origin and evolution of Okinawa Trough has been explored through out the Trough by scientists all over the worlds.Sever- al hvdrothermal fields have been found in the middle part of Okinawa Trough.Tectonophysical features of topography heatflow distrihution, seismicitv and magnetic anomaly of three hvdrothermal fields including southwest Amami hvdrothermal field.Iheva deep hydrothermal field and Izena caldron hvdrothermal field in the middle Okinawa Trough were studied. The results show that all the hvdrothermal fields distribute in the central grahen and locate at the slope of caldera or of central ridge with high and vary heatflow distrihution, active seismic activities and fluctuating magnetic anomaly.It is found that the hvdrothermal fields have close relationship with tectonic zoon.In the area of Rvukvu T-A-Ba svstem, the upwelling of mantal materials beneath the trough due to the suhduction of Pacific Plate provides heat energy for the hvdrothermal activity.The faults formation in the process of trough expending provides space for the hydrothermal activity.
Hvdrothermal activity is widely occurring along the active plate boundaries and intraplate volcanic centers which is exchanging heat and material between the lithosphere and the oceans.Okinawa Trough is an important part of Rvukv T-A-ha system汕ich is in the collision and suhduction zone between a oceanic block and continental block and is reported to he in the early stage of back-arc spreading with a rift structure and an embryonic marginal hasin} its origin and evolution may he one of the most interseting problems in geophysics and geology today.Hvdrothermal activity as a window and clue of studying the origin and evolution of Okinawa Trough has been explored through out the Trough by scientists all over the worlds.Sever- al hvdrothermal fields have been found in the middle part of Okinawa Trough.Tectonophysical features of topography heatflow distrihution, seismicitv and magnetic anomaly of three hvdrothermal fields including southwest Amami hvdrothermal field.Iheva deep hydrothermal field and Izena caldron hvdrothermal field in the middle Okinawa Trough were studied. The results show that all the hvdrothermal fields distribute in the central grahen and locate at the slope of caldera or of central ridge with high and vary heatflow distrihution, active seismic activities and fluctuating magnetic anomaly.It is found that the hvdrothermal fields have close relationship with tectonic zoon.In the area of Rvukvu T-A-Ba svstem, the upwelling of mantal materials beneath the trough due to the suhduction of Pacific Plate provides heat energy for the hvdrothermal activity.The faults formation in the process of trough expending provides space for the hydrothermal activity.
2001, 19(1): 55-59.
Abstract:
A lot of reefs have been discovered in Honghuavuan Formation of Lower Ordovician in the Central Yangtze Platform.Their rock comparisons contain two types.One is baffle stone.Another is binding stone.Their reef-building organisms contwin five types.They are hluegreen alga(containing blue bacterium and Girvanella),Galathium,BatostorrUc,Pulchrilamirya,and Archaeoscyphia as representation of rock sponge.They composite five types of reef-building organism community. Is hluegreen alga community(S-community),Galathium-hluegreen algae community(G S community),Archaeoscyphia- Galathium community(A-C community),Batostorruc-Galathium community(B-Q community),Batostotruc-Galathium-hlue-green algae c/iommunity(B-C-S community). Ecological environment of each of reef-building organism community and the most lithofacies assemblage of host rock may indicate characteristics of each communitv} which includes water body environment and the most depth range suitable.Each community can adapt normal shallow sea of warm clean rich sunshine and oxygen and cyclic better. But the most suitable depth may he different.S-community represents shallow water and small energy.C-S community and B-C-S com-munity may he 5-10 m and medium-large water energy.B-C community and A-C community may he 10-20 m and large water energy. Organism belt has been discovered in reefs of thickness over Sm in the study area. Organism belt is a result of organism community evolution and is the most intuitive evidence of organism community evolution.Organism belt within reefs from bottom to up may indicate two models of community evolution.The trend of their evolution is①A-C community or B-C com-munity→C-S community or B-C-S community→S-community②S-community→GS community or B-C-S community→A-Ccommunity or B-G community.This is an entire course of community from growth to death. Organism richness of community interior has also been changed with time. Because the most suitable water depth of each community is different the force of organism community evolution may he sea level change.According to the most suitable water depth of reef-building organic community detailed change of sea level can he diagnosed in reef-building term. Relative sea level change is from a falling course of 20-10 m→10-5 m→5 m to a rising of 5 m→10-5 m→20-10 m.The largest change magnitude of sea level is about 15 m.This is similar to the former. So, according to the reef-building organic community evolution can quantitatively study small magnitude sea level change.
A lot of reefs have been discovered in Honghuavuan Formation of Lower Ordovician in the Central Yangtze Platform.Their rock comparisons contain two types.One is baffle stone.Another is binding stone.Their reef-building organisms contwin five types.They are hluegreen alga(containing blue bacterium and Girvanella),Galathium,BatostorrUc,Pulchrilamirya,and Archaeoscyphia as representation of rock sponge.They composite five types of reef-building organism community. Is hluegreen alga community(S-community),Galathium-hluegreen algae community(G S community),Archaeoscyphia- Galathium community(A-C community),Batostorruc-Galathium community(B-Q community),Batostotruc-Galathium-hlue-green algae c/iommunity(B-C-S community). Ecological environment of each of reef-building organism community and the most lithofacies assemblage of host rock may indicate characteristics of each communitv} which includes water body environment and the most depth range suitable.Each community can adapt normal shallow sea of warm clean rich sunshine and oxygen and cyclic better. But the most suitable depth may he different.S-community represents shallow water and small energy.C-S community and B-C-S com-munity may he 5-10 m and medium-large water energy.B-C community and A-C community may he 10-20 m and large water energy. Organism belt has been discovered in reefs of thickness over Sm in the study area. Organism belt is a result of organism community evolution and is the most intuitive evidence of organism community evolution.Organism belt within reefs from bottom to up may indicate two models of community evolution.The trend of their evolution is①A-C community or B-C com-munity→C-S community or B-C-S community→S-community②S-community→GS community or B-C-S community→A-Ccommunity or B-G community.This is an entire course of community from growth to death. Organism richness of community interior has also been changed with time. Because the most suitable water depth of each community is different the force of organism community evolution may he sea level change.According to the most suitable water depth of reef-building organic community detailed change of sea level can he diagnosed in reef-building term. Relative sea level change is from a falling course of 20-10 m→10-5 m→5 m to a rising of 5 m→10-5 m→20-10 m.The largest change magnitude of sea level is about 15 m.This is similar to the former. So, according to the reef-building organic community evolution can quantitatively study small magnitude sea level change.
2001, 19(1): 71-78.
Abstract:
More attention has been paid to the report of hvdrocarhon from E31、N1、N21 clastic rock reservoir in Yucjin area Qaidam hasin, northcrnwcst China. Based on research of approximate one hundred cast thin sections and mcrcurv intrusion curve from 15 wells, some results on E31、N1、N21 elastic rock reservoir in Yuejin area have been obtained.as follows:①The elastic rock reservoir was composed of fcldspathic sandstone } lithic arkosc and fcldspathic litharcnitc which is characterized by lower composition and texture maturity②The elastic rock reservoir has undergone compaction, pressure dissolution, authigcnc(fcrroan calcite, dolomite, anhydrite, cuthalitc, fcrroan dolomite pyrite ) ccmcntation and dissolution, which results in the forming of overwhelming relic primary intcrgranular pore.Corrclatahlc beds from eastern Yucjin and western Yucjin have different diagcnctic-porosity evolution because of their different burial depths which results in a more favourable reservoir in western Yucjin than in eastern Yuejin,③E31、N1、N21 elastic rock reservoir developed under distrihutarv channel sand flat and braided channel microfacics.Reservoir quality was controlled by composition and texture maturity, matrix material and diagcnctic environment}depth especially),④E3, elastic rock reservoir from western Yucjin characterized by very large, large and medium pore,Ⅱ-grade( high porosity and medium permeability ) in reservoir quality and a combination of large porefine throat while E3 elastic rock reservoir from eastern Yucjin did large and medium pore,Ⅴ-graded (very low porosity(very low permeability) in reservoir quality and a combination of medium pore-very fine throat. N1 elastic rock reservoir in Yucjin area characterized by very large large and medium pore,Ⅳ-andⅤ-grade( low porosity and very low permeability) in reservoir quality and a combination of large pore-very fine throat.
