Displacement Of Gas From Porous Media By Water
Authors: Legatski Max W. , Katz Donald L. , Tek M. Rasin , Gorring Robert L. , Nielsen R.L. 
Published: December 2007

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This paper is to be presented at the 39th Annual Fall Meeting to be held in Houston, Tex., on Oct. 11–14, 1964, and is considered property of the Society of Petroleum Engineers. Permission to publish is hereby restricted to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of the Journal of Petroleum Engineers or the Executive Secretary. Such abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in JOURNAL OF PETROLEUM TECHNOLOGY or SOCIETY OF PETROLEUM ENGINEERS JOURNAL is granted on request, providing proper credit is given that publication and the original presentation of the paper.

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This paper examines the knowledge available on predicting the residual gas left behind an advancing water front in a water-drive producing gas reservoir or gas storage reservoir. It is concluded that measurements of residual gas should be made in the laboratory on cores by water flooding since only a general relationship between residual gas and porosity was found. Calculations of saturation distribution can be made for water flooding of reservoir rock but such calculations require a knowledge of the residual gas saturation by imbibition and the saturation at zero gas permeability - alternate ways of noting the residual gas content.

Imbibition rate measurements are shown to provide a non-destructive method for scanning cores for inhomogeneities.

Introduction

The determination of the residual gas saturation behind a water table rising into a gas zone of known characteristics has application in estimating the recovery of gas from water drive reservoirs and in understanding the results of water movement in gas storage operations. Geffen, et al. in 1952 made an experimental study of gas displacement by water. The research of Gorring and Nielsen was directed toward a further understanding of this problem. This paper summarizes the current knowledge from the literature and presents the recent studies on the process by which gas is entrapped behind an encroaching water front.

Consider the problems faced by the engineer dealing with a gas reservoir subject to water drive or aquifer gas storage reservoir. What is the gas-water saturation distribution at the gas-water interface and what will be the effectiveness of the water in displacing gas when gas is produced? What information should be procured in order that the best possible determination can be made of the residual gas which remains behind the advancing water front?

During the development of aquifer gas storage reservoirs, the drainage of water by gravity from upper zones is an important factor in creating the gas bubble.