1998 Vol. 16, No. 4
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Display Method:
1998, 16(4): 1-7.
Abstract:
The history of regional tectonic subsidence and sea level changes are tw o majo r factors of four factors in sequence stratigraphy.The dynamic model of tecto nic subsidence curves from the Devonian to the Triassic in the study area has been reconstructed by the approach of back stripping.The evolution succession of the basin , which is from the passive continental margin, mature passive continental margin, peripheral foreland basin to post orogeny foreland basin, is identified.At the same time, the curves of sea level changes in the Permian and Triassic have been inversed by the inform ation of sedimentary systems tract, seismic section and isotope of carbon and oxygen.The sea level changes in the study area are in synchronism w ith the global sea level changes. The period of sea level rising in the study area lasts to Changxingian Age of Late Permian and the time of sea level falling is Dalong Age of Late Permian.The sea level changes of Late Triassic in the study area are rising and the global sea level chenges is m ainly in falling stage.It is relative to the o rogenic overthrusting.
The history of regional tectonic subsidence and sea level changes are tw o majo r factors of four factors in sequence stratigraphy.The dynamic model of tecto nic subsidence curves from the Devonian to the Triassic in the study area has been reconstructed by the approach of back stripping.The evolution succession of the basin , which is from the passive continental margin, mature passive continental margin, peripheral foreland basin to post orogeny foreland basin, is identified.At the same time, the curves of sea level changes in the Permian and Triassic have been inversed by the inform ation of sedimentary systems tract, seismic section and isotope of carbon and oxygen.The sea level changes in the study area are in synchronism w ith the global sea level changes. The period of sea level rising in the study area lasts to Changxingian Age of Late Permian and the time of sea level falling is Dalong Age of Late Permian.The sea level changes of Late Triassic in the study area are rising and the global sea level chenges is m ainly in falling stage.It is relative to the o rogenic overthrusting.
1998, 16(4): 14-20.
Abstract:
The wave process of sedimentary basin is a form of earth' s crust movement, which is controled by both cosmogony and earth evolution. Tht distribution of stratigraphic sequence in time and space is determined by the evolution of sedimentary wave processes. Based on the discussion of the theory of sedimentary wave processes technique approach and working method the distribution and formation of stratigraphic sequences of Sinian Quaternary ws studied by using the predictive function of the sedimentary wave cruves studing the starting and ending time of deposition and erosion and the erosional quantity of the unconformities.In the aspects of theory and method the author was trying combining the sediementary wave processes of the study of sequance stratigraphy and put forward the concept of the well connected correaltion figure of stratigraphic frame work and sedimentary wave processes and its making steps. The figure reflects the position and the forming time of unconformities thd distrbution of the stratigraphic sequence and interprets the forming processes of the stratigraphic framework preserved, as well as its origin It is a helpful attempt to study the connection of sedimentary wave processes and the sequence stratigraphy.
The wave process of sedimentary basin is a form of earth' s crust movement, which is controled by both cosmogony and earth evolution. Tht distribution of stratigraphic sequence in time and space is determined by the evolution of sedimentary wave processes. Based on the discussion of the theory of sedimentary wave processes technique approach and working method the distribution and formation of stratigraphic sequences of Sinian Quaternary ws studied by using the predictive function of the sedimentary wave cruves studing the starting and ending time of deposition and erosion and the erosional quantity of the unconformities.In the aspects of theory and method the author was trying combining the sediementary wave processes of the study of sequance stratigraphy and put forward the concept of the well connected correaltion figure of stratigraphic frame work and sedimentary wave processes and its making steps. The figure reflects the position and the forming time of unconformities thd distrbution of the stratigraphic sequence and interprets the forming processes of the stratigraphic framework preserved, as well as its origin It is a helpful attempt to study the connection of sedimentary wave processes and the sequence stratigraphy.
1998, 16(4): 27-31.
Abstract:
At the geologic setting of shallow-water delta.distributary channels on plain palin can stretch into lake very long distance by sediment filling and the lake level frequent fluctuation.developping obvious subaqueous channel at wide shallow water delta front.At the same time,the lake level fluctuation,hydrodynamics,suchas channel,wave and offshore current,will change the distribution of sedimentary materials,and results in delta front sandbodies sheetlization,which mainly occurs in the subaqueous channel sandbodies.Along with the climate become more moist,the frequence and range of lake level fluctuation is also smaller,and the hydrodynamics reworks the distribution of sedimentary materials on delta front and sandbody sheetliation become weaker at the same time.
At the geologic setting of shallow-water delta.distributary channels on plain palin can stretch into lake very long distance by sediment filling and the lake level frequent fluctuation.developping obvious subaqueous channel at wide shallow water delta front.At the same time,the lake level fluctuation,hydrodynamics,suchas channel,wave and offshore current,will change the distribution of sedimentary materials,and results in delta front sandbodies sheetlization,which mainly occurs in the subaqueous channel sandbodies.Along with the climate become more moist,the frequence and range of lake level fluctuation is also smaller,and the hydrodynamics reworks the distribution of sedimentary materials on delta front and sandbody sheetliation become weaker at the same time.
1998, 16(4): 62-70.
