Numerical Simulation Of Competing Chemical Flood Designs

Abstract Two chemical flooding design philosophies:a small slug, high concentration, "soluble oil" system, anda large slug, dilute concentration, "optimal salinity" design, were investigated in pursuit of a chemical system suitable for testing pursuit of a chemical system suitable for testing in the Department of Energy (DOE)/Gary Operating Company Micellar - Polymer demonstration project in the Bell Creek field, Montana. As part of the process selection algorithm, laboratory core flood process selection algorithm, laboratory core flood results were matched using a numerical simulator. The simulator was then used to predict areal and vertical field performance. For the particular systems investigated and for this specific application, the "soluble oil" system appears to hold the greatest promise for success. Introduction Of the various surfactant flood design strategies that have been proposed, two distinct philosophies have emerged. One school of thought philosophies have emerged. One school of thought advocates the use of a small slug of high surfactant concentration, holding that miscibility between the slug and neighboring fluids is the primary mechanism of displacement. The other school believes that miscibility cannot be long sustained with small slugs and proposes using larger slugs of more dilute surfactants, relying on the attainment of ultra-low interfacial tension, instead of miscibility, to recover tertiary oil. These differing design philosophies were investigated by two major oil companies in pursuit of a surfactant system suitable for pilot testing in the DOE/Gary Operating Company Bell Creek Micellar - Polymer Demonstration Pilot. Union Oil Company, long a proponent of the small slug, high concentration, "soluble oil" system was contracted by Gary Operating Company, the field operator, to design a process suitable for Bell Creek. For contrast, Atlantic Richfield, a large working interest owner of the Bell Creek field, elected to investigate the alternative of a large, dilute slug, following the "optimal salinity" principles proposed by Exxon. proposed by Exxon. It is definitely not the intent of this paper to make any generalization as to the relative merits of these two design philosophies. Instead, the intent is to present experimental and numerical results for a specific application of chemical flooding systems, developed by two companies who have elected to follow differing design philosophies. DESCRIPTIONS OF DESIGNS The Union and A.R.Co. "optimum designs" for Bell Creek call for injection of the slugs of chemicals listed in Table 1. Noting the injection composition of the surfactant slugs, we shall hereafter refer to Union and A.R.Co. processes as the "soluble oil" (SO) and high water content (HWC) processes, respectively. The two Bell Creek designs utilize the same polymer, basically the same surfactant, but polymer, basically the same surfactant, but different cosolvents, different preflushes and different salinities. The HWC design specifies a uniform salinity, slightly less than reservoir salinity, throughout the process; the SO design specifies different salinities for each slug, the preflush and micellar slug salinities being higher and the polymer slug salinity being lower than reservoir polymer slug salinity being lower than reservoir salinity. DESCRIPTION OF SIMULATOR Simulation work was accomplished using the INTERCOMP Chemical Flood Simulator. The model solves for six components (or species) in two fluid phases.