The total organic carbon(TOC)in the marine source rock of the Ordos Basin mostly ranges from 0.2%to 0.5%.The industrial standard commonly states that the TOC value has to be no less than 0.5%(0.4%for high mature or ov...The total organic carbon(TOC)in the marine source rock of the Ordos Basin mostly ranges from 0.2%to 0.5%.The industrial standard commonly states that the TOC value has to be no less than 0.5%(0.4%for high mature or over-mature source rock)to form large petroleum reservoirs.However,gas source correlation indicates that the natural gas in the Jingbian gas field does receive contribution from marine source rocks.In order to determine the effect of carboxylate salts(or called as organic acid salts)on TOC in highly mature source rocks with low TOC value,we sampled the Ordovician marine source rock and the Permian transitional facies source rock in one drilled well in the southern Ordos Basin and performed infrared and GC-MS analysis.It is found that both kerogen-derived organic acids and carboxylate salt-conversed organic acids exist in both marine and transitional facies source rocks.The carboxylate salt-conversed organic acids mainly come from the complete acidification of carboxylate salts,which confirms the presence of carboxylate salts in the marine source rocks.Although the C16:O peak is the main peak for the organic acids both before and after acidification,the carboxylate salt-conversed organic acids have much less relative abundance ahead of C16:O compared with that of the kerogen-based and free organic acids.This observation suggests that the kerogen-based and free organic acids mainly decarboxylate to form lower carboxylic acids,whereas the carboxylate salt-conversed organic acids mainly break down into paraffins.By using calcium hexadecanoate as the reference to quantify the kerogen-derived and carboxylate salt-conversed organic acids,the high TOC(>2.0%)marine source rocks have low carboxylate salt content and the low TOC(0.2%–0.5%)marine source rocks contain high content of carboxylate salt.Therefore,for the marine source rocks with 0.2%–0.5%TOC,the carboxylate salts may be a potential gas source at high maturity stage.展开更多
Theoretical and practical knowledge regarding low-mature gasses is of significant importance to identifying potential natural gas resources.Light hydrocarbon parameters and C and H isotopes are useful tools to identif...Theoretical and practical knowledge regarding low-mature gasses is of significant importance to identifying potential natural gas resources.Light hydrocarbon parameters and C and H isotopes are useful tools to identify low-mature gas.Twenty gas samples were collected from the Turpan-Hami Basin for light hydrocarbon analyses.The results showed that the light hydrocarbon components of natural gases contain high methylcycloxane,high isoparaffin and low benzene.This implies that the gas-generating parent materials are of typical humus type and the paleoenvironment is a fresh water sedimentary environment.These features are consistent with the geological setting of the basin.Comparative studies of isoheptane,heptane,and the carbon isotopic compositions of methane in natural gases,and other maturity indices indicated that natural gases in the Turpan-Hami Basin are dominated by low-mature gas formed during the low evolution stage of Jurassic coal seams.The parent materials are of type III,and the maturation degree was in the low evolution stage.These are the fundamental characteristics of low-mature gas.Results of light hydrocarbon research provided further evidence to suggest that the Turpan-Hami Basin is a large-scale gas producer of low-mature gas in China.It is likely that this resource will play an important role in future exploration and development of low-mature gas in China.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.41173035&41322016)National Key Foundational Research and Development Project(Grant No.2012CB214800)the National Science & Technology Special Project(Grant No.2011ZX05005-004-004)
文摘The total organic carbon(TOC)in the marine source rock of the Ordos Basin mostly ranges from 0.2%to 0.5%.The industrial standard commonly states that the TOC value has to be no less than 0.5%(0.4%for high mature or over-mature source rock)to form large petroleum reservoirs.However,gas source correlation indicates that the natural gas in the Jingbian gas field does receive contribution from marine source rocks.In order to determine the effect of carboxylate salts(or called as organic acid salts)on TOC in highly mature source rocks with low TOC value,we sampled the Ordovician marine source rock and the Permian transitional facies source rock in one drilled well in the southern Ordos Basin and performed infrared and GC-MS analysis.It is found that both kerogen-derived organic acids and carboxylate salt-conversed organic acids exist in both marine and transitional facies source rocks.The carboxylate salt-conversed organic acids mainly come from the complete acidification of carboxylate salts,which confirms the presence of carboxylate salts in the marine source rocks.Although the C16:O peak is the main peak for the organic acids both before and after acidification,the carboxylate salt-conversed organic acids have much less relative abundance ahead of C16:O compared with that of the kerogen-based and free organic acids.This observation suggests that the kerogen-based and free organic acids mainly decarboxylate to form lower carboxylic acids,whereas the carboxylate salt-conversed organic acids mainly break down into paraffins.By using calcium hexadecanoate as the reference to quantify the kerogen-derived and carboxylate salt-conversed organic acids,the high TOC(>2.0%)marine source rocks have low carboxylate salt content and the low TOC(0.2%–0.5%)marine source rocks contain high content of carboxylate salt.Therefore,for the marine source rocks with 0.2%–0.5%TOC,the carboxylate salts may be a potential gas source at high maturity stage.
基金supported by the National Petroleum Major Projects (2008ZX05008-001)the National Natural Science Foundation of China (40703001)
文摘Theoretical and practical knowledge regarding low-mature gasses is of significant importance to identifying potential natural gas resources.Light hydrocarbon parameters and C and H isotopes are useful tools to identify low-mature gas.Twenty gas samples were collected from the Turpan-Hami Basin for light hydrocarbon analyses.The results showed that the light hydrocarbon components of natural gases contain high methylcycloxane,high isoparaffin and low benzene.This implies that the gas-generating parent materials are of typical humus type and the paleoenvironment is a fresh water sedimentary environment.These features are consistent with the geological setting of the basin.Comparative studies of isoheptane,heptane,and the carbon isotopic compositions of methane in natural gases,and other maturity indices indicated that natural gases in the Turpan-Hami Basin are dominated by low-mature gas formed during the low evolution stage of Jurassic coal seams.The parent materials are of type III,and the maturation degree was in the low evolution stage.These are the fundamental characteristics of low-mature gas.Results of light hydrocarbon research provided further evidence to suggest that the Turpan-Hami Basin is a large-scale gas producer of low-mature gas in China.It is likely that this resource will play an important role in future exploration and development of low-mature gas in China.
