论文详情
鄂尔多斯盆地东缘LX地区二叠系石盒子组发育河流相致密砂岩储层,具有低孔、低渗且非均质性强的特点,优选“甜点”是取得产能突破的关键。勘探结果表明,基于叠后振幅属性预测气层存在多解性。对比分析井旁地震道集发现,气层和干层的叠前AVO响应特征存在差异,且与储层参数具有一定相关性。为此,从研究区沉积模式入手,建立泥砂泥3层介质模型,通过开展变参数AVO正演模拟,分析孔隙度、厚度以及含气饱和度变化对截距属性(P)和梯度属性(G)的影响。模拟结果表明,孔隙度和厚度是决定AVO响应特征的主控因素。通过构建AVO定量解释模版,并拟合截距和梯度属性与孔隙度和厚度之间的数学函数关系,实现孔隙度和厚度的半定量定量预测。应用结果表明,“甜点”预测结果与已钻井吻合率较高,孔隙度和厚度定量预测误差控制在20%以内,依据预测结果部署的新钻井L6井获得了高产天然气,取得了良好的应用效果。
The LX area is located in the northern part of the JinXi fold belt,at the eastern margin of the Ordos Basin.Fluvial tight sandstone reservoirs are developed in the Permian Shihezi Formation in the LX area,and are characterized by low porosity,low permeability,and strong heterogeneity.Identifying the sweet spots with high porosity and large thickness is the key to achieve high production.The post-stack amplitude attribute,however,cannot distinguish gas sandstones from dry sandstones,because both of them exhibit strong amplitude.By analyzing the pre-stack CRP gather in areas next to the wells,the AVO responses of gas and dry sandstones are different,and are closely related to the rock properties.In this study,a three-layer model was built based on the analysis of the regional sedimentary environment.A series of AVO synthetic modeling trials were carried out to analyze the effects of porosity,thickness,and gas saturation on the intercept and the gradient parameter.The modeling results indicated that porosity and thickness are the key factors influencing the AVO responses.Finally,an AVO quantitative interpretation template was established,and the function between porosity and thickness,with its intercept and gradient,was derived.This method was applied in the LX area,for which the prediction results were well consistent with the drilling data,with an error in terms of predicted porosity and thickness smaller than 20%.Based on the prediction results,the L6 well was drilled and high production was achieved.
中海石油(中国)有限公司科技项目(YXKY-2019-ZY-04)资助。