| Title | Preliminary Results of Deep Geothermal Drilling and Testing on the Island of Montserrat |
|---|---|
| Authors | Paul BROPHY, Bastien POUX, Gene SUEMNICHT and Paul HIRTZ |
| Year | 2014 |
| Conference | Stanford Geothermal Workshop |
| Keywords | Geothermal, Exploration, Montserrat, Caribbean, Soufriere Hills, volcano, magnetotellurics, reservoir, drilling, well test results. |
| Abstract | Montserrat is an active volcanic island in the Caribbean Lesser Antilles arc. Renewed eruptive activity from the Soufriere Hills volcano since 1995 destroyed the main town of Plymouth and left approximately a third of the island uninhabitable. As a result, such an active volcanic heat source suggests a great potential for geothermal electrical power generation as is the case with many of the Caribbean islands In 2009 and at the request of the Government of Montserrat, EGS, Inc. completed a resource assessment of the island and developed a conceptual exploration model of the potential geothermal resource. Exploration work included geologic mapping, geophysical and geochemical surveys. Based on structural geology, geochemistry, magnetotelluric and time-domain EM data and microseismic interpretations, high priority areas were defined for exploratory drilling. Preferred sites were identified in a zone protected from potential hazards, mostly pyroclastic flows, within a faulted graben between St George’s and Garibaldi Hills where MT interpretations suggested an altered clay cap covered a potential hydrothermal system. Two successful wells were drilled in this faulted graben in the central-southern part of the island during 2013. MON-1 was drilled to a total depth of 2298m and encountered at least one fractured zone at 2191m and static bottom hole temperatures of +230°C. MON-2 was drilled approximately 500m northeast to a total depth of 2870m. Based on circulation losses, the wellbore crossed several fracture zones encountering bottom hole temperatures of 260°C. A preliminary 30 day flow test of MON-1 indicates the well is capable of producing 92.5 kph total mass flow and 32.5 kph steam at wellhead temperatures of 165°C and 7.5 bars. Additional testing is planned to determine the nature and extent of the resource but the two wells appear to be capable of supplying the current 2MW electrical load of the island. |