CO2-Foam Field Pilot Test in a Sandstone Reservoir

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 190312, “CO2-Foam Field Pilot Test in Sandstone Reservoir: Complete Analysis of Foam-Pilot Response,” by P.D. Patil, T. Knight, A. Katiyar, SPE, and P. Vanderwal, The Dow Chemical Company; J. Scherlin, SPE, Fleur De Lis Energy; P. Rozowski, SPE, The Dow Chemical Company; M. Ibrahim and G.B. Sridhar, SPE, Schlumberger; and Q.P. Nguyen, SPE, The University of Texas at Austin, prepared for the 2018 SPE Improved Oil Recovery Conference, Tulsa, 14–18 April. The paper has not been peer reviewed. This paper presents an analysis of a CO2-foam-injection pilot in the Salt Creek Field, Natrona County, Wyoming. The pilot was successful in demonstrating deeper conformance control and improvement in sweep efficiency, which resulted in 25,000 bbl of incremental oil. A 22% decrease in the amount of CO2 injected also was realized as a result of better use of CO2 compared with the baseline. Introduction Foam-assisted CO2 enhanced oil recovery (EOR), commonly referred to as CO2-foam EOR, has been proposed as an effective technology for correcting sweep inefficiencies caused by gravity segregation and reservoir heterogeneity. The central concept of CO2-foam EOR is the in- situ generation of a viscous emulsion of CO2 and water stabilized by a surfactant at reservoir conditions. Because the apparent viscosity of a CO2/water/surfactant system is much higher than that of CO2 itself, the mobility of CO2 is significantly reduced. In the reservoir, the generation of foam occurs first in the zones preferentially swept by CO2, gradually diverting CO2 to unswept zones where oil saturation is typically higher. An important feature of the CO2 foam is that the foam strength, and hence the mobility reduction, weakens in the zones where there is substantial oil saturation. As a result, the foam does not interfere with the CO2 displacement process once the CO2 is diverted into zones with substantial oil saturation. Salt Creek Foam Pilot Although the CO2 flood in the Salt Creek Field, begun in 2004, has been very successful, certain isolated patterns were seen to exhibit high CO2 production and inefficient CO2 use, most likely because of the channeling of fluids through high-permeability, low-volume zones and the gravity override of the injected fluid. A CO2-foam pilot was undertaken to test whether these conditions could be remediated. An inverted-five-spot pattern in the Phase V area of the field was screened as the best candidate for the CO2-foam EOR pilot (Fig. 1). The pilot injector was labeled as 22SE30 and the four production wells to be monitored were wells 15SE30, 14SE30, 26SE30, and 28SE30. While other papers have been devoted to the Salt Creek foam pilot, this paper focuses on the injection-well response, the interwell tracer analysis, and the production response from the monitored producer wells in the pilot area. The authors discuss the injection and production responses for 2 years and 8 months of data. The foam injection in the field was completed in June 2016.