Two-Bank Miscible Tertiary Oil Recovery Process

Abstract Results of a laboratory investigation of a two-bank, water-driven, miscible tertiary oil recovery process indicate that substantial quantities of additional oil can be obtained from flooded out reservoirs under favorable conditions. This process uses an initial bank of tertiary amyl alcohol followed by a second bank composed of sodium xylene sulfonate, methanol, a thickener, and water. These two banks can be driven through a reservoir by a large, thickened water bank driven, in turn, by formation water. Although technically feasible the process does not appear economically process does not appear economically attractive at this time. Introduction Development of a solvent bank which will yield a miscible displacement of oil by water is of considerable interest to the oil industry since it can provide a combination of the benefits of the high displacement efficiency of miscible processes with the favorable injection characteristics of water. Water is cheap and readily available in most locations, and the technology for its injection is well developed. Consequently, methods for improving its displacement efficiency are highly desirable. Two-bank miscible processes are based on the thesis that more favorable phase behavior can be achieved using two banks of solvent rather than one. Fig. 1 illustrates a typical process in which a preferentially oil-soluble solvent slug miscibly displaces oil and immiscibly displaces water. This bank is driven by a bank of a preferentially water-soluble solvent which in turn is driven by water. In each case a miscible displacement is achieved. In the subject process, the first bank is composed of an oil miscible alcohol and the second of a mixture of methanol and an aqueous solution of a low molecular weight aromatic sulfonate. This system offers improved miscibility and mobility characteristics over previously studied two-bank processes.