The Effect of Different Hysteresis Models On Water-Alternating-Gas (WAG) Process

Enhanced oil recovery (EOR) or tertiary recovery is vastly applied to mostly mature and
depleted oil reservoirs nowadays. One of the many EOR techniques is the Water-
Alternating-Gas (WAG) process whereby water and gas are alternately injected for
periods of time to provide better sweep efficiency hence improve oil recovery. !t is well
known that whenever the fluid saturations undergo a cyclic process, relative
permeability display hysteresis effects. Recent studies have been done on establishing
the effect of hysteresis on WAG process. However, different hysteresis models will
have different assumption and methods which eventually affects the production profile
and recovery of an oil field. The main objective of this project is to quantify the effect of
different hysteresis models (Carlson and Killough's model) on a conceptual model using
black oil simulation. In addition to the main objective, sensitivities studies on the model
without hysteresis were done to obtain optimum values prior to running the model with
hysteresis. Hysteresis effect always results in higher oil recovery and oil production rate
compared to the model without hysteresis. The quantification of both the hysteresis
models shows that Killough's model results in higher oil recovery compared to
Carlson's model. This is due to the fact that Killough uses particular equations to
produce the scanning curve where else Carlson's scanning curve is produced by shifting
the imbibitions curve horizontally until it cuts the drainage curve at the maximum nonwetting
phase saturation. The way the scanning curve (intermediate imbibiton curves) is
generated differs in both the models. This quantification of different hysteresis models
can help in obtaining more precise prediction of forecasting oil recovery in the future.
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