Field Management and Expansion Potential of the Momotombo Geothermal Field Using Numerical Simulation and Conceptual Modeling

The Momotombo geothermal field has been in development since the 1960s, with most drilling completed in the 1970s, and was on line with its first 35 MWg geothermal flash power plant in September 1983. The field has had several operators in its operational history, with installed capacities of 35-77 MWg and generation from 8-69 MWe. Generation was 22.5 MWe at the time of the study.

Momotombo Power Company recently became the owner/operator of the concession of the Momotombo field, and a complete assessment of wellfield performance and well conditions was initiated to assess the feasibility of increasing generation to 42 MWg. This review included a numerical simulation of the field, which also requires a strong geologic conceptual model. Previous reservoir models focused on the producing field, but did not account for sources of pressure support to several wells from outside the core of the field area. A new conceptual model was developed, and a numerical simulation of the field was used to validate and adjust assumptions in the conceptual model, resulting in a very robust conceptual and numerical model.

The resulting, integrated model suggests the existence of an area of primary recharge and upwelling that is currently undeveloped and partially connected to the existing development, providing pressure and heat support to wells closest to that area. There appear to be significant developable reserves in this area, and additional exploration is recommended to determine the extent and possible secondary outflow areas.

Within the history matching process of the numerical model, two downhole well bore failures were identified. Candidates for well remediation have been identified to increase generation from existing wells to increase generation to 42 MWe. Areas for expansion were revealed to better utilize installed capacity, and a plan to increase generation through the 15-year contract life will be implemented.

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