An Easily Applied Black Oil Model Of Caustic Waterflooding
Authors: Breit V.S. , Mayer E.H. , Carmichael J.D. 
Published: December 2007

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.