Piping Design Considerations for Geothermal Steamfields

Abstract

The piping systems in a geothermal steamfield provide the means to transfer the geothermal fluids from the production wellpads to the power plant and to the points of disposal. They also have an integral role in the conditioning of fluids to optimise the efficiency of the energy conversion plant and to achieve high plant availability and flexibility to respond to resource change. While the piping system is typically lower cost than the wells and power plant, it is critical to maximising the performance from these major capital investments. As such, these systems constitute a key component of any geothermal development, and design must integrate many factors to guarantee the project success. Hence, the project should include appropriate piping engineering from the concept design and feasibility studies to the commissioning and start-up of the steamfield. Any geothermal steamfield project brings a series of inherent challenges to the designer that may include: well production uncertainty, fluid characteristics, injection well permeability, well and equipment O&M requirements, silica polymerization, future steamfield expansion options, unexpected changes in the reservoir, geotechnical issues, and environmental and community constraints. These field-specific variables drive customised configuration of every single steamfield design. Therefore, the challenge is to apply proven piping design methodologies and standardised practices to address these specific configuration issues in the most efficient but effective manner. This paper discusses common steamfield piping design considerations, particularly for the design of production and injection wellpads, separation stations, brine injection pumping stations, and steam venting stations. These standardised subsystem designs provide cost effective design elements that can be integrated into the customised cross country piping system and jointly meet the operational requirements of the fluid delivery and disposal system.