致密砂岩储层中气体渗流规律实验研究

为了揭示苏里格气田致密砂岩中气体渗流规律,采用物理模拟方法测试了不同含水条件下不同气驱压力时气体流量,在考虑气体偏差因子、黏度和压力关系基础上,研究了压力、气体偏差因子、黏度与流量的关系。结果表明:致密气藏中气体需要突破一定门槛压力,才能在砂岩孔隙内产生有效流动,岩心渗透率越低、含水饱和度越高,门槛压力越大,当气驱压力突破门槛压力后,气体在砂岩中渗流时表现出黏性流特征;随气驱压力增加,压力/气体偏差因子/黏度与流量的关系会由非线性关系转变为线性关系;岩心渗透率≥1×10~(-3)μm~2时,气体以线性渗流为主;岩心渗透率为(0.1～1)×10~(-3)μm~2时,当气驱压差1 MPa,气体以线性渗流为主;岩心渗透率≤0.1×10~(-3)μm~2时,当含水饱和度为20%,出现气相渗流门槛,当气驱压差3 MPa,气体才能达到线性渗流;渗透率0.345×10~(-3)μm~2时,随渗透率增加,配产界限值先快速增加,之后增速变缓;在渗透率相同条件下,储层含气饱和度愈高,则配产界限值愈高。

EXPERIMENTAL STUDY ON THE SEEPAGE LAWS OF THE GAS IN TIGHT SANDSTONE RESERVOIRS

In order to reveal the seepage laws of the gas in the tight sandstone of Sulige Gasfield,the gas flows Qg under the different driving pressures and watercuts were tested by the physical simulation experiment.The relationships between the p/Z/μ and Qg were studied on the bases of the gas deviation factor,viscosity and pressure.The achievements show that the gas must breakthrough the starting pressure to effectively flow in the sandstone pores of the tight gas reservoir.The lower the core permeability is and the higher the water saturation is,the higher the start ing pressure will be.When the driving pressure breaking through the starting pressure,the flow of the gas in the sandstone becomes viscous;with the increase of the driving pressure,the relationships between p/Z/μ and Qg transform from nonlinear to linear;when the core permeability is bigger or equal to 1.0×10-3μm2,the linear flow is the principal flow;when the core permeability is in the range of (0.1-1.0) × 10-3μm2 and the driving pressure is bigger than 1.0 MPa,the linear flow is the main flow;when the core permeability is smaller or equal to 0.1 × 10-3 μm2,the water saturation reaches 20％,the gas seepage threshold emerges,the linear flow emerges when the driving pressure is bigger than 3.0 MPa;when the permeability is smaller than 0.345×10-3μm2,with the increase of the permeability,the limitation of the allocation production increases rapidly and then the amplification becomes slow;under the condition of the same permeability,the higher the gas saturation in the reservoir is,the higher the limitation value will be.