Uncertainties about natural gas source and hydrocarbon accumulation seriously restrict oil and gas exploration in the Lianggaoshan Formation(J_(2) l)in the Eastern Sichuan Basin,which has demonstrated great exploratio...Uncertainties about natural gas source and hydrocarbon accumulation seriously restrict oil and gas exploration in the Lianggaoshan Formation(J_(2) l)in the Eastern Sichuan Basin,which has demonstrated great exploration potential in recent years.This study determines the origin of natural gas and the hydrocarbon accumulation model of J_(2) l in the Eastern Sichuan Basin.A new sample pretreatment method named gas purge-microsyringe extraction was employed and confi rmed to be a practical and eff ective method for preparing condensate oil and collecting source rock extract samples.The source rocks of J_(2) l exhibited moderate to good qualities,characterized by high TOC values,dominance of type Ⅱ_(1) and Ⅱ_(2) kerogens,and high thermal maturities.Biomarker and aromatic characteristics revealed that the source rocks of J_(2) l were deposited in brackish water with weak anoxic conditions.The natural gas in J_(2) l was an organic thermogenic gas generated from the secondary cracking of crude oil,indicating that this natural gas was mainly derived from the source rocks of J_(2) l.The condensate oil-source rock correlation further confi rmed the accuracy of the gas-source correlation results.Based on burial,thermal and hydrocarbon-generating histories,two hydrocarbon charging periods(141–133 Ma and 119–112 Ma)and four hydrocarbon accumulation periods of J_(2) l were determined.Combined with structural evolution,depositional histories and reservoir conditions,a simple gas reservoir accumulation model of J_(2) l was developed,which was identifi ed as a“self-generating and self-storing”gas reservoir.展开更多
There is great controversy regarding the origin and source of natural gas in the Lower Triassic Feix-ianguan Formation in the Eastern Sichuan Basin.This seriously restricts the study of natural gas dy-namics in the Fe...There is great controversy regarding the origin and source of natural gas in the Lower Triassic Feix-ianguan Formation in the Eastern Sichuan Basin.This seriously restricts the study of natural gas dy-namics in the Feixianguan Formation and thus hampers natural gas exploration in the region,so further study is urgently required.Using experimental tests of natural gas composition,stable isotopes,and noble gas isotopes with gas chromatography(GC)and mass spectrometry(MS)studies of source rock and reservoir asphalt saturated hydrocarbons,the natural gas geochemical characteristics,the genetic identification and a gas-source comparison of the Feixianguan Formation were studied.Then,con-strained by the thermal history,the histories of gas generation and expulsion were restored by basin simulation technology.Finally,a gas accumulation model was established for the Feixianguan Formation.The results showed that(1)the H_(2)S-rich and H2S-poor gas reservoirs of the Feixianguan Formation are distributed on the east and west sides of the Kaijiang-Liangping trough in the Eastern Sichuan Basin,respectively.The carbon and hydrogen isotope compositions of the natural gas in the gas reservoirs are generally heavy and have typical characteristics of high-maturity dry gas reservoirs.(2)The natural gas of the Feixianguan Formation is organic thermogenic gas,which is mainly oil-type gas generated by the secondary cracking of crude oil.The gas-generating parent material is mainly type II kerogen.(3)The natural gas of the Feixianguan Formation in the Eastern Sichuan Basin was mainly generated by argil-laceous source rocks of the Upper Permian Longtan Formation.(4)Natural gas accumulation occurred as follows:the paleo-structure heights were filled with crude oil in the Early Jurassic,and paleo-oil res-ervoirs were formed in the Feixianguan Formation;during the Middle-Late Jurassic,the paleo-oil res-ervoirs were cracked when the reservoir temperatures rose above 160 C,and paleo-gas reservoirs were formed.Since the end of the Late Jurassic,the paleo-gas reservoirs have been adjusted and reformed to form the present-day natural gas reservoirs.These results provide a basis for studying natural gas accumulation dynamics of the Feixianguan Formation in the Eastern Sichuan Basin.展开更多
Isotopic compositions of noble gases, i.e. He Ar Kr and Xe, are measured in natural gases from the Zhongbu gasfield in the Ordos Basin. And heavy noble-gas isotopes (Kr, Xe) are here first used in geochemically studyi...Isotopic compositions of noble gases, i.e. He Ar Kr and Xe, are measured in natural gases from the Zhongbu gasfield in the Ordos Basin. And heavy noble-gas isotopes (Kr, Xe) are here first used in geochemically studying natural gases and gas-source correlation. Isotopic compositions of heavy noble gases in natural gases, especially Xe, show two-source mixing in the Zhongbu gasfield. Gas sources are somewhat different in the northeast and the southwest of the gasfield. Generally, the gas source of the Lower Paleozoic makes a greater contribution in the southwest than in the northeast in the field. Two kinds of gases can be differentiated from isotopic compositions of heavy noble gases and from their relation with the Ar isotopic composition. Therefore, the comprehensive study on isotopic compositions of light and heavy noble gases can supply more useful information on gas-source correlation and tracing.展开更多
