地质条件约束下川北二叠系大隆组富有机质页岩热模拟生烃过程及特征研究  

Characteristics and hydrocarbon-gernerating process of the organic-rich shale of Permian Dalong Formation in North Sichuan:Pyrolysis experiments with geological constraint

作　　者：戴海亮 沈斌 李开开[1,3] 张小涛 徐学敏 许智超[2] 周晶晶 Dai Hailiang;Shen Bin;Li Kaikai;Zhang Xiaotao;Xu Xuemin;Xu Zhichao;Zhou Jingjing(School of Energy Resource,China University of Geosciences(Beijing),Beijing,100083,China;National Geological Experimental Testing Center,Beijing,100037,China;Beijing Key Laboratory of Unconventional Natural Gas Geological Evaluation and Development Engineering,Beijing,100083,China)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]国家地质实验测试中心,北京100037 [3]非常规天然气地质评价与开发工程北京市重点实验室,北京100083

出　　处：《南京大学学报（自然科学版）》2020年第3期382-392,共11页Journal of Nanjing University（Natural Science）

基　　金：中国地质调查局地质调查项目(DD20190086);国家自然科学基金(41972154)。

摘　　要：选取川北大隆组低熟富有机质页岩样品作为实验对象,综合考虑了地质约束条件(静岩压力、流体压力和地层水等因素)对生烃作用的影响,从低熟到过成熟进行了全系列的热模拟,并对各温度点的热产物进行气体组分及同位素分析.结果表明:热模拟实验产生的烃类气体产率随温度升高而增大,在500℃达到峰值,随后明显下降并趋于平稳.烃类气体产率的降低与静岩压力、流体压力以及孔隙发育有着密切关系.压力的不断增大抑制了页岩中有机质的分解,并导致孔隙度降低和孔径减小,排烃不畅,影响了生烃产率.滞留于样品中的重烃组分发生热裂解,最终形成了以高CH4含量特征的原油裂解气,并呈现鲜明的ln(C2/C3)随温度变化特征和碳同位素部分倒转现象.研究为大隆组深层页岩气的有效开发提供前期基础性实验数据和生烃、演化特征方面的成果支持.Semi-closed thermal simulation experiments were performed on the immature organic-rich shale samples from the Dalong Formation in northern Sichuan Basin,taking into account the geological constraints,e.g.,static rock pressure,fluid pressure,and formation water.Gas composition and carbon isotope of the thermal products at each temperature point were determined.The results show that the productivity of hydrocarbon gas increases with temperature(with a peak at 500℃)and then show a generally decreasing trend.It seems that the decline in the productivity of hydrocarbon gas is closely correlated with the change of static rock pressure,fluid pressure and porosity.The increasing pressure with progressive burial seems to have retarded the pyrolysis process and promoted porosity destruction and pore-size decrease,finally leading to the block of hydrocarbons expulsion and decline in the productivity of hydrocarbon gas.The heavy hydrocarbons left in the samples were then subjected to thermal cracking and formed hydrocarbon gas,showing a distinguishable correlation between ln(C2/C3)and temperature and the local reversal in carbon isotopes.This study provides basic experimental data and great insights into characteristics and hydrocarbon-gernerating process for the shales in Dalong Formation,and have application for further exporation of deep shale gas.

关 键 词：地质约束 热模拟实验 生烃特征 孔隙演化 碳同位素 深层页岩气 

分 类 号：P618.13[天文地球—矿床学]