Wellhead Generating Plants: KenGen Experience

Abstract

Installation of small 2-5 MWe plants on the wellhead was adopted at Olkaria in 2012 as an early generation strategy. The concept has now been expanded to involve more or less permanent units utilizing up to three wells (15 MWe) located on a single well pad. This strategy appeared quite attractive, at least at the beginning, as it was deemed to stimulate the market to invest in small plants and possible joint ventures once the concept is proven. It also assured operators of the field of early revenue pending completion of drilling and construction of power plants of the conventional type/size. Two plants were piloted, one 5 MWe plant at OW-37A in Olkaria east field and another in the virgin Eburru field both operated by KenGen. Portable wellhead units at Olkaria are condensing type and consist of turbo-generator, cooling tower, condenser, gas extraction system, electrical and control system and auxiliary equipment. Unlike conventional geothermal plants, these wellhead generating units have little permanent civil works and have shorter pipelines. They are designed to fit into containers or skid mounted to facilite easy transfer from one well pad to another as candidate well(s) may be abandoned to pave way for more permanent works. This paper discusses the strategy and offers a comparative study on the performance of such plants vis-à-vis conventional size plants operating at Olkaria.