Pressure-transient analysis of oil wells after a short-term disturbance of a formation

This paper investigates a numerical model of non-stationary fluid filtration in the vertical well vicinity after a short-term disturbance of a formation taking into account the skin effect and wellbore storage effect. The numerical solution to the problem is compared with an approximate solution to the Muskat problem, which is obtained by the method of sequentially changing stationary states. The influence of formation permeability and skin factor on the bottomhole pressure build-up is studied. The wellbore storage effect has been shown to completely mask indications of the bottomhole zone. For low-permeability formations, the pressure build-up process is time-consuming. Hence, the flow-over techniques should be used to investigate them.
A method for interpreting pressure-transient data based on the theory of solving ill-posed inverse problems is proposed. The method determines the formation permeability, skin factor, and formation pressure values using the measured bottomhole pressure profile after a short-term disturbance of the formation. Estimates of the well productivity index and formation pressure are in good agreement with those obtained using the integral and Muskat methods. In contrast to the methods based on the Muskat solution, the proposed method allows the assessment of the skin factor.