莺歌海盆地地层压力特征及其石油地质意义

利用地震速度、声波测井和中途测试等资料 ,研究了莺歌海盆地地层压力的特征及分布 ,分析了早期自源超压及其伴生的滞烃作用和它们对油气初次运移的影响。莺歌海盆地强烈超压主要是压实不均衡的结果 ,超压的分布受沉降 -沉积速率和盆地充填岩性的控制 ,超压界面明显起伏 ;超压层段异常低的热解峰温和高生成指数反映了超压的滞烃作用 ,超压及其滞烃作用是有机质热演化异常的主要原因 ,也是决定盆地天然气成藏过程的重要因素。

CHARACTERISTICS OF GEOPRESSURE IN YINGGEHAI BASIN AND ITS SIGNIFICANCE IN PETROLEUM GEOLOGY

This paper has studied characteristics and distribution of overpressure in Yinggehai Basin using seismic velocity,well logs and DST data,and analysed early self sourced overpressure and its retention effect on hydrocarbon expulsion.The intense overpressure in the basin is produced mainly by an unbalanced compaction,and its distribution is obviously controlled by subsidence/sedimentation rates and basin fill lithology,with the top of overpressure undulating strongly.The overpressured intervals generally have abnormally low Rock Eval T max and high production index,reflecting a retention of generated fluids including hydrocarbons.Overpressure and its retention effect on hydrocarbon expulsion are the main cause of abnormal organic matter maturation,and the important factors controlling gas accumulation in the basin.