Assessing the Performance of Thermally Active Polymer as an In-Depth Conformance Technology in a Mature Waterflooded Reservoir: A Recent Field-Scale Case Study Utilizing Interwell Tracers in Argentina's Largest Oil Producing Field

Abstract

Waterflooding has been a widely practiced method globally for numerous years, and it has been proven in the field to effectively enhance oil recovery in oil-bearing reservoirs, surpassing primary production methods. Despite its considerable potential for boosting oil recovery, waterflooding faces several challenges that can impede its performance, including reservoir heterogeneities, reservoir structural complexities, and unfavorable mobility ratios. Over the past five years, an extensive multidisciplinary effort has been undertaken to address these waterflood challenges and enhance waterflood sweep efficiency in Argentina. As a result, a cutting-edge conformance technology called Thermally Active Polymer (TAP), also known as BrightWater®, has been successfully implemented in Cerro Dragon, one of Argentina's largest oil-producing fields, yielding encouraging outcomes. To assess the efficacy of TAP as a reservoir-triggered conformance agent, two sets of interwell tracer tests (IWTT) were conducted: one before TAP injection and another after TAP injection when an oil response was detected. These IWTTs represented the first instance of flow pattern change identification within the targeted segment of the reservoir. Additionally, they enabled the quantification of transit time changes subsequent to the in-depth conformance treatment. The study also revealed the establishment of new communication paths while the previously existing paths became less active following TAP placement. The results obtained from the IWTT tests aligned remarkably well with the expectations derived from conceptual numerical modeling. Furthermore, a distinct correlation was observed between the changes in sweeping profiles observed through tracers and the oil and water production responses on the production side. This confirmed that the thermally active polymer reduced the flow capacities of thief zones, thereby allowing previously unswept segments of the reservoir to come into greater contact with the injected water. The findings of this study hold significant implications for the effective execution and design of in-depth conformance treatment programs. Moreover, the study equips end users with quantitative tools for more detailed post-monitoring performance evaluation. TAP has emerged as one of the most widely practiced in-depth conformance technologies for both onshore and offshore applications due to its short execution times, small treatment slug sizes, and ease of injection under various reservoir conditions.