山西沁水盆地石炭-二叠系煤层生排烃史分析

通过对沁水盆地石炭-二叠系煤层夹矸及煤层顶板砂岩石样品中的包裹体类型、与矿物的共生关系以及包裹体均一化温度研究,结合山西南部上古生界煤层埋藏史及热史演化分析,讨论了太原组和山西组煤层的排烃历史。结果表明,太原组和山西组煤层排烃主要发生在晚三叠世末期煤层抬升释压以来,大体可以分为中侏罗世、早白垩世早期和晚白垩世一直到古新世三期。早期有过煤成油的阶段,并且有一定规模的排油过程;主要的排气阶段正好与热催化生油气阶段和热裂解生凝析气阶段相对应,那么可以认为热解气和热裂解气是煤层气的主要组成部分。煤储层中液态烃与煤层夹矸及顶板岩石中液态烃组成特征存在着明显差别,可能是由排烃过程吸附分馏作用和不同成熟度液态烃的混合作用不同所致。甾烷和藿烷总体组成特征相似,说明煤层、煤层夹矸及顶板砂岩中油气来源于煤层。

The History Analysis of Hydrocarbon Expulsion from the Coal Beds in the Carboniferous-Permian in Qinshui Basin, Shanxi

Through the synthetically study on the homogenization temperature and occurrence in the authigenic minerals of fluid inclusions in the terrane between or above the coal beds in the Carboniferous-Permain in the Qinshui basin, Shanxi, three stages of expulsion of hydrocarbon from the coal beds were known. Combining with the conclusion of basin evolution, it is deduced that the filling of hydrocarbon happened during J2, the early of K1 and K2 - E1. In the early stage, coal beds produced coal-generating oil. The stages of expulsion of nature gas are corresponding with the phase of thermocatalysis and thermal cracking, respectively. So the coal-bed gas in the Qinshui basin is mostly composed of gas of thermocatalysis and thermal cracking. The extracted hydrocarbon residues of the coal and the sandstones are appreciably different, because of difference of fractional distillation and the filling of different degrees of hydrocarbon in the coal beds and the sandstones.