E - Fixed Constructions – 21 – B
Patent
E - Fixed Constructions
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B
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E21B 7/06 (2006.01) E21B 7/08 (2006.01) E21B 7/20 (2006.01) E21B 21/06 (2006.01) E21B 21/08 (2006.01) E21B 21/12 (2006.01)
Patent
CA 1097329
DRILLING METHOD AND APPARATUS FOR LARGE DIAMETER PIPE ABSTRACT OF THE DISCLOSURE A method and apparatus is disclosed for installing a large diameter pipe--in the range of 30 inches diameter-- for spanning an obstacle, such as a river, along an invert arcuate underground path. An inclined drill rig, having a mud supply system and power pod, includes an angularly inclined ramp and driven car for crowding, without rotation, a pipe either pre-bent to a preselected and constant radius of curvature or a straight pipe into the ground. The pipe at its head includes an articulated drill head, which by appropriate articulation, assures placement of the pipe along a radius of curvature equal to the pre-bent radius of curvature of the pipe. The articulated drilling head includes a hydraulic system for articulating and driving the cutting head and pumping mud and tailing from the pipe path. Two discrete mud systems are used. The first mud system is utilized to entrain and carry away cuttings. The second mud system is combined with a flared skirt about the point of the drill head articulation to provide a clean and high lubricity annulus of mud about the advancing drill string. The density of the first mud system can be used to vary the drill string mass, while the density of this second mud system can be used to vary the density of the fluid in which the drill string is buoyantly supported. Serendipi- tously the forces of drill string mass and drill string buoyancy can be balanced with respect to one another to provide neutral buoyancy within wide limits, thus insuring a neutrally buoyant force to prevent comment forces of sticking encountered despite wide ranges of pipe size. Advancement of the drill string occurs along an arcuate path of constant curvature from entrance into the ground to exit from the ground by crowding the large diameter pipe only (without rotation) to avoid pipe stressing due to either pipe rotation or change of radius of curvature in the pipe from end to end. Provision is made to precisely monitor drill head site pressures and volume of materials introduced into and taken from the drill site to prevent sticking.
316371
Cherrington Martin D.
Fetherstonhaugh & Co.
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