Staged Asset Deployment – Commercial and Technical Advantages of Using a Wellhead Generation Unit

Abstract

The typical geothermal development schedule for new fields may span five to ten years. Managing the cash flow for these enterprises, which demand considerable up-front exploration and drilling investments far before economical financing is available or generation can become commercial, can be challenging. Wellhead generation units can offer multiple benefits: provide an early cash flow to offset development costs, offset diesel engine fuel costs for drilling rigs, mitigate risk on the resource assessment by allowing longer-term flow tests, and set the stage for the development of larger, more efficient power plants to be operated long term. In this paper we present a financial evaluation of a standard six-year development plan, considering the insertion of a wellhead unit at the appropriate stage of development. We conduct this evaluation at a high level based on general assumptions; site-specific characteristics would require a more diligent evaluation based on local conditions such as tax implications, funding options, ownership structure(s), depreciation, resale, etc. We present a number of technical options for wellhead units, including backpressure turbines, condensing units, binary units, and surplus equipment, and compare their relative merits. The transition to the long-term power station is discussed. A number of case studies of successful implementation in countries such as Mexico, Nicaragua, and Costa Rica are presented with these dicsussions.