Modeling wellbore pressure with application to multi-stage, acid-stimulation treatment

Abstract

Estimation of bottomhole pressure during a matrix-acidizing treatment provides the information needed to accurately determine the evolution of skin factor during and after the treatment. It could be a very complicated process, especially when compressible fluids, such as foams, are involved. Existing models for estimating bottomhole pressure during a matrix-acidizing treatment ignore the volume reduction of compressible fluids and its effect on the bottomhole pressure. This research developed a model that uses a unique solution to the mechanical energy balance equation, to calculate the bottomhole pressure from known surface measurements during foamed acid stimulation. The model was used to evaluate two stimulation treatments. Field examples are presented which illustrate the application of the model to optimize stimulation treatments. Properly accounting for the flow behavior and tracking the injected volume of the foam diverter used during the treatment resulted in more reliable and accurate bottomhole pressure profile.