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Monday, May 27th, 2024
British Drilling and Freezing Company Limited
Private Road No 3.
Colwick Industrial Estate
Nottingham, NG4 2BB
+44 (0)115 9611300
+44 (0)115 9617338

- HGSL Gas Storage

In 2005 E.ON acquired the rights to build a new gas storage facility in Cheshire from Scottish Power comprising eight underground salt solution cavities. When complete the facility will have a total storage capacity of 165 million cubic metres of gas, equivalent to half the gas used by the whole of the UK on an average day, making it strategically important in securing UK gas supplies in times of need.

Underground gas storage cavities are constructed in ancient naturally occurring salt deposits that have been buried deep underground. For each cavity a borehole is drilled into the salt layers and water is circulated in a controlled manner to dissolve the salt and create a liquid filled cavity. Eventually this becomes large enough to be filled with highly compressed gas to form an underground storage cavity. The impermeable properties of the salt keep the gas safely confined.

E.ON appointed BDF to carry out the specialist work of constructing the boreholes utilising Rig 18 and Rig 29, work began on site in April 2006. Rig 18 was used to install the surface casing and drill the upper section of the holes. A 36" diameter hole was drilled to 30m and 30" casing set and cemented. Reverse circulation drilling continued at 24" diameter to 300m; Rig 18 then moved to the next well to allow Rig 29 to complete each well in succession.

Rig 29 continued drilling the 24" section using conventional circulation to an average depth of 460m where 185/8" casing was set and cemented. At this level the casing had penetrated the top of the salt deposits by 10m. Drilling continued at 171/2" diameter, reaching an average total depth of 715m. 13-3/8" casing was then set and cemented at 570m prior to installing two leaching strings of 10-3/4" and 7" casing.

Wire line coring was carried out on several wells in conjunction with geophysical logging to prove the integrity of the salt.

The contract was successfully completed in May 2007, ahead of programme and on budget.

Once the client's surface infrastructure was in place and initial stages of leaching had commenced, BDF's Rig 30 was mobilised to site to undertake the workovers associated with the cavity formation. The gas storage facility is scheduled to be operational by 2012.