一种生、排烃量计算方法探讨与应用

A method for calculating the quantity of hydrocarbon generation and expulsion

烃源岩的生烃量等于其残烃量与排出烃量之和。利用氯仿沥青“A”/总有机碳参数随深度的变化关系 ,可求出烃源岩的残烃率。在烃源岩演化过程中 ,(S1+S2 ) /总有机碳 (生烃潜力指数 )减小的唯一原因是有烃类从烃源岩中排出。无论生烃机制如何 ,烃源岩的现今生烃潜力指数与油气排出以前的原始生烃潜力指数之间的差值始终代表当前每克有机碳的排烃量 (排烃率 ) ,据此可计算生成未熟—低熟油的烃源岩的排烃量。将排烃率与对应的残烃率叠加 ,可求出烃源岩的油气发生率 ,结合烃源岩的厚度、面积、密度及有机碳丰度等资料 ,可计算生烃量。在东营凹陷八面河油田应用此方法发现 ,该区下第三系沙三段、沙四段的泥岩与油页岩的生、排烃演化模式不同 ,泥岩的生烃量巨大 ,但排烃效率很低。图 3表1参

Hydrocarbon generating quantity of source rock is the sum of hydrocarbon remaining quantity in the source rock and hydrocarbon expelling quantity from the source rock. Hydrocarbon retention rate in the source rock can be obtained by analyzing the ratio of the extracts 'A' over TOC. The decrease of ( S 1+ S 2)/TOC, which is the hydrocarbon generation potentials, during the evolution of source rock indicates that parts of the hydrocarbons generated by the source rock have been expelled from the source rock. No matter what the hydrocarbon generation mechanism of the source rock is, the difference between the current hydrocarbon generation potential index of source rock and the original hydrocarbon generation potential index before the hydrocarbon expelling from source rock always stands for current hydrocarbon expelling quantity of a unit weight of organic carbon (i.e. hydrocarbon expelling rate), based on this, it is able to calculate the hydrocarbon expelling quantity from source rocks in which unmatured low matured oil were generated. The hydrocarbon generation quantity of the source rock can be calculated through extracting hydrocarbon generating rate of source rocks and combining with the data about the source rock, such as thickness, area, TOC, vitrinite reflectance, kerogen type and density obtained. Application results of the method in Bamianhe oil field in Dongying depression indicate that the hydrocarbon generation and expulsion evolutionary patterns of mudstones and shales of Members S 3 and S 4 in Lower Tertiary of this area are different, the hydrocarbon generating quantity of mudstones is much larger, but its hydrocarbon expulsion efficiency is lower than that of shale.