2003 Vol. 21, No. 3
column
Display Method:
2003, 21(3): 367-372.
Abstract:
According to core observation, the coarse clastic rock in the area is studied in detail with seismic data and well logging date. The result shows that the coars e clastic rock is formed in wet alluvial fan. The lithologic character, geolog ic climate feature and the types of micro-facies in the Guantao Formation are analyzed and the models of facies are also concluded in this paper. Through detailed study, the paper further illuminate that the base level cycle has effect on sedimentary facies.
According to core observation, the coarse clastic rock in the area is studied in detail with seismic data and well logging date. The result shows that the coars e clastic rock is formed in wet alluvial fan. The lithologic character, geolog ic climate feature and the types of micro-facies in the Guantao Formation are analyzed and the models of facies are also concluded in this paper. Through detailed study, the paper further illuminate that the base level cycle has effect on sedimentary facies.
2003, 21(3): 381-390.
Abstract:
Hongshuibao is located in the northwest of Jingtai county, about 45km to the c ounty town, Gansu province. The area is in the east part of Caledonian folded belt of the North Qilian Mountain, stratigraphic units developed well. Fossils are abund ant, engage relationship is clear. The Upper Carboniferous Series is consists of Hongshuibao formation, Yanghugou formation and Taiyuan formation. Sedimentary e nvironment and facies changed from lagoon-tide flat, tributary river barrier t o the deltaic plain, clearly a regression sequence.
Hongshuibao is located in the northwest of Jingtai county, about 45km to the c ounty town, Gansu province. The area is in the east part of Caledonian folded belt of the North Qilian Mountain, stratigraphic units developed well. Fossils are abund ant, engage relationship is clear. The Upper Carboniferous Series is consists of Hongshuibao formation, Yanghugou formation and Taiyuan formation. Sedimentary e nvironment and facies changed from lagoon-tide flat, tributary river barrier t o the deltaic plain, clearly a regression sequence.
2003, 21(3): 398-403.
Abstract:
We have found in Shexian and Xiuning Counties of South Anhui that ther e are some turbidite interlayers and a debris flow caused olistostrome near the to p of the Lantian Formation of the lower member of the Upper Sinian, and t here are some siliceous storm sediments in the Piyuangcun Formation of the top m ember of the Upper Sinian.These discoveries indicate that the area of South Anh u i belongs to a hemipelagic or shallow environment when sedimentation occurs duri ng the late Sinian,not a pelagic environment as being usually believed,at lea st the sedimentary surface was not lower than the wave base of the storm.
We have found in Shexian and Xiuning Counties of South Anhui that ther e are some turbidite interlayers and a debris flow caused olistostrome near the to p of the Lantian Formation of the lower member of the Upper Sinian, and t here are some siliceous storm sediments in the Piyuangcun Formation of the top m ember of the Upper Sinian.These discoveries indicate that the area of South Anh u i belongs to a hemipelagic or shallow environment when sedimentation occurs duri ng the late Sinian,not a pelagic environment as being usually believed,at lea st the sedimentary surface was not lower than the wave base of the storm.
2003, 21(3): 416-420.
Abstract:
The determination of depositional environments is an effective means for basin a nalysis, palaeogeography and palaeoclimate study and oil reservoir judgement. Qu artz has relative high hardness and chemical stability, therefore its sedimentar y grain surface features can well reflect the depositional environments. And usi ng electronic scan microscope to study quartz grain surface microscopic features is also an effective method to analyze depositional environments. Although it h as been widely accepted that there occurred desert sediments in the early Cretac eous Zhidan Group in the Ordos Basin, the systematic analysis of quartz sand grain surface microscopic features is lack. This paper shows the result of the quartz sand grain surface microscopic feature analysis from the Louhe Formation and Luohandong Formation of the early Cretaceous Zhidan Group in the Ordos Basin. It reaches that the microscopic features are of distinct eolian characteristic s and the analysis can easily distinguish eolian from hydrogenic sediments. Ther efore, our study confirms the existence of the Cretaceous desert in the Ordos Ba sin with the respect of quartz sand surface microscopic features.
The determination of depositional environments is an effective means for basin a nalysis, palaeogeography and palaeoclimate study and oil reservoir judgement. Qu artz has relative high hardness and chemical stability, therefore its sedimentar y grain surface features can well reflect the depositional environments. And usi ng electronic scan microscope to study quartz grain surface microscopic features is also an effective method to analyze depositional environments. Although it h as been widely accepted that there occurred desert sediments in the early Cretac eous Zhidan Group in the Ordos Basin, the systematic analysis of quartz sand grain surface microscopic features is lack. This paper shows the result of the quartz sand grain surface microscopic feature analysis from the Louhe Formation and Luohandong Formation of the early Cretaceous Zhidan Group in the Ordos Basin. It reaches that the microscopic features are of distinct eolian characteristic s and the analysis can easily distinguish eolian from hydrogenic sediments. Ther efore, our study confirms the existence of the Cretaceous desert in the Ordos Ba sin with the respect of quartz sand surface microscopic features.
2003, 21(3): 428-433.
Abstract:
A paper entitled discovery of authigenic monazite in Precambrian sedimentary roc k of Dalian area and its significance has been issued in the《Acta Sedimentologi ca Sinica》 (1999). After that we have got financial support for continuing stud y by the Chinese National Natural Scientific Foundation (No.40172044).This pape r introduces the new achievements of the mudstone study as follows: (1) characte ristic chemical composition: K2O 11.94%, Al2O3 16.47%, SiO 2 61.91%; REE 330.69,μg/g, LREE 266.15μg/g, Ce 130.80μg/g; La(N)/Yb(N) 12.44,δEu 0.75,δCe 1.17;(2)the main rock-frming mineral composition is phengite,which is determin ed by electron probe analysis of enery spectrum and wave spectrum methods and co mpared with X-ray diffraction curve. The phengite was altered from illite by in fluence of deep diagenesis and Mesozoic thrust tectonic movement; (3) the authig enic monazite was also suffered by the diagenetic and tectonic influences showin g in the crystal form types such as scattered mini-grains, single needle-like crystal, aggregate of crystals and connected crystals, etc. The size of authigen ic monazite crystals is from 1 to 60 μm, which are quiet different from the sh ort monoclinic prism taken from metamorphic, magmatic rocks or clastic placers. According to above, this paper concludes that the mudstone is a K and REE rich one, which created favorable inner-outside environment for authigenic monazite formation. Meanwhile this paper emphasized on that the wide spread Proterozoic strata in North China might contain many REE-rich beds with authigenic monazite to be used for U, Th-Pb isotopic timing study. It is proposed that the REE-ri ch beds might be the mineral source of the huge rare earth mineral deposits of t he Baiyun Obo along the margin of North China platform.
