Document Type : Research Paper
Authors
1
Department of Petroleum, Mining, and Materials Engineering, CT.C., Islamic Azad University, Tehran, Iran Post Doctorate Fellowship, Department of Earth Science and Ocean, University of British Columbia, Vancouver, Canada
2
Assistant Professor, Department of Petroleum, Mining, and Materials Engineering, CT.C., Islamic Azad University, Tehran, Iran
10.22050/ijogst.2026.368129.1661
Abstract
The mechanisms of Low-Salinity Water (LSW) flooding in carbonate reservoirs remain less well understood than in sandstones. This study investigates the role of rock composition through a comparative experimental analysis of genuine limestone from the Shadegan oil field and pure synthetic calcite. Core flooding tests, contact angle measurements, zeta potential analysis, and pH monitoring were conducted under reservoir conditions (70°C, 100 bar). Results show that tertiary LSW injection recovered 14.5% of the initial oil in place in limestone, compared to only 3.4% in pure calcite. This significant difference is attributed to a more pronounced wettability shift towards water-wet conditions (42° contact angle reduction vs. 16° in calcite), driven by a stronger negative zeta potential shift (-7.7 mV vs. -4.1 mV) in the genuine rock. XRF analysis revealed the presence of silica, sulfate, and phosphate impurities in the limestone, which amplified the surface charge alteration. The study concludes that trace non-clay minerals significantly enhance LSW efficacy in carbonates, providing new insights for optimizing EOR in complex carbonate formations.
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