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Abstract Bottom hole buildup pressures on three Wyoming pumping wells have been determined based on liquid level in the annulus as determined from a computerized acoustic device. These buildup data correspond to a naturally fractured reservoir which produces oil, gas and water. Basic formulations and three case histories are presented:The case of a well with after flow effects where the buildup data are properly matched using type curves for dual-porosity systems with restricted (pseudo steady state) interporosity flow and the pressure derivative.The case of a stimulated well in a naturally fractured reservoir. In this situation a conventional log-log crossplot of delta p vs. time results in two parallel straight lines with slopes equal to 0.5. Separation between the two lines allows calculation of the storativity ratio, omega.The case of a well in a layered naturally fractured reservoir with variable afterflow effects. In this case a log-log plot of delta p vs. time shows two parallel straight lines with slopes equal to 1.0. A good match of the data is obtained with a dual-porosity model and the pressure derivative starting at the second 1.0 slope straight line. Acquisition of the raw data, conversion into bottom hole buildup pressures, and analysis utilizing dual-porosity models are presented in detail. It is concluded that pumping wells in naturally fractured reservoirs can be properly evaluated when all phases flowing are taken into account. The same procedure and formulations presented in this work can be utilized for analysis of conventional single-porosity reservoirs by making Warren and Root's omega equal to 1.0. DESCRIPTION OF EQUIPMENT The Automatic Acoustic Bottomhole Pressure system determines the depth to the liquid level, and measures and records the casinghead pressure in a well, unattended. The frequency of data point collection may be specified by the operator. The equipment consists of an electronic package, a wellhead assembly, interconnecting cables, a 12 volt battery, and a small gas supply container. P. 577^