A paper entitled discovery of authigenic monazite in Precambrian sedimentary roc k of Dalian area and its significance has been issued in the《Acta Sedimentologi ca Sinica》 (1999). After that we have got financial support for continuing stud y by the Chinese National Natural Scientific Foundation (No.40172044).This pape r introduces the new achievements of the mudstone study as follows: (1) characte ristic chemical composition: K2O 11.94%, Al2O3 16.47%, SiO 2 61.91%; REE 330.69,μg/g, LREE 266.15μg/g, Ce 130.80μg/g; La(N)/Yb(N) 12.44,δEu 0.75,δCe 1.17;(2)the main rock-frming mineral composition is phengite,which is determin ed by electron probe analysis of enery spectrum and wave spectrum methods and co mpared with X-ray diffraction curve. The phengite was altered from illite by in fluence of deep diagenesis and Mesozoic thrust tectonic movement; (3) the authig enic monazite was also suffered by the diagenetic and tectonic influences showin g in the crystal form types such as scattered mini-grains, single needle-like crystal, aggregate of crystals and connected crystals, etc. The size of authigen ic monazite crystals is from 1 to 60 μm, which are quiet different from the sh ort monoclinic prism taken from metamorphic, magmatic rocks or clastic placers. According to above, this paper concludes that the mudstone is a K and REE rich one, which created favorable inner-outside environment for authigenic monazite formation. Meanwhile this paper emphasized on that the wide spread Proterozoic strata in North China might contain many REE-rich beds with authigenic monazite to be used for U, Th-Pb isotopic timing study. It is proposed that the REE-ri ch beds might be the mineral source of the huge rare earth mineral deposits of t he Baiyun Obo along the margin of North China platform.
2003, 21(3): 441-447.
Abstract:
According to the research on detrital composition of Mesozoic sandstone, it is p roposed that the detrital maturity of the sandstone in Beipiao (Jin-yang) basin is low, and these sandstones contain abundant volcanic lithics,quartz and felds par. Combining basin tectonic setting and sedimentary sequence feature, it can b e deduced that the upper-Triassic sedimentary detritus was eroded from the upli fted regions around the basin. During early Jurassic, Liaoxi area experience d intensely tectonic activation, accompanied by inhomogeneous uplifting, an d Beipiao (Jin-yang) basin subsided and expanded. The Archean basement rocks might have become an important source of the upper Jurassic as a reault of the southeast-trending thrust faulting. In early Cretaceous, the tectonic setting of Liaoxi area changed from squeezing to stretching, and Beipiao (Jinyang) basin ceased evolution. It can also be seen that Dickinson QFL triangle diagram is n ot completely suitable to the western Liaoning province.
According to the research on detrital composition of Mesozoic sandstone, it is p roposed that the detrital maturity of the sandstone in Beipiao (Jin-yang) basin is low, and these sandstones contain abundant volcanic lithics,quartz and felds par. Combining basin tectonic setting and sedimentary sequence feature, it can b e deduced that the upper-Triassic sedimentary detritus was eroded from the upli fted regions around the basin. During early Jurassic, Liaoxi area experience d intensely tectonic activation, accompanied by inhomogeneous uplifting, an d Beipiao (Jin-yang) basin subsided and expanded. The Archean basement rocks might have become an important source of the upper Jurassic as a reault of the southeast-trending thrust faulting. In early Cretaceous, the tectonic setting of Liaoxi area changed from squeezing to stretching, and Beipiao (Jinyang) basin ceased evolution. It can also be seen that Dickinson QFL triangle diagram is n ot completely suitable to the western Liaoning province.
2003, 21(3): 461-466.
Abstract:
Terrigenous detritus samples extracted from a piston core A23, located in the so uthern Okinawa Trough, were analyzed in terms of the grain-size characteristics. The results show that the terrigenous sequences in the core can be divided int o two parts on the basis of the variations in the grain-size parameters. The l ower sequence is characterized by constant grain-size parameters; whilst the up per part is controlled by turbidite layers with a thickness of about 2～20 cm, which caused very large variations of the parameters. The large variation of gra in-size composition and distribution of the turbidite sequences significantly disturbed the normal formation of the sediment sequences. The gain-size distri bution modes and parameters of a turbidite bed were analyzed in detail, which sh ow very regular variation in the bed. According to all grain-size character istics of the core, the depositional environment and sediment dynamics is very c omplex and the main mechanism of the transportation of the terrigenous material from East China Sea Shelf to the trough is in the form of bedload through canyo ns. Furthermore, pretreatment to the marine sediments is important, which enable s us to compare the grain-size characteristics between terrigenous detritus and the bulk grain-size.
Terrigenous detritus samples extracted from a piston core A23, located in the so uthern Okinawa Trough, were analyzed in terms of the grain-size characteristics. The results show that the terrigenous sequences in the core can be divided int o two parts on the basis of the variations in the grain-size parameters. The l ower sequence is characterized by constant grain-size parameters; whilst the up per part is controlled by turbidite layers with a thickness of about 2～20 cm, which caused very large variations of the parameters. The large variation of gra in-size composition and distribution of the turbidite sequences significantly disturbed the normal formation of the sediment sequences. The gain-size distri bution modes and parameters of a turbidite bed were analyzed in detail, which sh ow very regular variation in the bed. According to all grain-size character istics of the core, the depositional environment and sediment dynamics is very c omplex and the main mechanism of the transportation of the terrigenous material from East China Sea Shelf to the trough is in the form of bedload through canyo ns. Furthermore, pretreatment to the marine sediments is important, which enable s us to compare the grain-size characteristics between terrigenous detritus and the bulk grain-size.