More attention has been paid to the report of hvdrocarhon from E31、N1、N21 clastic rock reservoir in Yucjin area Qaidam hasin, northcrnwcst China. Based on research of approximate one hundred cast thin sections and mcrcurv intrusion curve from 15 wells, some results on E31、N1、N21 elastic rock reservoir in Yuejin area have been obtained.as follows:①The elastic rock reservoir was composed of fcldspathic sandstone } lithic arkosc and fcldspathic litharcnitc which is characterized by lower composition and texture maturity②The elastic rock reservoir has undergone compaction, pressure dissolution, authigcnc(fcrroan calcite, dolomite, anhydrite, cuthalitc, fcrroan dolomite pyrite ) ccmcntation and dissolution, which results in the forming of overwhelming relic primary intcrgranular pore.Corrclatahlc beds from eastern Yucjin and western Yucjin have different diagcnctic-porosity evolution because of their different burial depths which results in a more favourable reservoir in western Yucjin than in eastern Yuejin,③E31、N1、N21 elastic rock reservoir developed under distrihutarv channel sand flat and braided channel microfacics.Reservoir quality was controlled by composition and texture maturity, matrix material and diagcnctic environment}depth especially),④E3, elastic rock reservoir from western Yucjin characterized by very large, large and medium pore,Ⅱ-grade( high porosity and medium permeability ) in reservoir quality and a combination of large porefine throat while E3 elastic rock reservoir from eastern Yucjin did large and medium pore,Ⅴ-graded (very low porosity(very low permeability) in reservoir quality and a combination of medium pore-very fine throat. N1 elastic rock reservoir in Yucjin area characterized by very large large and medium pore,Ⅳ-andⅤ-grade( low porosity and very low permeability) in reservoir quality and a combination of large pore-very fine throat.
2001, 19(1): 85-89.
Abstract:
Middle Jurassic-Earlv Cretaceous Qiangtang foreland basin is located between Jinshajiang suture belt and Bangong-Nu-jing suture belt.It is an important petroliferous basin in the north of Qinghai-Xizang Plateau.This had been basin elongates in E-W direction with 800 km long and 200 km to 300 km wide.Both of the northern and southern margins of the basin are large suture belt and linked to thrusting of large suture belt, so the Qiangtang foreland basin belongs to composite foreland basin according to Jordan's classification of the foreland hasin(1988).~ The foreland basin had been filled with 3 000-6 000 m thick marine sediments of Middle Jurassic to Earlv Cretaceous.The spacial changes of the stratigraphy indicate that the basin texture looks like a symmetric hody, and it can he subdivided into three tectonic paleogeomolphic units from north to south e.g. northern hasin, center uplift and southern basin.The sedimentary thickness in the north varies from 3 000 to 6 000 m, and from zero to 1 000 m in center uplift and from 3 000 to 5 000 m in the south, The thickness changes of filled, show that the occurrence of the Mesozoic filling stratig- raphy is in the north and the south of the basin thicker than in the center uplift of the basin.There are two centers of suhsidence of the basin the front of suture belt. Both of them are located in the front of the suture belt of the south and north foredeep belt.The basin is one of common foreland basins between suture belt and belongs to typical symmetric foreland basin.This kind of basin geometry is related to basement uplifts and thrusts in the cratonic edge of the mountain belt, wihich allows huge svnsedimentarv molasse sediments to he preserved. Middle Jurassic to Early Cretaceous tectonic sequence is bounded by unconformitv and composed of the Quemocuo formation, Buqu formation Xiali formation Suowa formation and Xueshan formation which is more than 3 000 m in depth.A tectonic sequence is a body of genetically-related strata isolated by unconformity and it had been deposited in a basin-formed stage responding to a thrusting episode.The provenance and constituent of the clasts in sandstone and conglomerate indicate that there are three provenances in the foreland hasin, including Jinshajiang suture belt, Bangong-Nujiang suture belt and the center uplift of the later was formed in the late Triassic.There are three marginal fades belts in the basin recognized, two of them distribute in the front of suture helt, one of them distributes in the both side of center uplift.The sedlmentarv fades can he symmetrically subdivided into four fades belt from center uplift to north or to south namely center uplift foreland slope fore-deep and the foothill of thrust belt.The statistic measured data of cross-bedding,rippled mark and flute mold indicate that there are two palaeocurrents systems and one drainage distribution pattern in the hasin, the center uplift was drainage division. The uplifting amplitudes of the center uplift can provide information on the thrusting strength of both suture belt.The highland of the center uplift characterised by fan, fan delta conglomerate mark that Jingshajiang tectonic belt or Bangong- Nujlang tectonic belt Were thrusted severely t0 produce lots of tectonic load which led to rise the center uplift scverelvn whereas the topography of underwater uplift in the center uplift characterised by carbonate hank and ramp mark that the Jingshajiang tectonic belt or Bangong-Nujiang tectonic belt was in the course of static times.So the evolution of the basin can he divide in to five stages by the emplacement of large thrust sheets on both side of the basin by Bangong-Nujiang suture belt Jingshajiang suture belt.
Middle Jurassic-Earlv Cretaceous Qiangtang foreland basin is located between Jinshajiang suture belt and Bangong-Nu-jing suture belt.It is an important petroliferous basin in the north of Qinghai-Xizang Plateau.This had been basin elongates in E-W direction with 800 km long and 200 km to 300 km wide.Both of the northern and southern margins of the basin are large suture belt and linked to thrusting of large suture belt, so the Qiangtang foreland basin belongs to composite foreland basin according to Jordan's classification of the foreland hasin(1988).~ The foreland basin had been filled with 3 000-6 000 m thick marine sediments of Middle Jurassic to Earlv Cretaceous.The spacial changes of the stratigraphy indicate that the basin texture looks like a symmetric hody, and it can he subdivided into three tectonic paleogeomolphic units from north to south e.g. northern hasin, center uplift and southern basin.The sedimentary thickness in the north varies from 3 000 to 6 000 m, and from zero to 1 000 m in center uplift and from 3 000 to 5 000 m in the south, The thickness changes of filled, show that the occurrence of the Mesozoic filling stratig- raphy is in the north and the south of the basin thicker than in the center uplift of the basin.There are two centers of suhsidence of the basin the front of suture belt. Both of them are located in the front of the suture belt of the south and north foredeep belt.The basin is one of common foreland basins between suture belt and belongs to typical symmetric foreland basin.This kind of basin geometry is related to basement uplifts and thrusts in the cratonic edge of the mountain belt, wihich allows huge svnsedimentarv molasse sediments to he preserved. Middle Jurassic to Early Cretaceous tectonic sequence is bounded by unconformitv and composed of the Quemocuo formation, Buqu formation Xiali formation Suowa formation and Xueshan formation which is more than 3 000 m in depth.A tectonic sequence is a body of genetically-related strata isolated by unconformity and it had been deposited in a basin-formed stage responding to a thrusting episode.The provenance and constituent of the clasts in sandstone and conglomerate indicate that there are three provenances in the foreland hasin, including Jinshajiang suture belt, Bangong-Nujiang suture belt and the center uplift of the later was formed in the late Triassic.There are three marginal fades belts in the basin recognized, two of them distribute in the front of suture helt, one of them distributes in the both side of center uplift.The sedlmentarv fades can he symmetrically subdivided into four fades belt from center uplift to north or to south namely center uplift foreland slope fore-deep and the foothill of thrust belt.The statistic measured data of cross-bedding,rippled mark and flute mold indicate that there are two palaeocurrents systems and one drainage distribution pattern in the hasin, the center uplift was drainage division. The uplifting amplitudes of the center uplift can provide information on the thrusting strength of both suture belt.The highland of the center uplift characterised by fan, fan delta conglomerate mark that Jingshajiang tectonic belt or Bangong- Nujlang tectonic belt Were thrusted severely t0 produce lots of tectonic load which led to rise the center uplift scverelvn whereas the topography of underwater uplift in the center uplift characterised by carbonate hank and ramp mark that the Jingshajiang tectonic belt or Bangong-Nujiang tectonic belt was in the course of static times.So the evolution of the basin can he divide in to five stages by the emplacement of large thrust sheets on both side of the basin by Bangong-Nujiang suture belt Jingshajiang suture belt.
2001, 19(1): 96-100,124.
Abstract:
Field measurement of surface airflow,sand transport and sedimentary processes on the modern dunes(harchan dune) the main ridges and secondary ridges of networks dune)was conducted in southeastern Tengger Desert to refine aeolian cross-strata as an indicator of paleaowind direction. It has been found that the velocity and direction of lee-side secondary airflow varied with dune morphology and primary wind direction and their interactions.Three types of lee-side secondary flow occurred in this example separated flow, attached flow, and deflected flow. These flow is controlled at least two factors, lee-slop morphology and primary wind direction relative to dune crestline.Separated flow, characterized by lower wind velocity typically occurred on the dunes with steeper(>20°)lee-slop in the conditions where primary wind direction is perpendicular to dune crestline.Attached flow with higher velocity occurred on the gentle lee slop(<20°).The attacked flow could he deflected in the oblique primary wind environment but not deflected in transverse flow conditions.The direction of the lcc-side deflected flow is in accordance with the direction of crcstlinc of dunes regardless of the incident angle values of oblique wind.Further analysis has also found that the magnitude of lcc-side secondary wind velocity is the cosine function of primary wind direction relative to dunes which can he expressed by natural log cosine relationship: U1=Uc{K*ln(cos(i)〕+A}.0
Field measurement of surface airflow,sand transport and sedimentary processes on the modern dunes(harchan dune) the main ridges and secondary ridges of networks dune)was conducted in southeastern Tengger Desert to refine aeolian cross-strata as an indicator of paleaowind direction. It has been found that the velocity and direction of lee-side secondary airflow varied with dune morphology and primary wind direction and their interactions.Three types of lee-side secondary flow occurred in this example separated flow, attached flow, and deflected flow. These flow is controlled at least two factors, lee-slop morphology and primary wind direction relative to dune crestline.Separated flow, characterized by lower wind velocity typically occurred on the dunes with steeper(>20°)lee-slop in the conditions where primary wind direction is perpendicular to dune crestline.Attached flow with higher velocity occurred on the gentle lee slop(<20°).The attacked flow could he deflected in the oblique primary wind environment but not deflected in transverse flow conditions.The direction of the lcc-side deflected flow is in accordance with the direction of crcstlinc of dunes regardless of the incident angle values of oblique wind.Further analysis has also found that the magnitude of lcc-side secondary wind velocity is the cosine function of primary wind direction relative to dunes which can he expressed by natural log cosine relationship: U1=Uc{K*ln(cos(i)〕+A}.0
2001, 19(1): 107-112.
