川西坳陷煤系烃源岩成熟度特征及成熟度指标对比研究

烃源岩热演化程度是判断一个盆地是否具备生油能力的重要指标之一,然对热演化程度的定量识别标志较多,针对热演化程度不同或参数获取的难易程度而有所选择.研究基于川西坳陷龙泉驿斜坡LS1井J_1x,T_3x~5,T_3及T_3t等4个主要烃源岩层位的17个样品的镜质体反射率(R_0)、岩石热解及芳烃色质指标等分析测试,时研究区上三叠统须家河组及侏罗系主要烃源岩成熟度特征进行系统分析表明,研究区源岩镜质体反射率分布在0.97～1.59之间,T_(max)值平均为488.67,R_(OMPI1)值介于1.01～1.56之间,R_(O(3-MCH/1-MCH))值介于1.05～1.57之间,表明本区烃源岩处于成熟-高成熟阶段.芳烃各项指标随深度增大趋势明显.尤其是MP11和3-甲基屈/1-甲基屈(3-MCH/1-MCH)随深度变化更为明显,且和R_0与深度的变化趋势高度相似,而MDBI指数和4-甲基-二苯并噻吩/1-甲基-二苯并噻吩(4-MDBT/1-MDBT)与深度的相关关系相对较差,但总体仍呈现出逐渐增大的趋势.成熟度指标对比研究,证实镜质体反射率仍是较为成熟,易于横向对比的成熟度指标,芳烃色质参数MPI1和3-甲基屈/1-甲基屈(3-MCH/1-MCH)由于其较少受各成岩环境的影响,从而具有潜力的成熟度判别指标.研究还将MPI1及3-MCH/1-MCH通过计算转化成R_(OMPI1)及R_(O(3-MCH/1-MCH>))以实现在获取R_0困难亦可进行对比.

COMPARATIVE RESEARCH ON MATURITY FEATURE AND MATURITY INDICATOR OF COAL SOURCE ROCK FROM WEST SICHUAN BASIN DEPRESSION

The degree of thermal evolution of source rocks is an important criterion to determine oil-generating capacity for a basin. However,there are a lot of quantitative criteria for the determi-nation of thermal evolution. This article is based on the research of 17 specimens from 4 major hy-drocarbon source rocks of J_1z, T_3X~5 , T_3X~3 and T_3t, sampled from LS1 wells of Longquanyi in West Sichuan Depression. It is showed that the vitrinite reflectance of source rock ranges from 0.97 to 1.59,T_(max) has an ave0rage value of 488. 67,R_(OMPI1) is between 1.01 ～ 1. 56,R_(O(a-MCH/1-MCH)) values ranged from 1.05 to 1.57. All of the data show that this area belongs to mature to high mature hydrocarbon source rocks. The trend of aromatic hydrocarbon indicators is clearly increasing with depth,especially,the MPI1 and 3-MCH/1-MCH changes with depth more apparently,similar to the change of R_O with depth. However, the MDBI index and (4-MDBT/1-MDBT) have a poor correlation with the depth. But generally,it shows a gradual in increasing tendency. Comparative study of maturity index confirmed that vitrinite reflectance is an indicator for the horizontal corre-lation of maturity. Aromatics color quality parameters of MPI1 and 3-MCH/1-MCH are less sus-ceptible to the effects of various diagenetic environments, and thus are potential indicators for the determination of maturity.