2003, 21(3): 473-481.
Abstract:
Under the predictive study of the global climate change at present, the dating ages of the high-resolution and the change law revealed by the carbon and oxy ge n isotopic composition from cave stalagmites have made a great contribution for the breakthrough and filling gaps in this field. The high-resolution cl im ate records from 109.00 ka B.P. to 65.90 ka B.P. have been obtained through TIMS -U series dating of 11 samples and carbon and oxygen isotopic analysis of 79 sampl es from No.1 stalagmites in the south part of Guizhou. The No.1 stalagmite began to grow before 109.00 ka B.P. and stopped to grow after 65.90 ka B.P.,its ave rag e growth rate is 4.58mm/100a and is the sediment of the late Pleistocene. The st udy of No.1 stalagmite section in the Qingxin cave reveals that its age and isot ope records can be compared with the oxygen isotopic records of deep-sea cores or sediments at 5a, 5b and 5c phase of Ⅴstage and Ⅳ stage and Lishi Loess beds(L2) in the north of China. The carbon and oxygen isotopic records of stalagmite reveal that these tw o stages between 109.0～102.5 ka B.P. and 86.6～82.0 ka B.P. represented the war m-humid climatic environment and indicated the strong influence of the Asian (Southeast) summer monsoon, the rainfall increased more,the δ 18 O trende d to lowre or negative and the air temperature rose.The stage from 102.5 ka B.P. to 86.6 ka B.P. represented the cold-cool semi-arid and warm-cool humid cli matic envi ronment and indicated that the Asian (Southeast) summer monsoon was gradually weak, the meteoric water was decreased gradually, the δ 18 O was much h e avier, and the air temperature gradually decreased. And the stage from 78.92 ka B.P. t o 65.90 ka B.P. represented the dry-cold climatic environment and indicated tha t t he Asian (Southeast) winter monsoon and the Northwest cold air mass were streng thened, the meteoric water was decreased gradually, the δ 18 O was much hea vier, a nd the air temperature went down quickly,and is the cold beginning period of the last glacial period. In addition, we have determined that the termination point of the last intergla c ial period is 78.92±0.7 ka B.P.,and this age is the beginning point of the las t glacial period at the same time and can be taken as the boundary age of MIS4/5 according to the precise dating age of TIMS-U series and the records of carbo n and oxygen isotopes from No.1 stalagmite of Qixin cave in Guizhou. The determina tion of the record chronological is not only of stratigraphic significance, but also is chronological significance.
Under the predictive study of the global climate change at present, the dating ages of the high-resolution and the change law revealed by the carbon and oxy ge n isotopic composition from cave stalagmites have made a great contribution for the breakthrough and filling gaps in this field. The high-resolution cl im ate records from 109.00 ka B.P. to 65.90 ka B.P. have been obtained through TIMS -U series dating of 11 samples and carbon and oxygen isotopic analysis of 79 sampl es from No.1 stalagmites in the south part of Guizhou. The No.1 stalagmite began to grow before 109.00 ka B.P. and stopped to grow after 65.90 ka B.P.,its ave rag e growth rate is 4.58mm/100a and is the sediment of the late Pleistocene. The st udy of No.1 stalagmite section in the Qingxin cave reveals that its age and isot ope records can be compared with the oxygen isotopic records of deep-sea cores or sediments at 5a, 5b and 5c phase of Ⅴstage and Ⅳ stage and Lishi Loess beds(L2) in the north of China. The carbon and oxygen isotopic records of stalagmite reveal that these tw o stages between 109.0～102.5 ka B.P. and 86.6～82.0 ka B.P. represented the war m-humid climatic environment and indicated the strong influence of the Asian (Southeast) summer monsoon, the rainfall increased more,the δ 18 O trende d to lowre or negative and the air temperature rose.The stage from 102.5 ka B.P. to 86.6 ka B.P. represented the cold-cool semi-arid and warm-cool humid cli matic envi ronment and indicated that the Asian (Southeast) summer monsoon was gradually weak, the meteoric water was decreased gradually, the δ 18 O was much h e avier, and the air temperature gradually decreased. And the stage from 78.92 ka B.P. t o 65.90 ka B.P. represented the dry-cold climatic environment and indicated tha t t he Asian (Southeast) winter monsoon and the Northwest cold air mass were streng thened, the meteoric water was decreased gradually, the δ 18 O was much hea vier, a nd the air temperature went down quickly,and is the cold beginning period of the last glacial period. In addition, we have determined that the termination point of the last intergla c ial period is 78.92±0.7 ka B.P.,and this age is the beginning point of the las t glacial period at the same time and can be taken as the boundary age of MIS4/5 according to the precise dating age of TIMS-U series and the records of carbo n and oxygen isotopes from No.1 stalagmite of Qixin cave in Guizhou. The determina tion of the record chronological is not only of stratigraphic significance, but also is chronological significance.
2003, 21(3): 487-494.
Abstract:
By system cluster analysis on sorting coefficient, percentage of sand and clay i n modern sediments, The modern sedimentary environment in Qiqu Archipelago area can be well classified into three types of sub-environments, which are in line with the environmental features there. In addition to hydrodynamic function, sediment ary environment is strongly affected by material sources and topography. Among 3 factors by which sedimentary environment is well classified, the factor of perc entage of sand is the variable which is most significantly affected by material sources, and sorting coefficient is the parameter which is most sensible to the reciprocal functions between currents and topography. The sensibility of skewnes s to variation of sedimentary environment is finite. Kurtosis can hardly be used to classify sedimentary environment. Particular hydrodynamic condition should b e also taken into account.
