Integrity-Constrained Laboratory Screening of EOR Methods for Heavy-Oil Carbonate Reservoirs

Abstract

Enhanced oil recovery (EOR) screening is commonly initiated from reservoir and fluid properties, displacement mechanisms, and expected recovery potential. In technically complex offshore systems, however, a candidate method may be unsuitable for further development if the associated fluids and operating conditions intensify corrosion, inorganic scaling, organic deposition, emulsion persistence, phase instability, or near-wellbore damage. This study develops an integrity-constrained pre-pilot laboratory screening workflow for the integrated Field X-Field Y system. The workflow integrates brine chemistry and water-compatibility calculations, corrosion and inhibitor tests, wax-appearance-temperature (WAT) and viscosity data, emulsion stability, PVT recombination, and filtration compatibility. Untreated corrosion rates reached 11.586 mm/year at the electrical submersible pump outlet and 2.942 mm/year at the wellhead. Field X-Field Y formation-water mixing was compatible at 60 °C, whereas cooling to 30–50 °C increased predicted BaSO4-dominated precipitation, with 18.849 mg/L at 30 °C for the 75/25 mixture; the broader marine-water case reached 58.79 mg/L under the evaluated low-temperature/low-pressure condition. Field Y DST-1 was the most restrictive oil in the organic-deposition screen, with 10.6 wt.% paraffin and WAT evidence spanning 17.4–22.4 °C. Artificial emulsions retained up to 70% water for Field X DST-3 and 80% for Field Y DST-1. For the selected associated-gas analogue, a gas-oil ratio not above 90 m³/t at 18 MPa and 60.5 °C was used as the single-phase recombination boundary. The six-domain matrix was reformulated as an equal-weight ordinal qualification-burden index rather than a recovery-ranking tool; WAG had the highest burden (S=15; R=2.50), and this position remained unchanged under ±25% one-at-a-time criterion-weight perturbations. The framework therefore identifies operational-integrity constraints and the laboratory qualification required before direct displacement corefloods, compositional simulation, and pilot validation; it does not quantify incremental oil recovery.