Kuparuk Field Reservoir Management After 40 Years

Abstract

The giant Kuparuk Field (Figure 1), the second largest oil field on the Alaska North Slope and one of the largest oil fields in the United States, has been on production for 41 years. The field, a legacy asset in the ConocoPhillips portfolio, contains more than 7.5 Bstb OOIP with 2.5 Bstb in the C Sands and 5.0 Bstb in the A Sands. Production commenced in December 1981 and has cumulated to date more than 2.5 Bstb oil through water-flooding, immiscible water-alternating gas (IWAG) and miscible water-alternating-gas (MWAG) injection. Currently, the field produces about 60,000 stb/d oil, 515,000 bbl/d water and 105 MMscf/d gas, and injects 625,000 bbl/d water and 80 MMscf/d gas through 3 central processing facilities (CPF1, CPF2, and CPF3, located as shown in Figure 1), 45 drillsites, and about 700 active wells. Although the Kuparuk Field is mature, recent studies highlight the potential to optimize the oil recovery. Static and dynamic data along with benchmark studies indicate that the underlying Kuparuk A Sands are of lower maturity than the overlying Kuparuk C Sands. Significant A Sands recovery improvement is possible with strategic reservoir management practices. Several activities were undertaken to understand relative immaturities across the field and investigate methods to improve the performance of Kuparuk A Sands. These include: identifying geologically controlled reservoir performance regions, developing a state-of-the-art full field reservoir model, testing pattern realignment that combines infill drilling with reconfiguration of existing wellbores, and conducting injectivity treatments in various parts of the field. The analysis of available data shows the benefits of increasing the throughput in the Kuparuk A Sands through voidage balancing, improved produced water and gas handling strategies, waterflood pattern realignment, continued in-fill drilling, and increased injectivity. Kuparuk reservoir management has been revised to focus future activities around these core strategies tailored to specific reservoir regions. The intent of this paper is to document strategies that can be implemented to revitalize mature waterflood fields, specifically those that have been developed with commingled reservoirs.