致密砂岩气藏储层孔喉中气体分子运动特征

气藏储层岩石孔喉细小，连通关系极其复杂，研究气体分子在其中的运动特征对于气藏开发工程具有重要意义。通过气体分子运动、多孔介质孔喉特征和实验测试分析，对这一问题进行了研究，结果表明：低渗致密储层岩石孔喉中，气体分子运动表现出黏性流和扩散流两种形态；当地层压力较高时，气体分子平均自由程远远小于岩石孔喉直径，表现出黏性流，对气井产能贡献大；当地层压力较低时，气体分子平均自由程接近甚至大于岩石孔喉直径，表现出扩散流，对气井产能贡献小。在气藏开发过程中，针对渗流场中某一特定位置，气体需要特定能量才能产生有效流动，这种使气体产生有效运动的能量即为气体渗流启动压力。采用了两种实验方法对这一参数进行了测试，一种是经典的流量–压差方法；一种是气藏衰竭开采物理模拟实验方法；对该参数取得了一定程度认识。

The Molecular Motion of Natural Gas in the Pore and Throat of Tight Sand Rock

As the pore and throat of tight sand rock are very thin and connection relation is especially complex，studying the molecular motion of natural gas is very important for gas reservoir exploitation. So we did many experimental tests and get some useful results which show that there are two kind of shapes for gas flow in tight sand rock. Under high reservoir pressure， the gas molecular mean free path is much smaller than the pore diameter so it is viscous flow and is good for gas production. Under low reservoir pressure，the gas molecular mean free path is close to or even bigger than the pore diameter，and it is diffusive flow and is bad for gas production. The gas in the vadose region can flow effectively only with enough energy. The energy is the kickoff pressure that make gas flow. The kickoff pressure is different in different position，and there is a function between the kickoff pressure and the vadose region. Two experimental methods have been used to test the function.