By system cluster analysis on sorting coefficient, percentage of sand and clay i n modern sediments, The modern sedimentary environment in Qiqu Archipelago area can be well classified into three types of sub-environments, which are in line with the environmental features there. In addition to hydrodynamic function, sediment ary environment is strongly affected by material sources and topography. Among 3 factors by which sedimentary environment is well classified, the factor of perc entage of sand is the variable which is most significantly affected by material sources, and sorting coefficient is the parameter which is most sensible to the reciprocal functions between currents and topography. The sensibility of skewnes s to variation of sedimentary environment is finite. Kurtosis can hardly be used to classify sedimentary environment. Particular hydrodynamic condition should b e also taken into account.
2003, 21(3): 500-505.
Abstract:
Sediments are taken from the clean reach in the Baotou section of the Yellow Riv er as the adsorbent, the mixed solution system made up of Pb 2+, Cu 2+, Zn 2+ and Cd 2+ as the adsorbate, experimental research has been car ried out on the competition adsorption of the Yellow River sediments on heavy me tals. The experiment has clarified the competitive adsorption order of Pb 2+ ≥ Cu 2+ Zn 2+ ≥ Cd 2+, the cooperative adsorption relation of Cu—Pb, Zn—Cd and the resistant adsorption relation of Cu—Zn, Cu—Cd, Pb— Zn and Pb—Cd. The study is of great significance in evaluating the potential ri sk of heavy metals in the river sediments.
Sediments are taken from the clean reach in the Baotou section of the Yellow Riv er as the adsorbent, the mixed solution system made up of Pb 2+, Cu 2+, Zn 2+ and Cd 2+ as the adsorbate, experimental research has been car ried out on the competition adsorption of the Yellow River sediments on heavy me tals. The experiment has clarified the competitive adsorption order of Pb 2+ ≥ Cu 2+ Zn 2+ ≥ Cd 2+, the cooperative adsorption relation of Cu—Pb, Zn—Cd and the resistant adsorption relation of Cu—Zn, Cu—Cd, Pb— Zn and Pb—Cd. The study is of great significance in evaluating the potential ri sk of heavy metals in the river sediments.
2003, 21(3): 513-521.
Abstract:
Based on the geochemical analysis of dark argillite,carbonaceous mudstone and crude oil samples, the tectonic and sedimentary characteristics has als o been studied. The type of source rocks, organic maceral constituent of coal me asure source rocks, hydrocarbon generation mechanism and organic abundance, type and maturity characteristics have been analyzed. The result shows that the type of source rocks are typical humics and the coal measure argillite,carbonaceous mudstone and coal of Badaowan Formation, Sangonghe Formation and Xishanyao For mation could produce hydrocarbon, especially in Badaowan and it is the main sour ce rocks. There existed the processes of hydrocarbon formation in both south sag and north sag in Bohu depression. One stage of hydrocarbon generation existed i n south sag and two stages in north sag.
Based on the geochemical analysis of dark argillite,carbonaceous mudstone and crude oil samples, the tectonic and sedimentary characteristics has als o been studied. The type of source rocks, organic maceral constituent of coal me asure source rocks, hydrocarbon generation mechanism and organic abundance, type and maturity characteristics have been analyzed. The result shows that the type of source rocks are typical humics and the coal measure argillite,carbonaceous mudstone and coal of Badaowan Formation, Sangonghe Formation and Xishanyao For mation could produce hydrocarbon, especially in Badaowan and it is the main sour ce rocks. There existed the processes of hydrocarbon formation in both south sag and north sag in Bohu depression. One stage of hydrocarbon generation existed i n south sag and two stages in north sag.
2003, 21(3): 528-532,538.
Abstract:
Natural gas from the gas pool reservoired in Upper Paleozoic sandstone of Sulige miao area is wet gas that is characterized by high content of heavy hydrocarbon and low dry coefficient;otherwise,natural gas from Ordovician weathering crust g as pool in Jingbian area belongs to dry gas for its low content of heavy hydroar bon and high dry coefficient.The istotpic composition of Suligemiao gas has the tendency of δ13 C1<δ13 C4, but Ji ngbian gas tends to be δ13 C1<δ13 C3. The isotopi c difference of heavy carbon alkane is much larger between Suligemiao and Jinybi an natural gas.Particularly,the carbon isotope of ethane of Suligemiao gas is hi gher than that of Jingbian.The difference is equal to 3.6%.According to individu al carbon isotopes and compositions of natural gas,it can be seen that the Sulig emiao Permian gas is coalbed gas,and the Jingbian Ordovician gas is gaseous mixt ure.Average R o of Suligemiao gas and its source rock is equal to 1.29%～1.39% according to CH 4 isotope values, which is consistent with R o of the Permian rock.A little of CO 2 content is found in Suligemiao and Jing b ian natural gas.In terms of the carbon isotope values,it is believed that inorga nic CO 2 exists in well Su5 in Suligemiao and well Lin1, Lin5 in Jingbian.The rest are all organic CO 2.In combination with hydrocarbon gas and CO 2,the n atural gas in Suligemiao could be divided into coal-formed gas with organic CO 2 and inorganic CO 2.The maturity of coal-formed gas in Suligemiao reaches middle to high stage and the corresponding R o is 1.29%～ 1.39%,which i s in line with the maturity in Permian coal.
Natural gas from the gas pool reservoired in Upper Paleozoic sandstone of Sulige miao area is wet gas that is characterized by high content of heavy hydrocarbon and low dry coefficient;otherwise,natural gas from Ordovician weathering crust g as pool in Jingbian area belongs to dry gas for its low content of heavy hydroar bon and high dry coefficient.The istotpic composition of Suligemiao gas has the tendency of δ13 C1<δ13 C4, but Ji ngbian gas tends to be δ13 C1<δ13 C3. The isotopi c difference of heavy carbon alkane is much larger between Suligemiao and Jinybi an natural gas.Particularly,the carbon isotope of ethane of Suligemiao gas is hi gher than that of Jingbian.The difference is equal to 3.6%.According to individu al carbon isotopes and compositions of natural gas,it can be seen that the Sulig emiao Permian gas is coalbed gas,and the Jingbian Ordovician gas is gaseous mixt ure.Average R o of Suligemiao gas and its source rock is equal to 1.29%～1.39% according to CH 4 isotope values, which is consistent with R o of the Permian rock.A little of CO 2 content is found in Suligemiao and Jing b ian natural gas.In terms of the carbon isotope values,it is believed that inorga nic CO 2 exists in well Su5 in Suligemiao and well Lin1, Lin5 in Jingbian.The rest are all organic CO 2.In combination with hydrocarbon gas and CO 2,the n atural gas in Suligemiao could be divided into coal-formed gas with organic CO 2 and inorganic CO 2.The maturity of coal-formed gas in Suligemiao reaches middle to high stage and the corresponding R o is 1.29%～ 1.39%,which i s in line with the maturity in Permian coal.
