Report released on first geothermal drilling in Montserrat


By Nerissa Golden

BRADES, Montserrat (GIU) — The government of Montserrat has released the first official report on the findings of the geothermal assessment conducted by Dr Graham Ryan of the Institute of Earth Science and Engineering, University of Auckland in New Zealand.

According to the report, drilling began on Montserrat’s first geothermal well, MON-1, on 17 March. “The goal, for this or any other such well, is to source a high temperature and a permeable zone with an inflow of hot water, aka a ‘feeder zone’. These elements enable us to produce geothermal energy from a well.

“Prior to drilling, EGS and Dr Graham Ryan created models of Montserrat’s geothermal system using information from surveys conducted in 2009. These models were used to determine preferential areas to drill. The preliminary studies also suggested a good likelihood that permeable zones would be reached in the 1,500-2,000 meter range. However, precise location of these permeable zones is not possible at the current time (in fact, predictions of permeable zones is currently the focus of intense scientific research).

“MON-1 was originally designed to be drilled to a maximum depth of 2,000 meters. However, while temperatures were high there was no indication of permeable zones that would allow hot water to flow into the well. Therefore the well was deepened to a depth of 2,298 meters; a permeable zone was found at 2,142 m.

“Overall, information that has been gathered while drilling has matched well with the models’ predictions. Initial temperature testing during and after drilling of the well indicated temperatures of around 250 ˚C, even higher than originally expected. Early testing also indicates an inflow of hot water or a ‘feeder zone’ at a depth of 2,142 meters – 142 meters below the planned depth for the well.

“Having successfully sourced both high temperatures and promising permeability the decision was made to stop drilling the well. Measurements of temperature and pressure were made in the well with a specialised tool and a ‘slotted liner’ was run to the bottom of the well. The well is ‘cased’ down to 1,150 meters, which means that steel tubing has been cemented in place from the surface down to that depth. The ‘slotted liner’, a steel tube with holes cut into it, is hung from the bottom of the casing to the bottom of the well. The liner prevents the walls of the well from collapsing inwards and allows the hot water to flow into and up the well.

“The well will now be capped with a valve and allowed to warm up. Temperature and pressure measurements will be made over several weeks as the well warms up. When the well is fully warmed it will be ‘flow tested’ for several days to determine how much power it can produce,” the report states.

Now that the initial drilling of MON-1 has been successfully completed, the drill rig is being dismantled and will be reassembled at the second well site, called MON-2.

The Iceland Drilling Company (IDC) is conducting the drilling operation, which is being fully funded by Britain’s Department for International Development (DfID) as part of its support of capital investment projects aimed at making Montserrat more financially independent.

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