Prior work has shown that ammonia is a useful alkali for alkaline-surfactant-polymer (ASP) chemical floods. This paper extends the application of ammonia as alkali to high acid number oils. Ammonia as alkali seems ideal for high acid number oils as no appreciable ionic strength is generated by ammonia in solution, and the prospect for highly performing AP formulations exists (no cosurfactant required). Furthermore, the high number of moles of alkali/kg from ammonia is advantageous for the efficiency of logistics which is an especially critical factor in remote locations.

Our results show that for the specific crude oil and reservoir brine utilized in this study highly performing AP formulations are not obtained. The optimal salinity of petroleum soap from the crude oil is lower than the salinity of softened reservoir brine so a low-cost process is not possible without desalinization. Furthermore, the petroleum soaps do not generate low IFT with the soft brine, and an AP flood only recovered 7% of Sor.

With surfactants and crude oil evaluated in this paper ammonia is a suitable replacement for sodium carbonate for ASP formulations only if additional sodium chloride is added to the formulation in soft brine. Presently, the minimum amount of additional sodium chloride needed for high oil recovery is 0.5%. Economic evaluations need to be performed to determine the lowest cost option including an evaluation of logistics, (0.3% ammonia + 0.5% NaCl), or 2% sodium carbonate.

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