Hydrocarbons can be preserved in sedimentary deposits by absorption and includingsof diagenetic minerals during their formation from organic matter by catagenesis.Acidolysis hydrocarbon is mainly composed of C<sub&...Hydrocarbons can be preserved in sedimentary deposits by absorption and includingsof diagenetic minerals during their formation from organic matter by catagenesis.Acidolysis hydrocarbon is mainly composed of C<sub>1</sub>--C<sub>5</sub> gaseous hydrocarbons included indiagenetic minerals, such as carbonate and aluminosilicate. Its chemical展开更多
Based on the organic geochemical data and the molecular and stable carbon isotopic compositions of natural gas of the Lower Permian Fengcheng Formation in the western Central Depression of Junggar Basin,combined with ...Based on the organic geochemical data and the molecular and stable carbon isotopic compositions of natural gas of the Lower Permian Fengcheng Formation in the western Central Depression of Junggar Basin,combined with sedimentary environment analysis and hydrocarbon-generating simulation,the gas-generating potential of the Fengcheng source rock is evaluated,the distribution of large-scale effective source kitchen is described,the genetic types of natural gas are clarified,and four types of favorable exploration targets are selected.The results show that:(1)The Fengcheng Formation is a set of oil-prone source rocks,and the retained liquid hydrocarbon is conducive to late cracking into gas,with characteristics of high gas-generating potential and late accumulation;(2)The maximum thickness of Fengcheng source rock reaches 900 m.The source rock has entered the main gas-generating stage in Penyijingxi and Shawan sags,and the area with gas-generating intensity greater than 20×10^(8) m^(3)/km^(2) is approximately 6500 km^(2).(3)Around the western Central Depression,highly mature oil-type gas with light carbon isotope composition was identified to be derived from the Fengcheng source rocks mainly,while the rest was coal-derived gas from the Carboniferous source rock;(4)Four types of favorable exploration targets with exploration potential were developed in the western Central Depression which are structural traps neighboring to the source,stratigraphic traps neighboring to the source,shale-gas type within the source,and structural traps within the source.Great attention should be paid to these targets.展开更多
The discovery of the Bozhong 19-6 gas field has opened a new frontier for deep gas exploration in the Bohai Bay Basin,with a great potential for further gas exploration.However,poor understanding of oil and gas origin...The discovery of the Bozhong 19-6 gas field has opened a new frontier for deep gas exploration in the Bohai Bay Basin,with a great potential for further gas exploration.However,poor understanding of oil and gas origin has been limiting the exploration progress in this area.To clarify the origin of condensate oil and gas in Bozhong 19-6 gas field,this study adequately utilized the organic geochemical analysis data to investigate the composition and geochemical characteristics of condensate oil and natural gas,and analyzed the relationship between condensate oil and the three sets of source rocks in the nearby subsags.Results show that the lighter components dominate the condensate oil,with a forward type predominance.The parent material of crude oil was primarily deposited in a shallow,clay-rich,low-salinity,weakly reducing aquatic environment.The condensate and natural gas have similar parent source characteristics and maturity,with Ro ranging from 1.4%to 1.6%.Both are products of high maturity stage,indicating that they are hydrocarbon compounds produced by the same group of source rocks in the same stage.Oil-sources correlation shows that condensate oil and gas mainly originate from the source rocks of the third member of Shahejie Formation in the nearby subsags of the Bozhong 19-6 structural belt.展开更多
