Solvent-Aided Polymer-Flooding: Novel Hybrid Method to Unleash the Potential of a Deep Extra-Heavy Oil Middle-Eastern Reservoir

Extra-heavy oil accumulation in the Lower Burgan reservoir of the Abdali field in Northern Kuwait exhibits a viscosity ranging from 6000 to more than 15000 cP at depths of ∼9000 ft. This paper investigates development solutions including assisted lift natural depletion, polymer injection, and solvent drive for efficient and commercial production of these reserves. The study builds upon the findings presented in two previously published papers by Al-Murayri et al. (2024) , which laid the foundation for this work.

Prior research covered characterizing heavy downhole samples mixed with liquid solvents, creating a comprehensive EOS model for crude oil and solvent mixtures, and conducting polymer coreflood tests. In this study, the EOS model together with the polymer and solvent coreflood results were incorporated for large-scale reservoir simulations. A sector model was highly refined to accurately depict such complex flow displacement. To maximize oil recovery and project NPV, existing wells were reused to design a hybrid EOR method combining depletion, solvent injection, and polymer flooding. Additionally, the feasibility of single-well cyclic solvent injection was assessed.

The best development plan involved three years of natural depletion, followed by three years of liquid solvent injection and continuous polymer drive for as long as the process remains economically viable. Natural depletion was chosen because Abdali’s sand is unconsolidated, making it an attractive option. Depletion initially lowers reservoir pressure, allowing for higher injection rates. Sand production has been, however, flagged as an operational challenge. Simulating polymer injection alone led to significant oil recovery, but its injectivity required verification in a pilot trial due to the absence of observed shear-thinning effects in the laboratory.

Liquid solvent injection was proved to be crucial at various stages. Downhole solvent injection aids in liquid lifting. Near the wellbore, solvent mixed with oil enhances injectivity. Single-well or Inter-well solvent injection creates low-viscosity fluid regions, which can be back-produced or pushed by the polymer. This process can continue as long as solvent loss is minimized.

To the best of our knowledge, the literature on solvent injection has so far focused on vapour solvents. A hybrid liquid solvent and polymer injection for extra-heavy oil recovery has not been studied before. This study proved the feasibility of such a development. When applied at pilot scale, the proposed approach can potentially evolve into a unique opportunity to verify the efficiency and practicality of commercial development. Upon establishing techo-commerical feasbility, this can unlock significant extra-heavy oil reserves.