典型Ⅱ_2-Ⅲ过渡型褐煤近地质条件下生排油模拟研究

Simulation of hydrocarbon generation and expulsion for brown coal with transitional organic matter type Ⅱ_2-Ⅲ under near geological conditions

煤作为一类有机质高度富集的烃源岩,在生油窗内其生排油能力一直存在着争议。以未成熟典型Ⅱ_2-Ⅲ过渡型褐煤为例,利用自研的DK-Ⅱ型地层孔隙热压生排烃模拟实验仪,开展煤在有限空间体系内,在不同温度、上覆压力负载和水介质流体压力共同作用下的生排油模拟研究。模拟实验结果表明:在成熟度R_o≤0.82%的各个演化阶段,煤均以生油为主,阶段生油产率显著高于生气产率,成熟度0.68≤R_o≤0.82%阶段,为煤主生油阶段,该阶段的生油量占总生油量的53.66%;在成熟度R_o>0.82%的各个演化阶段,煤均以生气为主。煤不仅可以生油,而且当总油产率达到30 mg/g TOC左右时就可以有效排油,主生油窗内煤岩的排油能力优于泥岩烃源岩。煤在主生油窗内的烃气和二氧化碳产率显著高于泥质烃源岩的烃气和二氧化碳产率,应是造成煤成油可以高效排油的重要因素。

The potential of oil generation and expulsion within the oil-window of coal as a kind of source rocks with high rich-organic matter is controversial for a long time.Study on the simulation of hydrocarbon generation and expulsion for an immature typical brown coal with transitional organic matter type Ⅱ2-Ⅲ in confined system,under the conditions of water existing,different temperature,overburden and internal fluid pressure,was carried out,using DK- Ⅱhydrocarbon generation and expulsion simulation experimental instrument. The results of simulation experiment show that coal mainly generates oil at each evolution stage of the maturity Ro≤0.82%,and the yield of generation oil is obvious higher than the yield of generation hydrocarbon gas,the main oil generation stage of coal is at 0. 68 ≤ Ro≤0. 82%,the percentage of episodic quantity of generated oil to total oil is 53.66%; and coal mainly generates hydrocarbon gas at each evolution stage of the maturity Ro0.82%. Coal not only can generate oil,but also can expel oil withhigh efficiency when the oil yield reaches about 30 mg/g TOC,the percentage of expulsion oil of coal is obvious higher than the percentage of expulsion of mudstone within main oil-window.The yields of hydrocarbon gas and CO2 of coal is obvious higher than the yields of hydrocarbon gas and CO2 of mudstone within main oil-window.This may be an important factor causing coal with higher expulsion oil efficiency.