川西坳陷天然气中烷烃气碳同位素倒转成因分析  

Genetic Analysis on the Alkane Carbon Isotopic Reversal of Natural Gas in the Western Sichuan Depression

作　　者：王鹏[1] 沈忠民[1] 刘四兵[1] 吕正祥[1] 王乐闻[2] 陈婷[3] 

机构地区：[1]成都理工大学油气藏地质及开发工程国家重点实验室,成都610059 [2]中国石化上海海洋油气分公司研究院,上海200120 [3]中原油田天然气产销厂,河南濮阳457000

出　　处：《地质科技情报》2014年第1期137-143,共7页Geological Science and Technology Information

基　　金：国家自然科学基金项目(41172119)

摘　　要：在充分认识可能造成天然气中烷烃气碳同位素倒转原因的基础上,分别对川西坳陷构造变形强度不同的北段、中段、南段3地区天然气中烷烃气碳同位素倒转成因进行了分析。结果表明,构造变形强度相对较弱的北段与中段地区,烷烃气碳同位素倒转相对较少发生,倒转现象仅出现在须二段,北段烷烃气碳同位素倒转成因是同源不同期天然气混合,中段2类烷烃气碳同位素倒转成因分别是同源不同期天然气混合与不同成因天然气混合;构造变形强度相对较大的南段地区,烷烃气碳同位素倒转现象明显增多,中侏罗统、须四段与须二段都有倒转发生,中侏罗统与须四段倒转成因主要是同型不同源天然气混合,而须二段倒转成因则为天然气同源不同期混合。对川西坳陷烷烃气碳同位素倒转特征与构造变形强度的关系分析表明,构造变形强度对烷烃气碳同位素倒转有一定的影响,在构造变形强度相对较大的地区,构造变形对烷烃气碳同位素倒转的发生起了促进作用,使得该地区碳同位素倒转现象更为常见。Analysis of the different reasons of alkane carbon isotopic reversal in the northern, the middle and the southern member of the western Sichuan Depression is made in this study. The results show that： in the northern and middle member, the tectonic deformation is relative weaker, alkane carbon isotopic re versal phenomenon only occur in T3x2 and its reason is the mixing of gas from one source rock but of dif- ferent maturity; the two types of reversal reasons in middle member are the mixing of gas from one source rock but of different maturity and the mixing of gases from sapropelic sources and humic source;the tecton- ic deformation and alkane carbon isotopic reversal phenomenon is much stronger in the southern member （J2, Tax4 and TaxZ）, and the reversal reason for J2 and Tax4 is the mixing gas from the different source rock but of the same type, and that of the Tax2 is the mixing gas from one source rock but of different ma turity. The relationship between alkane carbon isotopic reversal and tectonic deformation indicates that the tectonic deformation plays an important role in promoting alkane carbon isotopic reversal and leads the car- bon isotopic reversal phenomenon more common in the area.

关 键 词：川西坳陷 烷烃气 碳同位素倒转 构造变形 

分 类 号：P618.13[天文地球—矿床学]