Specification

Background

[0001] This invention provides a work platform for coiled- tubing downhole operations apparatus and method, for safe, efficient, and relatively inexpensive extended access to the elevated top of the section of riser pipe necessary for the use of coiled tubing for downhole operations, such as drilling, production, intervention, logging, work-over, and fracturing the reservoir.

[0002] The increasing use of coiled tubing, rather than using segmented drill pipe, provides advantages associated with not having to stop and assemble and disassemble drill pipe, and not requiring use of a tall derrick for drilling and for subsequent downhole operations. Coiled-tubing operations make use of a bottom-hole assembly (or "BHA") for all tools, including drilling tools, and therefore do not rotate the tubing. There is thus no need for a rotary table. Operations using coiled tubing can be run in a balanced, over-balanced, or under-balanced state. Running under- balanced helps prevent the forcing of fluids into the underground formation, therefore killing all or part of the well.

[0003] Coiled-tubing operations require a length of riser pipe above the well-head and blowout preventer, in order to straighten the tubing. It is normal to have three ten-foot sections of riser pipe, or thirty feet, above the blowout preventer. These sections place the injector and access to the entry point of the tubing between approximately thirty to forty feet above the ground for onshore operations. This elevated equipment has to be inspected and serviced often, and so a safe and stable work platform must be located at the elevated entry point of the riser shaft. [0004] Although an expensive derrick is not needed for the assembly and disassembly of drill pipe, a derrick might be used to provide the elevated work platform. Such a derrick would be expensive, and perhaps prohibitively so for certain operations. Alternatively, scaffolding might be erected to provide a work platform. But such scaffolding is complex, time-consuming to put in place, is subject to being thrown out of adjustment relative to the top of the riser pipe, is difficult to climb, and does not provide an optimum work platform.

[0005] There is a thus need for a work platform for coiled-tubing downhole operations that is safe, efficient, and inexpensive relative to a derrick or scaffolding, and further is fixed in place relative to the top of the riser pipe, and may be left in place for extended periods of time.

Summary of the Invention

[0006] The present invention provides a work platform for coiled-tubing downhole operations apparatus and method, for safe, efficient, and relatively inexpensive extended access to the elevated top of the section of riser pipe necessary for the use of coiled tubing for downhole operations such as drilling, production, intervention, logging, work-over, and fracturing the reservoir. The invention is achieved by providing a shell-like riser-pipe sleeve which attaches securely, but removably, to the top section of riser pipe itself, in such a way that balanced support is obtained without placing dangerous strain on the riser pipe, and by further providing a shell-like platform securely, but removably, connected to and supported by the riser-pipe sleeve, which in turn is supported by the riser pipe itself.

Brief Description of Drawings

[0007] Reference will now be made to the drawings, wherein like parts are designated by like numerals, and wherein:

[0008] FIG. 1 is a schematic overview of the work platform for coiled-tubing downhole operations of the invention in use;

[0009] FIG. 2 is a perspective view of the work platform for coiled-tubing downhole operations of the invention, assembled;

[0010] FIG. 3 is a partially exploded view of the work platform for coiled-tubing downhole operations of the invention;

[0011] FIG. 4 is a perspective view of the work platform for coiled-tubing downhole operations of the invention in use on a riser pipe, with guy wires attached; [0012] FIG. 5 is a schematic view of the work platform for coiled-tubing downhole operations of the invention in use, before being mounted on a riser pipe;

[0013] FIG. 6 is a partially exploded view of the work platform for coiled-tubing downhole operations of the invention in use on a riser pipe;

[0014] FIG. 7 is a partially exploded view of the riser-pipe sleeve of the work platform for coiled-tubing downhole operations of the invention; and

[0015] FIG. 8 is a schematic view of an embodiment of the work platform for coiled-tubing downhole operations of the invention having a lift for moving persons and equipment.

Detailed Description of the Invention

[0016] Referring to all figures generally, embodiments of the work platform for coiled-tubing downhole operations invention method 200 and apparatus 100 are illustrated.

[0017] Referring to FIG. 1, the work platform for coiled-tubing downhole operations provides a safe, efficient, and relatively inexpensive work platform for extended access to the elevated top of a section of riser pipe. The riser pipe is necessary for proper use of coiled tubing. The riser-pipe sleeve sections 10 and the raised platform sections 20 are indicated. Schematically shown is the coiled tubing entering an injector located at the top of the riser pipe, which is rising from a blowout preventer connected to a well head. The work platform for coiled-tubing downhole operations is additionally secured by guy wires running from the riser-pipe sleeve sections 10 to the ground.

