Sweep Efficiency in Miscible Displacement in A Five-Spot Pattern
Authors: Ali S.M. Farouq , Stahl C.D. 
Published: December 2007

This paper was prepared for the SPE Rocky Mountain Regional Meeting to be held in Casper, Wyo., May 22–23, 1967. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copies. The abstract should contain conspicuous acknowledgement 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 simple technique for calculating the sweep efficiency in miscible displacement in a five-spot pattern is described. The technique utilizes two simplifying approaches. The first of these consists in the division of a flow pattern into channels, bounded by streamlines, and the subsequent division of channels into cells of equal volume, as proposed by Higgins and Leighton, for waterflood calculations. The second feature is the use of a "cell model" for the simulation of miscible or alcohol displacement. The combination was used for predicting the sweep efficiency, fluid production behavior and the distribution of the remaining fluid in the flow pattern. The computational scheme takes into account variations in the viscosities of multicomponent mixtures with composition and the equilibrium phase behavior of the fluid system involved.
The computed results were compared with the experimental data obtained in the present investigation, as well as with the experimental and field data reported by various investigators. The agreement was good, thus indicating that the assumptions of constant boundary flow channels, and negligible material transport across the channels constitute good approximations to the physical situation.
The computational technique used is equally applicable to various other flow patterns. Moreover, it permits the inclusion of complicating features, such as spatial variation of formational permeability.

Introduction
In the past, considerable attention has been directed toward miscible displacement as a technique for increasing oil recovery. To a lesser extent, alcohol flooding or the alcohol-slug process has been the subject of several investigations, as a process for recovering oil from waterflooded reservoirs. While in miscible displacement basically two miscible fluids are involved, in alcohol flooding three fluids are present, the displacing fluid being miscible with the oil and water in place. The displacing fluid can consist of an alcohol or other solvent. The process involving the use of an alcohol has been found to be economically unattractive. However, certain variations of the basic process show a great deal of promise for recovering oil from depleted reservoirs. Therefore, the mechanism of the simpler case of alcohol flooding is of considerable interest both from theoretical and practical viewpoints.
The present paper discusses a technique for calculating sweep efficiency in a five-spot pattern during miscible displacement or alcohol flooding.