増進回収した油田水再注入に向けた産出水の系外CO2鉱物化

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🔬研究者:系外鉱物化と低塩分水攻法の界面化学的シナジーを定量化する実験研究の出発点となる。

🏢実務担当者:産出水処理とCO2利用を組み合わせ、廃棄物コスト削減と回収率向上を狙う油田・CCUS事業者に実装の枠組みを提供する。

🏛政策担当者:EOR随伴のCO2固定を炭素除去としてどう扱うか、CCUSインセンティブ設計やMRV整備の論点を提示する。

The continued rise in anthropogenic carbon dioxide (CO2) emissions presents a critical environmental challenge, intensifying the need for scalable carbon capture, utilization, and storage (CCUS) strategies. Although geological sequestration remains the most established approach for long-term CO2 storage, its large-scale deployment is often limited by high capital costs and limited direct economic return. Ex-situ CO2 mineralization has emerged as a promising alternative that enables permanent carbon storage while generating valuable mineral products such as calcium carbonate (CaCO3) and magnesium hydroxide (Mg(OH)2). This paper reviews ex-situ mineralization chemistry, examines established EOR mechanisms, explains the potential synergies between the two processes, references prior experimental validation, and conceptually connects PW carbonation to engineered water reinjection in depleted oil fields. In this approach, CO2 is dissolved into divalent-ion-rich produced water (PW), followed by alkalinization using sodium hydroxide (NaOH) to promote precipitation of CaCO3 and Mg(OH)2. Because PW already contains dissolved calcium (Ca2+) and magnesium (Mg2+), no mineral dissolution step is required, enabling a direct aqueous carbonation pathway that leverages existing oilfield waste streams. Beyond mineral formation, the carbonation process fundamentally modifies PW chemistry by depleting divalent ions and altering pH/alkalinity (primarily due to NaOH addition and subsequent precipitation). These changes create opportunities to engineer treated PW for reinjection into depleted oil fields. Reduced concentrations of Ca2+ and Mg2+ may influence rock–brine interfacial interactions, alter slip-plane charge, and promote wettability alteration, all of which are central mechanisms in low-salinity waterflooding. In addition, the elevated alkalinity present after carbonation and precipitation can enhance recovery through in-situ surfactant generation resulting from NaOH addition, leading to reduced oil–water interfacial tension (IFT) and improved microscopic displacement efficiency. Experimental evidence from recent studies demonstrates that carbonated and alkalized PW can reduce IFT, shift wettability toward more water-wet conditions, and improve oil recovery performance. By integrating carbon utilization chemistry with reservoir engineering principles, this work outlines a technically grounded, operationally relevant pathway for simultaneously storing carbon, valorizing PW, generating mineral byproducts, and enhancing tertiary recovery.

• semanticscholar https://doi.org/10.2118/232242-msfirst seen 2026-10-02 05:28:27