Cantilever Drilling Structure

The present invention relates to drilling rigs and to methods of moving them from well to well. In the past, rigs were set up to move in large pieces or in one piece from well to well. This was done by rolling the rig on large rubber tire wheels, skidding the rig on rails using winches or hydraulic jacks, or by mounting it on rollers that ride on rails and pulling the rig on these rails with a truck. Then after a rig is moved off of a well, a flow line is usually attached to the well head so that production can begin. These lines are typically positioned a few feet above ground level and are directed perpendicular to the well row. Any number of wells can be positioned in a row and spacing between wells in a row might range from 30 to 110 feet in a drilling area such as in North Ak. wherein the production wells are usually closely spaced and arranged in rows.

Existing rigs used in such drilling areas are configured to straddle the well row. Thus, once the flow or other lines are connected to the well head area, the rig cannot travel down the well row. This presents a problem if the operator decides to drill between two existing wells in a row. In that case in the past he would either have to remove the flow lines, or disassemble and reassemble the rig, or move the rig so that it is positioned in a direction perpendicular to the row from the opposite direction of the flow line extensions. The first two alternatives are very time consuming, costly and hazardous and the third is not always possible because there usually is not sufficient room in the lease or on the artificial offshore island for the rig to manuver.

Accordingly, it is the principal object of the present invention to provide a novel drilling structure or rig and a method for moving it relative to the well heads.

Another object of the present invention is to provide a novel drilling structure which is easily and quickly maneuverable in a small area, as on a small lease or on an artificial offshore island.

A further object of the present invention is to provide a novel drilling structure which is easily movable from a well to a nearby second well without the need for disassembling the rig or removing the flow lines.

A still further object of the present invention is to provide a novel drilling structure which is adapted to move along the well row without interfering with the flow lines.

Another object of the present invention is to provide a novel drilling structure which can readily, easily and safely drill between existing wells in a row so that the wells can be drilled closer together.

Other objects and advantages of the present invention will become more apparent to those persons having ordinary skill in the art to which the present invention pertains from the following description taken in conjunction with the accompanying drawings.

FIG. 1 is an elevational view of a drilling structure embodying the present invention illustrated from the "off-drillers" side.

FIG. 2 is a side elevational view of the drilling structure of FIG. 1 illustrated from the "V"-door side.

FIG. 3 is a side elevational view of the drilling structure of FIG. 1 illustrated from the "drawworks" side.

FIG. 4 is a top plan view of the drilling structure of FIG. 1 illustrated in its working environment.

FIG. 5 is an enlarged side elevational view of one of the support legs of FIG. 3 illustrated from the drawworks side.

FIG. 6 is a side elevational view of the support leg of FIG. 5 illustrated from the driller's side.

FIG. 7 is an enlarged top plan view of the drill floor skidding mechanism of the drilling structure of FIG. 1.

FIG. 8 is a cross-sectional view taken along line 8--8 of FIG. 8.

FIG. 9 is an enlarged view of the claw mechanism of FIG. 8.

FIG. 10 is an enlarged cross-sectional view taken along line 10--10 of FIG. 8.

FIG. 11 is an enlarged plan view of the wheel steering assembly of the drilling structure of FIG. 1 illustrated in isolation and showing in detail the wheel steering mechanism.

FIG. 12 is a side elevational view of the wheel steering assembly of FIG. 10 showing in detail the wheel raising and lowering mechanism.

FIG. 13 is a schematic view of the drilling structure of FIG. 1 illustrating the structure weight, loads, and reactions.

FIGS. 14A and 14B are schematic views of the hydraulic circuits for the drilling structure of FIG. 1.

FIGS. 15 through 18 are side schematic views similar to FIG. 1 illustrating the operating sequence for moving the drilling structure along the well row.

FIGS. 19 through 22 are sequential schematic views illustrating the movement of the sdrilling structure in a direction perpendicular to the well row.

Referring to FIGS. 1 through 4 a preferred embodiment of the present drilling structure is illustrated generally at 30. Drilling structure 30 basically comprises a base unit shown generally at 32 and a drilling rig mast assembly, which is shown generally at 34, supported by and positioned above the base unit. Base unit 32 is movable on a wheel assembly shown generally at 36 and can be moved on wheel assembly 36 to a position adjacent the well head W. In lieu of the present wheel assembly a roller system (not shown) using a flat-top roller such as that manufactured by Hillman Equipment Co., Inc. of Wall, N.J., placed between the base unit and a stationary rail beam can be used, or alternatively, a greased skidding beam (not shown) supporting the base unit can be used. When adjacent well head W the cantilever portion 38 of base unit 32 is positioned so that it extends over well head W and the extendable support leg 40 extends down from the outer end of cantilever portion 38 until it rests on the ground thereby supporting the drilling rig structure. Drilling rig mast assembly 34 is movable on and relative to base unit 32 between a drilling position positioned over the well head and on cantilever portion 38, as illustrated schematically in FIG. 15, and a moving position, about twenty feet away, positioned away from cantilever portion 38 towards the center of gravity of base unit 32 thereby providing a more stable configuration for lifting legs 40 and moving drilling structure 30 relative to the well head W, as best shown in FIG. 17. As shown by the load, shear and moment diagrams of FIG. 13 when in the drilling position, drilling structure 30 provides a stable drilling platform able to accept the wind and other forces to which it might be subject with no toppling moment forces being produced at either end. For example, for a 34 mph wind from the rear the overturning moment is 1310.0K, and the load at the rear wheels is 551.00K and 1364.00K at the front wheels. Thus, the rig will not overturn.

