DERIV: A Computer Program for Calculating Pressure Derivatives for Use in Hydraulic Test Analysis

TLDR

The derivative of pressure with respect to the natural logarithm of time improves diagnostic and quantitative analysis of slug and constant‑rate pumping tests by being highly sensitive to small pressure changes, enabling detection of wellbore storage, boundaries, and radial flow conditions. DERIV converts slug and pumping test data to derivative format, smoothing noisy data, correcting end‑effects, and allowing conversion of slug data to equivalent pumping responses. Test examples illustrate that pressure‑derivative analysis enhances the diagnostic and quantitative assessment of slug and pumping tests.

Abstract

Abstract Hydrologie test analysis based on the derivative of pressure (i.e., rate of pressure change) with respect to the natural logarithm of time has been shown to significantly improve the diagnostic and quantitative analysis of slug and constant‐rate pumping tests. The improvement in test analysis is attributed to the sensitivity of the derivative to small variations in the pressure change that occurs during testing, which would otherwise be less obvious with standard pressure change versus time analysis. The sensitivity of the pressure derivative to pressure change facilitates its use in identifying the effects of wellbore storage, boundaries, and establishment of radial flow conditions on the test. DERIV is a program for converting slug and pumping test data and associated type curves to derivative format. The program has features that permit the smoothing of noisy test data, accounts for pressure derivative end‐effects, and can be used to convert slug test data to equivalent pumping test responses. Test examples that demonstrate the use of pressure derivatives also are provided.