Combining solvent injection, electromagnetic heating, and hydraulic fracturing for multistage heavy oil recovery

To model the combined multistage technologies of radio-frequency electromagnetic heating (RF-EM), solvent injection, and hydraulic fracturing, a mathematical model was developed. It was assumed that the well was previously hydraulically fractured and then the solvent was injected through it with simultaneous RF electromagnetic irradiation. The radiator of RF-EM waves was located at the bottom of the injection well. When the electromagnetic waves were irradiated into the reservoir, the temperature rises and the viscosity of the liquid decreases around the fractured well. While “cold” solvent was injected, it was heated at the bottom of the well so that the heat was transferred into the fracture and reservoir by convection. This leads to an increase of reservoir coverage by heating. The area of the thermal effect was determined by the length of fracture, duration of solvent injection, reduction in oil viscosity, increasing injectivity due to rising temperature, and solvent–heavy oil mixing around the bottomhole. Multistage process of reservoir stimulation was considered: (1) «Cold» production of heavy oil through the fractured well, (2) shut (shutdown) of the well without treatment, (3) solvent injection into the fractured production well with simultaneous RF-EM heating, (4) well was suspended to “soak” without any treatment, and (5) production of heavy oil with solvent without heating. The most efficient scenario was the combined RF-EM heating/fracturing multistage production technology. Recurring stages of solvent injection/RF-EM heating allowed maximum use of thermal energy and achieved the most efficient production growth.