SPE 12667 Mechanisms of Immiscible COZ Injection in Heavy Oil Reservoirs, Wilmington Field, CA
by AlIan Spivak, Consultant, and C.M. Chima, Long Beach Oi/ Deve/opnent
Copyright 19S4 Society of PetroJeumEngineers of AlME This paper was presented at the 19S4 CaliforniaRegional Meeting held in LongBaach, CA, April 11-13, 19S4. The material ia subjectto correctionbythe author. Permission to copy is restrictedto an abstract of not more than 300 words, Write SPE, 6200 North Central Expressway, 64706, Drawer Dallaa,
Texaa 5206 7 USA. Telex 730989PEDAL. S ABSTRACT This paper describes the results of simulation etudies made to investigate the mechanisms of immiscible C02 injection in heavy oil reservoirs. The studies were undertaken to aasist in the design andmonitoring of two projects implemented in the Wilmington Field, Los Angelee County, California. An equation-of-state compositional simulator was used in these studies. The equation-of-state was adjuated to match saturation pressures and swelling data from the laboratory. Simulation runs were then made to investigate the effect of various parameters on the process. The paper relates the variouesimulator studies to the Long Beach Oil Development Company (LBOD) project in the Tar Zone, Fault Block V and the Xtra Energy project in the Ranger Zone, Fault Block I of the Wilmington Field. Both projects uae the same source of gas which is approximately 82% C02 and 18% N2. INTRODUCTION References 1 and 2 discuss the geology of the Wilmington oil field. Long Beach Oil Development Company and XtraEnergy Corporation are operating immiscible gaa injection projects at Wilmington and the source of gas for both projects is a Texaco refinery. The LBOD project has been in operation since March 1982 and the Xtra Energy Pi~jeet ~a~ ifii~ia:e~i= .Assg~~t 1983. -..”, “-” Champlin Petroleum operates an immiscible gas injection project in the Tar Zone, Fault Block III of the Wilmington Field using pureC02. Champlin3 conducted a pilot of the process commencing in March 1981 and is currently expanding the pilot area to a much larger project. Table 1 is a comparison of pertinent data for the LBOD and Xtra Energy projects. The LBOD project area has been under waterflood since 1961 and the current water cut is 947.. Therefore, the LBOD project is essen~i=~~y a &=rCiary pr~~e~~~ The XCr= S7nmrovr---------02 mFnieet has had only a small amount of water injection to date and therefore is a secondary process. Although the LBOD project is in the Tar Zone and the Xtra Energy project is in the Ranger Zone, the crude oil properties in the two projects are very similar. In both projects, gas will be injetted alternately with water until a predetermined total amount of gas has been injected. Thealternate gas and water injection will be followed by water injection only, until an economic limit is reached. MATCHING OF LABORATORY PVT DATA The compositional simulator uses the PengRobinaon4 equation-of-state for phase equilibrium calculations. A six component system was conaidered in this work, with the components and some of their properties listed in Table 2. Laboratory Studies using crude oilsamplea from the Tar V were performed by Chevron Oilfield Research Company.5 The Peng-Robinson equationof-state was adjusted to match saturation pressures and sweliing data for mixtures of the Tar V crude oil and either pure CO~ or a mixture of 82% C02 and 18% N2 (82/18). A comparison of the laboratory deterreinedsaturation pressures and the saturation pressures obtained from theequation-of-state is shown on Figure 1. The laboratory measured and the calculated swelling test data are shown on Table 3. Excellent matches were obtained in both cases. The parameters that were modified to obtain the matches were the @ of C25+ and ~ of N2, C02 and C25+ in the PengRobinson equation-of-atate. The modification that were made were relatively minor. OIL AND GAS VISCOSITIES For seven mixturee of...