Wellbore storage removal in pressure transient analysis for gas wells

Abstract

Wellbore storage (WBS) occurs due to fluid loading/unloading in the wellbore, when a well starts production or is shut-in. This phenomenon creates variable sandface rate and time lag between the surface production rate and the stable sandface rate. Wellbore storage effects can sometimes conceal important information and complicate well test analysis and interpretation. In well tests that suffer from long WBS, removal of WBS effects can usually recover important features in the reservoir signal and lead to significant improvement in identifying the reservoir model and calculating reservoir parameters. Until recently, WBS removal relied on direct deconvolution techniques that require accurate well test data. Presence of noise in the pressure and rate data usually makes direct deconvolution methods unstable. Well test pressure and rate data usually suffer from some noise, and therefore, application of direct deconvolution methods may not work.