A Study of the Effect of Gravity on Oil Recovery by Water Flooding
Authors: Talash Alvin W. , Crawford Paul B. 
Published: December 2007

This paper was prepared for the 41st Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Dallas, Tex., Oct. 2–5, 1966. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.
Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
A laboratory investigation of the effects of gravity on oil recovery by water flooding is presented and the operational details of the centrifugal reservoir model used in this study are described.
The effect of gravity on oil recovery was found to be an important factor in the early production history of a water flood. It was shown that increasing the value of g at which flooding took place resulted in earlier water breakthrough into the producing well and consequently lower recoveries. After two or more pore volumes of water had been injected, however, the total oil recovery was found to be substantially the same for all values of g at which the sand was flooded.

Introduction
The effect of gravity on oil recovery by water flooding has not been studied as extensively in the past as most other variables. In fact, a review of the literature reveals that the study of the effects of gravity has been limited for the most part to reservoirs producing by bottom water drive and by gravity damage. Several investigators have used a centrifuge to displace oil and water from very short cores.
Henley and others studied performance of systems producing entirely by bottom-water encroachment. The effects of well spacing, fluid mobilities, rates of production, capillary and gravity forces, well penetration and well completion techniques on the oil recovery performance were investigated. Two uniform unconsolidated sand-pack models were used. The performance was determined by material balance and by observation of the encroachment of dyed fluids into the models. These investigators found that their results agreed with those obtained mathematically when the conditions previously assumed in theoretical studies were matched. They concluded that the effects of gravity must be considered in estimating oil recovery because they can be a major influence on performance.
Hassler and Brunner were among the first to recognize the importance of the centrifuge in studying gravity drainage. They found that the average saturation of a core can be determined at different accelerations to which it is subjected by collecting and measuring the liquid that leaves the core. In this way-they were able to determine the relation between capillary pressure and saturation for a core.