四川盆地侏罗系致密砂岩弹性特征及岩石物理建模

近年来围绕四川盆地侏罗系陆相致密砂岩已取得了勘探突破，其中川中—川西过渡带具备形成大气田的地质条件，但对该套致密砂岩弹性性质变化规律的研究还较少，致使利用地震方法进行"甜点"储层预测的精度不高.本文利用四川盆地侏罗系沙溪庙组32块样品开展了系统的声学测量，在此基础上，分析了样品弹性性质的变化规律.结合X射线衍射矿物组分分析、扫描电镜、铸体薄片和岩石薄片特征确定了不同成岩作用对岩石储集性能的影响.研究结果表明，研究区致密砂岩储层表现为孔隙型储层，受差异性成岩作用影响，黏土含量、钙质含量和硅质含量的差异以及它们分布特征之间的差异对岩石弹性性质造成了很大的影响.在研究区对岩石物性及弹性性质有明显影响的成岩作用包括早期的钙质胶结作用、压实作用和溶蚀作用，因此针对不同时期的成岩作用对岩石弹性及物性的影响，利用接触-胶结模型、微分等效模量模型和临界孔隙度校正的Hashin-Shtrikman上限模型建立了研究区致密砂岩的岩石物理模型.

Elastic characteristics and petrophysical modeling of the Jurassic tight sandstone in Sichuan Basin

In recent years, a breakthrough has been made in the hydrocarbon exploration of the Jurassic continental tight sandstone in Sichuan Basin. It has clarified that the transition zone between central and Western Sichuan has the geological conditions to form large-scale gas fields. However, there are few studies on the elastic properties of this set of tight sandstone, resulting in the low accuracy of "sweet spot" reservoir prediction using seismic methods. To solve this problem, this study uses 32 samples from the Jurassic Shaximiao Formation in the Sichuan Basin to conduct a systematic acoustic measurement, based on which the change pattern of seismic elastic properties of the samples are analyzed. The effects of different diagenesis on rock reservoir performance are determined by integrating X-ray diffraction mineral composition analysis, scanning electron microscopy, and thin section characteristics of castings and rocks. Results show that the tight sandstone reservoirs in the study area behave like a porous type, and is affected by differential diagenesis. The differences in clay, calcium and silica contents as well as their different distribution characteristics have a great impact on the elastic properties of rocks. The early calcitic cementation as well as the compaction and dissolution with intense plastic clastic particles has significant impact on the rock porosities and seismic elastic properties in the study area. Therefore, the petrophysial model of the tight sandstone in the study area is established by using a contact-cementation model, differential equivalent modulus model and the Hashin-Shtrikman upper bounds for critical porosity correction, respectively.