Determination of in-Situ Remaining Oil Saturation Before ASP Flooding for Giant Sandstone Reservoir in North Kuwait

Summary An Alkaline Surfactant Polymer (ASP) pilot is planned for a giant sandstone reservoir in North Kuwait. The reservoir has good oil recovery, thanks to its favorable geological characteristics, light oil and strong aquifer support. However, the reservoir is exposed to very harsh salinity and temperature conditions that contribute to additional complexity of the envisioned development concept and the costs of the identified and field-tested optimum chemical ASP formulation. Therefore, the determination of remaining and residual oil saturations to water flooding are vital to assess the economic feasibility of ASP field development. The pilot designed 7 wells have been drilled in mature area of the reservoir and detailed open hole logs surveys were collected in addition to acquiring cores from 3 of the pilot wells in the target zone. Saturation logs show consistently uniform low oil saturation signaling the target zone remaining oil saturation is very close to true residual oil saturation. One of the pilot wells was successfully cored with water based-mud Liquid Trapper technology to reduce the range of uncertainties from quantifying remaining oil saturation. The Liquid Trapper fluids collected during the coring process were analyzed and only very slight traces of oil were detected. Full diameter cores, horizontal plugs, and vertical plugs in the least invaded parts in the middle of the core covering ∼100 ft interval were cut and prepared for Dean-Stark extraction to estimate oil and water saturation. The results from the analysis confirm low oil saturation range observed from the open hole logs, from a Single Well Chemical Tracer Test (SWCTT) in a nearby well and centrifuge SCAL experiments. However, water saturation estimates from the collected cores were subject to higher uncertainties that are attributed to inevitable artefacts from drilling, coring and core handling operations in addition to new insights on inherited limitations of data analysis from Dean-Stark extraction. The paper will address best practices on integrating data from different sources as well as capturing and highlighting lessons learned.