应用排烃门限理论评价汤原断陷泥质烃源岩

Applying the theory of hydrocarbon expulsion threshold to evaluating the carbon source rock in Tangyuan fault depression

采用伊兰—依通地堑东北端的汤原断陷汤参1井和汤参2井第三系泥质烃源岩的实际资料,应用排烃门限理论,研究其排油气特征,在此基础上建立了其排烃门限判别理论图版和排烃量定量评价理论图版。研究表明,C(母质丰度)值高但KTI(母质类型指数)值低的烃源岩与C值低但KTI值高的烃源岩均能进入排烃门限;烃源岩进入排烃门限的深度随C、KTI、Ro值的增大而减小,进入排烃门限后的排烃量随C、KTI、Ro值的增大而增大,C、KTI、Ro三者互补。一般而言,烃源岩进入排甲烷气门限早于进入排重烃气门限,进入排重烃气门限早于进入排油门限。评价结论是:汤参1井、汤参2井第三系泥质烃源岩属于非烃源岩到差烃源岩,大部分已进入排甲烷气和重烃气阶段,只有少数进入排油阶段。图2表5参2(周海燕摘)

By using the actual data of Tertiary muddy source rocks from Wells Tangcan 1 and Tangcan 2 of Tangyuan fault depression in the northern end of Yilan Yitong graben and applying the theory of hydrocarbon expulsion threshold (HET), the authors investigated the characteristics of hydrocarbon expulsion, and then built up the chart for identification criterion of hydrocarbon expulsion threshold of muddy source rocks in this area and the chart for quantitative evaluation of their hydrocarbon amount. The study shows that source rocks with a high level of organic matter abundance ( C ) but a bad kerogen type index ( KTI ) and those with a low level of C but a good KTI can both cross threshold of hydrocarbon expulsion. The burial depth at which source rocks reach the threshold point of hydrocarbon expulsion decreases with the increasing of C, KTI and R o, which are complementary to each other; the amount of hydrocarbon expulsion from source rocks become larger with increases of C, KTI and R o. Generally, source rocks cross heavy gas expulsion threshold later than methane expulsion threshold but earlier than liquid hydrocarbon expulsion threshold. The evaluation result is that the Tertiary muddy source rocks of Wells Tangcan 1 and Tangcan 2 belong to non and bad hydrocarbon types, which mostly cross methane and heavy gas expulsion stage, and little cross oil expulsion stage.