Optimised pipeline route design for connection of a make-up production well : case study of well OW-906 for Olkaria IV power plant, Kenya

Abstract

Over the course of the life of a geothermal project, the steam flow will generally decline due to natural drawdown effects or changes in the reservoir as the resource is exploited. This requires that from time to time, the steam is made up by connecting additional wells to the existing steam gathering system. This process can be very challenging given the constraints offered by an already existing framework. Moreover, it requires that proper selection of the pipeline routing and tie-in points is done to ensure that the make-up well is connected in the most cost effective manner. Consideration must be given to the existing separator stations and pipelines, to ensure that there is no additional expensive construction of steam field infrastructure, unless utterly necessary. Focus should be placed on ensuring that existing spare capacities are first exhausted before more infrastructure is put up. This work attempts to give a preliminary outline for the impending connection of well OW-906 to the already existing Olkaria Domes steam field that serves the Olkaria IV plant in Olkaria, Kenya. The main focus area is the use of Variable Topography Distance Transform (VTDT) method to identify the optimal pipeline routes that would allow connection of make-up wells as cost effectively as possible. This work shows that the use of VTDT has guided the selection of the optimal route for connection of make-up well OW-906. The cheaper option is construction of a new separator station at an optimal position near the well head and then connecting the steam pipeline to the nearest main steam pipeline from separators SD1 and SD4. Brine reinjection is also to be channelled to the nearest reinjection well OW-906A. This work is intended to provide a guide for the future when new wells make-up wells are to be connected to an existing steam gathering infrastructure.