Based on the chemical and stable carbon isotopic composition of natural gas and light hydrocarbons, along with regional geological data, the genetic type, origin and migration of natural gases in the L lithologic gas ...Based on the chemical and stable carbon isotopic composition of natural gas and light hydrocarbons, along with regional geological data, the genetic type, origin and migration of natural gases in the L lithologic gas field, the eastern slope of Yinggehai Sag were investigated. The results show that these gases have a considerable variation in chemical composition, with 33.6%–91.5% hydrocarbon, 0.5%-62.2% CO2, and dryness coefficients ranging from 0.94 to 0.99. The alkane gases are characterized by δ13C1 values of -40.71‰--27.40‰,δ13C2 values of –27.27‰– –20.26‰, and the isoparaffin contents accounting for 55%–73% of the total C5–C7 light hydrocarbons. These data indicate that the natural gases belong to the coal-type gas and are mainly derived from the Miocene terrigenous organic-rich source rocks. When the CO2 contents are greater than 10%, the δ13CCO2 values are –9.04‰ to – 0.95‰ and the associated helium has a 3He/4He value of 7.78×10^–8, suggesting that the CO2 here is crustal origin and inorganic and mainly sourced from the thermal decomposition of calcareous mudstone and carbonate in deep strata. The gas migrated in three ways, i.e., migration of gas from the Miocene source rock to the reservoirs nearby;vertical migration of highly mature gas from deeper Meishan and Sanya Formations source rock through concealed faults;and lateral migration along permeable sandbodies. The relatively large pressure difference between the “source” and “reservoir” is the key driving force for the vertical and lateral migration of gas. Short-distance migration and effective “source - reservoir” match control the gas distribution.展开更多
Methane dominated gas is one of the cleanest energy resources;however, there is no direct method to determine its source rock. Natural gases produced from the eastern Sichuan Basin together with seismic data were stud...Methane dominated gas is one of the cleanest energy resources;however, there is no direct method to determine its source rock. Natural gases produced from the eastern Sichuan Basin together with seismic data were studied for their sources and secondary alteration by thermochemical sulfate reduction(TSR). Our results demonstrate that Upper Permian to Lower Triassic(P_(3)ch-T_(1)f) gases in the surrounding of the Kaijiang-Liangping area show volatile organic sulfur compounds(VOSCs) δ^(34)S values close to those of the associated H_(2)S, and may have been altered by methane-dominated TSR, resulting in positive shift in methane δ^(13)C_(1)values with increasing TSR extents. Other(or group 2) gases produced from the P_(3)ch-T_(1)f reservoirs from the southern area and the Upper Carboniferous to Middle Permian(C_(2)h-P_(2)q) from the eastern Sichuan Basin are not significantly changed by TSR, show similar δ^(34)S values between the kerogens and some VOSCs, and may have been derived from the Lower Silurian and Middle Permian source rocks. This study demonstrates a case for the first time showing the δ^(34)S values of VOSCs can be used as a tool for direct correlation between non-TSR altered gas and source rocks. Methane-dominated gas pools can be found using gas and source rock geochemistry combined with seismic data.展开更多
基金supported by the grants from the National Natural Science Foundation of China(grant nos.41902153,42072140,42102133 and 42202170)Natural Science Foundation Project of Chongqing(grant nos.cstc2021jcyj-msxmX0455,CSTB2022NSCQ-JQX0031 and CSTB2022NSCQ-MSX1586)Science and Technology Research Program of Chongqing Municipal Education Commission(grant nos.KJQN202101544,KJZD-M202101502).
文摘Uncertainties about natural gas source and hydrocarbon accumulation seriously restrict oil and gas exploration in the Lianggaoshan Formation(J_(2) l)in the Eastern Sichuan Basin,which has demonstrated great exploration potential in recent years.This study determines the origin of natural gas and the hydrocarbon accumulation model of J_(2) l in the Eastern Sichuan Basin.A new sample pretreatment method named gas purge-microsyringe extraction was employed and confi rmed to be a practical and eff ective method for preparing condensate oil and collecting source rock extract samples.The source rocks of J_(2) l exhibited moderate to good qualities,characterized by high TOC values,dominance of type Ⅱ_(1) and Ⅱ_(2) kerogens,and high thermal maturities.Biomarker and aromatic characteristics revealed that the source rocks of J_(2) l were deposited in brackish water with weak anoxic conditions.The natural gas in J_(2) l was an organic thermogenic gas generated from the secondary cracking of crude oil,indicating that this natural gas was mainly derived from the source rocks of J_(2) l.The condensate oil-source rock correlation further confi rmed the accuracy of the gas-source correlation results.Based on burial,thermal and hydrocarbon-generating histories,two hydrocarbon charging periods(141–133 Ma and 119–112 Ma)and four hydrocarbon accumulation periods of J_(2) l were determined.Combined with structural evolution,depositional histories and reservoir conditions,a simple gas reservoir accumulation model of J_(2) l was developed,which was identifi ed as a“self-generating and self-storing”gas reservoir.
基金supported by the National Natural Science Foundation of China(Grant No.41972109)the Chengdu University of Technology Postgraduate Innovative Cultivation Program(CDUT2022BJCX004).
