Paper: Basic Derivative Diagnostics

Over the last decade the use of the pressure derivative as a diagnostic tool in pressure transient analysis has grown immensely. The modern well test analyst turns to the derivative log-log plot almost exclusively to formulate a first opinion on well test behavior. The pressure derivative essentially allows the analyst a magnified view of the distinctive pressure behavior associated with various wellbore and reservoir phenomena. This paper utilizes both real and simulated pressure transient data to illustrate common derivative responses due to selected wellbore and near-wellbore effects, reservoir types, and boundary conditions. Definitions of common well test analysis terminology are included. The information presented should allow individuals who are involved in well testing, but not necessarily confident in test analysis, to qualitatively comment on test results.