Boring or penetrating the earth – Enlargement of existing pilot throughbore requiring...
Reexamination Certificate
1999-11-08
2001-05-08
Tsay, Frank (Department: 3672)
Boring or penetrating the earth
Enlargement of existing pilot throughbore requiring...
C175S061000
Reexamination Certificate
active
06227311
ABSTRACT:
TECHNICAL FIELD
The present invention relates to horizontal boring for installation of cross-country pipelines, conduits, cables, and the like, beneath a surface obstruction or barrier such as a roadway or river.
BACKGROUND OF THE INVENTION
Pipeline must sometimes be installed under physical barriers such as waterways and buildings or other surface obstructions without disturbing the surface. Typically, this has been done through a process of drilling a pilot bore beneath the surface barrier along a preselected, partially arcuate path. Next, the pilot bore is usually reamed to a larger size as required for the planned services. A pipe line drilling rig is used for this purpose. The rig is mounted on an inclined ramp and includes a rotary drive with hydraulic means for moving the rotary drive up and down the length of the ramp to advance or withdraw the drill string. The ramp is typically provided as the deck of a flat bed trailer, equipped with tracks and a hydraulically powered chain drive mechanism for movement of the rotary drive. The trailer is spotted and dropped nose down on one side of the barrier. The rig is made ready to start drilling stabilizing the trailer deck with hydraulic outriggers and adjusting the ramp angle of inclination as desired for the hole to be drilled. The drill pipe comes in threaded lengths of from twenty-five to thirty-nine feet and generally, an excavating machine is pressed into service to be used as a crane for handling these pipe lengths. The process generally starts with digging a trench, so that the drill bit can bear perpendicularly against the surface where the hole is to enter. The trench also provides a pit for holding the large quantity of drilling mud normally required. As rotary drilling advances the hole, lengths of pipe are added to the drill string until the length planned for the initial tangent is reached. The pipe string is then pulled out of the hole so that a mud-powered drill motor can be installed in place of the rotary drill bit. The mud-powered drill motor is mounted with its drilling axis angularly offset from the drill string axis by approximately 2°, so as to cause the drill to advance along a predictable arcuate path. The drill motor is positioned with its angularly offset axis oriented upward. Thus positioned, running the drill motor and advancing the drill string by axial hydraulic force only, without drill string rotation, generates an upwardly curving hole. Since the radius of hole curvature is predictable, calculations can determine the additional length of drill pipe needed to bring the hole to the surface or to make a transition to a predetermined tangent for reaching the surface. The bore has a larger diameter than the drill pipe for drilling fluid or “mud” circulation. This allows cuttings to be removed from the hole by mud circulation through the drill pipe, across the cutting face, through the open annulus and back to the surface.
Starting a straight “horizontal” hole can be difficult, especially if the entry point is more than a few feet from the end of the trailer, because the drill pipe tends to droop under its own weight. Physical considerations, such as the size and location of the trench and mud pit, often dictate an entry point twenty-five feet or more from the end of the trailer. In these cases, starting a straight hole is particularly difficult and it is important to get the hole started straight in order to follow a predictable path.
Unlike in vertical drilling, where drill string weight crowds the drilling tool against the cutting surface, the crowding force in this type of more or less horizontal drilling must be applied by pushing on the drill string. As the hole gets longer, the drill string reaches a length where it is unstable under the necessary column load, so that it deflects and bears randomly against the side of the hole. This deflected, off-center pipe can also cause whipping between the rotary drive and the hole entry point. Fluted members called stabilizers, sized to pass through the bore diameter with minimal clearance, are fitted to the drill string at intervals. The stabilizers center the drill string in the bore and help in holding direction as the hole progresses. The stabilizers also help to control pipe whipping.
Another problem peculiar to horizontal drilling is the difficulty in supporting the pipe to hold the male and female threaded ends in axial and angular alignment as lengths are added to or removed from the pipe string. This problem is worsened by increasing droop as the unsupported pipe length between the end of the ramp and the entry point increases.
Therefore, a first object of the present inventions is to provide apparatus for guiding the drill pipe so as to facilitate drilling a straight hole at entry. A second object is that this apparatus prevent drill pipe “whipping” by keeping it centered while drilling. A third object is that this apparatus facilitate re-entry of the hole when the drill pipe has been pulled out. A fourth object is that this apparatus be capable of supporting the drill pipe between the hole and the end of the inclined ramp so that the threaded end is held in alignment with the rotary drive while pipe is added to or removed from the drill string and yet another object is that this apparatus be made in a form that does not interfere with the normal coupling of a trailer mounted horizontal drilling rig.
SUMMARY OF THE INVENTIONS
The present inventions contemplate improved apparatus for achieving the aforesaid objectives by providing apparatus for supporting and centralizing drilling pipe in a more or less horizontal drilling rig. Practice of the present inventions uses some steps and apparatus well known in the pipeline drilling arts and therefore, not the subject of detailed discussion herein.
A “Vee” shaped trough is extended past the end of the inclined ramp and located in line with the rotary drive to support the drill pipe string as it is driven to rotate. A similar inverted “Vee” shaped member is mounted at each end of the trough with a hinged connection so that it can be placed in a closed, pipe confining position or in an open, unconfining position. Both the trough and the inverted, pipe confining member are lined with slabs of low friction, abrasion resistant material for contact with the rotation pipe. The substantially square clearance path through the trough and pipe confining members is large enough to allow passage of the pin and box drill pipe connections but suffices to provide guidance and centralizing to the drill string. The trough is mounted in such a manner as to be removable when necessary for transportation and furthermore, the mounting provides for controlled vertical movement of the trough relative to the inclined ramp. This vertical movement enables adjustment to compensate for vertical deflection of the drill string when it is extended beyond the end of the ramp.
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Crutsinger & Booth
Ozzie's Pipeline Padder, Inc.
Tsay Frank
LandOfFree
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