1Oil and Gas Recovery Institute, National Iranian Oil Company, Tehran, I.R. IRAN
2Petroleum University of Technology, Tehran, I.R. IRAN
Water injection is an enhanced oil recovery method which is applied for number of reservoirs especially in the offshore fields around the world. Sea-water injection process is usually associated with important concerns affecting the efficiency, safety, and economy of the operation like formation damage, mineral scaling, early breakthrough and corrosion. Incompatibility between injected and formation waters may result in inorganic scale precipitation in the reservoir and then reduction of oil production rate (productivity loss) and water injection rate (injectivity loss). A comprehensive study supported by reliable modeling and experimental investigation will therefore, significantly improve the success of the operation. In this paper, mineral scale deposition phenomenon in Sirri-C offshore carbonate oil field under water injection is studied and its influence on reservoir performance and production rate is investigated. For this purpose, a series of experimental work has been conducted to study the compatibility of sea and formation waters. Amount and type of scales formed as the result of mixing different portions of these waters have been applied and incorporated with simulation studies. STARS simulator (from CMG 2005) that is capable of evaluating the effect of scale formation on reservoir performance allowing for alteration of permeability and the flow path has been used in simulation study. One of the major contributions of this work is to incorporate the equilibrium conditions, reaction rates and solubility parameters for various scale types in reservoir simulation, so the results can be more realistic. The simulation results show that in Sirri-C oil field, scale formation undermines the productivity index and has a major impact on reservoir performance.
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