利用生排烃动力学研究海相及煤系烃源岩的残留烃及其裂解成气特征

以煤与海相泥岩的块状样品为研究对象进行多升温速率下的排烃模拟实验,借助生烃动力学方法处理实验模拟结果,对煤与海相泥岩的残留烃特征进行了研究。结果表明:海相泥岩残留烃在Ro为1.0%时达到高峰,然后逐渐降低,而煤中残留烃在Ro为1.0%时达到高峰后便基本上保持稳定。煤吸附能力比海相泥岩的强,其残留烃量也比海相泥岩大。成熟作用对于煤及海相泥岩残留烃都有很大的影响。高过成熟阶段海相地层中烃类构成以油藏或输导层中原油裂解气为主,源岩中的残余液态烃也有一定的贡献,而煤在排烃结束以后煤中分散液态烃对裂解气的贡献更大些。煤中残留烃主要是前期形成的烃类由于排烃效率不高而聚集起来的,而海相残留烃基本上随着残余生烃潜力的降低而降低,这一方面说明海相残留烃受生烃作用的影响,另一方面也受排烃效率的影响。模拟样品中的残留烃及残余生烃潜力均可以与自然样品对比,表明了该方法的实用性。

Residual Hydrocarbon and Its Secondary Cracking Gas Characteristics of Marine and Coal Source Rocks by using Kinetic Simulation Methods of Hydrocarbon Generation and Expulsion

A series of multiheating-rated hydrocarbon expulsion simulation experiments were conducted to the source rock blocks and the characteristics of residual hydrocarbons were studied by using kinetic methods. The results indicate the content of residual hydrocarbon in marine mudstone reaches to the peak when Ro is around 1.0% and then decreases gradually; and the content of residual hydrocarbon in coal keeps steady after reaching its peak around Ro=1.0%. The content of residual hydrocarbon in coal is greater than that in marine mudstone due to its high adsorption and low expulsion rates. Maturation has high influence on the residual hydrocarbon in both marine mudstone and coal. Gases generated from marine source rocks in high-over maturity stages are mainly from the secondary cracking of the oil expulsed from or retained in the source rocks while the gases generated from dispersed residual hydrocarbons in coal account for majorities. The residual hydrocarbon in coal is mainly the accumulated hydrocarbon that is generated at the early stages while the residual hydrocarbon of marine mudstone decreases as the residual hydro- carbon generation potential. This study indicates that residual hydrocarbon content of marine mudstone is controlled by hydrocarbon generation and expulsion capabilities. The residual hydrocarbon and residual hydrocarbon generation potential of the simulated samples can compared with those of natural samples, which indicates the applicability of this method.