rod basket workover rig free sample

Workover-Office-completion-graphics-and-calculations includes an easy start with 17 of the most common well completions, plus Cement Plugs, Xtree schematic, Liners, Tie Backs, Packer Calculations, Field Testing Production Rates, Tubing Movement Calculations, Rod Pump Completions, Operator Report, 20 item GLM spacing, operators report and field reports plus Final Well Completion Report.

Workover-Office-completion-graphics-and-calculations includes an extended library of over 1000 hi-resolution workover and completion graphics completely automated on button clicks instead of drag and drop to give you a first class professional finish to your Wellbore schematics. Your final well report can be exported to your well file with a simple click as a single linked Excel worksheet, or emailed directly to the client

Workover-Office-completion-graphics-and-calculations, now includes the layout for a Frac Manifold iron library added to the program, complete with straights, 90° bends, tees, valves, pressure shut down valves, the complete package for a professional graphic output

One common piece of heavy equipment used to produce hydrocarbons from the earth is referred to as: a workover rig, a completion rig, or a pulling unit. Such a thing can do many tasks, but it is primarily used to hoist damaged tubing from a well and lower undamaged tubing into a well so that oil and gas can flow more freely. A workover rig can also be used to “complete,” repair, or swab a well to maximize its rate of fluid production.

A workover rig comprises a truck carrying a telescoping mast and a winch. In use, the truck is backed up to a well, the mast is raised, and the lifting of tubing is initiated using the winch. A typical, workover rig is used only during daylight hours. A workover rig cannot drill into the earth unless equipped with a special “power swivel” that moves up and down while turning drill pipe extending into the well.

Thousands of men in the United States work upon workover rigs and are interested in workover rigs. It is believed that many would like to own a functioning model of such a rig. Duplicating every feature of a workover rig in a mass-produced model, however, is not practical since many features would be tiny and especially costly to make. Changes are necessary in the various apparatus that: pivots the mast to its substantially perpendicular, upright orientation, telescopes the mast to its full length, and hoists tubing.

In light of the problems associated with replicating a full-size workover rig at a small scale, it is a principal object of the invention to provide a toy workover rig with means for pivoting, telescoping, and hoisting that are lifelike in operation if not exact in appearance.

It is another object of the invention to provide a toy workover rig of the type described that is radio controlled. A person with minimal experience can operate the toy workover rig without resort to prolonged training, study aids, or additional tools. An oil and gas operator can even employ my toy workover rig during a new hire"s orientation session to provide a familiarity with a rig"s working parts and function.

It is an object of the invention to provide improved elements and arrangements thereof in a toy workover rig for the purposes described which is lightweight in construction, inexpensive to make, and fully dependable in use.

The toy workover rig in accordance with this invention achieves the intended objects by featuring an extensible mast that is pivotally fastened to a wheeled truck. A remotely-controlled pivoting assembly is connected to the truck for selectively moving the mast from a horizontal, traveling position to a vertical, operating position. A remotely-controlled telescoping assembly is connected to the truck for selectively extending the mast from a retracted position to an extended position. A remotely-controlled hoisting assembly is connected to the truck for lifted selected objects within the mast.

The foregoing and other objects, features and advantages of my toy workover rig will become readily apparent upon further review of the following detailed description of the preferred embodiment illustrated in the accompanying drawings.

Referring now to the FIGS., a toy workover rig in accordance with the present invention is shown at 10. Workover rig 10 includes a truck 12 that carries an extensible mast 14 at its rear. Mast 14 can be selectively moved from a horizontal, traveling position to a substantially perpendicular, vertical, operating position by a pivoting assembly 16. A telescoping assembly 18 is employed to selectively extend mast 14 to its full height. A hoisting assembly 20 selectively lifts a joint of tubing 22 within mast 14. Assemblies 16, 18 and 20 of the rig 10 are operated by remote control.

Truck 12 includes an elongated body 24 that is supported above the ground by a number of rotatable wheels 26. A cab 28 is affixed to the front of body 24. A pair of upright braces 30 is affixed to the rear of body 24 for pivotally securing mast 14 thereto. Each of braces 30 has a diagonal member 32 and a vertical member 34 being connected together so as to form an inverted V-shape. The tops of braces 30 are positioned at a height that is somewhat greater than that of cab 28 and carry hinges 36 to which mast 14 is pivotally connected. A mast support 38 is affixed to body 24 behind cab 28 for holding mast 14 above cab 28 when mast 14 is pivoted downward for safe movement of workover rig 10 from place to place. A dummy motor 40 is affixed to body 24 adjacent support 38.

Body 24 is provided with a number of ground-engaging stabilizers 42 and 44 to prevent it from tipping when mast 14 is pivoted substantially perpendicular upright and telescoped. A pair of center stabilizers 42 is provided at the midpoint of body 24 with one being located on each side of body 24. Each of stabilizers 42 has a guide sleeve 46 in the bottom of body 24 and an arm 48 that fits snugly, yet slidably, within sleeve 46. Each sleeve 46 is configured such that, when a moderate pushing or pulling force is applied to the associated arm 48, arm 48 is moved within sleeve 46 along an axis that extends downwardly and outwardly from body 24. When fully extended, each arm 48 contacts the ground at a point that is not beneath body 24 thereby preventing body 24 from tipping sideways. Additionally, a pair of rear stabilizers 44 is provided at the rear of body 24 with one being located on each side of body 24. Each stabilizer 44 has a vertically oriented, guide sleeve 50 in the bottom of body 24 that is internally, helically threaded. A helically threaded rod 52 is screwed into each sleeve 50. When screwed outwardly, each rod 52 is brought into contact with the ground beneath body 24 preventing body 24 from tipping rearwardly.

Housing 54 carries several joints of tubing 22 for lifting by rig 10. Two columns of hooks (not shown) are affixed to one of side walls 60 so that the hooks of each column have horizontally positioned counterparts in the other column. The columns are set at a distance apart that is somewhat less than the length of a joint of tubing 22. Removably positioned on each pair of horizontally spaced hooks is a joint of tubing 22.

A ladder 76 is affixed to, and extends along, truss 68 l. Beneath ladder 76, an operator"s platform 78 is pivotally fastened to truss 68 l. Platform 78 has a pair of pegs 80 that carry a detachable handrail 82. Handrail 82 has a pair of pins 84 at its bottom that can be inserted into a pair of tight-fitting sockets (not shown) in the outer edge of platform 78. When mast 14 is pivoted substantially perpendicular upright, platform 78 is manually pivoted to a horizontal orientation and pins 84 are inserted into the sockets to hold the handrail 82 in a vertical orientation.

