Higher oil recovery after waterflood in carbonate reservoirs is attributed to increasing water wettability of the rock that in turn relies on complicated surface chemistry. In addition, calcite mineral reacts with aqueous solutions and can alter substantially the composition of injected water by mineral dissolution. Carefully designed chemical and/or brine flood compositions in the laboratory may not remain intact while the injected solutions pass through the reactive reservoir rock. This is especially true for a low-salinity waterflood process, where some finely tuned brine compositions can improve flood performances, whereas others cannot. We present a 1D reactive transport numerical model that captures the changes in injected compositions during water flow through porous carbonate rock. We include highly coupled bulk aqueous and surface carbonate-reaction chemistry, detailed reaction and mass transfer kinetics, 2:1 calcium ion exchange, and axial dispersion. At typical calcite reaction rates, local equilibrium is established immediately upon injection. In SI, we validate the reactive transport model against analytic solutions for rock dissolution, ion exchange, and longitudinal dispersion, each considered separately. Accordingly, using an open-source algorithm (Charlton and Parkhurst in Comput Geosci 37(10):1653–1663, 2011. https://doi.org/10.1016/j.cageo.2011.02.005), we outline a design tool to specify chemical/brine flooding formulations that correct for composition alteration by the carbonate rock. Subsequent works compare proposed theory against experiments on core plugs of Indiana limestone and give examples of how injected salinity compositions deviate from those designed in the laboratory for water-wettability improvement.

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碳酸盐岩油藏盐度注水化学成分：理论

碳酸盐岩油藏注水后较高的石油采收率归因于岩石的水润湿性增加，而这反过来又依赖于复杂的表面化学。此外，方解石矿物会与水溶液发生反应，并且可以通过矿物溶解来显着改变注入水的组成。当注入的溶液通过反应性储层岩石时，实验室中精心设计的化学和/或盐水驱组合物可能不会保持完整。对于低盐度水驱过程尤其如此，其中一些微调的盐水成分可以改善驱油性能，而其他则不能。我们提出了一个一维反应输运数值模型，该模型捕获了水流过多孔碳酸盐岩期间注入成分的变化。我们包括高度耦合的本体水溶液和表面碳酸盐反应化学、详细的反应和传质动力学、2:1 钙离子交换和轴向分散。在典型的方解石反应速率下，注射后立即建立局部平衡。在 SI 中，我们针对岩石溶解、离子交换和纵向分散的解析解来验证反应输运模型，每一个都单独考虑。因此，使用开源算法（Charlton 和 Parkhurst in Comput Geosci 37(10):1653–1663, 2011. https://doi.org/10.1016/j.cageo.2011.02.005），我们概述了一个设计工具指定化学/盐水驱替配方，以纠正碳酸盐岩的成分变化。