Geochemical modeling and experimental evaluation of high-pH floods: Impact of Water¨CRock interactions in sandstone

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• 作者：Mahdi Kazempour ; Eric Sundstrom ; Vladimir Alvarado  ; ;   ; ^{valvarad@uwyo.edu}
• 关键词：Alkaline flood ; Anhydrite ; pH buffering ; Oil recovery ; Chemical flooding
• 刊名：Fuel
• 出版年：2012
• 出版时间：February 2012
• 年：2012
• 卷：92
• 期：1
• 页码：216-230
• 全文大小：3523 K

文摘

Injection of alkaline solutions in reservoir leads to mineral dissolution and precipitation, possibly resulting in changes in permeability and porosity, and consequently altering solution pH. Accurate prediction of pH, alkali consumption and aqueous chemistry changes are required to design suitable chemical blends in alkaline-polymer (AP) or alkaline-surfactant-polymer (ASP) flooding. Excessive consumption of alkali can result in degradation of flood performance and lower than expected oil recovery. We report state-of-the-art geochemical simulation results for sandstone reservoir mineral assemblages and alkali solutions (NaOH, Na₂CO₃, and NaBO₂) employed in AP and ASP formulations. Single-phase high-pH corefloods were completed using Berea sandstone and reservoir samples to calibrate and validate geochemical simulations. Results show that rock-fluid interactions depend strongly on mineral type and amount, alkaline solution injection flowrate, and composition of the injected and formation water. Anhydrite, a commonly found calcium sulfate, significantly impacts pH buffering capacity, water chemistry and permeability damage against conventional alkali agents in chemical flooding particularly for Na₂CO₃, but no significant pH buffering is observed during NaBO₂ flooding. Experimental data and model results show that the pH-buffering effect is maintained even after several pore volumes of alkaline solution are injected, if a sufficient fraction of relevant minerals is present. The end consequence of this is insufficient alkalinity for reactions with the oil phase and the likely formation damage.