A work floor 86 is pivotally connected to bottom section 14 b. Work floor 86 comprises a U-shaped plate 88 having a pair of ground engaging legs 90 hingedly fastened thereto. One of a pair of hinges 92 pivotally connect the front of plate 88 to the bottom of lateral truss 681 and the other of hinges 92 pivotally connects the front of plate 88 to the bottom of lateral truss 68 r. A cutout (not shown) in the front of plate 88 between hinges 92 provides additional ground access for traveling block 94 and items carried thereby. When mast 14 is pivoted substantially perpendicular upright, plate 88 is manually pivoted to a horizontal orientation to the rear of mast 14 and legs 90 are pivoted downwardly to a vertical orientation to engage the ground and retain plate 88 in a horizontal orientation.

The top section 14 tof mast 14 has a U-shaped cross section being somewhat smaller than that of bottom section 14 bso that top section 14 tcan slide easily therein. Top section 14 thas a base truss 96 adapted for slidable positioning against base truss 66. Base truss 96 carries a ladder 98 and connects together a pair of lateral trusses 100 rand 100 ladapted for slidable positioning against lateral trusses 68 rand 68 l. Each lateral truss 100 rand 100 lhas a tubing board brace 102 affixed to, and extending rearwardly from, the bottom thereof. A pulley 104 is mounted atop each tubing board brace 102. Above each tubing board brace 102 and remote from pulley 104, a rod basket brace 106 is affixed to, and extends rearwardly from, each lateral truss 100 rand 100 l.

A rearward pair of pulleys 104 is rotatably secured to brace bar 102 by a pair of support brackets 126. Pulleys 104 rotate independently of one another and assist in the raising and lowering of a tubing board 128 and rod basket 130 described hereinbelow.

Tubing board 128 is pivotally connected to top section 14 tand extends rearwardly from it. Tubing board 128 has a U-shaped retainer 132 that is pivotally connected at its front to tubing board braces 102. Affixed to the rear of retainer 132 are a number of forwardly facing tines 134 that define spaces therebetween for racking pieces of tubing 22 lifted by traveling block 94. One of a pair of handrails 136 is rigidly affixed to each of the opposite sides of retainer 132. For compact storage when mast 14 is pivoted downwardly onto mast support 38, another handrail 138 is pivotally secured at its bottom to the rear of retainer 132.

Rod basket 130 is pivotally connected to top section 14 tand extends rearwardly from it. Rod basket 130 has a U-shaped retainer 140 from which a basket member 142 is suspended by its U-shaped top rail 144. For compact storage, retainer 140 is pivotally connected at its front to rod basket braces 106 and the rear of top rail 144 is pivotally connected to the rear of retainer 140. (The front of retainer 140 is open and configured in a manner that prevents retainer 140 from pivoting to a position more than a few degrees beyond horizontal when mast 14 is pivoted to an upright, substantially perpendicular position.) Extending sideways from the front of top rail 144 is a pair of retaining pins 146 that abut the top of retainer 140 and maintain basket member 142 in an upright, substantially perpendicular position when the mast 14 is pivoted substantially perpendicular upright.

Pivoting assembly 16 operates to swing mast 14 substantially perpendicular upright on hinges 36. Pivoting assembly 16 includes an electric motor 148 mounted atop truck body 24 between braces 30. Motor 148 drives a gearbox 150 that effectively increases torque. Gearbox 150 has a horizontal driveshaft 152 that is rotated by motor 148.

Telescoping assembly 18 operates to lift top section 14 tabove bottom section 14 bwhen mast 14 is swung to an upright orientation by pivoting assembly 16. Telescoping assembly 18 includes an electric motor 168 affixed to the bottom of bottom section 14 bbetween lateral trusses 68 rand 68 l. Motor 168 drives a gearbox 170, also affixed to the bottom of bottom section 14 b, having two meshing gears for transmitting power from the motor 168 to a driveshaft 172 extending upwardly from the gearbox 170.

Telescoping assembly 18 has a jackscrew 174. Jackscrew 174 is a helically threaded rod that extends the length of bottom section 14 b. The bottom of jackscrew 174 is affixed to the top of driveshaft 172 and rotates therewith.

A user of workover rig 10 can easily distinguish when top section 14 thas reached the upper limit of its travel. The first and easiest way to make such a determination is to see that the top portions of trusses 66, 68 rand 68 land the bottom portions of trusses 96, 100 rand 1001 line up horizontally. Another way involves an examination of tubing board 128 and rod basket 130. Their principle features should extend horizontally and vertically so that it is substantially perpendicular.

Tubing board 128 and rod basket 130 are tied to a pair of cords 184 that automatically extend them away from top section 14 tfor use or retract them onto top section 14 tfor storage and transport. Cords 184 extend from the top of bottom section 14 bthrough crown 108 and rod basket 130 to tubing board 128. Cords 184 have a length sufficient to hold tubing board 128 horizontal when top section 14 tis fully extended from bottom section 14 b. Cords 184 also have a length sufficient to hold tubing board 128 against top section 14 twith handrails overlapping and enclosing lateral trusses 68 rand 68 lwhen top section 14 tis retracted within bottom section 14 b.

Each of cords 184 contacts rod basket 130 at the rear of retainer 140 near its point of connection to basket 130. The cords 184 slide through socket members 186 on opposite sides of the retainer 140 in their passage from the top of handrail 138 to pulleys 188. A knot 190 is provided on each of the cords 184 between handrail 138 and socket member 186 so that, when cords 184 are pulled tight by moving top section 14 tinto bottom section 14 b, knots 190 engage the bottom of retainer 140 to pull it flush against top section 14 t. Basket 130, being free to pivot relative to retainer 140, swings compactly into top section 14 tbetween lateral trusses 100 rand 1001 and against elongated tube 178.

Pulleys 188 on opposite sides of workover rig 10 receive cords 184. As shown, cords 184 run under pulleys 124 and over pulleys 188. Pulleys 124 and 188 prevent cords 184 from binding and tangling while top section 14 tis being extended or retracted from bottom section 14 b.

A bell hanger rod 216 is positioned in the opening 210 of housing 192 beneath axle 212. Rod 216 connects the bottoms of side walls 194 together. Rod 216 is affixed at its opposite ends to side walls 194.

