碳酸盐岩生烃机制的新认识

作者通过逐阶抽提加热和逐阶加热模拟实验对碳酸盐岩的生烃机理进行了研究。研究中发现,(1)碳酸盐矿物对干酪根具有缩合脱氢作用,在较低温度下能促使干酪根降解成液态烃,从而也增加了气态烃的产率。(2)蒙脱石具有促进碳链断裂的作用,使液态烃在较低温度下向气态烃转化。(3)碳酸盐岩中粘土矿物的存在,影响了碳酸盐矿物对干酪根的缩合脱氢作用,从而降低了产烃率。(4)碳酸盐源岩生气高峰晚于泥质源岩。另外,通过对国内各地区各层系碳酸盐源岩剩余生气率的测定和低演化样品的模拟实验研究,可认为碳酸盐岩液态烃在地史上的运移率远高于泥质岩,纯灰岩可达60%,泥灰岩仅约25%。 

A NEW UNDERSTANDING OF HYDROCARBON GENERATION MECHANISM OF CARBONATE ROCKS

The mechanism of hydrocarbon generation in carbonate rocks are studied by step heating extraction and simulation. The authors found that (1) carbonate minerals have the influence of condensation and dehy-drogenation on kercgen,and can promote its degradation into liquid hydrocarbon under low temperature, thus increase the yield of gaseous hydrocarbon, (2) Montmorillonite is capable of promoting the breakage of carbon chains and the transformation of liquid hydrocarbon into gaseous hydrocarbon under low temperature; (3) The existence of clay mineral in carbonate rocks affects the condensation and dehydrcgenation of carbonate minerals over kerogen, thus the hydrocarbon generating rate is reduced; (4) The peak of gas generation for carbonate source rocks is later than that for muddy source rocks. Furthermore,based on the measurements of residual gas generating rates in carbonate source roeks, and simulations on samples with low maturation from different sequences in various areas of China, the migrating rate for liquid hydrocarbon in carbonate rocks during gee-history is considerable higher than that in mudstone, and it can reach as much as 60% for pure limestone, but only 25% for marlites.