A Study of Fireflood Field Projects (includes associated paper 6504)

Abstract

More than 40 domestic and foreign firefloods were reviewed. Regressionequations were developed for predicting production performanceof firefloods. Two screening guides were established for selecting reservoirs for the application of the fireflood process. Introduction Enhanced recovery methods that show most promise forcommercial application include hydrocarbon miscibleflood, carbon dioxide miscible flood, micellar flood, andthermal recovery methods. Since the first threeprocesses are applicable only to low-viscosity crudes (10 cpor less), the recovery of medium- to high-viscosity crudesdepends solely on thermal methods - steam stimulation, steamflood, and fireflood. A recent domestic survey showed that, of the threethermal methods, steam stimulation has been practicedexclusively in California and steamflood has been usedpredominantly there. Fireflood projects, on the otherhand, cover a much wider area including California, Texas, Louisiana, Oklahoma, Arkansas, Illinois, Mississippi, Nebraska, and Wyoming. This wide geographical distribution of fields amenable to firefloods clearlyindicates that firefloods are applicable to a broader range ofreservoir and crude properties than steam stimulation andsteamflood. More than 70 firefloods have been completed or are inprogress in the U.S. Firefloods also have been practicedin other countries such as Venezuela, U.S.S.R., Romania, and Japan. Varying information is available onmore than 40 domestic and foreign firefloods.The purpose of this paper is to review these firefloods and therebydevelop criteria for screening prospects for theapplication of the fireflood process. This paper first gives a general description of firefloodand its variations and discusses variables characterizingthe performance of firefloods. Screening guides forfireflood prospects are developed by two different statisticalapproaches - the confidence-limits approach and theregression-analysis approach. The choice betweenfireflood and steamflood is also discussed. Fireflood and Its Variations The most commonly used form of the fireflood process isdry forward combustion. The process is called drycombustion because no water is injected along with air.The combustion is forward because ignition occurs near the injection well and the burning front moves forward fromthe injection well to the production well. The advantageof this process is that an undesirable fraction of the crudeis burned in the form of coke, leaving clean sand in theregion behind the burning front. However, it has twolimitations. First, the produced oil has to pass through acold region of the reservoir. If the oil is highly viscous, liquid blocking will occur, which may terminate theprocess. Second, heat stored in the burned-out region isnot utilized efficiently because injected air is notsufficiently effective to carry the heat forward. Reverse combustion is a variation of the fireflood thatremedies the first limitation of the conventional fireflood.Ignition occurs near the production well and the burningfront moves countercurrent to the flow of the injected air.Since oil moves through a hot region toward the produced well, there is no upper limit to the viscosity of thereservoir crude. Reverse combustion is not as efficient asforward combustion because a desirable fraction of theoil is burned as the fuel, and the undesirable fraction remains in the region behind the combustion front. JPT P. 111^