Traveling block 94 has a pair of connecting rods or bells 218 suspended from it. Each of the bells 218 has a rod portion 220 at its center and an integral loop 222 affixed to the top of rod portion 220 and an integral loop 224 affixed to the bottom of rod portion 220. Each loop 222 is large enough for the free passage of rod 216 thereby permitting a large degree of pivoting and twisting motion of bells 218 on rod 216.

A hook 226 is suspended from rod 216 between bells 218. Hook 226 can be employed to catch and suspend miscellaneous tools used with rig 10. Optionally, hook 226 may incorporate a swivel mechanism 228 to permit it to rotate in any direction relative to rod 216.

The operation of workover rig 10 is by three-channel, remote control. A transmitter 250 broadcasts electrical operations signals to a receiver 252 carried within truck body 24 to activate one of a number of servos 254, 256 and 258 also carried within truck body 24. Activating servos 254, 256 and 258 closes dual-throw switches 260, 262, or 264 to selectively operate motors 148, 168 and 248 to move mast 14 or traveling block 94.

A joystick 266 on transmitter 250 controls the operation of the pivoting assembly 16. By moving a joystick 266 to the “up” position, an electrical operations signal is broadcast from transmitter 250 to receiver 252 carried within truck body 24. When such a signal is received, receiver 252 produces an electrical activation signal that activates servo 254 to move dual-throw switch 260 from its normally open position to a closed position in a “positive” sense, say, toward the top of FIG. 10. The closed switch 260 connects motor 148 to a battery 268 carried in truck body 24 in a way that causes lever arm 154 and mast 14 to rise from its initial horizontal position shown in broken lines in FIG. 2. Maintaining switch 260 in the closed position described permits mast 14 to rise to a vertical orientation with truck body 24 serving as a stop to further pivoting movement.

Joystick 266 can be manually moved by a user to the “down” position to broadcast another electrical operations signal from transmitter 250 to receiver 252. When this signal is received, receiver 252 produces an electrical activation signal that activates servo 254 to move switch 260 from its normally open position to a closed position in a “negative” sense, say, toward the bottom of FIG. 10. The closed switch 260 connects motor 148 to battery 268 in a way that provides electrical current to motor 148 in a direction that is opposite to that described in the previous paragraph so that motor 148 moves lever arm 154 and mast 14 downward toward support 38. Support 38 serves as a stop to the continued downward pivoting of mast 14.

When mast 14 is fully pivoted to an upright position, substantially perpendicular work floor 86 is manually pivoted away from bottom section 14 b. Then, with work floor 86 in a horizontal orientation, legs 78 are pivoted downwardly and engaged with the ground. Afterward, when play with rig 10 is complete, work floor 86 is returned to its original position against bottom section 14 band mast 14 is pivoted down upon support 38.

Joystick 270 on transmitter 250 controls the operation of the telescoping assembly 18. By moving a joystick 270 to the “up” position, another electrical operations signal is broadcast from transmitter 270 to receiver 252. When this particular signal is received, receiver 252 produces an electrical activation signal that activates servo 256 to move dual-throw switch 262 from its normally open position to a closed position in a “positive” sense, toward the top of FIG. 10. The closed switch 262 connects motor 168 to battery 268 in a way that causes jackscrew 174 to rotate and drive top section 14 tupwardly from bottom section 14 b. Maintaining switch 262 in the closed position, by holding joystick “up,” fully elevates top section 14 t.

When top section 14 trises from bottom section 14 b, tubing board 128 and rod basket 130 are automatically deployed from mast 14. The upward movement of top section 14 tputs slack in line—and permits tubing board 128 and rod basket 130 to fall away from top section 14 t. Of course, the retraction of top section 14 tinto bottom section 14 bputs line—under sufficient tension to pivot tubing board 128 and rod basket 130 upwardly into a retracted position in top section 14 t.

Joystick 272 on transmitter 250 controls the operation of the hoisting assembly 20. By moving a joystick 272 to the “up” position, an electrical operations signal is broadcast from transmitter 250 to receiver 252. When this signal is received, receiver 252 produces an electrical activation signal that activates servo 258 to move dual-throw switch 264 from its normally open position to a closed position in a “positive” sense and toward the top of FIG. 10. The closed switch 264 connects motor 248 to battery 268 in a way that causes spool 312 to wind up tubing line 208 thereby elevating traveling block 94. Maintaining switch 264 in the closed position, by holding joystick 272 “up,” raises traveling block 94 into crown 108.

When play with rig 10 is complete, mast 14 can be returned to a compact state like that found on a real workover rig that is being driven over the road. Rig 10 is most easily stored in this condition. Others may prefer to keep mast 14 in an upright, substantially perpendicular and fully extended condition. In this manner, rig 10 makes a great display model and focal point wherever set up.

While workover rig 10 has been described above with a high degree of particularity, it will be appreciated by those skilled in making toys that modifications can be made to it. For example, wheels 26 beneath cab 28 can be made to turn via remote control to steer truck 12 and a remotely controlled motor (not shown) can be added to drive a set of wheels 26 and propel truck 12 over the ground. (Such things are, of course, commonly found in r/c cars.) Also, downwardly pivoting toolbox doors 274, sidewalks 276 and movable ladders 278 can provide added realism. So, it is to be understood that my invention is not limited solely to workover rig 10, but encompasses any and all workover rigs within the scope of the following claims.

The claimed invention relates generally to well drilling and servicing equipment, and more specifically to portable rigs for handling pipe strings when making up and disconnecting long strings of pipe used in a bore hole during operations that are carried out in the exploration and production of petroleum and other fluids and minerals from substantial depths below the earth"s surface.

Production wells must be worked over from time-to-time due to either faulty downhole equipment or to some unusual or adverse well condition. For example, if the production string is damaged or leaking, it may be necessary to pull the tubing from the casing and replace it with new string. In a gas lift installation, the gas lift valves may not be in good working condition, and it therefore may be necessary to run exchange gas lift valves into the well. When tubing becomes plugged with sand, it is necessary to insert a tool such as a macaroni work string into the pipe to ream out or flush out the material clogging the flow of oil through the pipe. Other remedial service operations include gravel packs, fishing jobs, plug backs, recompletion requiring pulling and reinstallation of production tubing, drill-out of cement plugs, running sand screens and sand packing.

