Correlation of Surfactant-Induced Flow Behavior Modification in Gas Condensate Reservoirs with Dynamic Contact Angles and Spreading

Abstract

AbstractThe commonly encountered condensate blockage problem causes severe impairment of gas productivity as the flowing bottom-hole pressure falls below the dew point in gas condensate reservoirs. This study investigates the potential for improving gas relative permeability and enhancing oil (condensate) recovery by using low-cost surfactants to alter wettability in the near wellbore region as well as fluid-fluid spreading coefficient. Surfactant-induced wettability alterations have been derived from experimental measurements of dynamic contact angles and oil-water relative permeabilities.Coreflood experiments were conducted using two different rock-fluids systems: (1) Berea sandstone, condensate, synthetic brine and nitrogen; and (2) Parker sandstone, artificial retrograde gas, and synthetic brine at elevated pressures. The anionic surfactant, which was more effective in our previous work, has been used in this coreflood study. Contact angles were measured on quartz surface using Dual-Drop-Dual-Crystal (DDDC) technique and spreading coefficient was determined through measuring interfacial tensions using pendent drop method by drop shape analysis technique. Oil-water relative permeabilities were generated by history matching condensate recovery and pressure drop data obtained from the coreflood experiments.The shifts in oil-water relative permeability ratio curves indicated that the wettability of this Berea core-condensate-brine system altered to intermediate-wet induced by this anionic surfactant. The contact angle measurements for this system with surfactant also substantiated the wettability alterations to intermediate-wet. The results of subsequent gasflood using nitrogen showed 82% improvement in gas relative permeability for this system. Positive spreading coefficient obtained in all Berea core cases indicates that it has less influence on enhanced gas relative permeability compared to wettability alteration. Corefloods using artificially prepared retrograde gas mixture creating in-situ retrograde gas condensation within the core system also showed the improvement in gas relative permeability. This study thus demonstrates that surfactant-induced alteration of wettability and spreading coefficient have the benefits for improving gas and condensate production by mitigating the condensate blockage problem.