Transforming Challenges into Opportunities to Design Fit for Purpose Long Term Polymer Injectivity (LTPI) Pilots in Umm Gudair Minagish Oolite Reservoir, West Kuwait

Abstract

Umm Gudair Minagish Oolite is a highly heterogeneous reservoir with intermittent micritic units forming low permeability barriers to fluid flow. Based on screening/lab study, the polymer or surfactant-polymer flooding was proposed using normal 5 spot injection pattern. KOC decided to test only polymer flooding because of cost considerations. This study is to design fit for purpose long-term polymer injectivity (LTPI) pilot using produced water (salinity 230000ppm) with the objectives of testing injectivity, adsorption, breakthrough, resistance factor and response time within 6-12 months. Numerical simulation and economic modelling was used for this evaluation to explore various novel strategies. Various parameters were optimized to design Fit for Purpose LTPI pilot configurations using high salinity produced water. The laboratory experiments were conducted in conjunction with reservoir simulation to confirm the technical viability of polymer flooding using high-salinity water. In this study, we discuss existing challenges and how the same was transformed into opportunities by optimizing various parameters such as number of wells, well spacing, well location, perforation layer for injectors and producer and the economics to meet pilot objectives. The simulation results show that normal 2-spot injection pattern (2 injectors and 1 producer) with 80m well spacing and perforation in B-zone is a suitable solution for LTPI pilot within given time. Based on the above plan, one injector was drilled near the existing producer. The recent gyro survey demonstrated shifting of the sub-surface locations of both the producer and injector, thereby altering the well spacing. Further simulation incorporating the new locations indicated that the pilot would not meet the objectives within the piloting duration of 6 months because of shifting. Surface constrains hindered the shifting of drilling location for the second injection well to maintain 2-spot injection pattern. To overcome this challenge, additional simulation works performed to plan and drill the second injector well near another existing producer at 80m well spacing in a different area to test different rock types. Both LTPI pilot designs show higher incremental cumulative oil over water flood, faster polymer breakthrough (∼1 month), faster polymer response and oil peak within 6 months. In addition, using high salinity produced water for polymer flooding is expected to reduce piloting cost and increase operational efficiency by reducing operational problems associated with treatment and handling of less saline water.