When such service operations become necessary, a portable installation called a workover rig is brought to the well site and set up. Generally, these rigs consist of a derrick or mast which supports pulleys or block and tackle arrangements that are operable to pull the pipe string from the well. These prior art workover rigs are usually heavy and difficult to erect and further often have the limited operational capability of only being able to hoist or pull pipe from a well without the capability of snubbing or pushing pipe back into the well. Since these conventional workover rigs cannot develop a downward force to push a string of pipe into the well, in such operations the well must necessarily always be under control or "dead", as is known in the art. This may require a preparatory operation of injecting a suitable substance such as mud or "kill" fluid into the well to maintain sufficient column weight of fluid to resist the pressure within the well which is tending to force the tubing out. However, it is usually desirable to carry out the workover operations without resorting to the injection of "kill" fluid into the well since the well may be lost if the formation is damaged because of the presence of the workover "kill" fluid. In such "killing" workover operations, there is a very high risk that the productivity of the subsurface formation may decline so severely after killing the well that the well must be abandoned.

An overriding concern in the construction of workover rigs is to get the necessary equipment into and out of the well as rapidly and safely as is economically possible. This concern has led to the development of a portable well service rig having a transportable mast or derrick. Before the invention of the first portable well service unit, it was necessary to leave the drilling derrick in place over the well for use in future well service operations. The portable well service rig eliminated the need for a permanent derrick and thus materially reduced overall well service costs. The early portable rigs, however, were unloaded in a heap and later sorted out, and then assembled without any definite plans therefore consuming a substantial amount of time in rigging up. Even when unitized and transported on pallets, a significant amount of time was required for transporting, rigging up and dismantling the palletized equipment. In the palletized approach, the field assembly and erection of the mast, mast support structure and reeving of the hoist cable caused expensive but unavoidable delays. Therefore recent improvements to conventional portable workover rigs have focused on changes which simplify the operations of transporting, rigging up and dismantling.

One of the problems associated with the development of the portable workover rig is that of providing sufficient working space below the mast floor while limiting the mast and its supporting base to dimensions which permit its transportation across public highways. A working space must be provided below the mast floor in order that the mast can be supported vertically above and engage well head equipment which may extend as much as eight to ten feet above the elevation of the rig platform deck. The minimum height of the mast is determined primarily by the length of the sections of pipe string added to or removed from the pipe already in the well bore. However, if the mast is so high that its length and height clearance when in a horizontal position on the workover rig exceeds the limits allowed by the state, the mast must be at least partially disassembled or must be telescoped. Most wells have tubing sections which are in the range of thirty-six to forty feet long, so that the construction of a transportable mast assembly having a stroke for accomodating the removal or insertion of such tubing sections poses no problem insofar as complying with state highway regulations.

As mentioned above, the conventional practice has been to provide a mast having telescoping sections or having sections which must be separately assembled and erected on site. To provide ample clearance for the well head equipment, the mast floor has been elevated above the ground level by placing it on a mast substructure carried by the rig base platform. This substructure is normally fabricated of heavy structural steel in a massive weldment which must be separately transported. The loads it must bear are greater than those born by the mast, since the substructure must support not only the weight of the derrick with its pipe string load, but other loads, such as the rotary table and draw works as well. However, the length and height of the separate mast support base when combined with the reclining mast may in some cases exceed highway limits, so that separate transportation, field assembly and erection are required. Most conventional rigs provide separate support base and mast sections which may be unbolted and separately transported to provide the short lengths allowed for highway travel. However, additional rigging up and tear down time is required for such arrangements.

Other important considerations involved in the construction of portable workover rigs are the strength and stability of the mast. The mast must be constructed to safely carry all loads which will ever be used in the well over which it is placed. This is the collapse resistance caused by vertical loading, or the dead load capacity of the mast. The largest dead load which will be imposed on the derrick will normally be the heaviest string of production tubing run in the well. However, this heaviest string of tubing will not be the greatest strain placed on the mast. The maximum vertical load which will ever be imposed on the mast will probably be the result of pulling on equipment, such as drill pipe or casing, that has become stuck in the hole. Therefore it must be considered that, sometime during the useful life of the mast, severe vertical strain will be placed on it because the equipment has become stuck in the hole. Therefore the mast and its intermediate support platform must be constructed to withstand and react loads which will exceed the capacity of the hoist line which will be used on the rig.

The mast must be also designed to withstand the maximum wind loads to which it will be subjected. The horizontal force of the wind acting on the mast and production tubing is usually counteracted by using from one to three guy wires along each leg of the mast which are attached to "dead man" anchors located some distance from the mast. A "dead man" anchor is made from a short length of large pipe, a concrete block, or a short section of timber, which is buried in the ground to provide an anchor for the guy wire. A substantial amount of time and labor is expended in setting up the "dead man" support lines. Additionally, when carrying out workover operations off shore, there is no practical way to anchor the guy lines. A suitable structural alternative for the guy wire supports is necessary for reacting the wind loads, and the snubbing forces must also be reacted in order to drive production tubing into an offshore well against the downhole pressures which may be encountered. Therefore there is a continuing interest in improving the design of support substructure for free-standing masts which do not require guy wires for support.

As a result of the many improvements to portable workover rigs, such vehicles now transport practically all the necessary servicing equipment directly to the field locations and when servicing has been completed, remove the necessary equipment to another well in need of service in the same field or in a different field miles away. Thus the equipment necessary to service a number of wells each having different service requirements has been greatly reduced, and consequently the labor and cost, as well as the amount of equipment has correspondingly dropped. However, there still remains considerable interest in the provision of more efficient and simplified machines in order that the job of well servicing in general may be carried out efficiently and at reasonable cost.

It is, therefore, the principal object of the present invention to provide an improved general purpose workover rig having a unitized configuration which is transportable across public highways and which can be easily rigged up and dismantled in the field.

Still another object of the invention is the provision of a workover rig having a mast, a mast support substructure, and draw works in which the static load of the draw works is supported by a portable base platform member rather than by being supported by the intermediate mast support substructure.

Yet another object of the invention is the provision of a workover rig having draw works carried by a portable platform and a mast and mast support substructure which are separately movable from a reclining transport position to an erect operating position wherein erection and retraction of the mast and mast support assembly can be carried out without disturbing cable reeving on the mast or on the draw works.

An important object of the present invention is the provision of draw works for a workover rig which can be carried in a reclining position on a portable rig platform and which is operably connected to develop driving forces required for either hoisting or snubbing operations.

