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Geothermal project in St. Vincent & Grenadines facing challenges with drilled wells

Drilling rig on site at La Soufriere, St. Vincent, Caribbean (source: Stv Online)
Alexander Richter 31 Jan 2020

With the three wells drilled for the geothermal project on St. Vincent in the Caribbean, it is now planned to sidetrack wells and stimulate wells to see how to increase necessary permeability of the wells for planned geothermal power generation.

As reported locally this week, the three wells drilled for the geothermal project in St. Vincent & the Grenadines in the Caribbean show sufficient temperature, yet not the level of permeability required to guarantee the operation of a geothermal power plant.

“The conclusion in all of this as provided by the technical persons is that although the results in relation to the permeability have not gone favourably due to the very tight fractures that have limited the permeability, the tested temperatures on the wells were adequate for geothermal power,” Prime Minister Ralph Gonsalves told Parliament last Wednesday.

The prime minister said that the technical team will exhaust all options of well stimulation in an effort to open the fractures on the three wells and improve permeability.

He said that the technical team is optimistic that following the successful stimulation results of the well SVG 03, “they are hopeful that the others will be similar and in addition, strengthen the stimulation in 03”.

Drilling of the first well SVG01 lasted from April 30, 2019 to July 27, 2019, a duration of 89 days to a depth of 2,700 meters. With challenges due to the unstable formation in the well, it was necessary to correct the inclination of the well, which then though collapsed at a depth of 1,889 meters.  Total cost of drilling this well was $7.7 million and a temperature of 155 degrees Celsius was measured at a depth of 1,880 meters.  The project team sees still the possibility for making the well successful with drilling a side track from 1,800 to 2,700 meters and additional stimulation.

The second well, SVG03, was drilled between Aug. 7, 2019 and Oct 29, 2019, including seven days of stimulation to a depth 2,283 meters (total length 2,800 meters). The well collapsed at a depth of 1,627 meters and a sidetrack from 1,160 meters. Total cost of the well was $7.6 million. Temperature of the well was 220 degrees Celsius at the depth of 2,800 meters with though low permeability. Well testing is outstanding but it is planned to continue stimulation to increase flow capacity.

Drilling for the third well, SVG02 began on Nov. 4, 2019 and ended Jan. 15, 2020, including 19 days’ stimulation. Depth of the well is 2,990 meters (2,869 vertical depth). Drilling cost was $5.6 million with a temperature of 230 to 250 degrees Celsius. Also this well will have to be stimulated.

Together with the Caribbean Development Bank and the board of the St. Vincent Geothermal Company Ltd., efforts will be made to make the wells productive for the purpose of the project to develop a geothermal power project.

Sidetracking the first well, SVG01 is next on the agenda with stimulation using a downhole packer, to seal downhole at 1,700 meters. The same will then be tried to SVG03.

It is expected that testing will be concluded around July 2020, at that time estimates can be made about the possible capacity of the wells for power generation.

Source: iWitnessNews