文摘There is great controversy regarding the origin and source of natural gas in the Lower Triassic Feix-ianguan Formation in the Eastern Sichuan Basin.This seriously restricts the study of natural gas dy-namics in the Feixianguan Formation and thus hampers natural gas exploration in the region,so further study is urgently required.Using experimental tests of natural gas composition,stable isotopes,and noble gas isotopes with gas chromatography(GC)and mass spectrometry(MS)studies of source rock and reservoir asphalt saturated hydrocarbons,the natural gas geochemical characteristics,the genetic identification and a gas-source comparison of the Feixianguan Formation were studied.Then,con-strained by the thermal history,the histories of gas generation and expulsion were restored by basin simulation technology.Finally,a gas accumulation model was established for the Feixianguan Formation.The results showed that(1)the H_(2)S-rich and H2S-poor gas reservoirs of the Feixianguan Formation are distributed on the east and west sides of the Kaijiang-Liangping trough in the Eastern Sichuan Basin,respectively.The carbon and hydrogen isotope compositions of the natural gas in the gas reservoirs are generally heavy and have typical characteristics of high-maturity dry gas reservoirs.(2)The natural gas of the Feixianguan Formation is organic thermogenic gas,which is mainly oil-type gas generated by the secondary cracking of crude oil.The gas-generating parent material is mainly type II kerogen.(3)The natural gas of the Feixianguan Formation in the Eastern Sichuan Basin was mainly generated by argil-laceous source rocks of the Upper Permian Longtan Formation.(4)Natural gas accumulation occurred as follows:the paleo-structure heights were filled with crude oil in the Early Jurassic,and paleo-oil res-ervoirs were formed in the Feixianguan Formation;during the Middle-Late Jurassic,the paleo-oil res-ervoirs were cracked when the reservoir temperatures rose above 160 C,and paleo-gas reservoirs were formed.Since the end of the Late Jurassic,the paleo-gas reservoirs have been adjusted and reformed to form the present-day natural gas reservoirs.These results provide a basis for studying natural gas accumulation dynamics of the Feixianguan Formation in the Eastern Sichuan Basin.
基金This work was supported by the State Key Science and Technology Program (Grant No. 99-110-01-03).
文摘Isotopic compositions of noble gases, i.e. He Ar Kr and Xe, are measured in natural gases from the Zhongbu gasfield in the Ordos Basin. And heavy noble-gas isotopes (Kr, Xe) are here first used in geochemically studying natural gases and gas-source correlation. Isotopic compositions of heavy noble gases in natural gases, especially Xe, show two-source mixing in the Zhongbu gasfield. Gas sources are somewhat different in the northeast and the southwest of the gasfield. Generally, the gas source of the Lower Paleozoic makes a greater contribution in the southwest than in the northeast in the field. Two kinds of gases can be differentiated from isotopic compositions of heavy noble gases and from their relation with the Ar isotopic composition. Therefore, the comprehensive study on isotopic compositions of light and heavy noble gases can supply more useful information on gas-source correlation and tracing.
文摘Hydrocarbons can be preserved in sedimentary deposits by absorption and includingsof diagenetic minerals during their formation from organic matter by catagenesis.Acidolysis hydrocarbon is mainly composed of C<sub>1</sub>--C<sub>5</sub> gaseous hydrocarbons included indiagenetic minerals, such as carbonate and aluminosilicate. Its chemical
基金Supported by the National Natural Science Foundation of China(41802177,42272188)PetroChina Basic Technology Research and Development Project(2021DJ0206,2022DJ0507)Research Fund of PetroChina Basic Scientific Research and Strategic Reserve Technology(2020D-5008-04).
文摘Based on the organic geochemical data and the molecular and stable carbon isotopic compositions of natural gas of the Lower Permian Fengcheng Formation in the western Central Depression of Junggar Basin,combined with sedimentary environment analysis and hydrocarbon-generating simulation,the gas-generating potential of the Fengcheng source rock is evaluated,the distribution of large-scale effective source kitchen is described,the genetic types of natural gas are clarified,and four types of favorable exploration targets are selected.The results show that:(1)The Fengcheng Formation is a set of oil-prone source rocks,and the retained liquid hydrocarbon is conducive to late cracking into gas,with characteristics of high gas-generating potential and late accumulation;(2)The maximum thickness of Fengcheng source rock reaches 900 m.The source rock has entered the main gas-generating stage in Penyijingxi and Shawan sags,and the area with gas-generating intensity greater than 20×10^(8) m^(3)/km^(2) is approximately 6500 km^(2).(3)Around the western Central Depression,highly mature oil-type gas with light carbon isotope composition was identified to be derived from the Fengcheng source rocks mainly,while the rest was coal-derived gas from the Carboniferous source rock;(4)Four types of favorable exploration targets with exploration potential were developed in the western Central Depression which are structural traps neighboring to the source,stratigraphic traps neighboring to the source,shale-gas type within the source,and structural traps within the source.Great attention should be paid to these targets.
