涠西南凹陷C洼油气成藏动力学过程与充注历史

DYNAMIC PROCESSES OF HYDROCARBON ACCUMULATION AND CHARGING HISTORY OF C SAG IN WEIXINAN DEPRESSION

以油气成藏体系及成藏动力学理论为指导,在成藏基本地质要素分析的基础上,综合各种地质、地球物理、地球化学等资料,采用盆地数值模拟与油气地质综合分析相结合的研究方法,分析了涠西南凹陷C洼的流体动力场特征,动态重建了油气成藏动力学过程,恢复了流体充注历史。结果表明:C洼地区具有较高的地温梯度,流沙港组二段发育有异常超压,古今流体势分布具有较大的继承性;该区沉积充填与构造沉降具幕式变化特征,流二段烃源岩目前处于成熟—高成熟阶段,具有较高的生排烃速率,主要生排烃过程发生于中新世以来;C洼地区经历多次油气充注过程,其中东北部以早期为主,西南部以晚期充注为主。

Taking account of the theories of petroleum accumulation system（PAS） and petroleum accumulation dynamics, based on the characteristics of the PAS, the characteristics of the fluid dynamic field in C sag within the Weixinan Depression have been analyzed. Geological, geophysical and geochemical data were used,and basin modeling technique and petroleum geological colligation research methods adopted in the research. As the results,the petroleum accumulation processes were studied dynamically, and the hydrocarbon charging history was renewed. It suggests that the C Sag has higher geothermal gradient in the Second Member of the Liushagang Formation, with a fluid potential inherited from history. The sedimentation and tectonic subsidence show an episodic manner. The source rock of the Second Member of the Liushagang Formation had entered the period of mid high maturity and had higher rate of hydrocarbon generation-expelling. The main episode of hydrocarbon generation-expelling happened after Miocene. It is believed that C Sag had passed several times of hydrocarbon charging. The Northeast part was charged earlier and the Southwest part later.