 |
|
|
|
|
 |
 |
|||
January, 1959
Sea Boring
The National Coal Board’s sea-boring tower which started proving undersea reserves of coal about four miles off Blackhall Colliery, Durham, in August last year, has now been moved to its second position about two miles north and further exploratory proving of the undersea seams is now taking place.
The first borehole was in about sixteen fathoms of water and two miles east of the nearest undersea workings, the object being to provide additional information about the thickness and quality of the seams it is intended to mine from Blackhall and Horden Collieries. There has been doubts as to how far the coalfield extended southwards and eastwards under the seabed as there was evidence that inland the coal-bearing rocks ceased to exist within a few miles south of Blackhall Colliery. More knowledge was also needed of the limestone rocks which overlay the coal-bearing rocks in this locality as these are waterbearing which reduces the amount of coal it is possible to take from a given area.
The boring operations were very successful and an average depth of 29 ft. a day was obtained — a rate which compares favourably with boring on land. The seam thicknesses established included the High Main at 3 ft. 6 in., the Main Coal at 2 ft. 10 in., the Low Main at 3 ft. 7 in. and the Harvey at 2 ft. 8 in.
These indicate that the coal seams extend at least as far as expected and maintain their thickness and quality. It was also discovered that nearly 400 ft. of the mineral anhydrite, which is non-porous, overlies part of the coal-bearing rocks. This affords increased protection from the waterbearing limestone and therefore extends the areas of workable coal.
In addition to the coal seams which were expected to occur, a number of deeper seams such as the Busty and the Brockwell, which have been worked far to the west at Fishbum and Dean and Chapter Collieries, have been proved to be of workable thickness in the undersea area, though they are not workable inland for about 10 miles west of the coastline.
Article reproduced from a copy of the magazine held at National Mining Museum Scotland, Newtongrange, Midlothian.
Contains public sector information licensed under the 
