L00311 Gas Well Test Analysis under Water-Drive Conditions

For some 35 years groundwater hydrologists, and natural gas and oil reservoir engineers have studied the pressure-time response of a well to a change in production rate. Analysis of this sort of data can lead to information on well and reservoir character not available from any other current method. Examples include need for well stimulation, results of well stimulation (length of fractures, etc.), average in-place permeability, formation and wellbore storage, and presence of flow barriers and drainage limits, to list just a few items. But well test analysis for reservoirs which contact active water has been studied only in a limited way. Modern gas storage in aquifers and old gas or oil reservoirs, and conventional gas and oil reservoir studies require this information. This monograph presents the results of a two-year study of water-drive well test analysis.

Several computer programs capable of calculating the behavior of multiwell water-drive reservoirs were prepared. The programs superposed continuous line-source wells in infinite arrays to generate the unsteady pressure fields resulting from production of one or more wells in ideal rectangular reservoirs. Both producing pressures and shut-in pressures were examined to determine generally useful interpretative rules for reservoir analysis. In addition, it was possible to compute and plot the locations of stream lines moving from water interfaces to each well. The dividing stream line between well pairs was studied carefully to determine factors influencing the drainage areas of water-drive wells.