A Method of Alternating Steam and Water Injection for Recovering Heavy Oils

Abstract

Abstract Various techniques have been suggested for injecting steam into heave oil reservoirs that offer limited injectivity into the formation. These include the use of any water-saturated stringers that may be present in the pay or the use of horizontal wells to heat the reservoir from the injector to the producer. An experimental study was conducted using a scaled physical model to study the scenario with a horizontal well. The model was an element of symmetry from a reservoir having no initial fluid mobility. A horizontal well was placed at the base of the model to heat the formation from a vertical injector to a vertical producer. Results of injecting steam into the region heated by the horizontal well were disappointing due to low mass injection rates. It was possible to inject high mass rates using hot water as the injected fluid. This however, resulted in relatively low oil production rates. To obtain a balance between high mass injection rates and high oil production rates, a process of alternating steam and hot-water injection was developed. This allowed the reservoir to be heated as hot water was injected into the reservoir and oil to be produced by gravity drainage during steam injection. A number of alternating steam and hot water cycles were required before continuous steam injection at the maximum rate was possible. The initial heating time with the horizontal well was varied with minimal effect. Using the alternating process, an oil recovery of 76.4% was achieved.