Abstract

On the basis of surface energetics of solid-liquid and liquid-liquid interaction, our present concepts of oil-wet reservoirs and present concepts of oil-wet reservoirs and conventional waterfloods are subject to serious limitations. The significant part played by electrolytes in wettability played by electrolytes in wettability alteration floods and by small amounts of impurities in surfactant floods are interpreted as evidence to support the view that electrokinetic and interfacial forces play an important, but not yet clear, role in oil recovery processes.

Introduction

It is well known that by present methods only a third or less of the petroleum originally present in the oil reservoir can be economically recovered. The development of new methods for producing all or part of the oil thus left behind in the ground will not only be a major contribution to conservation, but will also increase our oil reserves at a time when these are being depleted at a rapidly increasing rate. The only means by which this can be achieved is through improvements in our recovery methods with the aid of new technology. The prospects of developing such new technology are good, because much remains yet to be learned about the mechanism of oil recovery and the related area of multiphase flow through porous media. Much of our work in oil recovery porous media. Much of our work in oil recovery research has been empirical, so far, with a fundamental approach to the understanding of multiphase flow through porous media on the basis of surface chemistry principles shows promise of being far more fruitful. A promise of being far more fruitful. A beginning has already been made in this direction with initially encouraging results, but much more remains to be done. This paper proposes to point out some of the apparent inconsistencies in our thinking in some aspects of petroleum recovery research from the viewpoint of petroleum recovery research from the viewpoint of surface chemistry and the necessity of clearing them before progress can be made in this area.

DARCY'S LAW AND MULTIPHASE FLOW

The petroleum engineer is interested mainly in understanding the distribution and flow of oil, water and gas in an oil reservoir and using such knowledge to enhance oil recovery. The presence of more than one phase in a porous medium generates large areas of interfaces in addition to the enormous surface area of the porous medium itself. These solid-fluid and fluid-fluid interfaces are associated with forces which are determined by the chemical nature of the fluids and the porous medium. Though such a system teems with interfacial forces, our present description of the flow process, nearly completely ignores them. In applying Darcy's law to multiphase flow we consider only one rock property, the relative permeability, and only one fluid property, the viscosity. property, the viscosity.

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