湖相富有机质泥质白云岩生排烃模拟及其对页岩油勘探的启示

富有机质湖相白云质泥岩、泥质白云岩及其贫有机质粉砂岩、白云岩夹层是我国陆相盆地页岩油勘探的重要领域，但目前针对湖相富有机质白云质泥岩或泥质白云岩在近地质条件下的生排烃一体化模拟研究尚属空白.以典型低熟富有机质泥质白云岩为例，开展了近地质条件下的生排烃一体化模拟实验，揭示了其呈现四阶段生排烃演化模式.结果表明，R_o ≤ 0.74%时为缓慢生油伴生烃气、排油能力有限阶段，0.74% < R_o ≤ 0.84%时为快速生油伴生烃气、排油能力逐渐增高阶段，0.84% < R_o ≤ 1.28%≈1.30%时为生烃气伴生油与油初始裂解、高效排油阶段，1.30% < R_o ≤ 2.00%时为油裂解烃气兼干酪根生烃气阶段；同时，R_o < 0.68%时滞留油主要以有机质吸附态赋存，而0.68% ≤ R_o ≤ 2.00%时滞留油主要以游离态赋存于矿物基质微-纳米级孔缝系统内.综合分析提出湖相泥质白云岩烃源层系有利页岩油勘探的成熟度范围为0.84%~1.30%. 

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

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 R_o is ≤ 0.74%. The second stage is characterized by rapid oil generation associated hydrocarbon gases and with incremental ability of oil expulsion when R_o 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% < R_o ≤ 1.28%≈1.30%. The fourth stage is characterized by oil cracking into hydrocarbon gas associated hydrocarbon gases generation from kerogen when R_o is > 1.30%. And the retained oil is mainly occurred as adsorption phase with organic matter at R_o < 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% ≤ R_o ≤ 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.