Drilling rig mast assembly 34 includes a mast 44 having a crown portion 46 including suitable pulleys supporting the travelling equipment 50. Midway up the mast a racking board 52 is mounted, and suitable winterizing construction 54 is constructed around the lower end of mast 44 directly above the dog house 56 and the choke house 58. Drilling mast assembly 34 is moved by a skidding floor mechanism, shown generally at 60, along and relative to base unit 32 between its drilling position and its moving position. Skidding floor mechanism 60 is supported on a base girder framework 62 comprising a series of I beams 64 best illustrated in FIGS. 7, 8, and 10. A subbox structure 66 is skidded along base grider framework 62 and, is best illustrated in FIG. 8, where it is shown in its drilling position by solid lines and its skidded moving position by phantom lines. A hydraulic cylinder 68 is provided for moving subbox structure 66 relative to base girder framework 62. Hydraulic cylinder 68 is pivotally attached at one end 70 to the subbox structure by an ear means 72 and, at the other end 74, the cylinder rod end is pivotally connected to a skidding claw mechanism shown generally at 76. Skidding claw mechanism 76, which is best illustrated in FIG. 9, rides under and on the claw track rail 78 of subbox structure 66. The skidding claw mechanism includes a four inch diameter dowel pin 80 manually rotatable to accommodate the desired skidding direction. Pin 80 is mounted vertically in a steel box 82, and the bottom of the pin is bevelled only on one side 84.

To move the subbox structure 66 and thus drilling rig mast assembly 34 from its drilling position to its moving position, hydraulic cylinder 68 is extended. Due to the bevel 84 of pin 80, the pin will move up without providing any resistance. When the pin reaches the next dowel hole 86, the cylinder is retracted. Since pin 80 is not bevelled on this side 88, it can provide a resisting force and subbox structure 66 is moved or skidded forward to its new position. To reverse the skidding direction, pin 80 is rotated 180 degrees, and the cylinder accordingly extended and retracted. Subbox structure 66 illustrated in FIG. 4 is one of the two parallel-spaced subbox structures 66 and 90. The one of FIG. 8 is positioned on the off driller side and a parallel generally identical subbox 90 is positioned on the opposite side and a similar hydraulic cylinder 92 illustrated schematically in FIG. 14A is provided for subbox structure 90. Suitable setback spreaders 93 and draw work spreaders 94, illustrated in phantom lines in FIG. 7, are connected to and positioned between subbox structures 66 and 90 and, when drilling rig mast assembly 34 is positioned over the centerline of the wellhead in its drilling position as illustrated, set back spreaders 92 and drill work spreaders 94 are positioned on opposite sides of the well head. The setback spreaders form a platform on which the drill pipe can be stored when tripping out of the well and the drawwork spreaders support the large hoist drawworks.

Extendable support leg 40 positioned at the outer end of the cantilever portion 38 is designed to be positioned in a first support position wherein the lower end 96 of the leg rests on the ground and supports the outer end of cantilever portion 38 and in a second lifted position wherein the lower end of the support leg is raised and spaced above the ground a sufficient distance, e.g. four feet, so that it may pass over the flow lines F when repositioning drilling structure 30. Referring to FIGS. 5 and 6, it is seen that an ear assembly 98 is attached to and depends from cantilever portion 38. A hydraulic cylinder 100 is pivotally attached at its cylinder end to ear assembly 98. An outer frame structure 102 depends from and is attached to the outer end of the cantilever portion 38 and cylinder 100 is positioned inside of it. An inner frame structure 104 having an outer diameter narrower than the inner diameter of outer frame structure 102 is provided and adapted to slide within the outer frame structure. Inner frame structure 104 is provided with a foot member 106 attached at its lower end 96 and which provides a flat ground engaging surface. On the upper surface of the foot member 106 a lower ear member 108 is positioned to which the cylinder rod end 109 of cylinder 100 is pivotally attached. It thus can be readily seen that when cylinder 100 is in its extended position, as in FIGS. 4 and 5, the inner frame structure is pushed out, in a telescoping movement, of the outer frame structure into its lengthened support position. When cylinder rod 109 is retracted, the foot member 106 of the inner frame structure is retracted vertically up into the outer frame structure. A second parallel extendable support leg 110 (see FIG. 3) spaced from extendable support leg 40 is found on the other side of the well head and is also movable between support and lifted positions by a similar hydraulic cylinder 111 shown schematically in FIG. 14A. Suitable cellar winterizing doors (not shown) can be attached to close between the base unit and the legs when in the support position thereby sheltering the well head area.

