Comparision of a cyclic steam stimulation analytical model using "PSEUDO - PERMEABILITY" with the conventional approach

Abstract

Cyclic Steam Stimulation (eSS) process is a proven commercial oil recovery process in helJ\Y oil reservoirs. CSS is mostly applicable for the reservoirs containing medium to • high viscosity oil. In IIllUly of the heavier rcserviors, steam is injected under high ~e to create fraclures (shear failure} in.the reservoir. The'"'changes in mass and heat transport properties created by steam invasion in the heterogenously deformed shear failure zone have been shO\\l1 to' be the important factors for recovery mechanism. TIlls work presents a new mathematical mode~ which considers the shear failure zone permeability in reservoir simulation by means of pseudo-relative permeability functiOJll!. • Fractures and microchannels are created in the shear failure zone of the reservoir during steam inj~tion period. It is asswned that these fractures and microchannels remain during productio.n.•period. As a result the reservoir permeability is altered from . the original value. In this new model the actual permellbility is calculated by using of pseudo-re1ativc penneability fimctiODS. The entire shear failure zone is divided !nto .two concentric elliptical cylinders. The inner and outer cylinder is CllIIed hot and warm 7.one respectively. The flow rate is calculated from the well located at the £eIIter of an elliptical reservoir geometry. The simulated results are obtained from this new model showing an excellent match with previously reported result in Olld Lake oil saniis. The various production perforrnancc parameters (OSR, CDOR, WOR) as well as oil and water productions are calculated in eight cycles of operation. An extensive sensitivity study has been done for different physical and reservoir parameters. TIlls model can be successfully used for simulating moderate to helJ\Y oil resenro/rs.