Flooding of Semi-Depleted Solution Gas Reservoir in Fullerton Field

Abstract

Abstract Little flooding experience or technology exist which are applicable to solution gas-drive reservoirs which have been depleted considerably below the bubble point. The Fullerton field pilot is an example of flooding under these conditions where an intermediate stage or depletion exists and the water flooding will be neither a pressure maintenance project nor a depletion flood. In the case of Fullerton field where the gas saturation is approximately 18.0 per cent of total pore volume, "fill-up" will not be reached for a number of years after flooding operations begin. During this period compressibility of fluids and relative permeability factors determine performance of producing wells. The non-steady-state performance which will be in effect for a considerable time cannot be directly predicted by any presently accepted theoretical means. The pilot flood has yielded considerable information which can be used in predicting performance during this important stage of flooding. The pilot has shown that favorable reactions on producing wells adjacent to injection wells are in effect long before a theoretical fill-up is obtained. This does not indicate poor performance, but merely that the reservoir fluids are compressed to the point where a significant oil bank is formed. This isolated pilot pattern flood, where all offset wells are producing, gives some indication of what might be expected under both pattern and line-drive flooding. The pilot has progressed to a point where sufficient stock-tank oil has been recovered, in the area under pattern flooding, to justify full scale flooding. In the area surrounding the pattern flood no means exist for confining fluid movement, and performance is a function of the interdependent combination of relative permeability, fluid saturation and fluid compressibility. This pilot flood has shown the degree to which outside offset producing wells respond prior to reaching gas-space fill-up and the degree to which productivity is affected by changes in saturation accompanied by only relatively slight pressure increase. Producing wells inside the pattern flood have shown the degree to which productivity can be affected by saturation change and a considerable increase in bottom-hole pressure.