Abstract:
The characteristics of sedimentology and petrology of the Middle Cambrian in western Shandong province show that: (1)The oolitic sediments developed at various places and stratum of no rth China are almost the allo- genic sediments, but no t the o riginal ”shoal”. They had been influenced by the changes of sea level and w ater current, so that the ooids was transported in a sho rt or long distance.In the study area, the oolitic limestone are not formed at the same time, it is time-transgressive(diachronons).In general, the horizon of oolitic limestone elevated gradually from SE to NW.That is the magnafacies, not the parvafacies.(2) The different texture of ooids occurred in the same oolitic limestone bed or thin band may be caused by the mixing of ooids form differ- ent places, termed the ”sedimentary mixing”, or ow ing to the ooids affected by the different diagensis after de- posit, termed the ”diagenetic mixing”. (3) Following the ooid deposit, the algal sediment composited of Epi- phyton developed.They occurred at the tidal flat, that is the algal flat.The algal sediments interbeded w ith the ooid sediments occurred off and between algal flats, as a result of frequent changes of sea level and tidal current.(4) The ooids (m ainly brick and radial texture) of the Zhangxia Formation lower member basically formed under the condition of stronger and medium active environment, the ooids (mainly arc texture) of the upper member basically fromed under the weaker active environments.(5)Before the Zhangxia Fo rmation up- per member and the Upper Cambrian Gushan Fo rmation, the obvious depositonal break caused by the sea level falling had happened.(6)Summarizing the sedimentary environment can be induce out the distribution situa- tion of sedimentary facies form near land to open sea. They are in turn: tidal(algal)flat facies near shore(ooid) sand sheet(or ridge)facies restricted water field(or lagoon)facies tida(ooid) bar facies open sea facies.
The characteristics of sedimentology and petrology of the Middle Cambrian in western Shandong province show that: (1)The oolitic sediments developed at various places and stratum of no rth China are almost the allo- genic sediments, but no t the o riginal ”shoal”. They had been influenced by the changes of sea level and w ater current, so that the ooids was transported in a sho rt or long distance.In the study area, the oolitic limestone are not formed at the same time, it is time-transgressive(diachronons).In general, the horizon of oolitic limestone elevated gradually from SE to NW.That is the magnafacies, not the parvafacies.(2) The different texture of ooids occurred in the same oolitic limestone bed or thin band may be caused by the mixing of ooids form differ- ent places, termed the ”sedimentary mixing”, or ow ing to the ooids affected by the different diagensis after de- posit, termed the ”diagenetic mixing”. (3) Following the ooid deposit, the algal sediment composited of Epi- phyton developed.They occurred at the tidal flat, that is the algal flat.The algal sediments interbeded w ith the ooid sediments occurred off and between algal flats, as a result of frequent changes of sea level and tidal current.(4) The ooids (m ainly brick and radial texture) of the Zhangxia Formation lower member basically formed under the condition of stronger and medium active environment, the ooids (mainly arc texture) of the upper member basically fromed under the weaker active environments.(5)Before the Zhangxia Fo rmation up- per member and the Upper Cambrian Gushan Fo rmation, the obvious depositonal break caused by the sea level falling had happened.(6)Summarizing the sedimentary environment can be induce out the distribution situa- tion of sedimentary facies form near land to open sea. They are in turn: tidal(algal)flat facies near shore(ooid) sand sheet(or ridge)facies restricted water field(or lagoon)facies tida(ooid) bar facies open sea facies.
1998, 16(4): 84-90.
Abstract:
The sandstone reservoir of Dongyin Formation, Oligocene Series in Dalujia area is one of the main produc- tion formation of Linpan Oil Field in the Eastern area of China.Its depositional system including delta, espe- cially the delta front part, and its sandbody genetic type including river -mouth bar, sublacustrine distributary channel, sublacustrine levee, sublacustrine crevasse splay and distal bar, have been identified though compre- hensive analysis on core, logging and well log data, and all these sandbody microfacies have different deposi- tional characteristics, well log facies, porosity and permeability.In addition, these sandbodies have strong in- traformational nonuniformity and not so strong an interstratal one.
The sandstone reservoir of Dongyin Formation, Oligocene Series in Dalujia area is one of the main produc- tion formation of Linpan Oil Field in the Eastern area of China.Its depositional system including delta, espe- cially the delta front part, and its sandbody genetic type including river -mouth bar, sublacustrine distributary channel, sublacustrine levee, sublacustrine crevasse splay and distal bar, have been identified though compre- hensive analysis on core, logging and well log data, and all these sandbody microfacies have different deposi- tional characteristics, well log facies, porosity and permeability.In addition, these sandbodies have strong in- traformational nonuniformity and not so strong an interstratal one.
1998, 16(4): 98-104.
Abstract:
Dis tinct com positional varaitions exist among hydrocarbo ns in open pores, colsed po res and bydrocarbon inclusions hos ted in minerals of reservoir rocks.In a pore scale, those heterogeneities are also indicated betw een free hy drocarbons and absorbed hydrocarbons by various minerals, reflecting compositional changes of hydro- carbons in reservoirs during hydrocarbon filling process.Analysis of those various hydrocarbons in reservoi r rocks could provide im porant infor mation for oil source correlations.