Base unit 32 comprises a first unit 112 and second unit 113 when viewed from the V door side as in FIG. 2. The upper portion of the base unit comprises a pipe and casing storage area 114 and positioned beneath pipe and casing storage area 114 are the equipment rooms and mud tanks, shown generally at 118. The present drilling rig structure is designed to rest on the equipment rooms and mud tanks 118 when in its drilling position and when it is desired to reorient the wheel assemblies 36. This is shown schematically in FIGS. 15 through 22. To raise base unit 32 off of the ground onto wheel assemblies 36, a wheel lifting mechanism, best shown at 120 in FIG. 12, is provided. It comprises essentially a T-shape member 122 with the pair of wheels 124 rotatably mounted on opposite ends of member 122 in a conventional manner. A double-acting hydraulic cylinder 126 with an approximate 36 inch stroke is attached at its cylinder end to a lower surface of the pipe and casing storage area 116. When energized it pushes against the middle leg portion of the T member 122 thereby pushing down on the wheel asssembly 36, forcing it against the ground and thereby lifting base unit 32 off of the ground until supported on the wheel assemblies 36. When it is desired to rotate the wheels 124 of wheel assembly 36 so that the drilling rig structure 30 can be maneuvered in at least a first direction and a second direction perpendicular to that first direction, a wheel steering mechanism, best illustrated generally at 128 in FIG. 11, is provided. Referring thereto, it is seen in a top plan view that double-acting hydraulic cylinder 130 having approximately a 141/2 foot stroke is horizontally disposed and pivotally attached at one end to base unit 30. At its opposite end it is pivotally attached to an angle bar member 132 which in a horizontal plane defines a 90 degree angle. Angle bar member 132 is attached at its other end to the T-shaped member 122. When cylinder 130 is retracted as at point A the wheels are turned 15 degrees. When the cylinder is extended as at point B, the wheels are turned 90 degrees and when fully extended as at point C the wheels are turned an extra 15 degrees. Each of the other seven pairs of wheels of drilling structure 30 are provided with similar rotating cylinders illustrated schematically in FIGS. 14A and 14B at 134, 136, 138, 140, 142, 144, and 146, and lifting cylinders 148, 150, 152, 154, 156, 158, and 160.

The operating procedure for moving the rig parallel to the well row is shown in FIGS. 15 through 18. As illustrated in FIG. 15, the rig is in its drilling position with drilling rig mast assembly 34 centered over the wellhead W. Drilling rig mast assembly 45 is then via the hydraulic skidding floor mechanism 60 skidded to its moving position in FIG. 16. The extendable support legs 40 are then lifted by retracting the hydraulic cylinders positioned therein. The entire rig is next lifted off of the ground by extending the wheel assembly cylinders with the wheels positioned in a direction generally parallel to the well row. With the rig in the position as shown in FIG. 17, the rig is driven by suitable hydraulic wheel drive motors, which are illustrated schematically at 162, 164, 166, and 168 in FIGS. 14A and 14B, with suitable hydraulic tanks, pumps, valves, and flow lines as shown being provided, on the wheel assemblies 36 to its new location or well. When at the new well the rig is lowered until resting on the ground by retracting the wheel assembly cylinders. The extendable support legs 40 are lowered by extending their hydraulic cylinders 100 until resting on the ground and supporting the outer end of the cantilever portion 38. Once positioned as shown in FIG. 18, drilling rig mast assembly 34 can then be skidded by skidding floor mechanism 60 to its drilling position over the new wellhead, as shown in FIG. 15, and drilling begun again.

The procedure for moving the drilling structure 30 perpendicular to a well row is illustrated schematically in FIGS. 19 through 22. The wheels are first turned as shown in FIG. 19, the rig floor skidded by the skidding floor mechanism 60 to its transport position, the extendable support legs 40 and 110 lifted, the rig raised by lowering the wheel assemblies 36, and the entire rig moved by energizing the wheel drive motors 162, 164, 166, 168 out of the well row as shown in FIG. 19. As shown in FIG. 20, the rig is next lowered by raising the wheels, the wheels are then turned 90 degrees by extending the horizontal wheel assembly cylinder 130, the rig is raised by lowering the wheels by extending cylinder 126, and the rig is then driven by its motors in a direction parallel to the well row. The next step, illustrated in FIG. 21, involves lowering the rig by raising the wheels by retracting cylinder 126, turning the wheels 90 degrees by retracting the horizontal wheel assembly cylinder 130, and moving the rig back over the well row. Now at the new well row when it is desired to place the rig in its drilling position, as shown in FIG. 22, the rig is lowered by raising the wheels, the extendable support legs are lowered, and the rig floor is skidded to its drilling position extending out on the cantilever portion until positioned over the new well. The entire moving procedures as just described are thus accomplished easily, quickly and without the need for disassembling and reassembling either the drilling rig structure on the flow lines.

From the foregoing detailed description, it will be evident that there are a number of changes, adaptations and modifications of the present invention which come within the province of those persons having ordinary skill in the art to which the aforementioned invention pertains. However, it is intended that all such variations not departing from the spirit of the invention be considered as within the scope thereof as limited solely by the appended claims.