SIMULATION OF CYCLIC STEAM INJECTION INCLUDING THE EFFECTS OF TEMPERATURE INDUCED WETTABILITY ALTERATION

Cyclic steam injection into representative, low‑permeability, hydraulically fractured, diatomaceous, heavy‑oil formations is investigated using reservoir simulation. Previous laboratory research has shown that diatomite reservoir rocks exhibit temperature‑dependent wettability. Water‑oil and liquid‑gas relative permeability are varied here and a reservoir simulator used to evaluate the effects on oil recovery. Sensitivity studies are carried out for actual field data compiled from literature for diatomaceous reservoirs. The various field parameters included in the analysis are relative permeability end points and viscosity variations with increasing temperature, rock and fluid properties (such as thermal conductivity and heat capacity), injected steam temperature, pressure, and quality, bottom hole pressure for injectors and producers. Through this analysis, the optimum injection, soaking, and production periods for each case are determined. The results indicate that the liquid‑gas relative permeability affects process performance most sensitively, because gas displacement determines the shape of the heated zone during cyclic steam injection. For the recovery of heavy oil from diatomaceous formations, realistic evolution of the liquid‑gas relative permeability at steam temperatures increases the oil recovery on the order of 100% in comparison to cases with no evolution of wettability with temperature.