Dis tinct com positional varaitions exist among hydrocarbo ns in open pores, colsed po res and bydrocarbon inclusions hos ted in minerals of reservoir rocks.In a pore scale, those heterogeneities are also indicated betw een free hy drocarbons and absorbed hydrocarbons by various minerals, reflecting compositional changes of hydro- carbons in reservoirs during hydrocarbon filling process.Analysis of those various hydrocarbons in reservoi r rocks could provide im porant infor mation for oil source correlations.
1998, 16(4): 109-113.
Abstract:
The authors present here a brief introduction of synse dimentary deformational process ob- tained from latest paleomagnetic results of Tertiary System in Kuche Depression.The results from synfolding test imply that primary magnetizations of Pliocene and Oligocene are mainly synsedimentary remanent magnetization.According to pleomagnetical data, structural activity is intense during Pliocene and Oligocene.As a result, It has geological significance to deduce struc- tural framew ork and corresponding structural trace which control distribution of oil and gas in Kuche Depression.
The authors present here a brief introduction of synse dimentary deformational process ob- tained from latest paleomagnetic results of Tertiary System in Kuche Depression.The results from synfolding test imply that primary magnetizations of Pliocene and Oligocene are mainly synsedimentary remanent magnetization.According to pleomagnetical data, structural activity is intense during Pliocene and Oligocene.As a result, It has geological significance to deduce struc- tural framew ork and corresponding structural trace which control distribution of oil and gas in Kuche Depression.
1998, 16(4): 118-123.
Abstract:
Based on the principle and method of M arkov Chain, the methematic model w as established in o rder to describe the forming process and the micro-sequence of coal seam, The follow ing conclusions have been draw n: (1) The test values are far more greater than the ci tical points at different confidence levels, the microlithoty pe sequence of coal seam is fi t to the Markov Process.(2)The statistic direction of the microlithoty pe sequence w ithin each sublayer has hardly effiect on the analy sis result.(3)The thickness of the main states will be in- creased and that of the secondary decreased during the simulation of microlithoty pe sequence.This thickness change will make the simulating microlithotype sequence simple and clear.(4)The location of each microli tho- type fo r a case w as defined through the model fitting to coal structure, so the heterogeneous characteristics of coalbed methance(CBM)w ere predicated.(5) The advantageous gas-storaging location in the coal seam can be forecasted by combining the anslysis of the specific surface area of pore and the gas-storaging capaci ties of the different macerals w ith the microli thotype sequence of coal seam.So a new insight to evaluation on geologi- cal conditions of CBM development has been given.
Based on the principle and method of M arkov Chain, the methematic model w as established in o rder to describe the forming process and the micro-sequence of coal seam, The follow ing conclusions have been draw n: (1) The test values are far more greater than the ci tical points at different confidence levels, the microlithoty pe sequence of coal seam is fi t to the Markov Process.(2)The statistic direction of the microlithoty pe sequence w ithin each sublayer has hardly effiect on the analy sis result.(3)The thickness of the main states will be in- creased and that of the secondary decreased during the simulation of microlithoty pe sequence.This thickness change will make the simulating microlithotype sequence simple and clear.(4)The location of each microli tho- type fo r a case w as defined through the model fitting to coal structure, so the heterogeneous characteristics of coalbed methance(CBM)w ere predicated.(5) The advantageous gas-storaging location in the coal seam can be forecasted by combining the anslysis of the specific surface area of pore and the gas-storaging capaci ties of the different macerals w ith the microli thotype sequence of coal seam.So a new insight to evaluation on geologi- cal conditions of CBM development has been given.
1998, 16(4): 128-132.
Abstract:
By means of the study on the 32 sample′s characters of composi tion, iso topes of carbon and hydrogen and serial isotopes of hydrocarbons, on the isotopic relationship of carbon and hydrogen, on the relationship be- tween hy drocarbonic composition and isotopes of carbon from methane, the paper gets new know leges about natural g ases' genetic ty pe of different wells in different oil andg ases fields as well as the origin of some natural g as depositions in N orthern Tarim, and supplies available information for exploration of oil and natural gases.
By means of the study on the 32 sample′s characters of composi tion, iso topes of carbon and hydrogen and serial isotopes of hydrocarbons, on the isotopic relationship of carbon and hydrogen, on the relationship be- tween hy drocarbonic composition and isotopes of carbon from methane, the paper gets new know leges about natural g ases' genetic ty pe of different wells in different oil andg ases fields as well as the origin of some natural g as depositions in N orthern Tarim, and supplies available information for exploration of oil and natural gases.
1998, 16(4): 140-144.
Abstract:
A ccording to the hydrous py roly sis results of immature source rock from O rdovician sys tem, average ap- parent activation energies and frequency fact ors of kerosene from t he Lower Paleozoic at different evaluation stages are calculated.I t indicates that the w hole evolution coures is not in accord w ith the firs t order reaction, but different evolut ion stag s are in accord wi th the first order react ion.T hese calculation results have impo rt anreference value to basin simulation and resource evaluation of source rock from t he Low er P alaeozoic and M id- dle nd U pper Proterozozic.