Still another object of the invention is the provision of a portable workover rig having a mast and mast support substructure which are separately movable from a reclining transport position over a portable base platform to an erect workover position overlying well head equipment lying either above or below the elevation of the portable base platform.

Yet another object of the invention is the provision of a base support substructure for an erectable mast and a carriage assembly for moving the base support substructure from a reclining transport position over a portable base platform to an erect workover position, the carriage assembly cooperatively coupled to the base platform for stabilizing the erectable mast in free-standing relation on the mast support substructure and for transmitting mast load reaction forces through the portable base platform.

Another object of the invention is the provision of a workover rig having an erectable mast supported on a cantilever support substructure which is movable from a reclining transport position overlying a portable base platform to an elevated position of use wherein the cantilever support base is extended beyond the portable base platform for carrying out workover operations.

Finally, it is an important object of the present invention to provide a powered drill sub assembly for carrying out drilling operations in combination with a transportable mast assembly which includes a vertically yieldable stab assembly interconnecting a powered drill sub to a traveling block thereby permitting vertical displacement of the power sub relative to the traveling block during tubing make-up and break-out operations while reacting torque forces which are produced by such operations.

The foregoing objects are achieved by a workover rig which is mounted on a portable base platform such as a skid or the bed of a trailer vehicle, and which features a collapsible mast assembly which is movable from a reclining transport position to an erect elevated position of use. The mast assembly is supported for freestanding operation by a carriage assembly including a cantilever substructure support base mounted on the rig support platform for pivotable movement from the reclining transport position to an elevated position of use. The carriage assembly includes lift arms coupled in parallel relation intermediate the cantilever support structure and the rig support platform, thereby defining a parallelogram throughout the range of movement of the mast support assembly for maintaining the cantilever support base in parallel alignment with the base platform. According to this arrangement, the mast and the carriage assembly are separately collapsible for transport in a low profile, reclining position over the base platform to comply with the length and height limitations established for public highways. The mast and the carriage assembly are separately erectable to an elevated operating position overlying well head equipment which may be disposed at an elevation either above or below the elevation of the portable base platform. The mast is connected in hinged engagement with the carriage assembly, and both the carriage assembly and the mast are separately driven from the transport position to the erect operating position by linear hydraulic actuators. The linear hydraulic actuators in combination with the carriage assembly serve to stabilize the mast for free-standing operation and transmit mast load reaction forces through the portable base platform. An important feature of this arrangement is the cantilever support substructure which is extended to an elevated operating position beyond the portable base platform for carrying out workover operations adjacent elevated well head equipment. A further advantage of this arrangement is that the mast, mast support substructure, and draw works can be carried in a collapsed, low profile transport position and both erection and retraction of the mast and mast support assembly can be carried out without disturbing the cable reeving on the mast and draw works.

According to an important aspect of the invention, the workover rig is provided with a mast, a mast support substructure, and draw works in which the static load of the draw works is supported by a portable base platform member rather than being supported by the intermediate mast support substructure. In this arrangement, the draw works includes a linear hydraulic actuator having rod and housing elements in which one of the elements is anchored to the base platform with the other element being mounted for movement along the base platform through a stroke pathway which extends transversely with respect to the mast. The traveling sheaves are cooperatively reeved with hoist and snub cables for developing driving forces required for either hoisting or snubbing operations. The advantage of this arrangement is that the intermediate mast support substructure must support only the mast in an erect operating position with the substantial weight of the draw works being supported by the portable base platform. This arrangement permits the mast support substructure to be easily movable from the reclining, low profile transport position to the elevated workover position without the burden of the draw works. Hoisting and snubbing operations are carried out by the draw works which includes a linear hydraulic actuator carried on the base platform, a load engaging traveling block supported for vertical movement along the mast by hoist and snub cables, and by traveling sheaves carried by the actuator through a stroke pathway which is oriented transversely with respect to the mast. In this arrangement the load engaging traveling block is driven upwardly or downwardly along the mast in response to extension and retraction of the rod and housing elements of the hydraulic actuator.

In yet another important embodiment of the invention, a vertically adjustable stack assembly is provided for accomodating the existing elevation of well head flange connections. The vertically adjustable stack assembly includes an adjustable support column assembly anchoring the rig platform to the well head casing, and an adjustable support column assembly interposed between the well head casing and the mast for transferring the weight of the mast from the intermediate mast support structure to the well casing. The vertically adjustable stack assembly simultaneously anchors the portable base platform to the well head casing, thereby stabilizing the mast support substructure, while relieving the burden of the mast from the intermediate mast support substructure. This arrangement helps stabilize the mast for free-standing operation on the mast support substructure and for transmitting mast load reaction forces through the portable base platform, thereby eliminating the need of dead man anchor lines which would otherwise be required for stabilizing the mast and for reacting dynamic mast loads.

Finally, the portable workover rig of the invention is adapted to perform drilling operations by the combination of a vertically yieldable stab assembly which interconnects a powered drill sub with a traveling block for permitting vertical displacement of the powered drill sub during make-up and break-out operations while simultaneously reacting torque forces which arise in response to rotary forces applied to the drill string. The vertically yieldable stab assembly includes upstanding stab receptacles anchored to the top side of the traveling block and stab elements downwardly depending from the under side of the powered drill assembly for engagement with the stab receptacles. Each stab element is supported for vertical reciprocal movement between retracted and extended positions, and each stab element is yieldably biased to the fully extended position, thereby permitting vertical displacement of the power sub relative to the traveling block during the make-up and break-out operations while reacting torque forces which are produced by operation of the powered drill sub.