2003, 21(3): 373-380.
Abstract:
Reservoir sandstone of Member 6 to 8 in Yanchang Formation (Triassic) in Xifeng oilfield of Ordos basin is typical of low porosity and low permeability, which has the characteristics of fine grain size, low compositional maturity, poor roundness and good sorting. Based on thin-section observation and analyses of c lay minerals, stable isotopes and physical property, this article takes researc h on diagenetic characteristics in Member 6 to 8 of Yanchang Formation, analyses their influence on reservoir physical property and determines diagenetic stage of reservoir sandstone. Meanwhile, this article indicates that the development o f high quality reservoir is dependent on the development of clay film, hydrocabo n emplacement grain dissolution in reservoir sandstone.
Reservoir sandstone of Member 6 to 8 in Yanchang Formation (Triassic) in Xifeng oilfield of Ordos basin is typical of low porosity and low permeability, which has the characteristics of fine grain size, low compositional maturity, poor roundness and good sorting. Based on thin-section observation and analyses of c lay minerals, stable isotopes and physical property, this article takes researc h on diagenetic characteristics in Member 6 to 8 of Yanchang Formation, analyses their influence on reservoir physical property and determines diagenetic stage of reservoir sandstone. Meanwhile, this article indicates that the development o f high quality reservoir is dependent on the development of clay film, hydrocabo n emplacement grain dissolution in reservoir sandstone.
2003, 21(3): 391-397.
Abstract:
Based on sequence stratigraphic research, depositional facies of the Lower Ganch aigou Formation have been studied carefully. It comprises alluvial-fan facies, braided stream facies, braided delta facies, fan-delta facies, lacustrine fac ies, and lacustrine floor fan facies, etc. In the 4 super-sequences identified, the distributions of depositional facies are discussed. According to the facies tracts, it can be concluded that the favorable reservoir facies are the lacustr ine floor fan in Shizigou area, the braided stream and braided delta in Araer ar ea, and the fan delta front in Ahati area.
Based on sequence stratigraphic research, depositional facies of the Lower Ganch aigou Formation have been studied carefully. It comprises alluvial-fan facies, braided stream facies, braided delta facies, fan-delta facies, lacustrine fac ies, and lacustrine floor fan facies, etc. In the 4 super-sequences identified, the distributions of depositional facies are discussed. According to the facies tracts, it can be concluded that the favorable reservoir facies are the lacustr ine floor fan in Shizigou area, the braided stream and braided delta in Araer ar ea, and the fan delta front in Ahati area.
2003, 21(3): 404-408.
Abstract:
Lithologic oil pool is one of the most important oil pool types in Songliao Basi n, and the front facies belt of delta is a favourable phase to form lithologic o il pool. Through the deepgoing study of sedimentary microfacies and sedimentary model of Baoqian delta during the different geological era, it can be dynamicall y shown that the sedimentary evolution process of the front facies belt of Baoqi an delta. The front facies belt sandbody underwent three processes of r egression and transgression and large-scale migration. The major direction of the mass-source gradually moved from southwest to northwest, and the shape of the flower-like delta changed from deep-lake lobe like shape to shallow- lake branch-like shape. This cognition plays an import ant role in the exploration of the lithologic oil pool that is controlled the mi gration law of the front facies belt of Baoqian delta at different sedimentary period in Songliao Basin.
Lithologic oil pool is one of the most important oil pool types in Songliao Basi n, and the front facies belt of delta is a favourable phase to form lithologic o il pool. Through the deepgoing study of sedimentary microfacies and sedimentary model of Baoqian delta during the different geological era, it can be dynamicall y shown that the sedimentary evolution process of the front facies belt of Baoqi an delta. The front facies belt sandbody underwent three processes of r egression and transgression and large-scale migration. The major direction of the mass-source gradually moved from southwest to northwest, and the shape of the flower-like delta changed from deep-lake lobe like shape to shallow- lake branch-like shape. This cognition plays an import ant role in the exploration of the lithologic oil pool that is controlled the mi gration law of the front facies belt of Baoqian delta at different sedimentary period in Songliao Basin.
2003, 21(3): 423-427.
Abstract:
The Ordovician reefs are important hydrocarbon reservoirs in Tarim Basin. It is significant to explore new methods for the comparative study between outcrop r eefs and those found in wells to understand their size and internal architectu re. Ground penetrating radar (GPR) and gamma-ray spectrometer h av e been used to detect Dawuzitage Hills Ordovician outcrops in Bachu area, Tarim Basin. GPR data indicate that most reefs are flat and lenticular or layered, whi c h is different from what have been found in outcrop surfaces by naked eyes. Smal l patches of reefs or reef bioherms have been widely revealed by high-resolu ti on GPR profiles. The layering character and slant bedding of channel-filled in tr aclasts of reefs are obvious in GPR profiles with the decimeter resolution. The gamma ray value of reef bafflestone is higher than those of sparrenite and sparr udit e, and lower than those of micritic limestone, wackstone, echinoderm grainstone and marlstone. In outcrop gamma-ray curves, reefs are of funneled, bell-shaped or box-shaped and layering feature of reef can also be reflected. The gamma radi oa ctivity of reefs in outcrop and in wells of Lunnan area has similar characterist ics.It provide good method for the comparative study between outcrop r eefs and those found in wells.
