The acidolysis gas in source rocks is the desorbed hydrocarbon gas in non-connected pores and carbonate crystal lattice,while the absorbed gas lies in the connected pores and is absorbed by surface.It is controversial...The acidolysis gas in source rocks is the desorbed hydrocarbon gas in non-connected pores and carbonate crystal lattice,while the absorbed gas lies in the connected pores and is absorbed by surface.It is controversial about whether to use absorbed gas or acidolysis gas in gas source correlation.Using the absorbed gas and acidolysis gas in the first member of the Middle Permian Maokou Fm(hereinafter referred to as Mao 1 member)of Fuling area in the Sichuan Basin,the differences of components and carbon isotopes between absorbed gas and acidolysis gas and their applicable conditions in gas source correlation were discussed.The results show that:(1)there are larger differences of components and isotopes between absorbed gas and acidolysis gas.The absorbed gas has more heavy hydrocarbons and heavier carbon isotope.This difference can be attributed to the easier diffusion of methane and light hydrocarbons in absorbed gas,leading to relatively enriched heavy hydrocarbons and heavier carbon isotope in absorbed gas;(2)acidolysis gas is a mixture of hydrocarbon gas formed during different stages,while absorbed gas is the result of equilibrium between diffusion and supply of hydrocarbon gas,which can result in the differences on carbon isotope sequences between them;(3)the characteristics of natural gas produced after acid fracturing in the Mao 1 member in Fuling area resembles those of acidolysis gas in source rocks,while the characteristics of natural gas produced without acid fracturing are more similar to those of adsorbed gas;(4)the natural gas pool of the Mao 1 member is a carbonate gas pool with self-generation and self-storage.It is concluded that for the gas pool formed after migration,its producing pays have not been processed by acid fracturing,the produced gas should be correlated with the adsorbed gas in source rocks;for the carbonate gas pool with self-generation and self-storage,acid fracturing is usually needed,and the produced gas should be correlated with the acidolysis gas in source rocks.展开更多
Based on correlation between geochemical characteristics of Sinian and Cambrian source rocks and discovered gas reservoirs,paleoand the analysis on geological conditions of reservoir formation,the sources of natural g...Based on correlation between geochemical characteristics of Sinian and Cambrian source rocks and discovered gas reservoirs,paleoand the analysis on geological conditions of reservoir formation,the sources of natural gas in the Sinian of Sichuan Basin have been discussed to sort out the contribution of Sinian source rocks to the gas reservoirs and effectiveness of Sinian primary gas-bearing system.Through the analysis of natural gas composition,carbon and hydrogen isotopes and effectiveness of Sinian accumulation assemblages,it is concluded that:(1)The natural gas derived from the Sinian source rock is characterized by low ethane content,heavy ethane carbon isotope and light methane hydrogen isotope,and obviously different from the gas generated by the Cambrian source rock.(2)The gas reservoirs discovered in Sinian Dengying Formation are sourced by Sinian and Cambrian source rocks,and the Sinian source rock contributes different proportions to the gas in the 4th member and the 2nd member of the Dengying Formation,specifically,39%and 55%to the 4th member in marginal zone and intra-platform,54%and 68%to the 2th member in the marginal zone and intra-platform respectively.(3)The effectiveness of the Sinian primary gas-bearing system depends on the gas generating effectiveness of the source kitchen,reservoir and combination of gas accumulation elements.For high-over mature marine source rocks at the Ro of less than 3.5%,besides gas generated from the thermal cracking of liquid hydrocarbon,the kerogen still has some gas generation potential by thermal degradation.In addition,the Sinian microbial dolomite still preserves relatively good-quality reservoirs despite large burial depths,which match well with other basic conditions for gas accumulation in central Sichuan paleo-uplift,increasing the possibility of Sinian primary gas-bearing system.The research results confirm that the Sinian primary gas-bearing system is likely to form large-scale accumulation.展开更多
基金supported by the National Major Science and Technology Project“Hydrocarbon generation and expulsion mechanism of marine source strata and evaluation technology”(No.:2017ZX05005-001-003)the Science&Technology Project of Sinopec Exploration Company“Evaluation on hydrocarbon generation potential in Mao 1 Member,Fuling area”(No.:35450003-17-ZC0607-0032).
