西湖凹陷中—下始新统宝石组油气地质与勘探潜力

PETROLEUM GEOLOGIC CHARACTERISTICS AND EXPLORATION POTENTIAL OF MIDDLE-LOWER EOCENE BAOSHI FORMATION IN THE XIHU SAG

西湖凹陷是东海陆架盆地油气勘探潜力最好的凹陷之一。通过西湖凹陷宝石一井中—下始新统宝石组井震资料 ,厘定了影响油气资源计算结果较大的关键参数 ,如烃源岩厚度、有机质油气产率、排聚系数等 ;建立了构造、沉积、孔隙度与油气生、运、聚模型 ,编绘了西湖凹陷宝石组生油岩厚度图、有机碳、Ro、生油气强度等值线图 ;采用BASIMS 4 5盆地综合模拟系统重现了西湖凹陷宝石组的地史、热史、生烃史、排烃史和运聚史 ,分析了宝石组空间展布特征与生、储、盖、圈、运、保等地质条件 ,提出并建立了宝石组含油气系统。利用多种方法定量计算的宝石组生烃量和资源量与西湖凹陷已证实的主力烃源岩系平湖组相似 ,认为宝石组是西湖凹陷又一重要烃源岩及油气勘探目的层系 。

The Xihu sag is one of the best oil potential basins in the East China Sea continental shelf. On the basis of logging and seismic data from Baoshi-1 well in the Xihu sag, key parameters of the middle-lower Eocene Baoshi Formation that can influence calculation of the hydrocarbon resources (such as thickness of the hydrocarbon source rock, production ratio of organic oil and gas, and discharge-accumulation coefficients) were collated and stipulated, models of structures, sedimentation, porosity and generation, migration and accumulation of hydrocarbon were established, and isopleths of thickness of source rock, organic carbon, Ro, and oil-producing strength of the Baoshi Formation were mapped. Synthetic basin simulation system of BASIMS 4.5 was used to reconstruct the histories of geology, thermodynamics, hydrocarbon generation, hydrocarbon discharge, migration and accumulation of the Baoshi Formation and to analyze the space distribution of the Formation and its geologic conditions such as oil generation, reservoir, capping, trapping, migration, and conservation. And on this basis, oil-bearing systems of the Formation were pointed out and set up. The hydrocarbon amount and resources of the Baoshi Formation quantitatively calculated using various methods are similar to those of the Pinghu Formation, a proven principal hydrocarbon source rock series in the Xihu sag. Therefore, the Baoshi Formation is considered another important hydrocarbon source system and target for exploration due to its great hydrocarbon potential.