Effect of non-Darcy seepage on productivity of tight gas reservoir

Abstract

In the process of gas reservoir development, with the production of formation fluid, the effective overburden pressure on the rock skeleton of the reservoir increases, and the rock is deformed under compression, which changes the physical properties of the rock (porosity, permeability, etc.), especially the influence on permeability. Stress sensitivity and threshold pressure gradient are important factors for non-linear seepage in tight gas reservoirs. This paper establishes an empirical prediction model through experimental tests and uses numerical simulation to analyze the effects on productivity. The experimental results show that the relationship between stress sensitivity and permeability is exponential, and there is a strong hysteresis effect. The starting pressure gradient of gas presents a power function relationship with water saturation and permeability respectively, and an empirical relationship is established to predict the starting pressure gradient by comprehensively considering the influence of permeability and water saturation. The single well productivity simulation shows that: The effect of starting pressure gradient on gas well development is greater than stress sensitivity. When starting pressure gradient or stress sensitivity is taken into account, the formation average pressure increases relative to each other and the stable production period decreases obviously.