Mulusa G. I.
Geothermal Development Company
A two-phase production well at Menengai geothermal field earmarked for steam supply for the 105MW power project has been subject to calcite scaling, hence requiring workovers to remove the scale to maintain production flows. Two workovers have been performed to date since 2011. After reviewing the well performance, the cause of the productivity decline was assessed to be calcite scale in the feedzone fractures near the wellbore. It was decided that the best option to maintain its optimum productivity was by injecting a chemical inhibitor. This paper reports on field studies and preliminary numerical analyses carried out to understand scaling mechanisms in the production well. The objective of this work is to integrate analyses of the field data and reactive transport modelling in an effort improve well performance in such a way to minimize production loss from scaling. To understand the scaling process and loss of production and factors that cause the deposition of calcite in the near-well formation were identified and the extent of their effect was simulated using the reactive geochemical transport modeling tool TOUGHREACT. A radial, one-dimensional model of the formation around the bottommost permeable aquifer was used and constrained with reservoir data, the mineralogy of the host rock, and the average composition of the two-phase fluid.
Keywords: Reactive transport model, scaling, calcite, production.
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