Abstract:
Some samples are gained from the south slope of Shennongjia mountain and five sporo-pollen zones are distinguished from the piedmont to the summit. Five main polynofloras are as follows: evergreen hroadle forest of subtropics below 800 m a.s.l, evergreen and deciduous hroadleved mixed forest of subtropics between 800-1 400 m a.s.l, deciduous hroadleved forest of warm temperate between 1 400-1 850 m a.s.l, conifer and hroadleved mixed forest of temperate hetween 1 850-2500m a.s.l, conifer forest of cold temperate above 2 500 m a.s.l.The polynofloras reflect the basic features of the modern plantation in Shennongjia region.Thev are identical in the vegetation type the number and spatial distribution of vegetation zones.Thev are similar in the height hounds of vegetation zones as well as component and its percentage of some plants.
Some samples are gained from the south slope of Shennongjia mountain and five sporo-pollen zones are distinguished from the piedmont to the summit. Five main polynofloras are as follows: evergreen hroadle forest of subtropics below 800 m a.s.l, evergreen and deciduous hroadleved mixed forest of subtropics between 800-1 400 m a.s.l, deciduous hroadleved forest of warm temperate between 1 400-1 850 m a.s.l, conifer and hroadleved mixed forest of temperate hetween 1 850-2500m a.s.l, conifer forest of cold temperate above 2 500 m a.s.l.The polynofloras reflect the basic features of the modern plantation in Shennongjia region.Thev are identical in the vegetation type the number and spatial distribution of vegetation zones.Thev are similar in the height hounds of vegetation zones as well as component and its percentage of some plants.
2001, 19(1): 130-135.
Abstract:
Representative samples from various geological conditions, such as special type of organic matter(suherenite, resinite and some kind of algae),organic matters ( OM ) reworked intensively by bacteria both in natural geological situation and lahoratorv, OM rich in sulfur existed in strong reductive environment and soluble OM, all these have been reported to have close relationship to the occurrence and enrichment of immature to low-mature oil.In addition some reference samples are collected in this paper. Based on the combination of constant heating experiments and the PY-GC techniques the relationship between the heating temperature and transformation ratio of OM to hydrocarbon(oil+gas),to oil and to gas for each sample mentioned above are obtained respectively. Afterwards the chemical kinetics behavior of OM to hvdrocarhon, to oil and to gas for each sample are discussed svstematicallv with the model of parallel first order reactions.The results indicate that: 1)the activation energy of OM to oil is generally lower than that of gas and the activation energy of OM to hydrocarbon is located in between of the above two or is close to one of them. These reflect the essential of the OM to gas is more difficult than it to gas and the process of hvdrocarbon generation is the superimposition of the process of OM to oil and to gas, 2) The weighted average activation energies of hydrocarbon generation from resinite, suherenite, OM rich in sulfur oil shale rich in algae biodegraded amorphous A formed from type I OM reworked intensively by microbe as well as soluble OM are indeed lower(the average activation energics of OM to oil and to hvdrocarhon are less than 197 kJ/mol and the one of OM to gas is less than 210 kJ/mol) than that of common kcrogcn.This is coincident with the fact that all these OM are closclv related to the occurrence of immature to low mature oil, which were reported cxtcnsivclv in literature.At the same time it can he seen that the activation energy of biodegraded amorphous D is lower than that of the same type of OM and the activation energy of OM reworked by microbe in lahoratorv shows somewhat decrease.This means that the intensive reworking of OM by microbe is favorable for the carlv generation of petroleum.The results mentioned above suggested that although the occurrence and enrichment of immature to low mature oil may relate to number of different geological conditions or factors their commonness is that thcv all have lower activation energy of hvdrocarhon generation than that of normal OM. The initial application of the chemical kinetics models shows that the OMs mentioned above do generate a larger amount of hvdrocarhons in a burial depth shallower than that of hvdrocarhon generation threshold for normal OM.This elucidates quantitativclv the generating mechanism of immature to low mature oil existed in various geological conditions.The study of this paper believes that not onlv it is theoretical credihility but also practical fcasihilitv to study the generation mechanism of immature to low mature from the theory of chemical kinetics.
Representative samples from various geological conditions, such as special type of organic matter(suherenite, resinite and some kind of algae),organic matters ( OM ) reworked intensively by bacteria both in natural geological situation and lahoratorv, OM rich in sulfur existed in strong reductive environment and soluble OM, all these have been reported to have close relationship to the occurrence and enrichment of immature to low-mature oil.In addition some reference samples are collected in this paper. Based on the combination of constant heating experiments and the PY-GC techniques the relationship between the heating temperature and transformation ratio of OM to hydrocarbon(oil+gas),to oil and to gas for each sample mentioned above are obtained respectively. Afterwards the chemical kinetics behavior of OM to hvdrocarhon, to oil and to gas for each sample are discussed svstematicallv with the model of parallel first order reactions.The results indicate that: 1)the activation energy of OM to oil is generally lower than that of gas and the activation energy of OM to hydrocarbon is located in between of the above two or is close to one of them. These reflect the essential of the OM to gas is more difficult than it to gas and the process of hvdrocarbon generation is the superimposition of the process of OM to oil and to gas, 2) The weighted average activation energies of hydrocarbon generation from resinite, suherenite, OM rich in sulfur oil shale rich in algae biodegraded amorphous A formed from type I OM reworked intensively by microbe as well as soluble OM are indeed lower(the average activation energics of OM to oil and to hvdrocarhon are less than 197 kJ/mol and the one of OM to gas is less than 210 kJ/mol) than that of common kcrogcn.This is coincident with the fact that all these OM are closclv related to the occurrence of immature to low mature oil, which were reported cxtcnsivclv in literature.At the same time it can he seen that the activation energy of biodegraded amorphous D is lower than that of the same type of OM and the activation energy of OM reworked by microbe in lahoratorv shows somewhat decrease.This means that the intensive reworking of OM by microbe is favorable for the carlv generation of petroleum.The results mentioned above suggested that although the occurrence and enrichment of immature to low mature oil may relate to number of different geological conditions or factors their commonness is that thcv all have lower activation energy of hvdrocarhon generation than that of normal OM. The initial application of the chemical kinetics models shows that the OMs mentioned above do generate a larger amount of hvdrocarhons in a burial depth shallower than that of hvdrocarhon generation threshold for normal OM.This elucidates quantitativclv the generating mechanism of immature to low mature oil existed in various geological conditions.The study of this paper believes that not onlv it is theoretical credihility but also practical fcasihilitv to study the generation mechanism of immature to low mature from the theory of chemical kinetics.
2001, 19(1): 141-144.
Abstract:
Research on chemical components and isotope composition of carbon and hydrogen of natural gases from the Tarim basin shows that all discovered gases in this basin are thermogenic.With respect to source organic matter there are two types of gases: 1)the oil-type gas, which generated from Sinian to lower Palaeozoic marine source rocks with the sapropelic organis matter with-44.5%。-33.8%0 of δ13C1,,-42.0%。-28.1%c of δ13C2,-35.4%。-28. 4%0 of δ13C3, and heavier than- 200%0 of δD1;2) the coal-type gas, which generated from Mesozoic terrestrial source rocks with the humic organic matter with-40.5%‘-33.1%0 of δ13C1,-29.7%。-21.3%c of δ13C2,-26.3%。-20.3%c of δ13C1,and lighter than-200%0 of δD1. Based on the geochemical characters and geological setting Tahei uplift region is regarded as having some reservoired gas pools formed by mixed mature oil-type gas with post matured oil-type gas.Some reservoired gas pools are formed by mixed mature oil-type gas with mature coal-type gas.
Research on chemical components and isotope composition of carbon and hydrogen of natural gases from the Tarim basin shows that all discovered gases in this basin are thermogenic.With respect to source organic matter there are two types of gases: 1)the oil-type gas, which generated from Sinian to lower Palaeozoic marine source rocks with the sapropelic organis matter with-44.5%。-33.8%0 of δ13C1,,-42.0%。-28.1%c of δ13C2,-35.4%。-28. 4%0 of δ13C3, and heavier than- 200%0 of δD1;2) the coal-type gas, which generated from Mesozoic terrestrial source rocks with the humic organic matter with-40.5%‘-33.1%0 of δ13C1,-29.7%。-21.3%c of δ13C2,-26.3%。-20.3%c of δ13C1,and lighter than-200%0 of δD1. Based on the geochemical characters and geological setting Tahei uplift region is regarded as having some reservoired gas pools formed by mixed mature oil-type gas with post matured oil-type gas.Some reservoired gas pools are formed by mixed mature oil-type gas with mature coal-type gas.