The Ordovician reefs are important hydrocarbon reservoirs in Tarim Basin. It is significant to explore new methods for the comparative study between outcrop r eefs and those found in wells to understand their size and internal architectu re. Ground penetrating radar (GPR) and gamma-ray spectrometer h av e been used to detect Dawuzitage Hills Ordovician outcrops in Bachu area, Tarim Basin. GPR data indicate that most reefs are flat and lenticular or layered, whi c h is different from what have been found in outcrop surfaces by naked eyes. Smal l patches of reefs or reef bioherms have been widely revealed by high-resolu ti on GPR profiles. The layering character and slant bedding of channel-filled in tr aclasts of reefs are obvious in GPR profiles with the decimeter resolution. The gamma ray value of reef bafflestone is higher than those of sparrenite and sparr udit e, and lower than those of micritic limestone, wackstone, echinoderm grainstone and marlstone. In outcrop gamma-ray curves, reefs are of funneled, bell-shaped or box-shaped and layering feature of reef can also be reflected. The gamma radi oa ctivity of reefs in outcrop and in wells of Lunnan area has similar characterist ics.It provide good method for the comparative study between outcrop r eefs and those found in wells.
2003, 21(3): 434-440.
Abstract:
Based on the investigations of 48 species of fossil spores and pollen referred to 31 genera found from the Upper Triassic Yongping and Wayaopu Formations in T uweihe region of northern Shaanxi, the Late Triassic palynoflora in the region was established in this paper. In accordance with the character of the palynoflora, the Late Triassic paleoecological environment in the region was discussed. The relation b etween the origin of petroleum and coal and the environment was involved. The re sults of this study confirm that the lacustrine depositional environments under warm/h ot and humid/wet climatic conditions might be favorable for the origin of petroleum, and the swamp/marsh depositional environments under warm/hot and humid/wet clima tic conditions might be favorable for the origin of coal.
Based on the investigations of 48 species of fossil spores and pollen referred to 31 genera found from the Upper Triassic Yongping and Wayaopu Formations in T uweihe region of northern Shaanxi, the Late Triassic palynoflora in the region was established in this paper. In accordance with the character of the palynoflora, the Late Triassic paleoecological environment in the region was discussed. The relation b etween the origin of petroleum and coal and the environment was involved. The re sults of this study confirm that the lacustrine depositional environments under warm/h ot and humid/wet climatic conditions might be favorable for the origin of petroleum, and the swamp/marsh depositional environments under warm/hot and humid/wet clima tic conditions might be favorable for the origin of coal.
2003, 21(3): 448-451,481.
Abstract:
This study has certified that investigating the characteristics of mic romorphology of Neogene red clay is also one of the effective methods to analyze the paleoclimate, and correlate and subdivide the strata. According to the ch aracteristics of micromorphology of Neogene red clay developed at Xiaqiang Villa ge, Xunyi County, Shaanxi Province, the Neogene paleoclimate of that area could be subdivided into four stages ranging from the bottom to the top, The first sta ge is around 6.8～5.3 Ma B. P. In this stage, the pedogenesis is generally weak; most of the grains are without directional arrangement; and the clay film is not cle ar. From these facts, we imagine the climate of that time was in a situation of cool-dry under the background of Neogene general climate of warm-humid. The s eco nd one is around 5.3～4.2 Ma B. P., with strong pedogenesis, directional arrange me nt of grains and well-developed drape-type clay film. The climate of t his stage might be the warmest and the most humid in all four stages. The third on e is almost in 4.2～2.6 Ma B.P.,and the pedogenesis in this stage is generally w eak, wi th only a little strong one appeared in this late period.We consider that the m ain climate condition of this stage was firsthg semiarid, then changed to semi- hum id. The fourth one is after 2.6 Ma B.P.,which had entered the Quaternary. In t his stage, the pedogenesis is extremely weak,with very few remained optical cla y film. These characteristics reflect the climate of this stage was very cold an d dry quite different from its previous Neogene general Climate. Within each of these four Paleoclimatic stages, the micromorphology also clearly shows the clim atic sub-changes and sub-fluctuations. Moreover, the boundary between the Mio cen e and the Pliocene, and also that between the Pliocene and the Quaternary could be determined at the beginning (or bottom)of the second stage (or part),and begi nning (or bottom)of the fourth stage (or part),respectively.
This study has certified that investigating the characteristics of mic romorphology of Neogene red clay is also one of the effective methods to analyze the paleoclimate, and correlate and subdivide the strata. According to the ch aracteristics of micromorphology of Neogene red clay developed at Xiaqiang Villa ge, Xunyi County, Shaanxi Province, the Neogene paleoclimate of that area could be subdivided into four stages ranging from the bottom to the top, The first sta ge is around 6.8～5.3 Ma B. P. In this stage, the pedogenesis is generally weak; most of the grains are without directional arrangement; and the clay film is not cle ar. From these facts, we imagine the climate of that time was in a situation of cool-dry under the background of Neogene general climate of warm-humid. The s eco nd one is around 5.3～4.2 Ma B. P., with strong pedogenesis, directional arrange me nt of grains and well-developed drape-type clay film. The climate of t his stage might be the warmest and the most humid in all four stages. The third on e is almost in 4.2～2.6 Ma B.P.,and the pedogenesis in this stage is generally w eak, wi th only a little strong one appeared in this late period.We consider that the m ain climate condition of this stage was firsthg semiarid, then changed to semi- hum id. The fourth one is after 2.6 Ma B.P.,which had entered the Quaternary. In t his stage, the pedogenesis is extremely weak,with very few remained optical cla y film. These characteristics reflect the climate of this stage was very cold an d dry quite different from its previous Neogene general Climate. Within each of these four Paleoclimatic stages, the micromorphology also clearly shows the clim atic sub-changes and sub-fluctuations. Moreover, the boundary between the Mio cen e and the Pliocene, and also that between the Pliocene and the Quaternary could be determined at the beginning (or bottom)of the second stage (or part),and begi nning (or bottom)of the fourth stage (or part),respectively.
2003, 21(3): 467-472.