A ccording to the hydrous py roly sis results of immature source rock from O rdovician sys tem, average ap- parent activation energies and frequency fact ors of kerosene from t he Lower Paleozoic at different evaluation stages are calculated.I t indicates that the w hole evolution coures is not in accord w ith the firs t order reaction, but different evolut ion stag s are in accord wi th the first order react ion.T hese calculation results have impo rt anreference value to basin simulation and resource evaluation of source rock from t he Low er P alaeozoic and M id- dle nd U pper Proterozozic.
1998, 16(4): 149-152.
Abstract:
Reservoir fluid ty pes are usually identified by logging well technology, repeat fo rmation test or geology ang geochemistry logg ing during drilling, and logging well interpreting is based on the physical property of reservoir fluids, there will be difficult in interpreting some low resistance oil intervals o r volcannic rock oil reservoirs.However reservoir geochemistry technology can be remedial for those defects, which can directly i- dentify reservoir fluid types(oil and g as)based on the fluid chemical character. authors use m ass-chormatography total ion chart of saturated hy drocarbon extracted from reservoir sand- stones to indentify reservoir fluid ty pes(oil and gas)).Fingerprints of oil saturated sandstones o r oil intervals show w ide n-alkane distribution, which ranges from C15 to C38, and is similar to those of oil sample; finger- prints from condensate sandstone show lig htly abbreviated n-alkane distribution, which ranges from C15 to C35, but the content of hig h hydrocarbon com pounds( C21) is apparently lower than that of oil sandstone; finger- prints from dry g as sandstone show a further abbreviated n-alkane distribution, which ranges from C15 to C28, the co ntent of high carbon compounds is very low, but the content of low carbon compounds is abundant, so this technology can be used to identify the types of reservoir fluid(oil and gas), reevaluate oil and g as intervals in old well whose log data is incomplete, and provide scientific evidence for optimizing acid treatment intervals.
Reservoir fluid ty pes are usually identified by logging well technology, repeat fo rmation test or geology ang geochemistry logg ing during drilling, and logging well interpreting is based on the physical property of reservoir fluids, there will be difficult in interpreting some low resistance oil intervals o r volcannic rock oil reservoirs.However reservoir geochemistry technology can be remedial for those defects, which can directly i- dentify reservoir fluid types(oil and g as)based on the fluid chemical character. authors use m ass-chormatography total ion chart of saturated hy drocarbon extracted from reservoir sand- stones to indentify reservoir fluid ty pes(oil and gas)).Fingerprints of oil saturated sandstones o r oil intervals show w ide n-alkane distribution, which ranges from C15 to C38, and is similar to those of oil sample; finger- prints from condensate sandstone show lig htly abbreviated n-alkane distribution, which ranges from C15 to C35, but the content of hig h hydrocarbon com pounds( C21) is apparently lower than that of oil sandstone; finger- prints from dry g as sandstone show a further abbreviated n-alkane distribution, which ranges from C15 to C28, the co ntent of high carbon compounds is very low, but the content of low carbon compounds is abundant, so this technology can be used to identify the types of reservoir fluid(oil and gas), reevaluate oil and g as intervals in old well whose log data is incomplete, and provide scientific evidence for optimizing acid treatment intervals.
1998, 16(4): 158-162.
Abstract:
The airborne particulates w ere sampled from the Xigu indus trial area, the railw ay, commercial and resi- dential mixed area and Panxuan Circle road area during heating period (March, 1994)and nonheating period (August, 1994).The carbon isotopic compositions of n-alkane series of the samples were analyzed by a MAT 252 ins tru- ment (GC-C-I RM S) 、We investigated the characteristics and distributions of the carbon isotopic compositions and concluded that (1)the δ13C values in w inter resemble that in summer except that both are similar in the Xig u industial area., (2)The results, calculated using a two-end model of the carbon isotopic compositions from nC21 and nC23 show that the air pollution of the Xigu industrial area is mainly caused by oil burning, that of the urban district coal burning during a heating period and oil burning of automobile during a nonheating period, and (3) oil burning pollution matter makes up over 60 % of the organic pollution one, caused chiefly by oil burning.
The airborne particulates w ere sampled from the Xigu indus trial area, the railw ay, commercial and resi- dential mixed area and Panxuan Circle road area during heating period (March, 1994)and nonheating period (August, 1994).The carbon isotopic compositions of n-alkane series of the samples were analyzed by a MAT 252 ins tru- ment (GC-C-I RM S) 、We investigated the characteristics and distributions of the carbon isotopic compositions and concluded that (1)the δ13C values in w inter resemble that in summer except that both are similar in the Xig u industial area., (2)The results, calculated using a two-end model of the carbon isotopic compositions from nC21 and nC23 show that the air pollution of the Xigu industrial area is mainly caused by oil burning, that of the urban district coal burning during a heating period and oil burning of automobile during a nonheating period, and (3) oil burning pollution matter makes up over 60 % of the organic pollution one, caused chiefly by oil burning.
1998, 16(4): 8-13.
Abstract:
The concept of depositional accommodation has been applied to sequence genesis analysis and sequence di- vision for continental rift basins with examples from Paleogene, Bohaiw an basin.The developing process and its major characteristics of a sequence, a qarasquence set and a parasequence in a continental rift basin can be in- terpretted respectively according to the changing of new space added during the 2nd, the 3rd and the 4th order episodic tectonic subsidence in corresponding to the volume of sediments supplied.Conditions to fo rm bounded surfaces of sequences and systems tracts can also be described and understood through an analysis of deposi- tional accommodation changes.As a result of accommodation evolution analysis, a new concept, the turn - round surface of accom modation variation, has been introduced and applied to recognize boundaries of se- quences and systems tracts.
