Abstract The Aishwariya Barmer Hill (ABH) is a low-permeability (0.1–2 md), high-porosity (avg. 25%) multilayered Porcellanite oil reservoir in western India, developed through hydraulically fractured horizontal wells. Enhancing recovery of such low permeability reservoirs beyond the typical depletion range of 5–12% requires the application of secondary and tertiary recovery mechanisms. However, low permeability, reservoir heterogeneity, and presence of hydraulically fractured wells present significant challenges in implementing these techniques. Key risks include injectivity sustenance, poor conformance, and delayed production responses, compounded by the limited field applications of such recovery techniques in reservoirs of comparable permeability. This paper presents a multidimensional approach for identifying techno-commercially viable IOR/EOR processes, while addressing the associated risks and challenges. The methodology began with analogue field evaluations, followed by analytical techniques to estimate ultimate recovery for various processes such as waterflooding, polymer flooding and immiscible gas injection. Fractional-flow theory (Buckley-Leverett) and modified methods (Koval theory) were applied for initial screening. Suitable processes including Water-Alternating-Gas (WAG) and Gas Huff and Puff, were then evaluated through detailed simulation models replicating field conditions. A key consideration was incorporating geomechanics into the models to accurately simulate hydraulic fractures and injection behavior. Hydraulic fractures were modelled using actual pumping data, and water flood pilot results were integrated to validate injection-production dynamics. The feasibility of implementing these processes beyond current development plans was evaluated alongside a risk assessment using a traffic light system, identifying the need for additional studies including core flooding, PVT and geomechanical analyses. Water-flooding and gas EOR demonstrated the high recovery potential. Thermal and polymer methods were deemed infeasible due to technical feasibility and low injectivity. Gas huff-and-puff was ineffective in this permeability range because of gas migration away from injectors, while continuous gas injection suffered from immiscibility and early gas breakthrough. Both WAG and waterflooding showed the highest recovery potential; however, WAG is more operationally complex and expensive than waterflooding. Injection pressure is a critical factor for waterflood as below-fracture pressure injection leads to low injectivity, while above-fracture pressure injections can adversary impact sweep efficiency. Surfactants may enhance spontaneous imbibition and improve sustained water injection. Key factors for successful waterflooding include water quality, optimized injection patterns, conformance control, and injection pressure management relative to the fracture gradient. "Halo" reservoirs represent a unique challenge within the tight oil spectrum, where flooding is promising but difficult and unforgiving. Unlike traditional EOR/IOR screening, which focuses on rock-fluid interaction, injectivity remains a significant uncertainty for low-perm reservoirs. The workflow presented here provides a framework for selecting the most feasible EOR processes, balancing technical, economic, and operational considerations.
Singh et al. (Mon,) studied this question.
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