基于CT扫描的致密砂岩渗流特征及应力敏感性研究

认识低渗透储层的渗流特征对油气开采和储层改造具有重要意义。为此，研究利用微CT扫描技术对致密砂岩岩样进行扫描，据此建立了能够精细刻画岩样的微观模型，运用COMSOL模拟了流体在岩石孔隙中的渗流特征，研究了致密砂岩的渗流特征及应力敏感性。研究结果表明:流体入口和出口间压差固定时，岩石的渗透率保持不变，与入口出口压力的具体数值无关；不同方向的岩石模型计算渗透率处在同一数量级但有微小差异；在侧向压力作用下，渗流路径变窄，通过渗流路径的整体速度下降，渗透率下降，但在孔隙相对较大的地方，由于路径变窄，流体速度较未加压力前略有上升。 

STUDY ON THE STRESS SENSITIVITY AND SEEPAGE CHARACTERISTICS OF TIGHT SANDSTONE BASED ON CT SCANNING

The understanding of seepage characteristics of low-permeable reservoir is of great significant for oil and gas production and reservoir reconstruction. Therefore, the micro CT scanning technology was used to scan the tight sandstone samples so as to establish a microscopic model that can accurately reflect real structures of rock samples. COMSOL was used to simulate the seepage characteristics of fluid in the pores of rocks, and the seepage characteristics and stress sensitivity of tight sandstone were studied. The results show that:When the pressure difference between the inlet and outlet of the fluid is a constant value, the rock permeability remains unchanged and has no correlation with the specific value of the inlet and outlet pressure. The calculated permeability of rock models in different directions is in the same order of magnitude but slightly different. Under the action of lateral pressure, the flow path narrows, and the fluid overall velocity through the seepage path decreases, which leads to the decrease of permeability. However, where the pore is relatively large, the velocity rises slightly compared with that before the pressure is applied due to the narrowing of the path.