2001, 19(1): 150-155.
Abstract:
Tabci field is separated into Lunnan fault-uplift Sangtamu fault-uplift and Jilakc anticline structucrc from north to sounth. Analysis of a range of Triassic crude oils in this area appears to indicate that neutral nitrogen compounds and alkylphcnols has a strong migration fractionation.In addition from the south of the field to the north the absolute conccntration of neutral nitrogen compounds has changed from large to small with relative enrichment for nitrogen-shielded isomers and parts of nitrogen-shielded isomers and nitrogen-exposed isomers relatively scarce in concentration.The concentrations of benzo(a)carbazole plus bcnzo〔c〕carbazole (〔a)+〔c〕),carbazole ( CA),mcthvlcarbazolcs( MCA)and dimcthvlcarbazolcs (DMCA)of crude oils in Sangtamu fault-uplift are obvious higher than those of Lunnan fault-uplift. For instance differences in the migration parameters between the LN44 well oil from Sangtamu fault-uplift and LN2 well oil from Lunnan fault-uplift arc very obvious,i.e-the amounts of[a]+[c],CA, MCA, DMCA decrease from 1.80 μg/g oil, 2.10 μg/g oil, 6.57 μg/ g oil, 13. 43 μg/g oil to 0. 49 μg/g oil, 0.93 μg/g oil, 4.39 μg/g oil, 1.02 μg/g oil.From south to north the[a]/[c] ratio in Jilakc structure is the highest ranging from 2.04 to 2.22, and the ratio in Sangtamu fault-uplift range from 0.98to1.94.However Lunnan fault-uplift is lower ranging from 0.71 to 1.25.The ratio of o-cresol to m-cresol and of 2, 6-to 2, 3-dimcthylphcnol, i.e.,the hydroxyl-group-shielded isomers are relatively enriched in the oils from the north of Tabci field.In the same fault-uplift the neutral nitrogen compounds of crude oils have migration frationation from the west of the fault uplift to the east as well as from TⅢ oil leg of the fault uplift to TⅠ oil leg.The results suggest that Triassic oils across Tabci field migrate laterally from Jilakc field to Sangtamu fault uplift and Lunnan fault uplift Trassic oils in the same fault uplift migrate and rcmigratc vertically from TⅢ oil leg to TⅠ oil leg and from the west of the fault to the cast.
Tabci field is separated into Lunnan fault-uplift Sangtamu fault-uplift and Jilakc anticline structucrc from north to sounth. Analysis of a range of Triassic crude oils in this area appears to indicate that neutral nitrogen compounds and alkylphcnols has a strong migration fractionation.In addition from the south of the field to the north the absolute conccntration of neutral nitrogen compounds has changed from large to small with relative enrichment for nitrogen-shielded isomers and parts of nitrogen-shielded isomers and nitrogen-exposed isomers relatively scarce in concentration.The concentrations of benzo(a)carbazole plus bcnzo〔c〕carbazole (〔a)+〔c〕),carbazole ( CA),mcthvlcarbazolcs( MCA)and dimcthvlcarbazolcs (DMCA)of crude oils in Sangtamu fault-uplift are obvious higher than those of Lunnan fault-uplift. For instance differences in the migration parameters between the LN44 well oil from Sangtamu fault-uplift and LN2 well oil from Lunnan fault-uplift arc very obvious,i.e-the amounts of[a]+[c],CA, MCA, DMCA decrease from 1.80 μg/g oil, 2.10 μg/g oil, 6.57 μg/ g oil, 13. 43 μg/g oil to 0. 49 μg/g oil, 0.93 μg/g oil, 4.39 μg/g oil, 1.02 μg/g oil.From south to north the[a]/[c] ratio in Jilakc structure is the highest ranging from 2.04 to 2.22, and the ratio in Sangtamu fault-uplift range from 0.98to1.94.However Lunnan fault-uplift is lower ranging from 0.71 to 1.25.The ratio of o-cresol to m-cresol and of 2, 6-to 2, 3-dimcthylphcnol, i.e.,the hydroxyl-group-shielded isomers are relatively enriched in the oils from the north of Tabci field.In the same fault-uplift the neutral nitrogen compounds of crude oils have migration frationation from the west of the fault uplift to the east as well as from TⅢ oil leg of the fault uplift to TⅠ oil leg.The results suggest that Triassic oils across Tabci field migrate laterally from Jilakc field to Sangtamu fault uplift and Lunnan fault uplift Trassic oils in the same fault uplift migrate and rcmigratc vertically from TⅢ oil leg to TⅠ oil leg and from the west of the fault to the cast.
2001, 19(1): 7-12.
Abstract:
The increasing awareness of tcmpcstitcs in the ancient record has correspondingly led to much consideration of their prcscrvahility.The main factors influencing the prcscrvahilitv are the net sedimentation rate Tthe hiogcnic mixing rate } and the magnitude of physical reworking. Theateroft has put forward the concept of time scales to attempt to solve this problem.The terms of transit time and dissipation time arc introduced.Transit time is related to the thickness of the hiogcnic reworking zone,the thickness of event beds and sedimentation rate.The hiogcnic reworking zone is also controlled by the animal size and the behavior engaged in during its generation.The determination of transit time is difficult because of the unstcadv and unpredictable mination of dissipation time is even more complicated than that of transit time.The dissipation time is controlled by manv factors such as the size of infauna, the behavior engaged in by the organisms, the dynamic interplay between the hcnthic community and the dcpositional event itself the dcsirahilitv of the event bed as a site for colonization and as a repository of food resources and the absolute time available for burrowing ctc.Unfortu- natelv, the preceding factors appear to resist quantification and therefore severely limit the effectiveness of existing mathcmatical models to explain tcmpcstitcs preservation in the rock record. Physical reworking of the substrate has a profound effect on the preservation of both the event hcd and the fair-wcathcr deposits.On the basis of comprehensive analyses of all factors influencing prcscrvational potential of event beds and cmpirical ohservations} both proximal upper-shorcfacc and middle-shorcfacc and distal shelf and lower offshore favor prcscr-vation of tcmpcstitcs but for markedly different reasons.The lowest prcscrvational potential for tcmpcstitcs appears to occur somewhere between the proximal and distal extremes.Such zones appear to correspond to proximal Cruziana ichnofacics suite of the upper offshore and distal portion of the lower shorcfacc.
The increasing awareness of tcmpcstitcs in the ancient record has correspondingly led to much consideration of their prcscrvahility.The main factors influencing the prcscrvahilitv are the net sedimentation rate Tthe hiogcnic mixing rate } and the magnitude of physical reworking. Theateroft has put forward the concept of time scales to attempt to solve this problem.The terms of transit time and dissipation time arc introduced.Transit time is related to the thickness of the hiogcnic reworking zone,the thickness of event beds and sedimentation rate.The hiogcnic reworking zone is also controlled by the animal size and the behavior engaged in during its generation.The determination of transit time is difficult because of the unstcadv and unpredictable mination of dissipation time is even more complicated than that of transit time.The dissipation time is controlled by manv factors such as the size of infauna, the behavior engaged in by the organisms, the dynamic interplay between the hcnthic community and the dcpositional event itself the dcsirahilitv of the event bed as a site for colonization and as a repository of food resources and the absolute time available for burrowing ctc.Unfortu- natelv, the preceding factors appear to resist quantification and therefore severely limit the effectiveness of existing mathcmatical models to explain tcmpcstitcs preservation in the rock record. Physical reworking of the substrate has a profound effect on the preservation of both the event hcd and the fair-wcathcr deposits.On the basis of comprehensive analyses of all factors influencing prcscrvational potential of event beds and cmpirical ohservations} both proximal upper-shorcfacc and middle-shorcfacc and distal shelf and lower offshore favor prcscr-vation of tcmpcstitcs but for markedly different reasons.The lowest prcscrvational potential for tcmpcstitcs appears to occur somewhere between the proximal and distal extremes.Such zones appear to correspond to proximal Cruziana ichnofacics suite of the upper offshore and distal portion of the lower shorcfacc.
2001, 19(1): 28-36.
