Importance

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Abstract

A directional drill attached to a drill string having periodic concentric collars is advanced in an inverted arcuate path to form a pilot hole underneath an obstacle followed by a larger concentric washover pipe. When the washover pipe reaches the surface on the other side of the obstacle a first reamer is attached to the end of the washover pipe exiting the drilling path, a second reamer of smaller diameter than the first reamer is attached to the other end of the first reamer by means providing for some separation between the two reamers, and a production casing of smaller diameter than the second reamer is attached to the other end of the second reamer with a swivel. The remaining length of the first portion of casing is supported some distance above the ground on rollers located above and beyond the exit point of the pilot hole. The reamers are operated by rotating the washover pipe and simultaneously drawing the washover pipe through the pilot hole. As the reamers are drawn through the pilot hole the first reamer enlarges the hole to a diameter greater than that of the casing. Drilling mud pumped through the washover pipe exits at the reamers to entrain the dislodged earth and the second reamer compacts it to form a bushing around the sides of the enlarged hole to lubricate the passage of the casing. The reaming operation may be performed without the production casing attached to the reamers followed by a second reaming operation with the casing attached in order to complete the installation.

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First Claim