The concept of depositional accommodation has been applied to sequence genesis analysis and sequence di- vision for continental rift basins with examples from Paleogene, Bohaiw an basin.The developing process and its major characteristics of a sequence, a qarasquence set and a parasequence in a continental rift basin can be in- terpretted respectively according to the changing of new space added during the 2nd, the 3rd and the 4th order episodic tectonic subsidence in corresponding to the volume of sediments supplied.Conditions to fo rm bounded surfaces of sequences and systems tracts can also be described and understood through an analysis of deposi- tional accommodation changes.As a result of accommodation evolution analysis, a new concept, the turn - round surface of accom modation variation, has been introduced and applied to recognize boundaries of se- quences and systems tracts.
1998, 16(4): 21-26.
Abstract:
Facies tracts division and correlation of progradational oil beds extremely affect the water injection response and recovery efficiency of reservoirs. Especially as to those low angle and thin progradational oil beds which do not occur progradational reflections on seismic profiles there is no effective method of finding out spatial distribution of every progradational bed sandbody.One example is the proximal turbidite fan reservoir of Zhuang 52 Shengli Oilfield. After the research on base level cycle high resolution sequence stratigraphy incorporated with 3D seismic interpretation it is found that the reservoir turns out to be composed of 20 progradational lobes of turbidite sandbodies instead of consisting of 4 sandbeds considered before.
Facies tracts division and correlation of progradational oil beds extremely affect the water injection response and recovery efficiency of reservoirs. Especially as to those low angle and thin progradational oil beds which do not occur progradational reflections on seismic profiles there is no effective method of finding out spatial distribution of every progradational bed sandbody.One example is the proximal turbidite fan reservoir of Zhuang 52 Shengli Oilfield. After the research on base level cycle high resolution sequence stratigraphy incorporated with 3D seismic interpretation it is found that the reservoir turns out to be composed of 20 progradational lobes of turbidite sandbodies instead of consisting of 4 sandbeds considered before.
1998, 16(4): 30-36.
Abstract:
The Strontium isotope composition of marine autogenetic minerals can reflect the sea level fluctuation trend during the minerals deposited. The analysis of the87Sr/86Sr ratio of Ordovician shows the sea level dropped in Early Ordovician and then rose continuously and stayed above the average level in M iddle and Late Ordovician in middle Tarim area. The study of oxygen isotopes indicates the dolostones of the Lower Ordovician are mainly penecontemporaneous dolostones which deposited in the sedimentary environment of the high salinity of the lower sea level. The trace elements geochemistry draws the same conclusion as that of the study of the isotope analysis. In brief, the variation trend of87Sr/86r ratio was reversely interrelated with the sea level fluctuation. Both oxygen isotopes and some elements made remarkably response to the sea level fluctuation during the O rdovician.
The Strontium isotope composition of marine autogenetic minerals can reflect the sea level fluctuation trend during the minerals deposited. The analysis of the87Sr/86Sr ratio of Ordovician shows the sea level dropped in Early Ordovician and then rose continuously and stayed above the average level in M iddle and Late Ordovician in middle Tarim area. The study of oxygen isotopes indicates the dolostones of the Lower Ordovician are mainly penecontemporaneous dolostones which deposited in the sedimentary environment of the high salinity of the lower sea level. The trace elements geochemistry draws the same conclusion as that of the study of the isotope analysis. In brief, the variation trend of87Sr/86r ratio was reversely interrelated with the sea level fluctuation. Both oxygen isotopes and some elements made remarkably response to the sea level fluctuation during the O rdovician.
1998, 16(4): 42-49.
Abstract:
The Cambrian silicalite formation, composed of black chert and black slate, is the host-rock of Laerma and Qiongmo gold deposits in western Qinling.The ore-bearing chert is characterized by bedded, laminated, mas- sive and pseudobrecciated structures which change regularly in space.The thickness of a chert bed generally varies from 30 to 200 meters.Host elements are simple and concentrated in the chert.Besides SiO2(95.30 % on average), only FeO, Fe2O3 and P2O5 reach or are more than 1.0 %.The ratios of FeO/Fe2O3 in all chert samples are mainly greater than 1, but the ratios of Sr/Ba are less than 1.The organic carbon concentrations of silicalite formation range mostly from 0.12 % to 8.14 %, the highest concentration being 22 %.REEs(rare- earth elements) are characterized by a low total content (ranging between 3.29×10-6～100×10-6), nega- tive Ce anormal and a gradually increasing NASC —normalized value with increasing atomic number of REEs. The δ30Si values of the chert in the area range mainly from + 0.4 ‰to 0.8 ‰.All the geochemical characteris- tics of the silicalite formation manifest that the silicalite formation deposited in the deep and half- deep sea en- vironment.
