Application of Polymer Gels as Conformance Control Agents for Carbon Dioxide EOR WAG Floods

With the production from mature oil fields declining, the increasing demand of oil urges towards more effective recovery of the available resources. Currently, the CO₂ floods are the second most applied EOR processes in the world behind steam injection. With more than 40 years of experience gained from CO₂ flooding, successful projects have demonstrated incremental oil recovery ranging from 7 to 15 % of the oil initially in place. Despite all of the success of CO₂ floods, sweep efficiency during CO₂ flooding is typically the stumbling block to better application of the technology. Poor sweep efficiency results in early breakthrough and extraction ineffectiveness leaving zones of high oil saturation intact.

Conformance control approach employs gel treatments to act as a blocking agents reducing channeling through fractures or high-permeability zones of oil reservoir without significantly damaging hydrocarbon productivity and improve the overall oil recovery from the flooding process. Accordingly, the goal of the gel is to maximize gel penetration and permeability reduction in high permeable zone while minimizing gel penetration and permeability reduction in less permeable zones of the reservoir. A successful treatment will direct the CO₂ away from the high permeability zones towards the lower permeability intact regions.

The gel conformance control studies showed encouraging results in minimizing the effect of heterogeneities directing the injected CO₂ to extract more oil from the lower permeability zones; the gel strength was evaluated in terms of breakdown and leakoff utilizing the production data aided with CT imaging analysis. Viscosified water during WAG coupled with CO₂ shows great promising results proving the superiority over continuous CO₂ injection or WAG.

This research aims at investigating gel treatments and viscosified water-alternating-gas CO₂ mobility control techniques. A set of experiments have been conducted to verify the effectiveness and practicality of the proposed mobility control approaches. Our research employed an imaging technique integrating an X-Ray CT scanner to obtain real time images when processed provide qualitative and qualitative evaluations to the coreflood to quantify and visualize improved sweep efficiency.