文摘The acidolysis gas in source rocks is the desorbed hydrocarbon gas in non-connected pores and carbonate crystal lattice,while the absorbed gas lies in the connected pores and is absorbed by surface.It is controversial about whether to use absorbed gas or acidolysis gas in gas source correlation.Using the absorbed gas and acidolysis gas in the first member of the Middle Permian Maokou Fm(hereinafter referred to as Mao 1 member)of Fuling area in the Sichuan Basin,the differences of components and carbon isotopes between absorbed gas and acidolysis gas and their applicable conditions in gas source correlation were discussed.The results show that:(1)there are larger differences of components and isotopes between absorbed gas and acidolysis gas.The absorbed gas has more heavy hydrocarbons and heavier carbon isotope.This difference can be attributed to the easier diffusion of methane and light hydrocarbons in absorbed gas,leading to relatively enriched heavy hydrocarbons and heavier carbon isotope in absorbed gas;(2)acidolysis gas is a mixture of hydrocarbon gas formed during different stages,while absorbed gas is the result of equilibrium between diffusion and supply of hydrocarbon gas,which can result in the differences on carbon isotope sequences between them;(3)the characteristics of natural gas produced after acid fracturing in the Mao 1 member in Fuling area resembles those of acidolysis gas in source rocks,while the characteristics of natural gas produced without acid fracturing are more similar to those of adsorbed gas;(4)the natural gas pool of the Mao 1 member is a carbonate gas pool with self-generation and self-storage.It is concluded that for the gas pool formed after migration,its producing pays have not been processed by acid fracturing,the produced gas should be correlated with the adsorbed gas in source rocks;for the carbonate gas pool with self-generation and self-storage,acid fracturing is usually needed,and the produced gas should be correlated with the acidolysis gas in source rocks.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA14010403)the China National Science and Technology Major Project(2016ZX05004,2016ZX05007-003)the Science and Technology Project of China National Petroleum Corporation(kt2020-01-03,2021DJ06)。
文摘Based on correlation between geochemical characteristics of Sinian and Cambrian source rocks and discovered gas reservoirs,paleoand the analysis on geological conditions of reservoir formation,the sources of natural gas in the Sinian of Sichuan Basin have been discussed to sort out the contribution of Sinian source rocks to the gas reservoirs and effectiveness of Sinian primary gas-bearing system.Through the analysis of natural gas composition,carbon and hydrogen isotopes and effectiveness of Sinian accumulation assemblages,it is concluded that:(1)The natural gas derived from the Sinian source rock is characterized by low ethane content,heavy ethane carbon isotope and light methane hydrogen isotope,and obviously different from the gas generated by the Cambrian source rock.(2)The gas reservoirs discovered in Sinian Dengying Formation are sourced by Sinian and Cambrian source rocks,and the Sinian source rock contributes different proportions to the gas in the 4th member and the 2nd member of the Dengying Formation,specifically,39%and 55%to the 4th member in marginal zone and intra-platform,54%and 68%to the 2th member in the marginal zone and intra-platform respectively.(3)The effectiveness of the Sinian primary gas-bearing system depends on the gas generating effectiveness of the source kitchen,reservoir and combination of gas accumulation elements.For high-over mature marine source rocks at the Ro of less than 3.5%,besides gas generated from the thermal cracking of liquid hydrocarbon,the kerogen still has some gas generation potential by thermal degradation.In addition,the Sinian microbial dolomite still preserves relatively good-quality reservoirs despite large burial depths,which match well with other basic conditions for gas accumulation in central Sichuan paleo-uplift,increasing the possibility of Sinian primary gas-bearing system.The research results confirm that the Sinian primary gas-bearing system is likely to form large-scale accumulation.