Abstract:
It is indicated that ferrimagnetic minerals dominate the magnetic properties of surface siliceous sediments in the Clarion-Clipperton (C—C) zone, northeastern equatorial Pacific. The ferrimagnetic minerals are mainly single domain (SD) an d superparamagentic(SP) in size. Magnetic parameters, together with TEM analysis, reveal the presence of bacterial magnetite, which undergoes dissolution to var ying extent. Such a phenomena is indicative of an active iron cycle involving mi crobes. Imperfect anti-ferromagnetic minerals show a higher content in the sed iments of the western region of C—C zone, and increase toward high latitude. It is suggested that, with increased distance from the equator, sediments become m ore oxidized.
It is indicated that ferrimagnetic minerals dominate the magnetic properties of surface siliceous sediments in the Clarion-Clipperton (C—C) zone, northeastern equatorial Pacific. The ferrimagnetic minerals are mainly single domain (SD) an d superparamagentic(SP) in size. Magnetic parameters, together with TEM analysis, reveal the presence of bacterial magnetite, which undergoes dissolution to var ying extent. Such a phenomena is indicative of an active iron cycle involving mi crobes. Imperfect anti-ferromagnetic minerals show a higher content in the sed iments of the western region of C—C zone, and increase toward high latitude. It is suggested that, with increased distance from the equator, sediments become m ore oxidized.
2003, 21(3): 482-486.
Abstract:
The analytic consequences show the changing laws of grain size and regional magn etic susceptibility in Mu Us sandy land, the grain size gradually becomes smalle r, while the magnetic susceptibility becomes larger from north to sout h. This phenomenon appears not only on the surface of Mu Us, but also obviously occurs on the same layer of different places, so it shows that Mu Us sandy la nd's forming process is closely related to the East Asian monsoon. According to the analyses from selected profiles, we know that, it is cold and dry in this re gion during the later Pleistocene, and early Holocene East Asian winter monsoon' s influence is obvious, so, it is a period of sand accumulation, when the layer s become thinner gradually from north to south. During Middle Holocene, it is wa rm and humid, influenced evidently by East Asian summer monsoon, so, it is an ob vious pedogenesis, when there are generally well-developed Holecene palaeosol( S0) from north to south, and the pedogenesis in the south is better than that in the north, the soil is also thicker than that in the north. From late Holocene to present, the climate changes tend to be dry and cold, but its changing exten t is smaller than that of last glacial period.
The analytic consequences show the changing laws of grain size and regional magn etic susceptibility in Mu Us sandy land, the grain size gradually becomes smalle r, while the magnetic susceptibility becomes larger from north to sout h. This phenomenon appears not only on the surface of Mu Us, but also obviously occurs on the same layer of different places, so it shows that Mu Us sandy la nd's forming process is closely related to the East Asian monsoon. According to the analyses from selected profiles, we know that, it is cold and dry in this re gion during the later Pleistocene, and early Holocene East Asian winter monsoon' s influence is obvious, so, it is a period of sand accumulation, when the layer s become thinner gradually from north to south. During Middle Holocene, it is wa rm and humid, influenced evidently by East Asian summer monsoon, so, it is an ob vious pedogenesis, when there are generally well-developed Holecene palaeosol( S0) from north to south, and the pedogenesis in the south is better than that in the north, the soil is also thicker than that in the north. From late Holocene to present, the climate changes tend to be dry and cold, but its changing exten t is smaller than that of last glacial period.
2003, 21(3): 495-499.
Abstract:
One core (CYLWA-1) from Phragrmites australis vegetated tidal flat, the Yangtz e Estuary, is selected to investigate the effect of plant on geochemical cycling o f iron and the magnetic properties of the sediments. The results show that Fe 2+ dominates in most layers of the sediments and increases with depth, except at a depth of 14～20 cm, where Fe3+ dominates due to the abundant distribution of live roots. In the oxidized layer of 14～20 cm, χ fd, χ ARM and χ ARM /SIRM decline, sug gesting coarsening of ferrimagnetic minerals. On the contrary, the obvious incre ase in B CR and SIRM/ χ indicates relative increase of imperfect an ti-ferromagneti c minerals. It is suggested that ferrimagnetic minerals be transformed into impe rfect anti-ferromagnetic iron oxides under oxidizing environment.
One core (CYLWA-1) from Phragrmites australis vegetated tidal flat, the Yangtz e Estuary, is selected to investigate the effect of plant on geochemical cycling o f iron and the magnetic properties of the sediments. The results show that Fe 2+ dominates in most layers of the sediments and increases with depth, except at a depth of 14～20 cm, where Fe3+ dominates due to the abundant distribution of live roots. In the oxidized layer of 14～20 cm, χ fd, χ ARM and χ ARM /SIRM decline, sug gesting coarsening of ferrimagnetic minerals. On the contrary, the obvious incre ase in B CR and SIRM/ χ indicates relative increase of imperfect an ti-ferromagneti c minerals. It is suggested that ferrimagnetic minerals be transformed into impe rfect anti-ferromagnetic iron oxides under oxidizing environment.
2003, 21(3): 506-512.
Abstract:
The crude oil in Dongying depression mainly came from underlayer of Member 3 and upperlayer of Member 4 source rocks in the Shahejie Formation. On the basis of abundant geochemical data, the authors analyzed the discrepancies in sedimen ta ry and geochemical characteristics of the two sets of source rocks. The underlay er of Member 3 developed in deep lake-semideep lake with saline water-semisal ine water, but the upperlayer of Member 4 formed in shallow lake-semideep lake wi th brine water-saline water. Moreover, the authors discussed the accumulatio n and preservation features of organic matter and pointed out that high paleo-pro duct ivity and anoxic environment controlled the formation of the two sets of excelle nt source rocks. Brine condition has an important effect on upperlayer of Membe r 4 and algal blooms controlled the formation of source rocks with rich organic m atter in upperlayer of Member 4 and underlayer of member 3.
The crude oil in Dongying depression mainly came from underlayer of Member 3 and upperlayer of Member 4 source rocks in the Shahejie Formation. On the basis of abundant geochemical data, the authors analyzed the discrepancies in sedimen ta ry and geochemical characteristics of the two sets of source rocks. The underlay er of Member 3 developed in deep lake-semideep lake with saline water-semisal ine water, but the upperlayer of Member 4 formed in shallow lake-semideep lake wi th brine water-saline water. Moreover, the authors discussed the accumulatio n and preservation features of organic matter and pointed out that high paleo-pro duct ivity and anoxic environment controlled the formation of the two sets of excelle nt source rocks. Brine condition has an important effect on upperlayer of Membe r 4 and algal blooms controlled the formation of source rocks with rich organic m atter in upperlayer of Member 4 and underlayer of member 3.
