Navigation close

Details

Chonais, Schottland

LMR Drilling UK won a contract for an HDD bore in Scotland, for which it had tendered to the Client, Chonais Hydro Ltd, in spring 2014. We can announce with pride that these HDD works have been executed successfully.

04.12.2014

The job site is located in the Scottish Highlands at Loch Carron, approximately 1h west of Inverness by car and 3 ½ hours west of Aberdeen. In that wild landscape a bore hole had to be constructed with the following parameters: 700 m in length, a height difference of 45m and a diameter of 1,150 mm.  A 900mm NB HPPE pipe was subsequently installed and formed an integral part of the high-pressure feed system to a hydro turbine lower down the mountainside.

LMR acted as the Main Contractor, thus being responsible for the HDD and pipe works. Preparation of the drill site and improvements to the access roads began on May 15th.

The Geotechnical Report described the ground conditions as metamorphic rocks with a hardness up to 300 MPa.  What it did not show was that the rocks would be extremely heterogeneous with regular changes in rock hardness and drilling characteristics.  As a consequence there were significant drilling problems both in the poor steering behavior of the pilot drilling assembly and with respect to the wear of drilling tools. The poor steering behavior of the pilot drilling assembly could be resolved by repeated adjustments of pilot drilling assembly. The wear of the drilling tools could only be counteracted by applying extensive and expensive special measures, which included among other things the use of the project-customised reaming tools.

These highly time-consuming works, in which the expansion of the borehole diameter became a major challenge, were completed by the end of August.  For reasons of operational safety and to demonstrate without jeopardising the bore itself that the bore hole was free of obstacles, check trips were done with a project-customised caliber body, that simulated the passage of the product pipe through the hole. Once these checks had proven that the hole was ready the product pipe was successful installed and on September 18th, 127 working after work commenced, the site was finally cleared.

alle news