四川盆地陆相天然气成因类型划分与对比

PARTITION AND CONTRAST ON GENETIC TYPE OF CONTINENTAL NATURAL GAS IN THE SICHUAN BASIN

沈忠民 姜敏 刘四兵 朱宏权 宫亚军

Shen Zhongmin Jiang Min Liu Sibing Zhu Hongquan Gong Yajun

油气藏地质及开发工程国家重点实验室(成都理工大学), 成都, 610059 2. 中国石化西南分公司勘探开发研究院, 成都, 610081 3. 中国石化 胜利油田西部新区研究中心, 山东, 东营, 257000

State Key Lab of Oil-gas Reservoirs Geology and Exploitation(Chengdu University of Technology), Chengdu, Sichuan 610059, China 2. Exploration and Production Research Institute of Southwest Branch Company, SINOPEC, Chengdu, Sichuan 610081, China 3. The Western New Research Center of Shengli Oilfield, SINOPEC, Dongying, Shandon 257000, China

对四川盆地天然气轻烃指纹、碳氢同位素、稀有气体同位素等进行了系统研究。天然气碳同位素δ13C1—δ13C2关系的分区和分层对比研究显示天然气受母质类型、成熟度及运移等多种因素影响。轻烃指纹表明川西坳陷天然气以腐殖型来源为主,川中、川南及川东地区天然气既有腐殖型也有腐泥型来源,天然气明显具有油型气特征。川西坳陷中段须二段天然气碳同位素δ13C1较高,而部分碳同位素δ13C2位于-28‰以下显示了其油型气和高成熟度特征,研究区其它样品分布区间相对集中,均表现为典型的煤型气特征。四川盆地海、陆相天然气可以利用δ13C2—δD1很好区分,氢同位素δD1=-140‰和碳同位素δ13C2=-28‰可将四川盆地海相和陆相天然气进行区分。稀有气体同位素表明天然气基本上为壳源成因,无幔源稀有气体的加入。

The paper studies systematically the light hydrocarbon fingerprint, carbon isotope, hydrogen isotope and noble gas isotope of natural gas in the Sichuan Basin. The natural gas carbon isotope C1-C2 relationship from different areas and formations show that the natural gas in the Sichuan Basin were affected by parent types of sources rock, maturity, migration and other factors. The light hydrocarbon fingerprint indicates the major source of natural gas in the Western Sichuan Depression is humus-type, the sources in southern Sichuan Basin, eastern Sichuan Basin and the central region of Sichuan Basin are both humus-type and sapropel type, and the natural gas are mainly oil-type gas. The C1 isotope of natural gas from T3x2 in the middle area of the Western Sichuan Depression are higher than other areas and C2 isotope are less than -28‰, which shows oil-type gas and higher maturity feature. The natural gases of other formations in study area are concentrating distribution relatively and display the typical feature of coal-related gas. The marine and continental natural gas in the Sichuan Basin could be distinguished by carbon isotope δ13C2=-28‰ and hydrogen isotope δD1=-140‰ of the natural gas. The noble gas isotope shows that the natural gas are shell source without the addition of mantle noble gases.

国家自然科学基金资助项目(40772804);“油气藏地质及开发工程”国家重点实验室(成都理工大学)基金项目

https://doi.org/10.11781/sysydz201006560