[0018] A working prototype of a preferred embodiment has been built. The prototype is sized and designed to accommodate a standard riser pipe section of 10 feet in length and 6.25 inches of outside diameter. The size of the floor surface of the prototype is 7 feet by 7 feet, or 49 square feet, with the riser pipe passing through the center of the square, which allows 3 feet of clearance minimum around the riser pipe, with extra floor space in the corners.

[0019] Another embodiment with an essentially circular or elliptical floor surface can be made, and may be more appropriate in some circumstances. The working prototype has two sections, each encompassing a half circle, which fit together to form a full-circle shell around the riser pipe, with just one common plane along which the sections are joined, and with the sections being pulled toward one another and toward the riser pipe. Another embodiment might have more than two sections, and therefore more than one single plane of joining. For example, three sections, each encompassing a 120-degree arc, would have three planes of joining, but each section would still be pulled toward the others and toward the riser pipe. An embodiment having more than two sections might be appropriate for very large installations, where size and weight makes handling easier with more numerous smaller sections, or where the disassembled work platform is to be transported in a small vehicle or container.

[0020] The working prototype and preferred embodiment of the invention uses welding for permanent attachment of units and sub-units, and steel bolts for secure but removable attachment of sections one to another for installation and use of the invention. Other methods of both permanent and removable attachment are known, and can be used in appropriate circumstances. The working prototype and preferred embodiment is constructed out of aluminum, which is electrically conductive and not magnetic, and steel, which is also electrically conductive and may or may not be magnetic depending upon the specific type of steel. For most common uses, the properties of conductivity and magnetism are irrelevant. In circumstances where those properties are detrimental to the installation, other metals and other materials, such as composite materials, can be used for construction of the work platform for coiled-tubing downhole operations.

[0021] The working prototype and preferred embodiment is constructed so that all electrically conductive pieces are in secure electrical contact with all of the other pieces, and with the riser pipe, when the work platform for coiled-tubing downhole operations is installed and in use. In normal use, the work platform for coiled-tubing downhole operations will be elevated between 30 and 40 feet above grade, and will be electrically bonded to earth ground through the riser pipe. Depending upon what other structures are adjacent to the site, the work platform for coiled-tubing downhole operations is likely to function as a lightning rod. Whenever non-conductive materials are substituted for metal materials, consideration should be given to any need for separate electrical bonding of units and sub-units in order to lessen any danger of lightning strike, or other electric shock to persons and equipment.

[0022] Referring to FIG. 2 & FIG. 3, an embodiment of the invention comprises two riser-pipe sections 10 and two raised platform sections 20. Each raised platform section 20 corresponds to a riser-pipe sleeve section 10. Optionally, the attachment of a raised platform section 20 to a riser-pipe sleeve section 10 can be made as a permanent attachment, such as welding, or as a secure but reversible attachment, such as bolts. The riser-pipe sections 10 are meant to fit tightly against the exterior surface of the riser pipe, like a shell, and are meant to be securely but removably attached one to the other at multiple points by bolts. The raised platform sections 20 are meant to surround the top portion of the riser pipe, and to be securely supported by the riser- pipe sleeve section 10 below, providing a work platform surrounding the top of the riser pipe.

[0023] Each raised platform section 20 is made of a tube frame 21 having a guardrail 22, as shown. A working prototype of the invention uses 3-inch x 3-inch x 1/8-inch aluminum tubing, welded together, as the tube frame 21 and the guardrail 22. A gateway 23 is provided in one of the raised platform sections 20 in order to allow passage of persons and equipment. This gateway should be secured by one of the standard means, such as installing a swinging or a retracting gate, installing chains, straps, or ropes, or installing a panel of strong fabric or mesh. The tube frame 21 is strengthened and stabilized by gussets 24, as shown. A working prototype uses 3/16- inch 6061 Aluminum Plate for the gussets, which are welded in place. Diagonal braces 25 are provided, which distribute the weight of the raised platform section 20 from the tube frame 21 to the midsection of the corresponding riser-pipe sleeve section 10. Again, 3-inch x 3-inch x 1/8-inch aluminum tubing is a satisfactory material for the diagonal braces 25.

[0024] Supported on top of the tubing frame 21 is a grate floor 26, which provides a safe floor surface. A working prototype uses 1.5-inch fiberglass grate, which provides sufficient strength and traction. Such a grate floor can be easily and inexpensively replaced, in sections, if it becomes worn or damaged.

[0025] Each raised platform section 20 is provided with a step-back or notch located at the middle of the tubing frame 21 member comprising the inside edge of the platform section 20, which is the edge closest to the other platform section 20 or sections in use. The step-backs, when brought together, form a hole or void essentially at the center of the assembled platform sections 20, through which the riser pipe will pass. Mounted to the step-back portion of each raised platform section 20 is a platform mounting plate 28 having a semi-circular opening sized to fit closely to the outside diameter of the riser pipe, and also having mounting holes in a pattern matching the corresponding sleeve mounting plate 18 disclosed in more detail below.

