New method evaluates efficiency of wellbore stimulation operations

A new technique has been developed for analyzing the bottom hole pressure at constant flow rate drawdown well tests. The method presented in this article enables calculation of the skin factor for stimulated oil wells. As a consequence of drilling and completion operations, most wells have reduced permeability near the borehole. Deposition of scales in the pores greatly reduces the permeability of formations around the well bore. This results in pressure loss through the skin and a corresponding reduction in well productivity. A well with a negative value of the skin requires a much smaller pressure drop in comparison with a well with a positive skin factor to maintain a constant fluid flow rate. the reservoir is a homogeneous and isotropic porous medium of uniform thickness, the porosity and permeability are constant, the fluid is small and has constant compressibility, constant fluid viscosity, small pressure gradients, negligible gravity forces, and laminar flow in the reservoir and the Darcy law can be applied.