Abstract:
Fcnghuoshan Group, with total thickness up to 4 782.8 m and geologic age from Earlv Eoccnc to Earlv oligocene, is widclv distributed in the Hoh Xil hasin, which is the largest Tcrtiarv scdimcntarv basin in the hinterland of the Tibetan plateau.The pile of sediments consists of gray-violet sandstone mudstonc and conglomerate.The evolution of dcpositional environment has undergone four periods: mainly fluvial environment during 56.0-52.2 Ma, lacustrinc environment during 52.2-43.1 Ma, fluvial and fan-delta environments during 43.1-38.3 Ma}~and mainly fluvial environment during 38.3 -32.0 Ma.Palcocurrcnt directions were changed to castsouthward from castnorthward in the early period then to north-ward in the late period.Thcsc changes indicate the dcpoccntcr of the Hoh Xil basin migrated eastward and northward. The evolution of the dcpositional environment and migration of the dcpoccntcr could he affected by early uplift of the Tibetan plateau
Fcnghuoshan Group, with total thickness up to 4 782.8 m and geologic age from Earlv Eoccnc to Earlv oligocene, is widclv distributed in the Hoh Xil hasin, which is the largest Tcrtiarv scdimcntarv basin in the hinterland of the Tibetan plateau.The pile of sediments consists of gray-violet sandstone mudstonc and conglomerate.The evolution of dcpositional environment has undergone four periods: mainly fluvial environment during 56.0-52.2 Ma, lacustrinc environment during 52.2-43.1 Ma, fluvial and fan-delta environments during 43.1-38.3 Ma}~and mainly fluvial environment during 38.3 -32.0 Ma.Palcocurrcnt directions were changed to castsouthward from castnorthward in the early period then to north-ward in the late period.Thcsc changes indicate the dcpoccntcr of the Hoh Xil basin migrated eastward and northward. The evolution of the dcpositional environment and migration of the dcpoccntcr could he affected by early uplift of the Tibetan plateau
2001, 19(1): 48-54.
Abstract:
The Qinling orogenie belt is located in the central China and is one of the most important intraeontinental progeny in the world.Devonian sedimentary basins are the major accumulation structures for Au-Ag-Ph-Zn deposits in the area.Fengtai Devonian pull-apart hasin} one of the accumulation basins in the Qinling orogeny, hosted a series of large-superlarge Au-Ph-Zn deposits such as Qiandongshan and Dongtangzi large Ph-Zn deposits and Baguamiao superlarge Au deposits.Leadzinc orehodies hosted at a suite of hvdrothermal depositional rocks in the three-order hvdrothermal basins.Therefore research on relationship between the hvdrothermal depositional faeies and the three-order hvdrothermal basin is the best way to understand the relationship between metal deposits and the hvdrothermal depositional basin. The concept of hvdrothermal sedimentary rock faeies at the Devonian in the Qinling progeny has been initiated.Relationships between tectonic hvdrothermal sedimentary faeies and paleo-geographic framework of sedimentary hasin, between hvdrothermal sedimentary faeies and mineralization of hvdrothermal depositions and between hvdrothermal sedimentary faeies and tectonic geographic framework are very important in the analysis of sedimentary basin.On the basis of associations of the hvdrothermal sedimentary facies, sedimentary lithofacies, and sedimentary svstem, the Qiandongshan-Shuangshipu third-order hvdrothermal depositional basin has been analyzed in this paper. Three depositional systems are recognized in the Qiandongshan-Shuangshipu third-order hvdrothermal depositional basin.Carbonate rock formation was formed in a shallow water environment at the beginning of the three-order basin while fine elastic rock formation was formed in a shallow water environment at the closedown of the three-order basin.The hvdrothermal depositional system between them was developed in half-deep or deep water limited reducing environment in the three-order hvdrothermal basin.NE-trending synfault were responsible for the formation of the Qiandongshan-Shuangshipu downfaulted three-order basin.Based on analysis of paleoteetonics and basin-filling sediments the data suggests that the Qiandongshan-Shuangshipu three-order basin with hvdrothermal depositions were probably formed in tectonics field of tensile-shear stress in the Middle-Late Devonian.
The Qinling orogenie belt is located in the central China and is one of the most important intraeontinental progeny in the world.Devonian sedimentary basins are the major accumulation structures for Au-Ag-Ph-Zn deposits in the area.Fengtai Devonian pull-apart hasin} one of the accumulation basins in the Qinling orogeny, hosted a series of large-superlarge Au-Ph-Zn deposits such as Qiandongshan and Dongtangzi large Ph-Zn deposits and Baguamiao superlarge Au deposits.Leadzinc orehodies hosted at a suite of hvdrothermal depositional rocks in the three-order hvdrothermal basins.Therefore research on relationship between the hvdrothermal depositional faeies and the three-order hvdrothermal basin is the best way to understand the relationship between metal deposits and the hvdrothermal depositional basin. The concept of hvdrothermal sedimentary rock faeies at the Devonian in the Qinling progeny has been initiated.Relationships between tectonic hvdrothermal sedimentary faeies and paleo-geographic framework of sedimentary hasin, between hvdrothermal sedimentary faeies and mineralization of hvdrothermal depositions and between hvdrothermal sedimentary faeies and tectonic geographic framework are very important in the analysis of sedimentary basin.On the basis of associations of the hvdrothermal sedimentary facies, sedimentary lithofacies, and sedimentary svstem, the Qiandongshan-Shuangshipu third-order hvdrothermal depositional basin has been analyzed in this paper. Three depositional systems are recognized in the Qiandongshan-Shuangshipu third-order hvdrothermal depositional basin.Carbonate rock formation was formed in a shallow water environment at the beginning of the three-order basin while fine elastic rock formation was formed in a shallow water environment at the closedown of the three-order basin.The hvdrothermal depositional system between them was developed in half-deep or deep water limited reducing environment in the three-order hvdrothermal basin.NE-trending synfault were responsible for the formation of the Qiandongshan-Shuangshipu downfaulted three-order basin.Based on analysis of paleoteetonics and basin-filling sediments the data suggests that the Qiandongshan-Shuangshipu three-order basin with hvdrothermal depositions were probably formed in tectonics field of tensile-shear stress in the Middle-Late Devonian.
2001, 19(1): 60-65.
Abstract:
Silurian bitumen-hearing sandstoncs in Central Tarim are shown to he a good case to study influence of hvdrocarhon emplacement on diagcncsis.We have carried it out by means of observation of thin sections, SEM of sandstoncs in congwnction with analysis of water chemistry, organic acid anions and δD,δ18O,87Sr/86Sr of oilficld water and homogenization tcmpcraturcs of fluid inclusions of the sandstoncs. It can he found that quartz secondary overgrowth coexists with reservoir bitumen.Bitumen may occur between quartz overgrowth and grains in coarser sandstoncs or occlude in the centre of pore in finer sandstoncs.Homogenization temperaturcs of organic inclusions are divided into 2 groups: 59.5-82℃ and 103-125℃,suggestive of at least 2 phases of oil emplacement.The latter is close to the present temperatures of the bore hole hottom, indicating that the late oil and gas cmplacement took place in the late Yanshan to early Himalava Orogcny and quartz overgrowth is not inhibited by oil cmplaccmenu and ccmcntation continucds to present day. Relationships between Br and Ca,Mg,Sr,Cl,CF(CF=Ca+Mg+Sr-SO4-HC03,meq/L) show that oilficld wato is evolved by suhacrial evaporation of scawatcr and subsequent mixing with meteoric water evidenced by relationship between δD and δ18O.Relative enrichment of Ca,Sr,K and depletion of Mg is explained to he a result of dissolution of K- feldspar,dolomitization of calcite and alhitivation of feldspar.87Sr/86Sr of 14 water samples range from 0.710 44 to 0.712 58,much larger than Silurian seawater, indicating that Rh-enriched dctrital minerals such as I}-feldspar, mica and illitc from sandstone or mudstonc contribute significant amount of 87Sr to oilficld waters. It is proposed that organic acids and anions } hydrocarbons he generated by as a result of meteoric water influx after oil emplacement. Organic acids enhance dissolution of minerals such as K-feldspar, quartz leading to generation of secondary porosity and supply additional Si necessary for quartz overgrowth. Si mass transport is through diffusion due to concentration difference as a result of Si precipitation on dctrital quartz.And this is the reason why quartz overgrowth was not inhibited.And Fe II in authigcnic minerals such as Fe-dolomite Fe-calcite and pyrite is mainly derived from reduction of Fe203 due to low Eh resulting from hydrocarbon emplacement. It can he found that bitumen-hearing sandstone is grey, dark grey, even black in comparison with color brown in most non- bitumen-hearing sandstone, suggesting that the former was bleached.~
Silurian bitumen-hearing sandstoncs in Central Tarim are shown to he a good case to study influence of hvdrocarhon emplacement on diagcncsis.We have carried it out by means of observation of thin sections, SEM of sandstoncs in congwnction with analysis of water chemistry, organic acid anions and δD,δ18O,87Sr/86Sr of oilficld water and homogenization tcmpcraturcs of fluid inclusions of the sandstoncs. It can he found that quartz secondary overgrowth coexists with reservoir bitumen.Bitumen may occur between quartz overgrowth and grains in coarser sandstoncs or occlude in the centre of pore in finer sandstoncs.Homogenization temperaturcs of organic inclusions are divided into 2 groups: 59.5-82℃ and 103-125℃,suggestive of at least 2 phases of oil emplacement.The latter is close to the present temperatures of the bore hole hottom, indicating that the late oil and gas cmplacement took place in the late Yanshan to early Himalava Orogcny and quartz overgrowth is not inhibited by oil cmplaccmenu and ccmcntation continucds to present day. Relationships between Br and Ca,Mg,Sr,Cl,CF(CF=Ca+Mg+Sr-SO4-HC03,meq/L) show that oilficld wato is evolved by suhacrial evaporation of scawatcr and subsequent mixing with meteoric water evidenced by relationship between δD and δ18O.Relative enrichment of Ca,Sr,K and depletion of Mg is explained to he a result of dissolution of K- feldspar,dolomitization of calcite and alhitivation of feldspar.87Sr/86Sr of 14 water samples range from 0.710 44 to 0.712 58,much larger than Silurian seawater, indicating that Rh-enriched dctrital minerals such as I}-feldspar, mica and illitc from sandstone or mudstonc contribute significant amount of 87Sr to oilficld waters. It is proposed that organic acids and anions } hydrocarbons he generated by as a result of meteoric water influx after oil emplacement. Organic acids enhance dissolution of minerals such as K-feldspar, quartz leading to generation of secondary porosity and supply additional Si necessary for quartz overgrowth. Si mass transport is through diffusion due to concentration difference as a result of Si precipitation on dctrital quartz.And this is the reason why quartz overgrowth was not inhibited.And Fe II in authigcnic minerals such as Fe-dolomite Fe-calcite and pyrite is mainly derived from reduction of Fe203 due to low Eh resulting from hydrocarbon emplacement. It can he found that bitumen-hearing sandstone is grey, dark grey, even black in comparison with color brown in most non- bitumen-hearing sandstone, suggesting that the former was bleached.~
2001, 19(1): 79-84.
