Thermal recovery: mature technology for EOR

From a technical viewpoint, thermal recovery processes are excellent EOR processes. Practically speaking, there are a number of operational difficulties associated with thermal recovery. Temperatures encountered in thermal recovery operations adversely affect monitoring, injecting, and producing equipment. Sand production is frequently severe, as many heavy oil reservoirs occur in either unconsolidated or semi-consolidated sands. In these reservoirs, heavy oil often serves as a cementation medium. When this oil is produced, sand readily migrates to the producing wellbore. Discussions of the solutions to operational problems occur in most field test reports. A major technical problem remaining is that of controlling steam placement, especially in heavy-oil reservoirs. The use of foams and/or gels is showing promise in steaming operations. Excessive heat losses can occur at both injection and production wells. Improved insulation materials and down-hole steam generation offer control of injection well heat losses. There is considerable discussion about the optimum steam quality to be injected. Commonly, 70 to 80 percent quality steam is injected, although a recent simulation study suggested 35 to 40 percent steam quality as being optimum for the conditions studied. Environmental control problems, particularly in surface steam generation operations, can be severe. The Vapor Therm and similar processes more » offer the advantage of disposing of combustion gases by injecting them along with steam. In spite of these and other operational problems, thermal processes are economic processes. Most of the projects summarized in March 1980 are listed as being economic. 5 figures, 1 table. « less