[0026] Referring to FIG. 4, assembled and in use, the work platform for coiled- tubing downhole operations surrounds the top portion of the riser pipe, which is the point where the coiled tubing will enter the riser pipe. Normally, there will be equipment, such as an injector, mounted to the top of the riser pipe. The work platform for coiled-tubing downhole operations provides a stable, secure work area at this critical location. The work platform for coiled-tubing downhole operations can be further stabilized with guy wires, as shown. Crossing of the guy wires ensures that each section is pulled toward the other section or sections and toward the riser pipe, avoiding any tendency to pull the assembled unit apart. In use, the lowest edge of the assembled riser-pipe sleeve sections 10 sits directly upon the flange attaching the highest section of riser pipe to the next highest section of riser pipe. The riser-pipe sleeve sections 10 fit closely to the outside surface of the riser pipe, like a shell, and are tightly pulled toward each other and toward the riser pipe, providing a secure attachment spread over a large portion of the riser pipe. The weight of the assembled work platform for coiled-tubing downhole operations is supported by the flange of the riser pipe combined with a large portion of the outside surface of the riser pipe.

[0027] Referring to FIG. 5, FIG. 6, & FIG. 7, the riser-pipe sleeve sections 10 comprise a shaped steel sleeve 11 having a mounting bar 12 on each long edge, reinforced by lateral ribs 13 and vertical ribs 14. Each shaped steel sleeve 11 section is semi-cylindrical and is sized to fit tightly to the outside diameter of the riser pipe. The long dimension of the shaped steel sleeve is oriented vertically, along the riser pipe, in use. When assembled, the sections of shaped steel sleeves 11 form a cylinder or tube surrounding the riser pipe like a shell. In an embodiment for use on riser pipe having a 6.25 -inch outside diameter, the inside diameter of the assembled shaped steel sleeve 11 sections is 6.5-inch, the thickness of the shaped steel sleeve is 3/16-inch A36 steel, and the vertical length of the shaped steel sleeve is 7 feet. Two mounting bars 12 are attached, each to a vertical edge of the shaped steel sleeve 11. The mounting bars 12 are attached from the top of the shaped steel sleeve 11 to a point near, but not on, the bottom edge. At the bottom edge, a length of approximately 5 inches is left without a mounting bar 12 attached. This length is left in order to prevent interference with, and preserve access to, the flange of the riser pipe and the connectors used to join the sections of riser pipe. In use, assembled, the mounting bars 12 with attached shaped steel sleeves 11 are brought together and securely fastened one to another by means such as steel bolts.

[0028] The outer surface of each shaped steel plate 11 is reinforced with lateral ribs 13 and vertical ribs 14, as shown. In a working prototype and preferred embodiment, the lateral and vertical ribs are made from 3/8-inch A36 steel plate and bar. No reinforcement is placed on the bottom length of approximately 5 inches of the shaped steel plate 11, in order to prevent interference with, and preserve access to, the flange of the riser pipe. A vertical rib with a protruding connection point, called a brace- connector rib 15, is used at approximately the middle of the riser-pipe sleeve 10 section, for connection of a diagonal brace 25. Two additional brace connectors 16 are attached to the outer surface of the shaped steel plate 11 at the approximate middle, as with the brace-connector rib 15. Cable connector ribs 17 are attached to the outer surface of the shaped steel plate 11 in the upper portion of the riser-pipe sleeve 10. The attachment should be made at a point that will allow access in order to connect and disconnect the cables or guy wires, and that will allow the cables to clear the diagonal braces 25 in use. The cables should be connected in a crossing arrangement, so that any given cable will pull the corresponding riser-pipe sleeve 10 section toward the other section or sections and toward the riser pipe.

[0029] A sleeve mounting plate 18 is attached at the top edge of the shaped steel plate 11 and mounting bars 12. The sleeve mounting plate 18 has a semi-circular opening sized to fit closely to the outside diameter of the riser pipe and has mounting holes in a pattern matching the corresponding platform mounting plate 28. In use, the sleeve mounting plate 18 and the platform mounting plate 28 for each section are attached one to the other by means such as steel bolts.

[0030] Referring to FIG. 8, an embodiment of the work platform for coiled-tubing downhole operations provides an elevator or lift 30 to transport persons and equipment between deck level and work-platform level.

[0031] Many changes and modifications can be made in the present invention without departing from the spirit thereof. I therefore pray that rights to the present invention be limited only by the scope of the appended claims.