Abstract

The effects of hot-plate heating and gravity drainage on steamflood performance were studied for a heavy oil reservoir using a numerical steamflood simulator. A one-eighth of a five-spot model representing the reservoir that was divided into two target sands by a shale layer was used for the study. The shale was assumed to be either continuous or discontinuous.

Simulation results show that when the lower target sand of a two-part reservoir is steamflooded, the upper sand becomes heated from below by a phenomenon known as "hot-plate heating." This phenomenon is seen to produce several important beneficial effects for subsequent steamflooding of the upper sand: (1) shortened project life, (2) early production contribution from the upper sand, (3) near vertical sweep of the upper sand by steam, and (4) lower cumulative steam-oil ratio. If the shale is discontinuous, steam can rise through the discontinuity and drive the heated oil in the upper sand toward the producer, thereby further accelerating oil recovery during steamflooding of the lower sand.

The simulation model was subsequently used to recommend an optimum operating strategy for this type of reservoir. The optimum strategy depends on whether cumulative oil-steam ratio or present-worth profit is used as the yardstick.