Limit Drainage Radius for Different Types of Wells in a Shale Reservoir

Abstract

The low porosity and permeability of shale deposits is due to the complex structure of the pores. Due to the threshold pressure gradient, fluid seepage in low-permeable reservoirs does not obey Darcy’s law. Horizontal well drilling and fracturing treatment are effective methods of developing lowpermeable reservoirs, since these methods increase the well drainage area. In the present study a mathematical model of gas flow in different types of wells is obtained on the basis of seepage theory. The pressure distribution and relationship between the threshold pressure gradient and limit well spacing are obtained using the point-source function and Laplace transforms. The limit well spacing increases with decreasing threshold pressure gradient. The method is of importance for determining an appropriate spacing between different combinations of different types of wells in the development of shale gas.