Improving Sweep Efficiency In A Mature Waterflood: Balcon Field, Colombia

Abstract

Abstract The Balcon Field, operated by HOCOL S.A., is located in Colombia's Upper Magdalena Valley Basin. Oil production began in 1988, reaching a maximum primary rate of 5,742 BOPD in January 1994. Secondary recovery started in 1996, achieving a maximum secondary production of 9,198 BOPD in June 2001. Subsequently, water production has increased rapidly accompanied by declining oil production, due primarily to reservoir heterogeneity and an unfavorable mobility ratio. The oil recovery factor as of July 2011, as a percentage of OOIP, is estimated to be approximately 30% at a current water cut of about 84%. This work presents a methodology to determine the feasibility of polymer gels to reduce water channeling, including water injection and production analysis, diagnostic charts, fluid movement and geological characterization. Results of this integrated analysis led to a comprehensive laboratory study to identify the appropriate gel formulation (e.g. polymer, polymer concentration and cross linker ratio) at reservoir conditions. The recommended gel system developed was validated by a core flood before field implementation. The first gel treatment was implemented in July 2010, followed by a second injection well treatment in an adjacent pattern with significant water channeling. The treatment designs included several stages of varying gel concentrations and injection rates, which were modified during the field implementation based on surface pressure response. Post treatment oil response occurred within approximately two months and payout was achieved in 6 months. As of April 2011 incremental oil of 212,000 bbl. has been produced. However, offset producers are still showing incremental production. These promising results led to a second (and ongoing) campaign in 2011. Polymer gels have been successfully applied in sandstones reservoirs for decades. However, reservoir characterization tools continue to evolve contributing to the improvement of conformance treatment designs. This field case study will provide an updated framework for operators considering chemical sweep improvement technologies as part of an integrated reservoir management strategy.