Inception of time-lapse micro-gravity monitoring of the great Olkaria geothermal field, Kenya

Philip Omollo, Jun Nishijima

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Microgravity monitoring forms an additional way of augmenting other reservoir monitoring data. Long-term time-lapse microgravity monitoring of the geothermal reservoirs can better evaluate the field fluid mass balance. The reinjection and injection strategies are good mitigation measures to reduce the possibility of subsidence in a geothermal field. These trends due to microgravity monitoring observation, especially the high gravity change observed over the monitoring from Northeast to East fields traversing to Southwest field, provides insight into the possible structural zone trend within the field that influence the reservoir through possible natural recharge in support of the field geological structural boundaries evidenced from the previous gravity structural analysis. The recharge to the Domes field is possibly through some sections of the Ring structure, while in the Northeast and East fields, the natural recharge seems to find its way to the field through some confirmed contact zones from previous gravity studies, the Ololbutot and Olkaria fault zones, while other influential structures and the fissure swarm alignment defining the Ol Njorowa gorge provide a possible barrier between the Domes field and the East production field. The general observation of the gravity change for the entire field during the monitoring period is minimal and stable, which could be attributed to the well-planned strategy of reinjection into the reservoir in addition to the natural recharge. Most observed changes are temporal and will vary with time based on reservoir system field operations and influences from the natural recharge system. Therefore, this observation may change with subsequent monitoring depending on the amount of mass extraction, reinjection, and natural recharge. Gravity monitoring will still play a key role in evaluating the mass balance effect in the field and ensuring sustainable future reservoir management.

Original languageEnglish
Article number102891
JournalGeothermics
Volume117
DOIs
Publication statusPublished - Feb 2024

All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • Geotechnical Engineering and Engineering Geology
  • Geology

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