叠前反演在西湖凹陷致密砂岩储层“甜点”预测中的应用

Prestack elastic inversion for sweet-spot prediction in tight reservoirs in Xihu Sag

在西湖凹陷B构造,高孔渗的储层“甜点”是该区花港组成藏的主控因素之一,利用地震资料开展致密砂岩背景下的储层“甜点”预测是该区增产增效的重要措施。研究区内4口井的弹性参数全面筛选分析结果表明,对花港组砂岩最敏感的弹性参数是泊松比,对储层“甜点”最敏感的弹性参数是密度。在叠前道集优化处理的基础上,由叠前AVO三参数反演得到最敏感的弹性参数数据体(泊松比和密度数据),以此为基础开展定量解释并预测砂体及储层“甜点”的分布。通过与沉积相对比分析,预测的花港组砂体平面展布特征与沉积相相吻合,储层“甜点”的分布受沉积相带的控制作用明显。基于砂体及储层“甜点”预测结果,在花港组新增落实一系列构造岩性圈闭,累计面积为102.6km2,为该区提高储层“甜点”钻遇率、扩展隐蔽油气藏勘探提供了有力的生产支撑。

In structure B of the Xihu depression,the search for sweet spots in high porosity-permeability reservoirs in the Huagang Formation is a critical task.The prediction of sweet spots by seismic exploration can increase the production and efficiency of the exploitation significantly.Through a comprehensive analysis of the elastic parameters of four wells in the target area,it was found that Poisson's ratio and density are the most sensitive parameters for the identification of the Huagang Formation and the sweet spots,respectively.Through an optimized processing of prestack gathers based on a prestack amplitude versus offset three-parameter inversion,information on the aforementioned parameters was obtained.Then,quantitative interpretation and prediction of the distribution of sand bodies and sweet spots were carried out.It was found that the planar distribution patters of the sandstone in the Huagang Formation is consistent with that of sedimentary facies,which strongly controls the distribution of sweet spots.Based on this result,a series of structural lithologic traps were identified in the formation,which cover a total area of 102.6km2.It is concluded that the proposed method provides a base for improving the sweet-spot drilling rate and expanding the exploration of the subtle oil and gas reservoirs in this area.