Preliminary design of the Menengai phase I steam gathering system

Abstract

The best piping configuration is the least expensive which offers the highest efficiency on a long term basis. This requires the consideration of installation cost, pressure loss effects on production, stress level concerns, fatigue failures, support and anchor effects, stability, expansion capacity, and easy maintenance, among others. The objective of this study is to design a steam gathering system which will provide an efficient arrangement to supply steam to four 100 MWe geothermal power plants while re-injecting all the excessive brine. In this study, three different scenarios based on different power plant locations are presented and analysed and the optimum pipeline configuration is selected considering minimal cost and pressure drop. In sizing two-phase flow pipelines, the superficial steam velocity has been restricted to a maximum of 40 m/s while the pipeline layout is carefully selected such that the flow is downwards. A minimum upward flow of 1% is allowed in twophase pipelines in cases where the two-phase flow has to go uphill; this reduces the possibility of slug flow regimes in the pipelines. The results show that building power plants in the same location offers the most efficient gathering system in terms of cost comparison, followed by the next best scenario of having power plants in two locations. The study has shown that it may be difficult to have centralized separator stations for all the wells due to high costs as a result of longer pipelines from some of the locations.