Waterflood residual oil saturation, in mixed wettability reservoirs, is often a strong function of pore volumes (PV) injected. The Endicott Field, Alaska displays typical mixed wettability behavior with coreflood remaining oil saturation varying from 40% at 1 PV to 12% at infinite PVs. Although only about 1 PV will be injected in the reservoir, surface film drainage may act to reduce oil saturation making determination of the correct effective residual oil saturation difficult.Accurate determination of waterflood residual oil saturation is essential for assessment of waterflood performance and evaluation of enhanced recovery processes. To minimize uncertainty in predicting effective residual oil saturation in mixed wettability reservoirs it is necessary to consider the competing effects of relative permeability, graVity forces, and imbibition capillary pressure. A mechanistic simulation approach is presented for scaling up laboratory results, that considers all active forces.References and Illustrations at end of paper.
The authors would like to acknowledge and express their appreciation to the US Department of Energy (DOE) Water Power Technologies Office (WPTO) for overseeing and funding this study to perform a critical review of hydropower geotechnical foundation practice and innovation opportunities. The following DOE WPTO staff were heavily involved in reviewing this report and supporting this study:
Many horizontal miscible gas floods experience relatively low vertical sweep efficiency due to gravity segregation of the injected solvent and reservoir liquids. This is true for the Prudhoe Bay Miscible Gas Project (PBMGP) in which the enriched-hydrocarbon miscible injectant (MI) is expected to sweep only approximately 30% of the reservoir volume in the project areas. The Prudhoe Bay reservoir has a relatively thick oil column, high inter-sand vertical permeability, high net-gross, and is generally developed on 80 acre (324 = 103 m2) well spacing.An infill drilling project was implemented in the Northwest Fault Block (NWFB) area of Prudhoe Bay (Fig. 1) to improve solvent sweep efficiency and increase EOR reserves. This project differs from many EOR infill drilling projects in that most of the additional recovery is attributable to EOR, with minimal improvement in waterflood recovery.The infill project is feasible because the reservoir is relatively thick, and sufficient EOR reserves are obtained from miscible displacement around new injectors. A significant increase in flood rate can also occur, resulting in production acceleration. Results of the project will guide analysis of infill drilling in other EOR areas at Prudhoe. The Prudhoe Bay Miscible Gas Project is the world's largest enriched-hydrocarbon miscible gas flood, and is located in northern Alaska, USA.
Introduction This extended abstract describes the use of infill drilling to improve solvent sweep efficiency and EOR recovery in a gravity dominated WAG flood. Much of the incremental oil recovery in the Prudhoe Bay Miscible Gas Project (PBMGP) is displaced from a relatively small volume of swept reservoir surrounding each WAG injector. Solvent override occurs due to high vertical permeability and the large density difference between solvent and reservoir fluids. Solvent rises to the top of the reservoir or underneath shales, forming cone-shaped swept intervals around WAG injectors (Figure 1). Vertical sweep by solvent in gravity dominated WAG floods can be improved by increasing the viscous-to-gravity ratio1,2. A higher viscous-to-gravity ratio (HVGR) expands the solvent swept areas around the injection wells before gravity segregation occurs. However, little can be done in the PBMGP to reduce gravity forces, and water and solvent injection rates are currently near the maximum attainable. Reduced well spacing remains the only viable method to increase viscous-to-gravity ratio. Most of the benefit from reduced well spacing is due to displacing oil from new WAG cones around the new injectors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.