FIG. 3 is a top plan view of the workover rig of FIG. 1 with the mast and carriage assembly removed which illustrates the layout of the draw works and related equipment on the deck of a portable rig support platform;

FIG. 7 is a side elevational view of a skid mounted workover rig having draw works and an erectable mast constructed according to the teachings of the present invention;

FIG. 10 is a perspective view which illustrates the arrangement of sheaves and reeving of cables for conducting snubbing operations on the workover rig shown in FIG. 1;

FIG. 11 is a perspective view which illustrates the arrangement of sheaves and reeving of cables for conducting hoist operations on the workover rig shown in FIG. 1;

FIG. 16 is a front elevation view of the completed vertically adjustable stack assembly shown interconnecting the mast support substructure and the rig support platform with the flanged connector of a well head assembly;

Referring now to the drawings, and more particularly to FIGS. 1-4, a workover rig 10 is shown having a transportable mast assembly 12 and draw works 14 supported on a portable trailer platform 16. The trailer platform 16 includes the usual longitudinal side frame rails 18, 20 which supports forward and rear decks 22, 24, respectively. The side rails 18, 20 are interconnected by the usual structural members, including a tailboard 26. The trailer platform 16 includes a fifth wheel connection 28 for attachment to a tractor, and rear wheels 30 supported by shock assemblies and leaf springs in the usual manner. Outrigger jacks or props 32 support the side frame rails 18, 20 to prevent tilting or overturning of the rig during operation and also for maintaining the orientation of the trailer platform 16 once it has been set up. The jacks 32 are preferably hydraulically actuated and are controlled from a central station so that the trailer platform 16 can be aligned in parallel with the ground or inclined in a tilted position for workover of slant wells. Each jack 32 is equipped with a stabilizer pad 34 for engaging a mud sill (not shown) so that the trailer load can be more evenly distributed. Slung underneath the side frame rails 18, 20 are tool boxes 36 and a spare tire 38. Anchored top side on the forward deck 22 is power unit 40 which develops the main hydraulic power for the draw works 14 and includes hydraulic pumps driven by a diesel engine. The power unit is coupled to a hydraulic reservoir 42 so that as the required pressure in the system exceeds predetermined levels, one or another pump automatically unloads into the reservoir 42 and all engine horse power is then diverted for driving the alternate pump(s). Immediately forward of the power unit 40 are a pair of fuel tanks 44, and overlying the fifth wheel connection 28 is a hose basket 46. Overlying the fuel tanks is an upstanding stop bar 47 for engaging the mast assembly and supporting it in spaced relation with the forward deck overlying the power unit and fuel tanks when the transportable mast assembly 12 is disposed in its reclining transport position, as illustrated in FIGS. 1 and 2. Also anchored to the trailer platform 16 intermediate the forward and rear decks is a guide tube 48 which is straddled by the hydraulic reservoir 42 for receiving the movable actuator element of the draw works 14 as will be discussed in greater detail below.

Referring again to FIGS. 1-4, the transportable mast assembly 12 comprises generally an elongated mast 50 pivotally mounted on a mast support substructure 52 which is in turn pivotally mounted on a mast carriage assembly 54 which is mounted for pivotal movement from a transport position shown in FIG. 2 to an elevated position of use shown in FIG. 1. The mast 50 is formed by two upstanding mast sections 50A, 50B which are laterally spaced to define a vertical load transport zone 56 through which a traveling block 58 is transported during pipe running operations. The upper ends of the mast sections 50A, 50B are structurally interconnected by a crown block 60 which improves the mechanical stability of the mast and which also serves to support crown block sheaves in a manner to be disclosed hereinafter. Each mast section 50A, 50B is defined by four leg members 62A, 62B, 62C and 62D, and 64A-D, respectively. The leg members are generally arranged at the corners of a square with the forward leg portions terminating in a clevis which receives a hinge pin 66 which pivotally secures the forward legs to the mast support substructure 52. Each mast section 50A, 50B is provided with girt members 68 and brace members 70 which are structurally interconnected with the leg members to insure rigidity of each mast section. A clevis 72 is anchored on opposite sides of the mast support substructure 52 for anchoring the rear legs 62B, 64B of the mast when it has been erected to the upright position.

The mast carriage assembly 54 includes forward and a rear lift arms 76A, 76B, respectively, pivotally coupled in clevis connections intermediate the cantilever support base 74A and the rear deck 24 on laterally opposite sides of the draw works 14. The lift arms are all the same length and are spaced in parallel with each other whereby the combination of each pair of lift arms with the cantilever support base and the rear deck defines a parallelogram for maintaining the mast support substructure 52 in parallel alignment with the trailer platform 16 throughout the range of movement of the mast support substructure 52 from the reclining transport position to the elevated position of use. The mast support substructure 52 is extended and retracted between the reclining transport position and the elevated position of use by a pair of double acting, telescoping hydraulic actuators 78 having housing and rod elements pivotally coupled to clevis connections carried on the forward cantilever support base portion 74A and the rear deck 24 on laterally opposite sides of the draw works 14. The mast 50 is similarly erected by hydraulic lift cylinders 80 which are coupled for pivotal movement intermediate the forward cantilever support base portion 74A and the forward legs 62A, 64C of the mast sections 50A, 50B, respectively.

Erection of the mast 50 to the upstanding, elevated workover position is preferably carried out by rotating the mast support substructure 52 from its reclining transport position to its fully extended upright position while the mast 50 remains in its reclining position. After the mast support substructure has been fully stabilized in the upright position, the hydraulic lift cylinders 80 are actuated to cause the mast 50 to be pivoted to its upright standing position on the cantilever support base 74. The hydraulic lift cylinders 78, 80 are continuously pressurized in order to further stabilize the mast support substructure and transmit mast loads to the trailer platform 16. Retraction of the mast 50 is carried out in the reverse order by first uncoupling the rear leg portions at the clevis 72 and retracting the double acting hydraulic lift cylinders 80 until the mast 50 is substantially horizontal. Thereafter, the hydraulic lift cylinders 78 are retracted until the mast support substructure is resting in its reclining transport position with the upper end of the mast resting on the tie-down bar 47.

The traveling block 58 is guided for vertical displacement along the rear legs 62A, 64D, which serve as guides, as can best be seen in FIGS. 4 and 23. The traveling block 58 includes a main cross member 98 which extends horizontally between the legs 62D, 64D and is provided with guide rollers 100 rotatably mounted about shafts 102 at either end of the frame. The periphery of each roller is concave to conform to the shape of the tubular members 62D, 64D and vertically guide the traveling block as it is reciprocated along the mast 50. A rotary table 104 is carried by the main cross member 98 of the traveling block to facilitate workover or drilling operations.

Referring to FIGS. 3, 4, 10, 11 and 19-21, the linear hydraulic actuator 92 is carried on the rear deck 24 of the trailer platform 16 and includes rod and cylinder housing elements 128 and 130, respectively. The rod element 128 is rigidly attached at one end to an anchor weldment 132 whereby the actuator assembly 92 is supported in spaced, parallel relation with the rear deck 24 so that the cylinder housing 130 can move freely in extension and retraction. Reciprocal movement of the cylinder 130 is stabilized by the guide tube 48 which receives the freely projecting end of the cylinder housing 130. The anchor weldment 132 includes a socket for engaging a threaded shaft portion 134 of the rod element 128.

