致密砂岩气藏有效渗流评价——以苏里格东区为例

Seepage Availability Evaluation in Tight Sandstone Gas Reservoir:Taking the East Area of Sulige Gasfield as an Example

针对致密砂岩气藏渗流阻力大、储量难动用的问题,提出了用主流喉道半径、可动流体饱和度、启动压力梯度和应力敏感系数作为评价致密砂岩储层渗流能力的主要参数。渗透率小于0.1×10^(-3)μm^(2)的为Ⅰ类储层,主流喉道半径为纳米级别的孔喉空间,束缚水饱和度最高,启动压力梯度大于0.1 MPa/m,应力敏感系数大于0.09,在该类储层内难以形成有效渗流;渗透率大于0.1×10^(-3)μm^(2)的为Ⅱ类储层,主流喉道半径为亚微米级别的孔喉空间,可动流体饱和度大于35%,启动压力梯度小于0.1 MPa/m,应力敏感系数小于0.09,在该类储层内易形成有效渗流。最终基于渗透率、启动压力梯度和应力敏感系数,建立了研究区的渗流区域图版。

In view of the problems of large seepage resistance and difficult production of reserves in tight sandstone gas reservoir,it is proposed to use the main throat radius,movable fluid saturation,threshold pressure gradient and stress sensitivity coefficient as the main parameters to evaluate the seepage capacity of tight sandstone reservoir.The reservoir whose permeability is less than 0.1×10^(-3)μm^(2) belongs to class I reservoir.The radius of mainstream throat is nanometer,the irreducible water saturation is the highest,the threshold pressure gradient is greater than 0.1 MPa/m,and the stress sensitivity coefficient is greater than 0.09.It is difficult to form effective seepage in this kind of reservoir.The reservoir whose permeability is greater than 0.1×10^(-3)μm^(2) belongs to classⅡreservoir.The radius of the mainstream throat is sub-micron,the movable fluid saturation is greater than 35%,the threshold pressure gradient is less than 0.1 MPa/m,and the stress sensitivity coefficient is less than 0.09.It is easy to form effective seepage in this kind of reservoir.Finally,the seepage chart of the study area is established based on permeability,threshold pressure gradient and stress sensitivity coefficient.