Development and Selection of Chemical Systems for Miscible Waterflooding

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the Improved Oil Recovery Symposium of the Society of Petroleum Engineers of AIME, to be held in Tulsa, Okla., March 22–24, 1976. 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 series of tests of progressively increasing complexity is used for evaluation of surfactants for oil recovery by miscible waterflooding (micellar flooding). Comparisons are made between new gas-oil and polybutene sulfonates and a reference mahogany sulfonate in 90–95 percent water formulations. Formulations of the new sulfonates exhibit higher tolerances to salinity and divalent ions than the mahogany. The steps in selection of flooding-fluids for a specific reservoir parallel the laboratory tests for surfactant evaluation. In addition, special adjustments are made based on the reservoir lithology. Major factors considered are fluid interactions associated with the presence of anhydrite, clays, sandstone vs. limestone rock and in-place waters. Introduction The miscible waterflooding process uses surfactant-based fluids (micellar slugs) to displace essentially all the oil from the pore space contacted. Typically, the miscible or micellar slug may be preceded by a controlled salinity bank to precondition the reservoir. The slug is displaced in turn by polymer-containing water. These micellar fluids can be classed in many ways. This paper considers three types of fluids with typical water contents of (1) oil-external, 50–85 percent water; (2) water-external, 90–95 percent water; and (3) low tension, 97–99 percent water. These fluids may contain, in addition to a surfactant, cosurfactants and salts, and added polyelectrolytes or polymers and sacrificial agents. Emphasis in this paper is on fluids of the second type, containing 90–95 percent water. In the development of the miscible waterflooding process, one first selects for initial field tests useful chemicals from those of commerce; then seeks to identify and develop truly large volume supplies of chemicals specifically suited for economic application to the miscible waterflooding process. Subsequently, chemical combinations for specific field applications are formulated. The purpose of this paper is to describe a pragmatic program to identify surfactants for development as miscible waterflooding agents. A further purpose is to describe the use of this program and special additional tests for design of micellar fluids for a specific field. Part I relates to selection of specific surfactants from those available on a large scale in commerce or from those which could be economically manufactured on a large scale.