While the first well drilled at the geothermal exploratory site at Bamboo Range was a success in relation to the heat that was found, the drilling team has not yet found the permeability they are looking for.
Earlier this week, Reykjavik Geothermal’s Thorleifur Finnsson told SVGTV that during the exploration process, the drilling team expects to drill three wells. He said while drilling the first well, they went down 2700 metres, which is 200 to 300 metres more than they thought they would need to in order to find the desired heat. Finnsson said the wells have been named Number One, Number Two and Number Three and drilling has now begun on well Number Three and well Number Two will be drilled last.
He said, there is also a possibility that they will revisit well Number One.
“Possibly if we are lucky in well Two, we will come back in well One and try to fix that so we will get permeability. But this is exploration and we don’t know exactly what is down there, so this is normal for the first well,” Finnsson told SVGTV.
Last month, Prime Minister Dr Ralph Gonsalves read a report on radio stating that at a depth of 2500 metres, the temperature was more than 250 degrees Celsius. He described this as a “great temperature” and said in the geothermal source itself, they have met the first permeability of the soil which was measured at 1.5 litres per second.
The heat extraction procedure requires heat transfer from hot rocks into the circulating fluid. The amount of flow through the rock is determined by the permeability of the bedrock, and it is thus a crucial parameter for the plant’s performance.
Finnsson said the drilling rig was moved from well Number One to well Number Three and up to Tuesday they had already reached down to 140 metres.
This well is being drilled in a South West direction, opposite to the direction of well Number One. It will be drilled to a similar size and depth as well Number One, that is 2700 metres, and is expected to be completed in 60 days.
He said Well Number One was drilled in 82 days, 22 days longer than expected.
Finnsson said they are hoping to drill the second well (well Number Three) on time but stated that while drilling well Number One, it became unstable after 1800 to 1900 metres.
The instability saw silt and sand falling into the well and blocking it, delaying the drilling process and Finnsson said they will return to well Number One with different equipment so they can go all the way down with the casing.
“We have learnt from that well so we will change how we drill,” he told SVGTV while adding that they are hoping they get the permeability they are looking for in the other wells.
He added, “we are learning. We are drilling South West and the third well will drill under
the mountain. There are three wells targeted and if we are successful with [the second well], we will drill [the third well] directly under Soufriere at 2.5 kilometres.”
Finnson said that if they are not successful, they will analyse what is happening and if they don’t find the heat or permeability to produce power, they will revise their ideas, “and see what happens.”
Finnson told SVG TV that at this point it is still too early to say whether the geothermal capabilities are up to standard but they have a program and a plan to complete and they must drill the second well to decide what happens next while they will have to go back to well Number One.
He said also that well One and Three go in different directions and Number Two is in between them and will be drilled deeper.