This paper describes the rectifications and extensions made to a Beta-type, three phase, three dimensional, numerical reservoir simulator which make possible the modeling of caustic and/or polymer possible the modeling of caustic and/or polymer displacement of oil. The performance of a caustic laboratory core flood has been matched using this new simulator. The simulation model developed from the core flood matches will be used to predict the performance of the caustic flood to be undertaken in the performance of the caustic flood to be undertaken in the Wilmington Field - Ranger Zone - Fault Block VII. The modified simulator for enhanced waterflooding accounts for the injection and/or production of up to six active agents in the aqueous production of up to six active agents in the aqueous phase. Any or all of these agents may be either phase. Any or all of these agents may be either caustic or polymer-type fluids or a combination of these two fluid types. The primary displacement effects of the caustic fluids are represented by changes in relative permeabilities to oil and water. This simplified permeabilities to oil and water. This simplified approach permits the modeling of enhanced recovery projects without the necessity of determining the projects without the necessity of determining the mechanisms of the displacement in minute detail. For Ranger Zone, Fault Block VII, caustic flood relative permeability curves and caustic consumption parameters for use in the numerical simulator were parameters for use in the numerical simulator were determined from linear displacement studies of conventional waterflooding and saline, caustic waterflooding using Ranger Zone crude oil and core samples. Introduction The Wilmington Field of Southern California is the largest field in California. The field has seven basic reservoir zones with crudes that have a relatively low gravity, high viscosity, and high organic acid content. The recovery efficiency for the waterflood of the Ranger Zone of the Wilmington Field has been low due primarily to a highly unfavorable mobility ratio between water and oil, and significant reservoir stratification. The concept of utilizing natural organic acids present in a crude oil to produce surfactants when present in a crude oil to produce surfactants when the oil is contacted by alkaline water — although limited to reservoirs with higher acid content oils — has potential economic advantages over the use of commercial surfactants owing to the high costs of these chemicals and the low cost of sodium hydroxide. Several mechanisms have been proposed for the improved oil recovery resulting from caustic waterflooding. Included among these mechanisms are (1) emulsification and entrainment, (2) wettability reversal (oil-wet to water-wet), (3) wettability reversal (water-wet to oil-wet) and (4) emulsifilcation and entrapment. The relationships between these possible mechanisms is necessarily more complicated in caustic waterflooding than in surfactant injection due to the complexity of the alkali-organic acid reactions which form soaps in-situ. Siefert has studied the naturally occurring emulsifiers in crude oil and found that the number in a specific crude oil may range into the hundreds. The Department of Oil Properties for the City of Long Beach and THUMS Long Beach Company, in conjunction with the United States Department of Energy, have undertaken a caustic waterflooding demonstration project in the Ranger Zone, Long Beach Unit, project in the Ranger Zone, Long Beach Unit, Wilmington Field to demonstrate the applicability of the caustic injection process to the recovery of that field's crudes. Included in this project is an extensive laboratory core flood analysis program and modeling of the caustic displacement process using a numerical simulator. The development of the numerical simulator and its use in modeling the core flood work performed to date are presented in this paper. CAUSTIC DISPLACEMENT PROCESS Although the possible mechanisms and chemical reactions in caustic flooding are very numerous and complex all the major mechanisms postulated are characterized by immiscible displacement of oil by aqueous solutions at greatly reduced interfacial tensions.

Summary This paper discusses the design of a simulator to model alkaline displacement mechanisms, along with the current understanding of in-situ caustic consumption. Assimilation of laboratory coreflood and rock consumption data, and their use in one- and two-dimensional (1D and 2D) limited-area simulations and in three-dimensional (3D) model of the entire pilot project are given. pilot project are given. This paper also reports simulation studies of alkaline flood behavior in a small 2D area of a field for various concentrations, slug sizes, long-term consumption functions, and two relative-permeability adjustment mechanisms. The scale-up of 2D simulation results and their use in a 271-acre [1096.7-ha], seven-layered, 3D model of the pilot are also discussed and 3D simulator results are compared with initial field alkaline flood performance. Finally, recommended additional applications of the simulator methods developed in this pilot and in other alkaline floods are discussed. Introduction Wilmington is one of the major fields in the U.S. and is typical of many of the Pliocene-Miocene reservoirs in the Los Angeles basin. These reservoirs, which are stratified and are often silty, have low oil gravities and high viscosities. Because of the unfavorable water/oil mobility ratio and stratification, waterflood recovery efficiencies have been low. Tests of Long Beach Unit Wilmington crude, including that from the Ranger zone, indicated that it possibly was amenable to recovery enhancement by alkaline flooding. The concept of activating the natural surfactants present in suitable crude oils by reaction with alkaline water has been noted to have EOR potential because of the low cost of the alkaline materials. Alkaline laboratory flood tests of Long Beach Unit Ranger crude in Berea cores were favorable. In 1976, the City of Long Beach (Unit Operator of the Long Beach Unit) and the U.S. DOE entered into a cost- and incremental-income-sharing contract for a large-scale alkaline pilot in the Ranger zone of Fault Block VII. The pilot and pertinent preliminary studies have been described in four annual DOE reports and a recent paper on the pilot. The pilot's configuration and properties are given in Figs. 1 and 2 and Tables 1 and 2. Preflushing with softened fresh water containing 1.0 wt% salt (NACl) began in early 1979. Alkaline injection with softened fresh water containing 0.4 wt% sodium orthosilicate and 0.75 wt% salt began in March 1980 and continued until Dec. 1983. Part of the plan for the pilot involved reservoir simulation studies to predict performance of the area under continued waterflooding and that anticipated under alkaline injection. These studies are the subjects of this paper.

An aggressive hydraulic fracturing campaign, involving over 360 wells, has been conducted at Prudhoe Bay, primarily within the waterflood region of the field. High declines in gross fluid production rates (oil plus water) were observed in the first few months after the fracture stimulations were performed. Work was initiated to determine the cause of these declines and to identify any actions which would mitigate them.A combination of diagnostic well work, field data analysis and reservoir studies to investigate the decline mechanisms are presented. The paper highlights the use of numerical simulation for investigating the reservoir mechanisms of decline, and the benefits associated with alternative waterflood management schemes.