Structural Control of Fluid Pathways in Active Geothermal Systems. Insights from Olkaria Geothermal Field, Kenya

Abstract

In volcanically active geothermal systems, pre-existing faults structures may serve as efficient pathways for migration and ascent of deep-seated fluids in the geothermal reservoir. Review of the geological structures reveals a structural control by both rift aligned faults and the proposed caldera ring structure. Understanding how pre-existing regional tectonic faults and caldera ring faults affect fluid flow to the surface is significant in detection of mass flow in deep geothermal wells. While it is inherent that some fault structures in Olkaria geothermal field have proved to be productive and act as efficient conduits for the ascent of geothermal fluids, others are known to be totally unproductive, in which case they act as barriers to fluid flow. This case study emphasizes the usefulness of structural features in active geothermal systems and their role in enhancing high permeability pathways by transferring deep-seated hydrothermal fluids to shallow levels of the system.