Cybernetics, A New Method Proposed For Estimating Performance Of Water Driven Reservoirs

Abstract

Abstract Cybernetics has been under development for almost 50 years but only during the past 20 years has it evolved into a scientific approach to aid in the analysis of systems existing in the so-called "black box". Petroleum reservoirs are always in the black Petroleum reservoirs are always in the black box category in that the precise reservoir shape, rock and fluid physical properties are never really known even though the reservoir is produced to abandonment. Cybernetics has been applied to a water-drive reservoir near abandonment conditions. The cybernetic method was found to forecast the performance of this reservoir quite accurately when only a small fraction of the fluid had been produced. Cybernetics does not require detailed information such as rock porosity, permeability, areas, thickness, fluid porosity, permeability, areas, thickness, fluid compressibilities, etc., desired for the conventional influx calculation. Introduction In the past 30 years the science of petroleum reservoir engineering has emerged petroleum reservoir engineering has emerged as a well-defined and highly technical branch of petroleum engineering. Extensive investments in facilities and personnel for the recovery of oil and gas are now made routinely on the basis of reservoir performances predicted by reservoir engineering studies. Reservoir engineers and research investigators are pioneering and developing new techniques for pioneering and developing new techniques for improving recovery of oil and gas. Greater accuracy in reservoir performance calculations will bring the industry closer to the ultimate goal of obtaining the maximum efficiency in the exploitation of petroleum reservoirs. The van Everdingen and Hurst technique of estimating performance of water-drive reservoirs based on compressible flow theory has been presented in the literature as the most generally successful. However, their method applies to radial reservoirs surrounded by infinite or radial aquifers of constant rock and fluid properties. k complete knowledge of the properties of the reservoir and aquifer is desired for applying the technique. The method also requires knowledge of the pressures at the boundary of the reservoir and quifer. Average reservoir pressures are usually used when the boundary pressures are not known. In practice, besides incomplete knowledge of reservoir properties, there is uncertainty in the aquifer properties, which are generally estimated from wells drilled in the reservoir. On the other hand, there exists uncertainty in the reservoir pressure history. Thus, all of these factors combined contribute to make the van Everdingen and Hurst technique of limited value in many practical cases.