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川中广安地区的致密含气砂岩储层具有分布广,丰度低的特点。采自该地区的砂岩样本孔隙度普遍偏低,孔隙连通性差。本文采用Mori-Tanaka模型分析致密砂岩样本的波速观测数据,基于理论与实验分析,给出了该地区砂岩骨架的物理模型。通过经验关系获取基质模量,将实验数据与Mori-Tanaka模型在不同孔隙形态时的预测值进行对比,结果显示实验数据与低纵横比的软孔模型比较接近。综合考虑基质模量和孔隙形态变化的影响,分析表明在矿物成分变化不大的情况下,样本的等效孔隙纵横比随孔隙度增加有上升的趋势。
The gas-tight sandstone reservoirs in Guangan area of central Sichuan have the characteristics of wide distribution and low abundance. Sandstone samples collected from this area generally have low porosity and poor pore connectivity. In this paper, the Mori-Tanaka model is used to analyze the velocity data of the tight sandstone samples. Based on the theoretical and experimental analysis, the physical model of the sandstone skeleton in this area is given. The matrix modulus was obtained through empirical relationship. The experimental data were compared with the predicted values of Mori-Tanaka model in different pore shapes. The experimental results show that the experimental data are close to those of low-aspect-ratio soft-hole model. Taking into account the influence of matrix modulus and pore morphology, the analysis shows that the equivalent pore aspect ratio of the sample tends to increase with the increase of porosity in the case of little change in mineral composition.