The linear hydraulic actuator 92 is double acting and includes a piston 136 slidably received within the cylinder housing 130 which partitions the interior of the cylinder housing into head and rod chambers 138 and 140, respectively. The rod element 128 comprises two concentric tubes 142, 144 for circulating hydraulic fluid into the head chamber 138 and rod chamber 140, respectively. The inner rod tube 142 has a bore 146 which connects the head chamber 138 in fluid communication with a stepped concentric blind bore 148 which communicates with a lateral hydraulic flow passage 150. Similarly, a lateral flow passage 152 communicates with an annular passage 154 which extends intermediate the inner rod tube and the outer rod tube. Hydraulic fluid discharged through the annular flow passage 154 circulates through discharge ports 156 which communicate with the rod chamber 140. Appropriate O-ring seals 158, 160 seal the pressure chambers against fluid leakage. An end cap 162 blocks off the end of the cylinder housing 130. It will be seen, therefore, that the piston rod element 128 remains fixed to the anchor weldment 132 so that pressurization of either the head or rod chamber of the cylinder housing 130 will cause the cylinder housing to extend or retract.

The guide tube 48 extends aft from the power unit 40 in concentric alignment with the cylinder housing 130. Guide plates 165 carried on the forward end of the cylinder engage the bore surface 167 of the guide tube 48 at opposite sides. The guide plates serve to slidably guide and stabilize the cylinder housing 130 as it extends and retracts in response to pressurization of the head and rod chambers. A guide bracket 163 carries the guide plates 165 in the annulus between the guide tube and cylinder element.

The reeving engagement of the hoist transmission system and the snub transmission system will not be described in connection with FIGS. 3, 10 11 and 21. The hoist power transmission system 94 applies a lifting force to the traveling block 58 which is developed by the linear hydraulic actuator 92, and also serves to transfer the load engaged by the traveling block 58 onto the mast 50. These functions are made possible by a pair of crown hoist sheave assemblies 184, 186 journalled in laterally spaced relation on the crown block 60 near the top of the mast 50. Base hoist sheaves 188, 190 are journalled near the bottom of the mast on a base sheave weldment 192 which is anchored to the tailboard 26, the aft deck 24 and the rod anchor weldment 132. Carried in reeved engagement with the crown hoist sheaves and the base hoist sheaves are hoist cable pairs 194, 196 which are firmly attached at one end to the top side of the traveling block 58 with the opposite end portions anchored to the base platform and tailboard. An intermediate length of each cable pair is extended upwardly along the mast, passing around the crown hoist sheaves 184, 186, respectively, extending downwardly along the mast and passing around the base hoist sheave assemblies 188, 190, respectively, extended forwardly along the aft dect 24 in parallel with the stroke pathway of the cylinder housing 130, passing around the traveling hoist sheave assemblies 174, 176, respectively, thence passing aft along the aft deck 24 and passing around the base hoist sheave assemblies 188, 190, respectively, and thence passing around the traveling hoist sheave assemblies once again thereby defining a multiple purchase of 4:1. In this arrangement, displacement of the cylinder housing will drive the traveling block a greater proportional distance through the load transport zone 56, thereby multiplying the stroke effect of the linear hydraulic actuator 92. For this arrangement, a nine foot stroke of the traveling sheaves is translated into a thirty-six foot traveling block stroke.

The traveling cross bar is provided with a pair of through holes 218, 220 through which the downward run of the snub cables 200, 202 passes without interference downwardly along the mast and in parallel with the hoist cables and passing around a base snub sheave assembly 222 which is journalled on the base sheave weldment 192. Thereafter, the snub cables 200, 202 extend forward along the aft deck and pass around a first platform snub sheave assembly 224, extending aft along the platform in passing around the traveling snub sheave assembly 180, extending forwardly along the platform in a parallel run to a second base snub sheave assembly 226 and thence aft along the platform and passing around the traveling snub sheave 182 and extending forwardly again along the base platform to the snub anchor 212, thereby defining a multiple cable purchase which corresponds to the hoist cable purchase. The platform snub sheaves and snub anchor are located forward of the position reached by the traveling snub sheave assembly at the limit of its travel and extension whereby the traveling block is reciprocated along the mast in response to extension and retraction of the cylinder housing relative to the stationary rod 128.

Extension and retraction of the cylinder housing 130 is controlled from the operator platform 126 which is horizontally supported from the aft legs of the mast at an elevation convenient for workover operations. The forward part of the platform (not shown) houses hydraulic valves that control the actuation of the various components as will be explained.

Referring now to FIG. 16, the workover rig 10 is set up adjacent a well site in which a well casing 230 is terminated by a lower well head flange 232 and is anchored by a concrete block 234 in the usual manner. As is conventional, a blow out preventer 236 is located above and connected to the lower well head flange 232. A slip 238 is located above and connected to the blow out preventer 236. Located above and connected to the slip is an energizable packer 240. The packer is coupled to an upper well head flange 242 disposed at an elevation above the trailer platform as indicated by the elevation reference line 244. The BOP slip and packer are all concentrically aligned with the well casing 230 so that a tubing string may be moved upwardly through the well casing along the bore axis 248 as the tubing string is run out of the well. Conversely, when running the tubing string 246 into the well, each section is moved downwardly through the packer, slip and blow out preventer into the well casing 230.

The blow out preventer 236 may be of any suitable type, but is preferably hydraulically energizable for engaging the tubing string 246 in a fluid sealing relation to prevent the well from blowing out. The slip 238 may also be of any suitable construction and is preferably double acting, i.e., is preferably capable of preventing both upward and downward movement of the production tubing string. The packer 240 may not be present on some well head installations, in which case the upper well head flange 242 is located at a different elevation. The precise elevation of the well head flange termination 242 varies from well to well depending upon the length of the well head equipment which is used for terminating the well. This variation in the elevation of the well head flange presents a problem for conventional portable workover rigs since the traveling block must be consentrically aligned with the well bore, and since it is generally desirable to interconnect the mast support substructure to the well casing to transfer the static weight of the mast from the mast support substructure to the well casing. As previously explained, it is also desirable to anchor the rig platform to the well casing to stabilize the free-standing mast and mast support substructure against wind loading and dynamic reaction forces developed during pipe running operations.