The Cambrian silicalite formation, composed of black chert and black slate, is the host-rock of Laerma and Qiongmo gold deposits in western Qinling.The ore-bearing chert is characterized by bedded, laminated, mas- sive and pseudobrecciated structures which change regularly in space.The thickness of a chert bed generally varies from 30 to 200 meters.Host elements are simple and concentrated in the chert.Besides SiO2(95.30 % on average), only FeO, Fe2O3 and P2O5 reach or are more than 1.0 %.The ratios of FeO/Fe2O3 in all chert samples are mainly greater than 1, but the ratios of Sr/Ba are less than 1.The organic carbon concentrations of silicalite formation range mostly from 0.12 % to 8.14 %, the highest concentration being 22 %.REEs(rare- earth elements) are characterized by a low total content (ranging between 3.29×10-6～100×10-6), nega- tive Ce anormal and a gradually increasing NASC —normalized value with increasing atomic number of REEs. The δ30Si values of the chert in the area range mainly from + 0.4 ‰to 0.8 ‰.All the geochemical characteris- tics of the silicalite formation manifest that the silicalite formation deposited in the deep and half- deep sea en- vironment.
1998, 16(4): 55-61.
Abstract:
T he C hang-Ping continental deposit red basin consists of five alluvial fans fo rming different three stages. T he different st ages fans were separated by special bounding surfaces respectively.The fan- roots w ere located at the north of the basin.T he palaeoflow direction w as fan shaped dist ributio n.T he average volume of the big g ravels and mixing coefficient w ere biggest in the fan root, and w ere decreased nonlinear progessively from fan root to fringe.T he material source area conty olled t he composition of g ravels. A ccording to quantification sedimentology features and fo rming set ting, it successively underw ent orlginal pregnancy, denude and st rong fill, three stages in the course of t he Basin evolution.T he proluvial events started in late C retaceous Period and finished in Eogene Period Eocene-O ligocene Epoch.
T he C hang-Ping continental deposit red basin consists of five alluvial fans fo rming different three stages. T he different st ages fans were separated by special bounding surfaces respectively.The fan- roots w ere located at the north of the basin.T he palaeoflow direction w as fan shaped dist ributio n.T he average volume of the big g ravels and mixing coefficient w ere biggest in the fan root, and w ere decreased nonlinear progessively from fan root to fringe.T he material source area conty olled t he composition of g ravels. A ccording to quantification sedimentology features and fo rming set ting, it successively underw ent orlginal pregnancy, denude and st rong fill, three stages in the course of t he Basin evolution.T he proluvial events started in late C retaceous Period and finished in Eogene Period Eocene-O ligocene Epoch.
1998, 16(4): 91-97.
Abstract:
The diagenesis and hydrocarbon accumulation w as studied by ways of petrology.mineralogy, X-ray diffraction analysis, organic inclusion and geochemistry in Zhu ⅢDepression, Pearl River Mouth Basin.It is suggested that the diagenetic stages are the early diagenesis and subphase A, B of late diagenesis.There aer different diagenetic history and genetic mechanism of secondary po re development zone in two major source sags of the depression.The hy drocarbon distribution is correlated w ith the illite/ smectite mixed layer clay min- eral conversion zone.The hydrocarbon accumulation of w enchang A Sag is in the fi rst and second clay mineral conversion zone, and over the first clay mineral conversion zone in Wenchang B Sag.The organic inclusions w ere formed in the diagenetic process.which contained rich information suchas the generation, evolution and mig ration of oil/ gas as well as reservoi r and so on.By studying the organic inclusions in Zhu Ⅲ Depression, it w as learned about the ty pe, distribution, homogenization temperature, the number of times oil/ gas mig ration and composition in the inclusions as well as the o rganic inclusion is correlated w ith the diagenesis. There are tw o migrations of oil and g as in Wenchand A Sag.The second time is the main period of oil and gas mig ration . There is only one peak of oil and gas mig ration in Wenchang B Sag.The secondary quartz in the sandstone from Zhuhai Fo rmation controls the hydrocarbon accumulatio n.
The diagenesis and hydrocarbon accumulation w as studied by ways of petrology.mineralogy, X-ray diffraction analysis, organic inclusion and geochemistry in Zhu ⅢDepression, Pearl River Mouth Basin.It is suggested that the diagenetic stages are the early diagenesis and subphase A, B of late diagenesis.There aer different diagenetic history and genetic mechanism of secondary po re development zone in two major source sags of the depression.The hy drocarbon distribution is correlated w ith the illite/ smectite mixed layer clay min- eral conversion zone.The hydrocarbon accumulation of w enchang A Sag is in the fi rst and second clay mineral conversion zone, and over the first clay mineral conversion zone in Wenchang B Sag.The organic inclusions w ere formed in the diagenetic process.which contained rich information suchas the generation, evolution and mig ration of oil/ gas as well as reservoi r and so on.By studying the organic inclusions in Zhu Ⅲ Depression, it w as learned about the ty pe, distribution, homogenization temperature, the number of times oil/ gas mig ration and composition in the inclusions as well as the o rganic inclusion is correlated w ith the diagenesis. There are tw o migrations of oil and g as in Wenchand A Sag.The second time is the main period of oil and gas mig ration . There is only one peak of oil and gas mig ration in Wenchang B Sag.The secondary quartz in the sandstone from Zhuhai Fo rmation controls the hydrocarbon accumulatio n.
1998, 16(4): 105-108.
