Engineering aspects of geothermal development in the Imperial Valley

Abstract

The existence of geothermal resources in the Imperial Valley of California has been known for many years. An accelerating pace of exploration has contributed to a belief that major developments are likely. In order to fulfill its function, the County of Imperial has decided to introduce a Geothermal Element into its General Plan. To provide the background necessary for preparing such an element, the County contracted with the University of California at Riverside and the Environmental Quality Laboratory at the California Institute of Technology to carry out appropriate investigations. These include questions of resource evaluation, engineering development, environmental impact, economics, regulation, and so forth. This document is a collection of reviews of engineering matters pertinent to the County's plan. The various subjects were chosen for their applicability to the plan or to the needs of other workers on the project. By gathering the separate sections together, it is hoped that the information will be more conveniently available and useful to County personnel and others. It is not a comprehensive treatment. Briefly, the contents include discussions of drilling practice, costs, and land requirements. Brief notes on reinjection and on fluid transmission follow. The section on power plants attempts to give scaling relationships for land area, costs, and performance, according to size and reservoir temperature. The problem of cooling power plants is important, particularly in an arid agricultural area. Cooling requirements, water availability, and water suitability are discussed in turn. The question of the interactions of the hydrologic cycle, withdrawals for cooling, and the Salton Sea are covered in a separate EQL document. Finally, there are sections devoted to nonelectrical uses for the geothermal resources, including production of fresh water and chemicals. The direct uses for geothermal heat are not included.