Borehole drilling

[coalgirl]

A drilling company are drilling for gas in the Midlands. They propose to drill a relatively small hole (about 150 mm diameter) to about 200 metres ( to locate a suitable strata) and then drill a horizontal hole to intercept the strata containing the gas. What equipment is used to drill a horizontal hole at the bottom of a vertically drilled hole.

[Huderon]

They steer the drill bit :-)
One brief outline is here and there are three techniqies described here, but a google search for horizontal drilling will give you a plenty of results.

[Clanad]

The science of directional drilling has made great advances over the years. Initially, it was known that a string of drilling pipe could be manipulated to drill "off perpindicular". This came about by accident since it was difficult to maintain perpindicular with strings of pipe exceeding 10,000 feet considering all of the weight suspended fromthe drilling rig. (Gas and some oil wells here in the western U.S. have reached nearly 20,000 feet.). The knowledge that came from such accidental or unintended non-vertical drilling was put to use. Today, downhole motors also known as Mud Motors are the latest advancement to drill nearly horizontally from the intiall vertical string...

[coalgirl]

Thank Heron and Clanad for your help, the sites you mention give me all the info I needed. Coalgirl

[coalgirl]

Sorry Huderon, I mispelt your name, noticed after I had pressed submit but too late to stop message. I blame the bad light but it is probably just old age. Coalgirl