Abstract:
The palaeo-hydrodyonamics during different geologic periods around middle giant gas field in O rdos Basin are restored use of Basin modeling and other technique.Acco rding to the distrbution of fluid (gas) potential, i t is discovered that the palaeo-hy rodynamic evolution history of U pper Palaeozoic Group since Triassic period (in which source rocks were matured)could be dividedinto three major stages, i.e.Triassic-Jurassic period, ear- ly C rtaceous epoch and late Creataceous epoch up to now.On the basis of sy nthetic analysis, the follow three characteristics have also been discovered: ( 1) the fo rmer three majo r stages of hydrodynamic evduition are closely to realated regional tectonic evoultion stage; (2) the distribution of fluid pressure is controlled by ralat- ed sedimentation (rate, thickness); (3) althoug h the objective layers is old (late Paleoaoic ear), the contribu- tion of compactional flow in hy drody namics is still evidently more than of g ravi tational flow, even in now a- days.
The palaeo-hydrodyonamics during different geologic periods around middle giant gas field in O rdos Basin are restored use of Basin modeling and other technique.Acco rding to the distrbution of fluid (gas) potential, i t is discovered that the palaeo-hy rodynamic evolution history of U pper Palaeozoic Group since Triassic period (in which source rocks were matured)could be dividedinto three major stages, i.e.Triassic-Jurassic period, ear- ly C rtaceous epoch and late Creataceous epoch up to now.On the basis of sy nthetic analysis, the follow three characteristics have also been discovered: ( 1) the fo rmer three majo r stages of hydrodynamic evduition are closely to realated regional tectonic evoultion stage; (2) the distribution of fluid pressure is controlled by ralat- ed sedimentation (rate, thickness); (3) althoug h the objective layers is old (late Paleoaoic ear), the contribu- tion of compactional flow in hy drody namics is still evidently more than of g ravi tational flow, even in now a- days.
1998, 16(4): 114-117.
Abstract:
The relative contents of coal macerals vary w ith geological time.Therefore, i t muse m ake errors to calcu- late the amounts of hydrocarbons generated during geohistory based on the present tes test maceral com posi- tions.The present paper gives out a method fo r recovering the relative content of coal m acerals in the geohisto- ry.The further research shows that the relative content variation of the liptini te is the largest during the geo- historical process, then are the virtrinite and fusini te.And the amounts of CH4, C 2-C 4 and liquid oil generated in coal during geohistory will be underestim ated if the calculation is based on the present maceral compositions Thei r maximum theoretical deviations can reach to as hig has 32.72 %, 3 2.25 % and 14.04 %, respectively.
The relative contents of coal macerals vary w ith geological time.Therefore, i t muse m ake errors to calcu- late the amounts of hydrocarbons generated during geohistory based on the present tes test maceral com posi- tions.The present paper gives out a method fo r recovering the relative content of coal m acerals in the geohisto- ry.The further research shows that the relative content variation of the liptini te is the largest during the geo- historical process, then are the virtrinite and fusini te.And the amounts of CH4, C 2-C 4 and liquid oil generated in coal during geohistory will be underestim ated if the calculation is based on the present maceral compositions Thei r maximum theoretical deviations can reach to as hig has 32.72 %, 3 2.25 % and 14.04 %, respectively.
1998, 16(4): 124-127.
Abstract:
In this paper 3 85 crude oil samples from 18 oil-bearing areas of China have been analysed fo r carbon and hydrogen isotopic compositions and part of their saturated and aromatic hydrocarbons have been analy sed fo r carbon isotopic compositions.Based on the analy tical data, the geochemical characteris tics of carbon and hydro- gen isotopes have been s tudied for tw o different types of oils, i.e., normal oil and light oil (condensate)and the hydrocarbon generating organic sources and depositional environments have been discussed combined wi th local geological background.The author propose that the δ13C values of light oil ( condensate)( δ13C-32.5 ‰～ - 24.3‰)are higher than that of normal oil ( δ13C-34.4 ‰～ -24.6‰).The variation of carbon isotopic composi tio ns of aromatic hydrocarbons of crude oils w as obviously affected by the inheritance effect of o rganic Continued on page 144 sources, consequently the δ13C values of aromat ic hy drocarbons could be used to identify crude oils generated from different organic sources. Lig ht oils (co ndensates) related t o marine facies have δD values higher t han - 15 0 ‰, w hereas that related to no nmarine facies have δD values(-21 0 ‰～-1 05 ‰) which basicly cover the δD dist ribution range of marine lig ht oils (condensates).Wit h t he depositional environments changes from fresh w ater to slig htly salt w ater to brackish w ater to marine salt water, δD values of light oils (condensates) become obviously heavier, indicating that δD values mainly related to the depositional environment.
