A Potentiometric Study of the Effects of Mobility Ratio on Reservoir Flow Patterns

Abstract

Abstract A potentiometric model technique is presented for determining the a real sweep efficiency of a five-spot well pattern, at and beyond breakthrough. A sharp interface between displaced and displacing fluids is assumed. Although the prototype system is referred to as a water flood operation, obvious changes in the notation and computations will adapt the results to other displacement processes. The results of the study include the following.Areal sweep efficiencies for a five-spot well pattern, at and beyond breakthrough, for mobility ratios (displacing to displaced fluid) of 4:1, 2:1, 1:1 and 1:4.Extension of potentiometric analysis to the investigation of the areal sweep-efficiency beyond breakthrough in a five-spot pattern by the application of conformal mapping and conductive-solid models.The use of layers of conductive fabric in representing mobility ratio changes in potentiometric models.The development of a probe mechanism for probing conductive solids. The results obtained by conductive-cloth models agree with earlier areal sweep efficiencies at breakthrough obtained by Aronofsky and Ramey on the potentiometric analyzer using electrolytic-tank models. Results beyond breakthrough differ from those obtained by the X-Ray Shadowgraph technique. Data from this study show that, for mobility ratios greater than one, water cut rises rapidly as fluid is produced after breakthrough. However, for mobility ratios smaller than one, a large increase in area swept resulted with only a small increase in water cut. Introduction In calculating reservoir performance of waterflooding operations and other fluid-injection programs, it is necessary to estimate the areal sweep efficiency before and after injected-fluid breakthrough into production wells. Influence of mobility ratio on oil-production history, before and after breakthrough for a five-spot well pattern, has been studied by X-Ray Shadowgraph techniques and by gelatin models. In none of these investigations was the transition zone controlled experimentally.