Abstract: The reservoir sandstone core samples from W3 formation of WXS depression were measured for density, porosity and acoustic velocity under pressure and temperature of formation condition in laboratory. A method based on core result and rock physics model was proposed to produce an advanced AVO response template capably showing integrated information of reservoir character (porosity and thickness) and saturation fluid. This method used the sandstone porosity as the key factor to construct the rock physics model based on the linear relationships of porosity-density and porosity-impedances in dry condition. Using Gassmann fluid replacement technique, the forwarding modeling results of AVO responses for different reservoir conditions were obtained, and then the AVO template was made by analyzing the distribution and shape characteristics of AVO clusters on intercept-gradient crossplots. Through this template the porosity, thickness and fluid type of reservoir could be estimated directly, and thus the non-uniqueness of AVO inversion due to complex geology was greatly reduced and the accuracy of direct hydrocarbon prediction could also be improved.

Key words: formation condition, sandstone reservoir, AVO template, rock physics model, forwarding analysis

摘要： 在实验室对WXS凹陷的W3地层岩芯样品进行了地层压力和温度条件下的密度、孔隙度和声波速度测试, 基于岩石物理模型提出一种集成目标储层孔隙度、厚度和饱和流体信息的AVO响应模板制作方法。该方法以砂岩孔隙度与干燥状态下的密度和纵、横波阻抗的线性关系为核心, 利用Gassmann流体替换技术构建岩石物理模型, 通过正演模拟获得不同储层条件下的AVO响应在截距-斜率交会图上的分布位置和形态特征, 最终制作出能综合反映储层性质(孔隙度和层厚)和饱和流体性质的AVO响应模板。通过该模板可以直观地预测目标储层的孔隙度和厚度范围及所含流体(水、油、气)情况, 从而降低了与地质因素密切相关的AVO反演多解性, 提高了直接进行烃类预测的准确性。

关键词: 地层条件, 砂岩储层, AVO模板, 岩石物理模型, 正演分析