Mechanism for enhanced oil recovery from carbonate reservoirs by adding copper ions to seawater

Abstract In existing or operating oil fields, enhanced oil recovery (EOR) methods are employed to increase production, which can contribute to meet fossil fuel demand. This research proposes a new EOR method by adding Cu(II) ions into the injected seawater, which shows a significant incremental oil production in carbonate reservoirs. An important remark in this study is the Cu(II) incorporation into the cores, with mineralization of atacamite on the carbonate surface, and copper complexation with the acid fraction of the oil. In addition, we observed oil removal up to the last monolayer on calcite surfaces. Based on these observations and first-principles calculations, we propose an EOR mechanism where the acidic oil desorbs from the rock surface by forming acid-copper complexes that are dragged by the injected fluids. In summary, we propose a simple and cost-effective EOR method with transition metals, which may significantly increase the yield of low-recovery carbonate reservoirs and reduce the environmental impact of exploring new reservoirs.