Results of the Injection Well Polymer Gel Treatment Program at the Rangely Weber

Abstract

The Rangely Weber Sand Unit is a large CO2 miscible WAG flood located in northwestern Colorado. Conformance improvement has become the key operating strategy due to the maturing flood's associated natural increase in operating expense and declining oil production. Conformance improvement is defined as improving the vertical and areal sweep of the reservoir and is one of the few strategies that will reduce operating expense and allow for the recovery of additional reserves. The many different technologies and techniques that have been deployed over the last decade to improve the conformance of the reservoir include: selective injection equipment, straddle packer assemblies, pattern re-alignment, cement squeezes, foam treatments, reduced half cylcle slug sizes, simultaneous injection, and polymer treatments. These attempts have met with varying degrees of success. Recent efforts using large volume (10,000 bbl) polymer gel treatments to treat injection wells have been very successful. This success is attributed to the fact that these treatments effectively impact the deep reservoir problem. Past near-wellbore treatments were not effective at preventing flow in the high permeability matrix and fracture pathways believed to be responsible for poor sweep. Results from 44 injection well treatments performed through mid 1997 are discussed. Individual treatment examples and full project economics are provided. Field modeling and forecasting to assess the impact of continued treatments over the next ten years is also included. P. 93

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