Abstract:
Non-mincrlizcd animal tissues may he fossilized in cxccptionallv taphonomic conditions.Anoxia and rapid burial do not prevent information loss through decav, but thcv do promote the preservation of non-mineralized tissues.Sterile environments inhibit dccay, but thcv are ephemeral on a geological time scale.Stable non-mineralized tissue fossils may he preserved either as organic remains}carhonaccous comprcssions) or by replication in authigcnic minerals.The most commonly occurring diagenetic minerals associated with exceptional preservation are pyrite conhonatcs and phosphates among which phosphates precipitate rapidly enough to replicate suhccllular details.Non-mineralized tissues, both volatilcs and rcfractorics, can he permineralized, coated/pscudomorphcd and castcd/molded by these authigcnic minerals.Activities of microbes destroy non-min-cralizcd tissues on the other hand some are necessary to drive the precipitation of authigcnic minerals.Burgess Shale-type preservation involves non-mineralized tissues preserved as organic remains but the dominants are replicated by hydrous aluminosilicatcs.Therefore the authigcnic mincralization is fundamental to preserving these fossils even though some organic rcamains are also present.
Non-mincrlizcd animal tissues may he fossilized in cxccptionallv taphonomic conditions.Anoxia and rapid burial do not prevent information loss through decav, but thcv do promote the preservation of non-mineralized tissues.Sterile environments inhibit dccay, but thcv are ephemeral on a geological time scale.Stable non-mineralized tissue fossils may he preserved either as organic remains}carhonaccous comprcssions) or by replication in authigcnic minerals.The most commonly occurring diagenetic minerals associated with exceptional preservation are pyrite conhonatcs and phosphates among which phosphates precipitate rapidly enough to replicate suhccllular details.Non-mineralized tissues, both volatilcs and rcfractorics, can he permineralized, coated/pscudomorphcd and castcd/molded by these authigcnic minerals.Activities of microbes destroy non-min-cralizcd tissues on the other hand some are necessary to drive the precipitation of authigcnic minerals.Burgess Shale-type preservation involves non-mineralized tissues preserved as organic remains but the dominants are replicated by hydrous aluminosilicatcs.Therefore the authigcnic mincralization is fundamental to preserving these fossils even though some organic rcamains are also present.
2001, 19(1): 90-95.
Abstract:
According to the field survcv formed before 0.7 Ma, and lahoratorv analvses, the residua of 3 periods arc indcntificd in the section of loess which arc composed of 1st.4th and 5th lavcr rcdhrown palcosols and the weathered loess lavcrs under them.Thcv mainly developed in the south-cast Loess Plateau and also exist in the middle of the Loess Plateau.The thickncss of residua almost varies from 3 to 6 m and normally consist of 3 to 4 layers.From top to hottom} 1st layer is red-brown palcosols,2nd layer is brown-red weathered broken loess 3rd layer is brown-yellow weathered broken loess with fcrriginous film the 4th layer is brown-yellow weathered broken loess without fcrriginous film.The apparent difference between residua and palcosol is that the thickness of the former is bigger than the latter and that there are 2 to 3 layers weathered loess more in residua than in palcosols.The macroscopic feature of weathered loess is the deeper color more weathering cracks and broken soil body. Particle size analysis revealed that component of clay particle in palcsols varies from 40% to 60%,and im weathered loess varies from 40 % to 45 %.Magnetic susceptibility in palcosol generally varies from 100 to 280(10-6SI),and in weathered loess varies from 60 to 100(10-6SI).The CaC03 content in weathered loess is mainllv less than 1%,and unweathered loess is usually above 8 %.This shows that weathered and unwcathcrcd loess layer are apparently different. The X-ray diffraction of six clay film samples reveals that the clay mineral in residua is mainlvmontmorillonite, secondlv is illitc and kaolinitc.So we can determine that the residua in loess is mont morillonitc-illitc types.The survey in the migrated depth of red fcrriginous clay film and CaC03 nodules indicate that the palcosol which converted into rcsiduun dcvclopcd strongly CaC03 and Fe203 in them obviously migrated out of the palcosol layer. The illuvial layer of CaC03 nodules is not at the bottom of palcosol, it lies in the weathered loess which is under the palcosol bottom 1 to 2 meters. Through the contrast the components of weathering section of the palcosols in loess and modern sub-tropical Ycllowbrown Earth are primarily same it developed more strongly than north sub-tropical residua. CaC03 and Fe203 migrated depth and microstructure identification indicate that CaC03 illuvial layer in the 1st,4th and 5th paleosols don' t belong to component part of paleosol section and acid medium occured during middle and late period developing these 3 paleosols which are leached forest soil.The annual mean temperature was about 17℃ when the 1st,4th and 5th residuum developed in Xi' an area and annual mean precipitation was 900 to 1 OOOmm} it is 4℃ higher than nowdav's annual mean temperature, and 300 to 400 mm more than nowdav's annual mean precipitation.The development of residua in loess indicates that the climatie zone migrated greatly at that time and the sub-tropical climate migrated at least to the middle of Loess Plateau.
According to the field survcv formed before 0.7 Ma, and lahoratorv analvses, the residua of 3 periods arc indcntificd in the section of loess which arc composed of 1st.4th and 5th lavcr rcdhrown palcosols and the weathered loess lavcrs under them.Thcv mainly developed in the south-cast Loess Plateau and also exist in the middle of the Loess Plateau.The thickncss of residua almost varies from 3 to 6 m and normally consist of 3 to 4 layers.From top to hottom} 1st layer is red-brown palcosols,2nd layer is brown-red weathered broken loess 3rd layer is brown-yellow weathered broken loess with fcrriginous film the 4th layer is brown-yellow weathered broken loess without fcrriginous film.The apparent difference between residua and palcosol is that the thickness of the former is bigger than the latter and that there are 2 to 3 layers weathered loess more in residua than in palcosols.The macroscopic feature of weathered loess is the deeper color more weathering cracks and broken soil body. Particle size analysis revealed that component of clay particle in palcsols varies from 40% to 60%,and im weathered loess varies from 40 % to 45 %.Magnetic susceptibility in palcosol generally varies from 100 to 280(10-6SI),and in weathered loess varies from 60 to 100(10-6SI).The CaC03 content in weathered loess is mainllv less than 1%,and unweathered loess is usually above 8 %.This shows that weathered and unwcathcrcd loess layer are apparently different. The X-ray diffraction of six clay film samples reveals that the clay mineral in residua is mainlvmontmorillonite, secondlv is illitc and kaolinitc.So we can determine that the residua in loess is mont morillonitc-illitc types.The survey in the migrated depth of red fcrriginous clay film and CaC03 nodules indicate that the palcosol which converted into rcsiduun dcvclopcd strongly CaC03 and Fe203 in them obviously migrated out of the palcosol layer. The illuvial layer of CaC03 nodules is not at the bottom of palcosol, it lies in the weathered loess which is under the palcosol bottom 1 to 2 meters. Through the contrast the components of weathering section of the palcosols in loess and modern sub-tropical Ycllowbrown Earth are primarily same it developed more strongly than north sub-tropical residua. CaC03 and Fe203 migrated depth and microstructure identification indicate that CaC03 illuvial layer in the 1st,4th and 5th paleosols don' t belong to component part of paleosol section and acid medium occured during middle and late period developing these 3 paleosols which are leached forest soil.The annual mean temperature was about 17℃ when the 1st,4th and 5th residuum developed in Xi' an area and annual mean precipitation was 900 to 1 OOOmm} it is 4℃ higher than nowdav's annual mean temperature, and 300 to 400 mm more than nowdav's annual mean precipitation.The development of residua in loess indicates that the climatie zone migrated greatly at that time and the sub-tropical climate migrated at least to the middle of Loess Plateau.
