Abstract

Reservoir-pressure data are needed as input for a variety of exploration, drilling, and completion activities. Unfortunately, pressure data are not public domain in many areas and so inefficiencies caused by suboptimal completion design, acreage acquisition, or production strategies can weaken financial returns. This problem is perhaps most acute in unconventional plays where ultra-low permeabilities prevent common pressure detection methods (e.g., mud weights) from providing reliable information. In this paper we present a method to rapidly mine publicly available well-test data and create pressure maps for reservoirs of interest. We illustrate the methods and results for an area of the South Texas Eagle Ford play. Input for our mapping comes from data (initial shut-in pressure, fluid density, vertical depth to the formation, and temperature) submitted to the state of Texas as part of the mandatory reporting requirements for gas wells (G–1 Forms) and oil wells (W–2 Forms) retrieved from the State of Texas Railroad Commission (RRC) website. The G–1 data can be converted to a bottom-hole pressure using an adaptation of the standard ρgh formula. Pressure estimation from W–2 data is less straightforward but pressures predicted from both data sources form a continuous trend that increases with depth. Despite the nature of the approximations and potential errors in our method, we demonstrate that, in agreement with published data, it shows the distribution of overpressures reasonably well for the Eagle Ford in our study area. We interpret the results to indicate that overpressures in that formation are primarily due to the thermal cracking of oil to gas. For many purposes, the ability to make quickly and inexpensively map pressures from public-domain data will more than compensate for any lack of precision in the pressure predictions at a specific well location.