In this paper 3 85 crude oil samples from 18 oil-bearing areas of China have been analysed fo r carbon and hydrogen isotopic compositions and part of their saturated and aromatic hydrocarbons have been analy sed fo r carbon isotopic compositions.Based on the analy tical data, the geochemical characteris tics of carbon and hydro- gen isotopes have been s tudied for tw o different types of oils, i.e., normal oil and light oil (condensate)and the hydrocarbon generating organic sources and depositional environments have been discussed combined wi th local geological background.The author propose that the δ13C values of light oil ( condensate)( δ13C-32.5 ‰～ - 24.3‰)are higher than that of normal oil ( δ13C-34.4 ‰～ -24.6‰).The variation of carbon isotopic composi tio ns of aromatic hydrocarbons of crude oils w as obviously affected by the inheritance effect of o rganic Continued on page 144 sources, consequently the δ13C values of aromat ic hy drocarbons could be used to identify crude oils generated from different organic sources. Lig ht oils (co ndensates) related t o marine facies have δD values higher t han - 15 0 ‰, w hereas that related to no nmarine facies have δD values(-21 0 ‰～-1 05 ‰) which basicly cover the δD dist ribution range of marine lig ht oils (condensates).Wit h t he depositional environments changes from fresh w ater to slig htly salt w ater to brackish w ater to marine salt water, δD values of light oils (condensates) become obviously heavier, indicating that δD values mainly related to the depositional environment.
1998, 16(4): 133-139.
Abstract:
discuss Relationships of organic sulfur in continental deposit low -mature source rocks and kinetics of py- rolysis hydrocarbon generation have been discussed.These rocks are gathered from Dongying depression in China and their organic matter maturities are not in excess of value Ro= 0.5 %( Ro as vitrinite reflectance). From studied results, we can observe such relationships as follows: ①There is a negative correlation between the organic sulfur contents and values of vitrinite reflectances.② The higher organic sulfur contents in these source rocks, the lower average activation energies of these rocks.③There is a positive correlation between or- ganic sulfur content and the least value( Emin)of activation energy distribution or the value (ESEmin)of activation energy distribution after soluable organic matter are extracted from these rocks. ④Soluable organic matter dis- tributing in the activation energy distributive intervals [ Emin,ESEmin] ( Emin < ESEmin) not only has hydrocarbons generation ability, but also there is a certain correlation trend between the yield of accumulating hydrocarbon and the sulfur content.⑤Putting all above aspects together, authors point out organic sulfur in low -mature Shasi(Es4)source rocks of Dongying depression maybe havea certain act on the course of hydrocarbon genera- tion in the study area.
discuss Relationships of organic sulfur in continental deposit low -mature source rocks and kinetics of py- rolysis hydrocarbon generation have been discussed.These rocks are gathered from Dongying depression in China and their organic matter maturities are not in excess of value Ro= 0.5 %( Ro as vitrinite reflectance). From studied results, we can observe such relationships as follows: ①There is a negative correlation between the organic sulfur contents and values of vitrinite reflectances.② The higher organic sulfur contents in these source rocks, the lower average activation energies of these rocks.③There is a positive correlation between or- ganic sulfur content and the least value( Emin)of activation energy distribution or the value (ESEmin)of activation energy distribution after soluable organic matter are extracted from these rocks. ④Soluable organic matter dis- tributing in the activation energy distributive intervals [ Emin,ESEmin] ( Emin < ESEmin) not only has hydrocarbons generation ability, but also there is a certain correlation trend between the yield of accumulating hydrocarbon and the sulfur content.⑤Putting all above aspects together, authors point out organic sulfur in low -mature Shasi(Es4)source rocks of Dongying depression maybe havea certain act on the course of hydrocarbon genera- tion in the study area.
1998, 16(4): 145-148.
Abstract:
Immature organic matter (peat) were pyrolysized at temperatures ranging from 200 ℃ to 400 ℃ under high pressure ranging from 0. 1 to 2GPa in a closed system, and alkane generated from organic matter was
Immature organic matter (peat) were pyrolysized at temperatures ranging from 200 ℃ to 400 ℃ under high pressure ranging from 0. 1 to 2GPa in a closed system, and alkane generated from organic matter was
1998, 16(4): 153-157.
Abstract:
The 57 Fe Mössbauer spectra of sulphate minerals from oxiydationzone of sulfide deposit in drought district have been determined at normal temperature in the paper.The results show that their Mössbauer spectra arecharacterized by the smaller isomer shifts, a w ider distribution range of quadrupole splittings, and no magnetic hyperfine splitting, etc.. Based on the research results obtained previously, the oxidation zone of sulfide deposit with clear zonality have been divided into Fe-M n gossan subzone, ferric vitriol subzone (subdivided into single-peak type, double- peak type, and triple-peak type etc.), ferriferous vitriol subzone and prim ary sulfide zone etc. vertical zones, according to their Mössbauer spectra at different vertical position, every subzone imply a certain physicochem ical condition and oxidation stage of sulfide deposit.
The 57 Fe Mössbauer spectra of sulphate minerals from oxiydationzone of sulfide deposit in drought district have been determined at normal temperature in the paper.The results show that their Mössbauer spectra arecharacterized by the smaller isomer shifts, a w ider distribution range of quadrupole splittings, and no magnetic hyperfine splitting, etc.. Based on the research results obtained previously, the oxidation zone of sulfide deposit with clear zonality have been divided into Fe-M n gossan subzone, ferric vitriol subzone (subdivided into single-peak type, double- peak type, and triple-peak type etc.), ferriferous vitriol subzone and prim ary sulfide zone etc. vertical zones, according to their Mössbauer spectra at different vertical position, every subzone imply a certain physicochem ical condition and oxidation stage of sulfide deposit.