文摘The discovery of the Bozhong 19-6 gas field has opened a new frontier for deep gas exploration in the Bohai Bay Basin,with a great potential for further gas exploration.However,poor understanding of oil and gas origin has been limiting the exploration progress in this area.To clarify the origin of condensate oil and gas in Bozhong 19-6 gas field,this study adequately utilized the organic geochemical analysis data to investigate the composition and geochemical characteristics of condensate oil and natural gas,and analyzed the relationship between condensate oil and the three sets of source rocks in the nearby subsags.Results show that the lighter components dominate the condensate oil,with a forward type predominance.The parent material of crude oil was primarily deposited in a shallow,clay-rich,low-salinity,weakly reducing aquatic environment.The condensate and natural gas have similar parent source characteristics and maturity,with Ro ranging from 1.4%to 1.6%.Both are products of high maturity stage,indicating that they are hydrocarbon compounds produced by the same group of source rocks in the same stage.Oil-sources correlation shows that condensate oil and gas mainly originate from the source rocks of the third member of Shahejie Formation in the nearby subsags of the Bozhong 19-6 structural belt.
基金Supported by the China National Science and Technology Major Project(2016ZX05024-005)
文摘Based on the chemical and stable carbon isotopic composition of natural gas and light hydrocarbons, along with regional geological data, the genetic type, origin and migration of natural gases in the L lithologic gas field, the eastern slope of Yinggehai Sag were investigated. The results show that these gases have a considerable variation in chemical composition, with 33.6%–91.5% hydrocarbon, 0.5%-62.2% CO2, and dryness coefficients ranging from 0.94 to 0.99. The alkane gases are characterized by δ13C1 values of -40.71‰--27.40‰,δ13C2 values of –27.27‰– –20.26‰, and the isoparaffin contents accounting for 55%–73% of the total C5–C7 light hydrocarbons. These data indicate that the natural gases belong to the coal-type gas and are mainly derived from the Miocene terrigenous organic-rich source rocks. When the CO2 contents are greater than 10%, the δ13CCO2 values are –9.04‰ to – 0.95‰ and the associated helium has a 3He/4He value of 7.78×10^–8, suggesting that the CO2 here is crustal origin and inorganic and mainly sourced from the thermal decomposition of calcareous mudstone and carbonate in deep strata. The gas migrated in three ways, i.e., migration of gas from the Miocene source rock to the reservoirs nearby;vertical migration of highly mature gas from deeper Meishan and Sanya Formations source rock through concealed faults;and lateral migration along permeable sandbodies. The relatively large pressure difference between the “source” and “reservoir” is the key driving force for the vertical and lateral migration of gas. Short-distance migration and effective “source - reservoir” match control the gas distribution.
基金financially supported by the National Natural Science Foundation of China (Grant No.41961144023)the Israeli Science Foundation (Grant No.3195/19)。
文摘Methane dominated gas is one of the cleanest energy resources;however, there is no direct method to determine its source rock. Natural gases produced from the eastern Sichuan Basin together with seismic data were studied for their sources and secondary alteration by thermochemical sulfate reduction(TSR). Our results demonstrate that Upper Permian to Lower Triassic(P_(3)ch-T_(1)f) gases in the surrounding of the Kaijiang-Liangping area show volatile organic sulfur compounds(VOSCs) δ^(34)S values close to those of the associated H_(2)S, and may have been altered by methane-dominated TSR, resulting in positive shift in methane δ^(13)C_(1)values with increasing TSR extents. Other(or group 2) gases produced from the P_(3)ch-T_(1)f reservoirs from the southern area and the Upper Carboniferous to Middle Permian(C_(2)h-P_(2)q) from the eastern Sichuan Basin are not significantly changed by TSR, show similar δ^(34)S values between the kerogens and some VOSCs, and may have been derived from the Lower Silurian and Middle Permian source rocks. This study demonstrates a case for the first time showing the δ^(34)S values of VOSCs can be used as a tool for direct correlation between non-TSR altered gas and source rocks. Methane-dominated gas pools can be found using gas and source rock geochemistry combined with seismic data.
