Successful Implementation of a Single Well Chemical Tracer SWCT Test fora Giant Sandstone Reservoir in North Kuwait

摘要

A one-spot EOR pilot was successfully completed to demonstrate the efficacy of a lab-optimized ASPformulation to mobilize remaining oil from a giant sandstone reservoir in Kuwait.This one-spot EOR pilot,which also referred to as a Single Well Chemical Tracer (SWCT) test,was a significant milestone in de-risking ASP flooding for multi-well pilot implementation.The vertical zone of investigation for the Raudhatain Zubair (RAZU) SWCT was chosen to be a confinedchannel sand with relatively homogeneous and representative properties in a producer near the proposedpilot area.Two SWCT tests were performed and the difference in residual oil saturation from post waterflood and post ASP injection tracer tests quantitatively determines the displacement efficiency of the ASPslug.The tracer chemicals for the tests included a hydrolyzing,partitioning tracer (ethyl acetate) and twoalcohols (n-propyl alcohol and isopropyl alcohol) that serve as cover tracer and material balance tracer,respectively,to ensure robustness of test interpretation.The water flood SWCT test showed ideal behavior with well-defined profiles.Interpretation of this testwas accomplished using a single layer model and showed that at the end of the water flood,the residualoil saturation to water was 0.24 ± 0.02% in the 23-ft interval for the SWCT test.The ASP tracer test wascomplicated due to poor injectivity,well mechanical issues,and dilution from a zone which did not acceptany SWCT test injection fluids but contributed substantially to production.Due to the dilution from anotherzone,the ASP tracer test profiles were more dispersed than the water flood tracer test but were adequatelymodeled using a two-layer model with irreversible flow.Analysis of the ASP SWCT test showed that theaverage oil saturation was reduced to 0.06 ± 0.05%,which represents a ~67% reduction in residual oilsaturation.Despite poor injectivity leading to a reduced polymer drive and taper injection and dilution from anotherzone resulting in a non-idealized tracer response,careful interpretation of the SWCT test measurementsresulted in a reliable estimate of the post-ASP oil saturation.The SWCT test results demonstrate thefeasibility of applying ASP flooding to increase oil recovery from a giant high-temperature sandstonereservoir in North Kuwait.