2001, 19(1): 101-106.
Abstract:
Based on the sporo-pollen analvscs of the core samples of Corcholc D-1 from the Dahuxun Lakc in the Qaidam Basin of the Qinghai Province, the sporo-pollen diagram may he divided into three palynofloral zones, i.e.Zone Q2,Zone Q3,and Zone Q4.In accordance with the characteristics of the palynofloras} the problems on the vcgctational evolution and the paleoclimatic changes in the past 500 ka were discussed.Ages of the scdimcntarv section of Corcholc D-1 are based on palcomagnetic dating.The results of this study indicate that the middle to late Middle Pleistocene(500-130 ka BP) palcoclimate might he a semi-wet type of the warm-temperate zone the Latc Pleistocene(130-10 ka BP) palcoclimatc might he a semi-arid type of the temperate zone and the Holocene(10-0 ka BP) palcoclimatc might he a arid type of the cool-tcm-pcratc zone in the Qaidam Basin. The Latc Pleistocene climatic changes coincide essentially with the evolution of cool and warm events recorded by the Guliya ice core from the Qinghai-Tibetan Plateau.
Based on the sporo-pollen analvscs of the core samples of Corcholc D-1 from the Dahuxun Lakc in the Qaidam Basin of the Qinghai Province, the sporo-pollen diagram may he divided into three palynofloral zones, i.e.Zone Q2,Zone Q3,and Zone Q4.In accordance with the characteristics of the palynofloras} the problems on the vcgctational evolution and the paleoclimatic changes in the past 500 ka were discussed.Ages of the scdimcntarv section of Corcholc D-1 are based on palcomagnetic dating.The results of this study indicate that the middle to late Middle Pleistocene(500-130 ka BP) palcoclimate might he a semi-wet type of the warm-temperate zone the Latc Pleistocene(130-10 ka BP) palcoclimatc might he a semi-arid type of the temperate zone and the Holocene(10-0 ka BP) palcoclimatc might he a arid type of the cool-tcm-pcratc zone in the Qaidam Basin. The Latc Pleistocene climatic changes coincide essentially with the evolution of cool and warm events recorded by the Guliya ice core from the Qinghai-Tibetan Plateau.
2001, 19(1): 125-129,135.
Abstract:
Although there have been large volumes of oil and gas discovered from the Tcrtiarv reservoirs in the western Qaidam basin, the source rocks have been believed as the mudstoncs and shalcs with high calcite contents and low organic carbon contents(TOC as low as 0.2%)which were deposited in the Tcrtiarv evaporate facics.The mudstoncs and shalcs are in great thick and distributed widclv in the western Qaidam basin. In general sense an effective source rock is referred to the rock with enough TOC which expels oil when its generating oil is over a saturation in the porosity of the rock at proper buried depths or subsurface temperatures.If a rock with very low TOC, its generating oil could not he over the saturation for oil to he expelled out, the rock was called as ineffective source rock.Most samples analyzed by previous studies belong to the ineffective source rocks as their original TOC too low. Therefore how to identify the effective source rocks is one of key aspects in petroleum resource assess mcnt on the Tertiary of the Qaidam basin. Bv scdimcntology study on the potential source rocks(dark colored mudstoncs and shalcs in the evaporate facics,the authors of this article discovered that there were significantly vertical changes in lithologics and TOC contents in the mudstones and shalcs, even in a single rhythmic layer of the rocks.The thickness of one rhythmic layer was mostly less than 1 or 2 meters.The rhythmic layer generally consists of marl, calcareous mudstone or shale, gyps shale saliferous shale gypsum and halite from the bottom to the top.The gray colored marls and calcareous shales took a large part of the thickness in the rhythmic layer but their TOC contents were generally less than 0. 4 %.The dark gray and black colored shalcs, gyps shalcs, and salifcrous shalcs were but rich in TOC(mostly over 0.8 0lo,some of them over 1% in small thickness(about 10-50 em) in one rhythmic laver,even over 2%).However~identifying the effective source rocks in such different lithologics becomes a kcv task in hydrocarbon resource assessment within the evaporate sequence.The authors designed a high pressured thermal simulation and combination with the Rock-Eva pyrolysis on the samples with different at least TOC contents and different lithologics, and found that the original TOC contents of the effective source rocks were over 0.4 0}o.The simulation and result were described in detail in this paper. This paper investigated the effective source rocks mainly on hydrocarbon generating from kcrogcn and expelling from the shales, but not on immature oil gcncrating and expelling. Therefore the effective source rocks postulated in this paper do not include the immature effective source rocks.The simulations conducted by the authors were ended corresponding to 0.9%-1.0 % of the R,,peak generation of oil from kcrogcn.ff no oil was expelled from the rock sample at the peak oil generation;.P.at about the rock was known gelled from the as ineffective oil source rock.But with increase of the thermal maturation gas could he from kcrogcn, the generated and exrock sample so that the rock might he called as effective gas source rock.However the maturity of the Tcrnary potential source rocks was not very high the corresponding R, is generally less than 1%,and little gas was generated from the source rocks.Therefore 0.4% of TOC is an useful standard for identifying the effective source rocks in the cvaporate sequence and a helpful index to finding the oil and gas in the Tertiary of the western Qaidam basin. Though the cffcctivc source rocks defined in this paper are much thinner and less volume than those described in previous studies much more oil may expel from the effective source rocks because of their high potential of oil generation than those of hulk volume of the marls and calcareous shales.~
Although there have been large volumes of oil and gas discovered from the Tcrtiarv reservoirs in the western Qaidam basin, the source rocks have been believed as the mudstoncs and shalcs with high calcite contents and low organic carbon contents(TOC as low as 0.2%)which were deposited in the Tcrtiarv evaporate facics.The mudstoncs and shalcs are in great thick and distributed widclv in the western Qaidam basin. In general sense an effective source rock is referred to the rock with enough TOC which expels oil when its generating oil is over a saturation in the porosity of the rock at proper buried depths or subsurface temperatures.If a rock with very low TOC, its generating oil could not he over the saturation for oil to he expelled out, the rock was called as ineffective source rock.Most samples analyzed by previous studies belong to the ineffective source rocks as their original TOC too low. Therefore how to identify the effective source rocks is one of key aspects in petroleum resource assess mcnt on the Tertiary of the Qaidam basin. Bv scdimcntology study on the potential source rocks(dark colored mudstoncs and shalcs in the evaporate facics,the authors of this article discovered that there were significantly vertical changes in lithologics and TOC contents in the mudstones and shalcs, even in a single rhythmic layer of the rocks.The thickness of one rhythmic layer was mostly less than 1 or 2 meters.The rhythmic layer generally consists of marl, calcareous mudstone or shale, gyps shale saliferous shale gypsum and halite from the bottom to the top.The gray colored marls and calcareous shales took a large part of the thickness in the rhythmic layer but their TOC contents were generally less than 0. 4 %.The dark gray and black colored shalcs, gyps shalcs, and salifcrous shalcs were but rich in TOC(mostly over 0.8 0lo,some of them over 1% in small thickness(about 10-50 em) in one rhythmic laver,even over 2%).However~identifying the effective source rocks in such different lithologics becomes a kcv task in hydrocarbon resource assessment within the evaporate sequence.The authors designed a high pressured thermal simulation and combination with the Rock-Eva pyrolysis on the samples with different at least TOC contents and different lithologics, and found that the original TOC contents of the effective source rocks were over 0.4 0}o.The simulation and result were described in detail in this paper. This paper investigated the effective source rocks mainly on hydrocarbon generating from kcrogcn and expelling from the shales, but not on immature oil gcncrating and expelling. Therefore the effective source rocks postulated in this paper do not include the immature effective source rocks.The simulations conducted by the authors were ended corresponding to 0.9%-1.0 % of the R,,peak generation of oil from kcrogcn.ff no oil was expelled from the rock sample at the peak oil generation;.P.at about the rock was known gelled from the as ineffective oil source rock.But with increase of the thermal maturation gas could he from kcrogcn, the generated and exrock sample so that the rock might he called as effective gas source rock.However the maturity of the Tcrnary potential source rocks was not very high the corresponding R, is generally less than 1%,and little gas was generated from the source rocks.Therefore 0.4% of TOC is an useful standard for identifying the effective source rocks in the cvaporate sequence and a helpful index to finding the oil and gas in the Tertiary of the western Qaidam basin. Though the cffcctivc source rocks defined in this paper are much thinner and less volume than those described in previous studies much more oil may expel from the effective source rocks because of their high potential of oil generation than those of hulk volume of the marls and calcareous shales.~
2001, 19(1): 136-140.
