惠民凹陷辉绿岩席对下伏烃源岩热影响模型研究

勘探发现渤海湾盆地惠民凹陷存在与火成岩席有关的油气藏.基于两种不同的热传导模型,数值模拟了该凹陷内一个孤立的辉绿岩席以及围岩的热演化,定量分析了岩席对下伏围岩的热影响.模拟结果表明:围岩孔隙水的汽化作用是影响岩浆-围岩热传输的重要因素,在孔隙水汽化的情况下,围岩经历的峰值温度比简单热传导模型低100℃左右;在热接触变质形成的角岩带内出现镜质体反射率的异常低值,无法通过常用公式计算围岩经历的峰值温度,但依据爆炸古温度方法得到的结果与热传输模拟结果一致,反映了该区域曾经历了高温(大于450℃)和高压环境.

Modeling study of thermal influence of diabase sill in Huimin sag on its underlying organic rich host rocks

Gas and oil reservior related to igneous sills was found in Huimin sag,Bohai bay by exploration.The thermal evolution of an isolated intrusive diabase sill and its host rocks in this sag was numerically simulated based on two types of heat conduction models.Thermal effect of this sill on the underlying host rocks was quantitatively analyzed.Simulation results indicate that pore-water vaporization is an important factor influencing the heat transfer of intrusive magma into host rocks.In the case of pore-water volatilization,the computed peak temperature of host rocks is as high as 100 ℃,lower compared with the simple heat conduction model.Anomalously low vitrinite reflectances occur in hornfels zone formed by contact metamorphism.Therefore,they can not be converted into the peak temperature based on some usual computational formulas.However,the converted peak temperature using bomb paleothermometer matches well with the prediction of one of heat conduction models.It is shown that the hornfels zone once experienced a high-temperature(above 450 ℃) and high-pressure environment.