2003, 21(3): 522-527.
Abstract:
The chemical components and isotopic compositions of fluid inclusions in differe nt carbonate reservoirs in Weiyuan,Ziyang and Longchang gas fields in the southwest of Sichuan Basin are measured by means of on-line mass spectrometry connected with magnetic force crushing equipment to break fluid inclusions unde r vacuum. Combining the geological characteristics of reservoirs, the sources of fluids of in the reservoirs are considered. Results are attained concerning tha t CH4 and CO 2 are mainly gas compositions in the fluid inclusions; the compo nents of fluid inclusions from reservoir protoliths in different ages are differ ent and the gas contents vary differently in the reservoir protoliths and the secondary veins in the same geological strata. CH 4 is the predominant gas composition in fluid inclusions trapped in reservoi r protoliths of Permian System, which is generally higher than 80%; While in Si nian system, CO 2 is the mainly gas composition, with the contents of above 60%. In the inclusions lying in asphalt veins in Sinian system, the contents of CH 4 are the lowest ones and those in reservoir protoliths are the second lowest. The contents of CH 4 in inclusions of the secondary dolomite veins are higher than both of the asphalt veins and reservoir protoliths, while the contents of CO 2 in this series are just on the contrary. According to the diversity of carb on isotopic components of CH 4 and CO 2 in reservoir protoliths, secondary min eral veins and asphalt veins respectively, this paper sheds light onto the intru sion pattern and process of petroleum and natural gas in different strata of res ervoirs in Permian system (P3 12A 、P3 12B ) and Sinia n system (Z 4、Z 3、Z 2).
The chemical components and isotopic compositions of fluid inclusions in differe nt carbonate reservoirs in Weiyuan,Ziyang and Longchang gas fields in the southwest of Sichuan Basin are measured by means of on-line mass spectrometry connected with magnetic force crushing equipment to break fluid inclusions unde r vacuum. Combining the geological characteristics of reservoirs, the sources of fluids of in the reservoirs are considered. Results are attained concerning tha t CH4 and CO 2 are mainly gas compositions in the fluid inclusions; the compo nents of fluid inclusions from reservoir protoliths in different ages are differ ent and the gas contents vary differently in the reservoir protoliths and the secondary veins in the same geological strata. CH 4 is the predominant gas composition in fluid inclusions trapped in reservoi r protoliths of Permian System, which is generally higher than 80%; While in Si nian system, CO 2 is the mainly gas composition, with the contents of above 60%. In the inclusions lying in asphalt veins in Sinian system, the contents of CH 4 are the lowest ones and those in reservoir protoliths are the second lowest. The contents of CH 4 in inclusions of the secondary dolomite veins are higher than both of the asphalt veins and reservoir protoliths, while the contents of CO 2 in this series are just on the contrary. According to the diversity of carb on isotopic components of CH 4 and CO 2 in reservoir protoliths, secondary min eral veins and asphalt veins respectively, this paper sheds light onto the intru sion pattern and process of petroleum and natural gas in different strata of res ervoirs in Permian system (P3 12A 、P3 12B ) and Sinia n system (Z 4、Z 3、Z 2).
2003, 21(3): 533-538.
Abstract:
Palaeozoic source rocks developed in Bohai Bay basin have the characteristics of multiple-burial, abnormally heated, secondary hydrocarbon generation, and multip le-reservoir formation. Based on the artificial simulation on secondary hydroca rbon generation and pyrolysis simulation on samples of different maturity, it is indicated that the evolution passway of secondary hydrocarbon gen eration do not follow the Tissot's model of continuous hydrocarbon generation. T h e obvious characteristics of secondary hydrocarbon generation is the lag effect and the degree of lag is related to the original maturity. The degree of lag is the least while R o is about 0.9%. This is determined by chemical kinetic m echanism. The activation energy distribution of secondary hydrocarbon generation indicate s that the intermediate products formed in the first hydrocarbon generation are not totally decomposed, and rapidly decomposed at the beginning of secondary hy drocar bon generation, but the chemical structure of kerogen quite solidify when cooled and become activated again during the secondary hydrocarbon generation. So the evolvement of secondary hydrocarbon generation present discontinuous pulse progr e ssion. According to the lag plate of secondary hydrocarbon generation and the ge ological condition of Bohai Bay basin, through the study of the history and stag e of hydrocarbon generation, and analyzing the obvious depth and ratio of secon dary h ydrocarbon generation, prospective areas of secondary hydrocarbon generation can be pointed out.
Palaeozoic source rocks developed in Bohai Bay basin have the characteristics of multiple-burial, abnormally heated, secondary hydrocarbon generation, and multip le-reservoir formation. Based on the artificial simulation on secondary hydroca rbon generation and pyrolysis simulation on samples of different maturity, it is indicated that the evolution passway of secondary hydrocarbon gen eration do not follow the Tissot's model of continuous hydrocarbon generation. T h e obvious characteristics of secondary hydrocarbon generation is the lag effect and the degree of lag is related to the original maturity. The degree of lag is the least while R o is about 0.9%. This is determined by chemical kinetic m echanism. The activation energy distribution of secondary hydrocarbon generation indicate s that the intermediate products formed in the first hydrocarbon generation are not totally decomposed, and rapidly decomposed at the beginning of secondary hy drocar bon generation, but the chemical structure of kerogen quite solidify when cooled and become activated again during the secondary hydrocarbon generation. So the evolvement of secondary hydrocarbon generation present discontinuous pulse progr e ssion. According to the lag plate of secondary hydrocarbon generation and the ge ological condition of Bohai Bay basin, through the study of the history and stag e of hydrocarbon generation, and analyzing the obvious depth and ratio of secon dary h ydrocarbon generation, prospective areas of secondary hydrocarbon generation can be pointed out.