Abstract:
The thermal simulation experiments on the catalytic degradation of Dongying asphaltene have been carried out by using pyrolvsis gas chromatography at the presence of mineral and salt.The isothermal experimental data are used to develop a kinetic model of the generation of the pyrolvsates including gas hvdrocarhon, light hydrocarbon and heavy hydrocarbon.It is found that K2CO3 acts as a catalyst to promote the generation of all pyrolvsates.At the temperature of 570℃,the yield of total hydrocarbons is increased by about 20% in the presence of K2CO3.Montmorillonite increases the veild of gas and light hydrocarbon but decreases the yield of heavy hydrocarbon.At the temperature of 570℃,the yield of total hydrocarbons is increased by about 10% in the presence of montmorillonite.The higher activation energy is obtained for the generation of heavy hydrocarbon in the presence of montmorillonite while the lower activation energies are calculated for other pyrolvsates. Finally, the mechanism of catalytic degradation of asphaltene is tentatively investigated.
The thermal simulation experiments on the catalytic degradation of Dongying asphaltene have been carried out by using pyrolvsis gas chromatography at the presence of mineral and salt.The isothermal experimental data are used to develop a kinetic model of the generation of the pyrolvsates including gas hvdrocarhon, light hydrocarbon and heavy hydrocarbon.It is found that K2CO3 acts as a catalyst to promote the generation of all pyrolvsates.At the temperature of 570℃,the yield of total hydrocarbons is increased by about 20% in the presence of K2CO3.Montmorillonite increases the veild of gas and light hydrocarbon but decreases the yield of heavy hydrocarbon.At the temperature of 570℃,the yield of total hydrocarbons is increased by about 10% in the presence of montmorillonite.The higher activation energy is obtained for the generation of heavy hydrocarbon in the presence of montmorillonite while the lower activation energies are calculated for other pyrolvsates. Finally, the mechanism of catalytic degradation of asphaltene is tentatively investigated.
2001, 19(1): 145-149.
Abstract:
Diamondoid hvdrocarhons have been identified in heavy hvdrocarhons collected from gas samples in Yinggehai and Qiongdongnan basins by MID/GC/MS method.The empirical relationship between methyl diamantane ratio and the corresponding vitrinite reflectance value has been established based on our data and data after Chen, 1996.This empirical relationship has been used to evaluate the maturity of gases from three gasfields in Yinggehai and Qiongdongnan basins.Based on this study gases from Yinggehai and Qiongdongnan basins are generally believed to he highly mature(Ra>1.5%),the recult is in accordance with other studies.So, methyl diamantane index is an effective parameter to evaluate the maturity of gas.Our work not only provides the method to identify the diamondoids in gas, but also extends the application of diamondoids.The study of hiomarkers and maturity of gases have very important rules for explaining some debatable questions such as the formation of gas reservoir and gas source rock in Ya13-1 gasfield.
Diamondoid hvdrocarhons have been identified in heavy hvdrocarhons collected from gas samples in Yinggehai and Qiongdongnan basins by MID/GC/MS method.The empirical relationship between methyl diamantane ratio and the corresponding vitrinite reflectance value has been established based on our data and data after Chen, 1996.This empirical relationship has been used to evaluate the maturity of gases from three gasfields in Yinggehai and Qiongdongnan basins.Based on this study gases from Yinggehai and Qiongdongnan basins are generally believed to he highly mature(Ra>1.5%),the recult is in accordance with other studies.So, methyl diamantane index is an effective parameter to evaluate the maturity of gas.Our work not only provides the method to identify the diamondoids in gas, but also extends the application of diamondoids.The study of hiomarkers and maturity of gases have very important rules for explaining some debatable questions such as the formation of gas reservoir and gas source rock in Ya13-1 gasfield.
2001, 19(1): 156-160.
Abstract:
Bv comparing nonhvdrocarhon compositions carbon isotope ratios of natural gases and reservoir inclusions in Wcivuan Areas( W ) and Zivang Areas( Z ) and lower Cambrian black shale is the main sources of natural gas.Time of structure formation is different between W and Z.The former is during Yanshanian orogcny and the latter Indosinian Orogcny, but Z structurc disappeared in Yanshanian Orogcny.So, natural gases for W arc made up of oil and kcrogcn-cracked gases, but the latto is important.However natural gases in Z are mainly made from oil-cracked gases. C1 / C1+ ratios of natural gases in W and Z are more than 99.62 %,therefore natural gases arc high and over-matured gases, and hydrocarbon gases of natural gases in Z are more abundant in high-yield wells than in low-yield ones.Contents of nitrogen gas in W Arca is higher than 6%,and less than 1.22% in high-yield wells and higher than 4.17 % in low-yield well in Z Arca. C1/C1+,contents of hydrocarbon gases and nitrogen hold out that natural gases in W are high and over-ma- turgid, and nitrogen gas originate from high and over-matured lower Cambrian black shale.Natural gases with high content of nitrogen and helium gases in W are mainly kcrogcn-cracked.Natural gases in high-yield wells in Z are oil-cracked.Because content of radioactive element and nitrogen in oil are much lower than in source rock oil-cracked gases must contain low content of helium and nitrogen gases.Natural gases in low-yield wells intcrfuscd by kcrogcn-cracked gases contain high con- tent of helium and nitrogen gases.Methane carbon isotope ratios are nearly 5‰ higher in W than in Z.Ra(%),based on δ13C1(‰)-Ra(%) formula, is 1% higher in W than in Z.Furthermore natural gases in W arc kcrogcn-cracked and those in Z are oil-cracked. Homogeneous temperatures( HT) of liquid hydrocarbon inclusions in W is in the range of 80℃ and 160℃,and amount of liquid hydrocarbon inclusions is small.Homogeneous temperature of abundant gaseous hydrocarbon inclusions in Wis in the range of 200℃ and 240℃.Homogeneous temperature of hydrocarbon inclusions in Z is in the range of 80℃ and 248℃,and having licquid, gaseous gaseous- liquid liquid-gaseous mainly liquid hydrocarbon inclusions.HT of liquid hvdrocarbon inclusions is in the range of 80℃ and 160℃,and the rest are in the range of 1500C and 2480C.Accumulated oil is small and hiodegraded, and oil-cracked gases in W are lack.Accumulated oil is large and oil-cracked gases in Z are ahundant. Differences of nitrogen and helium gas, methane carbon isotope ratios, HT and phase of hvdrocarhon inclusions prove that natural gases originating from lower Cambrian black shale in W are kerogen-cracked and those in Z are oil-cracked.
Bv comparing nonhvdrocarhon compositions carbon isotope ratios of natural gases and reservoir inclusions in Wcivuan Areas( W ) and Zivang Areas( Z ) and lower Cambrian black shale is the main sources of natural gas.Time of structure formation is different between W and Z.The former is during Yanshanian orogcny and the latter Indosinian Orogcny, but Z structurc disappeared in Yanshanian Orogcny.So, natural gases for W arc made up of oil and kcrogcn-cracked gases, but the latto is important.However natural gases in Z are mainly made from oil-cracked gases. C1 / C1+ ratios of natural gases in W and Z are more than 99.62 %,therefore natural gases arc high and over-matured gases, and hydrocarbon gases of natural gases in Z are more abundant in high-yield wells than in low-yield ones.Contents of nitrogen gas in W Arca is higher than 6%,and less than 1.22% in high-yield wells and higher than 4.17 % in low-yield well in Z Arca. C1/C1+,contents of hydrocarbon gases and nitrogen hold out that natural gases in W are high and over-ma- turgid, and nitrogen gas originate from high and over-matured lower Cambrian black shale.Natural gases with high content of nitrogen and helium gases in W are mainly kcrogcn-cracked.Natural gases in high-yield wells in Z are oil-cracked.Because content of radioactive element and nitrogen in oil are much lower than in source rock oil-cracked gases must contain low content of helium and nitrogen gases.Natural gases in low-yield wells intcrfuscd by kcrogcn-cracked gases contain high con- tent of helium and nitrogen gases.Methane carbon isotope ratios are nearly 5‰ higher in W than in Z.Ra(%),based on δ13C1(‰)-Ra(%) formula, is 1% higher in W than in Z.Furthermore natural gases in W arc kcrogcn-cracked and those in Z are oil-cracked. Homogeneous temperatures( HT) of liquid hydrocarbon inclusions in W is in the range of 80℃ and 160℃,and amount of liquid hydrocarbon inclusions is small.Homogeneous temperature of abundant gaseous hydrocarbon inclusions in Wis in the range of 200℃ and 240℃.Homogeneous temperature of hydrocarbon inclusions in Z is in the range of 80℃ and 248℃,and having licquid, gaseous gaseous- liquid liquid-gaseous mainly liquid hydrocarbon inclusions.HT of liquid hvdrocarbon inclusions is in the range of 80℃ and 160℃,and the rest are in the range of 1500C and 2480C.Accumulated oil is small and hiodegraded, and oil-cracked gases in W are lack.Accumulated oil is large and oil-cracked gases in Z are ahundant. Differences of nitrogen and helium gas, methane carbon isotope ratios, HT and phase of hvdrocarhon inclusions prove that natural gases originating from lower Cambrian black shale in W are kerogen-cracked and those in Z are oil-cracked.
