Simulation of Hydrocarbon Generation and Expulsion for Lacustrine Organic-Rich Argillaceous Dolomite and Its Implications for Shale Oil Exploration

Li Zhiming; Zheng Lunju; Jiang Qigui; Ma Zhongliang; Tao Guoliang; Xu Ershe; Qian Menhui; Liu Peng; Cao Tingting

Abstract：The organic-rich lacustrine dolomitic mudstone,argillaceous dolomite,organic-poor siltstone and dolomite interlayer are important areas for shale oil exploration in terrestrial basins in China.However,the research on the integration of hydrocarbon generation,expulsion and hydrocarbon accumulation in the lacustrine organic-rich dolomitic mudstone or argillaceous dolomite under near geological conditions is still blank.An integrate experiment of hydrocarbon generation and expulsion simulation from argillaceous dolomite rich in organic matter under near geological condition in confined systems,has been carried out with typical lower mature organic-rich argillaceous dolomite.The four-stage of hydrocarbon generation and expulsion evolution model is revealed.The results show that the first stage is characterized by relatively slow oil generation associated hydrocarbon gases and by limited ability of oil expulsion when Ro is ≤0.74％.The second stage is characterized by rapid oil generation associated hydrocarbon gases and with incremental ability of oil expulsion when Ro is in the range of 0.74％-0.84％.The third stage is characterized by hydrocarbon gas generation associated oil and oil initial cracking,and by oil expulsion effectively at 0.84％＜ Ro≤1.28％≈1.30％.The fourth stage is characterized by oil cracking into hydrocarbon gas associated hydrocarbon gases generation from kerogen when Ro is ＞1.30％.And the retained oil is mainly occurred as adsorption phase with organic matter at Ro ＜0.68 ％,and mainly occurred as free phase within micron to nano-scale pores and microfractures in mineral matrix of argillaceous dolomite at 0.68 ％ ≤Ro ≤2.00％.The range of thermal maturity for favorable shale oil exploration within lacustrine dolomite measures,is proposed at 0.84％-1.30％,on the basis of the results of simulation of hydrocarbon generation and expulsion for lacustrine organic-rich argillaceous dolomite,integrated with geological conditions and exploring economic benefit.