The lower support column assembly comprises a horizontal cross beam 254 which is adjustably connected to first and second upright support columns 256, 258 which are spaced in parallel with each other on laterally opposite sides of the flange connector 242. First and second struts 260, 262 project from the tailboard 26 of the trailer platform 16 for supporting the support columns 256, 258 in parallel alignment with the bore axis 248. The lower end of each support column 256, 258 is furnished with a threaded collar 264, 266, respectively, in which threaded posts 268, 270 are received in telescoping engagement. Because of this threaded, telescoping engagement, the effective length of the support columns is adjustable to drive a stack flange connector 272 carried by the cross beam 254 into compressive engagement with the well head flange connector 242. The stack flange connector 272 and the upper well head flange 242 each have through holes which are aligned for securely fastening the cross beam to the well head.

The upper support column assembly 252 is also vertically adjustable in order to transfer the weight of the mast from the cantilever support substructure 74 to the well casing 230. The upper support column assembly 252 comprises generally first and second upright support columns 286, 288 connected intermediate the cross beam 254 and the cantilever support substructure 74 on laterally opposite sides of the stack flange connector 272. The intermediate length of these upright support columns is vertically adjustable after the stack flange connector 272 has been secured to the well head flange connector 242 so that the weight of the mast 50 will be transferred from the cantilever support substructure 74 to the well casing 230. Sockets 290, 292 are anchored to the top side of the cross beam 254 on laterally opposite sides of the stripper bowl 280 for receiving the upright support columns 286, 288, respectively. The support columns are fastened in the sockets by means of through bolt and cap nut combinations 294. The upper ends of the upright support columns 286, 288 are threaded and project through the cantilever support substructure on opposite sides of the stationary slip bowl 75. The cantilever support base is connected to the upright support columns by means of lock nuts 296 tightened against the cantilever support base on both the top and bottom sides thereof. It is generally desirable to tighten the bottom lock nuts against the cantilever support base 74 to cause compression loading in the support columns 286, 288, so that the static load of the mast will be substantially transferred from the cantilever support substructure 74 to the well head casing 230. The upper lock nuts are also tightened so that upwardly directed snubbing loads will be transmitted through the adjustable stack connector assembly 228 to both the well head casing 230 and the trailer platform 16.

The bolster plates are provided with clevis fasteners 304, 306 for engaging the upright support columns 286, 288, respectively. Clevis bolts 308 secure the clevis fasteners to the upright support columns at a plurality of vertically spaced locations and intermediate the mast and the stack flange connector. Link elements 310, 312 are interconnected in a scissors arrangement on opposite sides of the bolster plates for permitting accordion-like movement of the bolster plates relative to each other in parallel stacked relation. When the intermediate length of pipe string 246 is received through the concentrically aligned openings 302, the vertically spaced bolster plates 300 cooperte to oppose radial deflection of the pipe string in response to severe compression loading. The link elements 310, 312 are pivotally suspended from the under side of the cantilever support base 74 and are anchored in place in spaced relation along the upper support columns by the clevis bolt fasteners. Any suitable number of bolster plates may be stacked, with the bolster spacing preferably being approximately one foot.

Turning now to FIGS. 22, 23 and 24, the powered drill sub assembly 314 is provided for carrying out drilling operations in combination with the transportable mast assembly 12 and draw works 14. The powered drill sub assembly 314 includes a drill sub 316 which is supported in vertically yieldable engagement with the traveling block 58 by means of a stab assembly 318. The purpose of the vertically yieldable stab assembly 318 is to permit vertical displacement of the drill sub relative to the traveling block during make-up and break-out operations while reacting torque forces which are produced by the operation of the powered drill sub. The stab assembly 318 comprises first and second upstanding stab receptacles 320, 322 anchored to the top side of the main cross member 98 and on laterally opposite sides of the pipe gripping assembly 116. The stab receptacles are disposed for engagement with stab elements 324, 326 which are supported for vertical reciprocal movement between retracted and extended positions. The stab elements depend downwardly from the under side of a cross beam 328, which is suspended above the traveling block by auxiliary hoist lines 327, 329. Centrally mounted on the cross beam 328 is the power drill sub 316.

Each stab element includes a tubular housing 330 anchored to the cross beam, and a stanchion 332 anchored to the cross bar and projecting through the tubular housing 330. A tubular piston 334 is telescopically received in overlapping engagement with the tubular housing 330. A spring 336 is coiled around the stanchion and anchored to the cross beam 328 and on its opposite end to the tubular piston for biasing the piston to its fully extended position. A stab rod 338 projects from the piston 334 for stabbing engagement with the stab receptacle. The stab rod is provided with a cavity 340 for receiving the lower end of the stanchion 332 when the piston 334 is fully retracted. A radially projecting collar 342 is secured to the piston near the union of the piston and stab rod for engaging the top of the stab receptacle.

When it is desired to work over an offshore well, the skid mounted transportable mast and draw works assembly 366 as shown in FIGS. 5 and 6, or alternatively, the skid mounted mast and draw works assembly 368 as illustrated in FIGS. 7, 8 and 9 is employed. In these arrangements, accessory equipment such as tools, power pack, pumps and other equipment are separately transported. Turning now to FIG. 5, the mast 50 is pivotally coupled to a mast support substructure 370 which is mounted on one end of a skid 372. The skid 372 is transported on a barge and when arriving at the offshore well, a heavy duty utility crane raises the skid mounted workover rig 366 on to the offshore platform adjacent the well head. The mast 50 is erected about a hinge pin 374 which is pivotally connected to the rear legs of the mast. A hydraulic lift cylinder 78 pivotally coupled between the skid and the mast drives the mast in rotation about the hinge pin 374 until the forward legs 62B of the mast are brought to a standing position on the mast support substructure 370 and locked into place by a suitable fastener. The hydraulic system is then connected to the power pack 40 which may be located at any convenient remote location.

Referring to FIG. 9, the skid 372 is formed by left and right side beams 376 attached to opposite sides of a structurally reinforced below-deck 378. The below-deck supports the linear hydraulic actuator 92 with the cylinder housing 130 being shown received within the guide tube 48. A super-deck 380 is anchored to the below-deck and is supported at an elevation above the linear hydraulic actuator and the associated sheave assemblies. Safety rails 382, 384 extend along the length of the super-deck on opposite sides thereof, and a pipe rack is secured to the super-deck intermediate the safety rails, thereby defining walkways 388, 390 intermediate the safety rails and the pipe rack. In the transport mode, the mast is carried in the pipe rack 386, and during workover operations pipe sections are stored in the pipe rack.

This website is using a security service to protect itself from o