Simulation of Prudhoe Bay Field Interference Test

Abstract

ABSTRACT An improved reservoir description of a Prudhoe Bay field water injectivity test site was obtained by simultaneously history-matching interference, pressure buildup and production history data with a black oil simulator. Water is currently being injected in a Sadlerochit reservoir inverted, five-spot pattern on the east side of the field. Pressure data were obtained prior to starting water injection. Interference testing was conducted by successively shutting in and producing each of the four corner wells, which are field production wells, and observing the pressure response at the water injection well in the center of the pattern. Pressure changes, varying from 2 to 8 psi, were measured with a downhole, high-sensitivity, quartz-crystal pressure transducer. While small, the pressure changes were measurable because two major shale complexes exist between the test interval and the large Prudhoe Bay field gas cap overlying the test area. Well spacing varied from 1600 to 2400 feet. Pressure buildup data were recorded for all five wells. A consistent reservoir description was developed from geological and engineering data. Interference and production history data were history-matched with an XYZ simulator and pressure buildup data were modeled with an RZ simulator. The upper shale complex is sealing, while the middle shale complex, lying immediately above the observation well perforations, allows some vertical communication. Type-curve matching the interference test gave much greater krokh/μ values for the tested interval than the XYZ history match. This occurred primarily because the interference test actually investigated zones above the tested interval.