Fa. Spane et Sk. Wurstner, DERIV - A COMPUTER-PROGRAM FOR CALCULATING PRESSURE DERIVATIVES FOR USE IN HYDRAULIC TEST ANALYSIS, Ground water, 31(5), 1993, pp. 814-822
Hydrologic test analysis based on the derivative of pressure (i.e., ra
te of pressure change) with respect to the natural logarithm of time h
as 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 sm
all variations in the pressure change that occurs during testing, whic
h 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 sto
rage, boundaries, and establishment of radial flow conditions on the t
est. 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 de
rivative end-effects, and can be used to convert slug test data to equ
ivalent pumping test responses. Test examples that demonstrate the use
of pressure derivatives also are provided.