摘要
According to gas compositional and carbon isotopic measurement of 114 gas samples from the Kuqa depression,accumulation of the natural gases in the depression is dominated by hydrocarbon gases, with high gas dryness(C1/C1-4)at the middle and northern parts of the depression and low one towards east and west sides and southern part.The carbon isotopes of methane and its homologues are relatively enriched in 13 C,and the distributive range ofδ13C 1 ,δ13C 2 andδ13C 3 is-32‰―-36‰,-22‰―-24‰and-20‰―-22‰,respectively.In general,the carbon isotopes of gaseous alkanes become less negative with the increase of carbon numbers.Theδ13C CO2 value is less than-10‰in the Kuqa depression,indicating its organogenic origin.The distributive range of 3 He/ 4 He ratio is within n×10-8 and a decrease in 3 He/ 4 He ratio from north to south in the depression is observed.Based on the geochemical parameters of natural gas above,natural gas in the Kuqa depression is of characteristics of coal-type gas origin.The possible reasons for the partial reversal of stable carbon isotopes of gaseous alkanes involve the mixing of gases from one common source rock with different thermal maturity or from two separated source rock intervals of similar kerogen type,multistages accumulation of natural gas under high-temperature and over-pressure conditions,and sufficiency and diffusion of natural gas.
According to gas compositional and carbon isotopic measurement of 114 gas samples from the Kuqa depression,accumulation of the natural gases in the depression is dominated by hydrocarbon gases, with high gas dryness(C1/C1-4)at the middle and northern parts of the depression and low one towards east and west sides and southern part.The carbon isotopes of methane and its homologues are relatively enriched in 13 C,and the distributive range ofδ13C 1 ,δ13C 2 andδ13C 3 is-32‰―-36‰,-22‰―-24‰and-20‰―-22‰,respectively.In general,the carbon isotopes of gaseous alkanes become less negative with the increase of carbon numbers.Theδ13C CO2 value is less than-10‰in the Kuqa depression,indicating its organogenic origin.The distributive range of 3 He/ 4 He ratio is within n×10-8 and a decrease in 3 He/ 4 He ratio from north to south in the depression is observed.Based on the geochemical parameters of natural gas above,natural gas in the Kuqa depression is of characteristics of coal-type gas origin.The possible reasons for the partial reversal of stable carbon isotopes of gaseous alkanes involve the mixing of gases from one common source rock with different thermal maturity or from two separated source rock intervals of similar kerogen type,multistages accumulation of natural gas under high-temperature and over-pressure conditions,and sufficiency and diffusion of natural gas.
作者
LIU QuanYou 1 ,QIN ShengFei 1 ,LI Jian 2 ,LIU WenHui 3 ,ZHANG DianWei 3 ,ZHOU QingHua 1 &HU AnPing 1 1 Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China
2 Langfang Branch of Research Institute of Petroleum Exploration and Development,PetroChina,Langfang 065007,China
3 Exploration and Production Research Institute,SINOPEC,Beijing 100083,China
基金
the National Natural Science Foundation of China(Grant No.40673018)
the China National Key Foundation Research and Development Project(Grant No.2003CB214603)
the Scientific Research and Technical Developmentof PetroChina(Grant No.07-01C-01-07)
