Production prediction of cyclic multi-thermal fluid stimulation in a horizontal well

Abstract Cyclic multi-thermal fluid stimulation (i.e., huff and puff) in a horizontal well is an effective way to recover offshore heavy oil reservoirs. To rapidly predict reservoir production performance, an analytical model for predicting the productivity of a cyclic multi-thermal fluid stimulation in a horizontal well was developed in this study. The underlying assumption in this study is that multi-thermal fluids spread around the horizontal well cylindrically at the beginning of injection and then along the top or bottom as the fluids contact those regions; this creates a composite reservoir with hot and cold zones. First, a production formula for a horizontal well in the composite reservoir described was derived using the equivalent flow resistance method from the water electric analogy principle. A heat diffusion model of multi-thermal fluids was then used to describe how the fluids spread out in the reservoir. Then, an evolution model of the physical fields was built by considering the enhanced oil recovery mechanism of multi-thermal fluids, which describes the evolution of temperature, pressure, oil viscosity, relative permeability curves, etc. during the huff-and-puff process. A new formula was used to determine the reduction in viscosity caused by carbon dioxide present in the fluid. The desired production prediction model was then established by coupling the developed production formula, heat diffusion model and evolution model. The analytical model was verified by numerical simulations and application to an offshore oil field. This study described an effective and quick method for productivity prediction, reservoir dynamic analysis and injection optimization.