PIPE PERFORATING APPARATUS AND METHOD
A method and apparatus for perforating pipe from its interior, and in particular for perforating plastic well casing in situ. A linear actuator drives a claw-shaped bit. Linear motion of the cylinder is converted to a pivoting of the bit in a radial direction by a deflector. In a preferred embodiment, the linear actuator is a hydraulic piston-cylinder assembly and the deflector is an inclined surface. Operation of the actuator in a first direction drives the bit into the inclined deflection surface, which causes the bit to pivot and protract radially outward of the tool housing to perforate the wall of a pipe. Operation of the actuator in the opposite direction pulls the bit back into the tool housing so that the perforator tool can be easily moved with a well casing.
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1. Field of the Invention
This invention relates generally to perforating pipe, and in particular to perforating plastic pipe well casings in situ.
2. Background Art
Decomposition in waste landfills, particularly in the hot and humid gulf coast region, creates methane gas. Accordingly, wells are drilled in landfills for the production of methane gas. Landfill gas wells are typically made of high density polyethylene (HDPE) or polyvinyl chloride (PVC) pipe.
As waste is added to a landfill on top of existing well field, the voids within the lower gas-producing region are compressed and the water levels are raised, which results in a reduced radius of influence and more difficult gas extraction. Typically, landfill addition has required the costly re-drilling of new wells to maintain adequate gas extraction rates.
It is therefore advantageous to be able to perforate existing gas wells in situ to raise the production zones as the landfill builds. Such ability provides for a longer useful life for existing gas wells, thus reducing the cost of methane production.
Some perforator tools are known in the art, but the perforations created by these devices have typically been small. As a result, these small perforations tend to close up, or “self-heal,” particularly in HDPE pipe. Perforators which create large openings have typically been too slow and inefficient for satisfactory use.
3. Identification of Objects of the InventionA primary object of the invention is to provide a method and apparatus for efficiently making large perforations in plastic well pipe from the inside of the pipe.
Another object of the invention is to provide a perforating apparatus that is easily run down serpentine wells and a method for moving the perforating apparatus past potential choke points.
SUMMARY OF THE INVENTIONThe objects described above and other advantages and features of the invention are incorporated in a method and a well perforator system that provides for simple and effective puncturing of plastic well casing in situ. A linear actuator drives a claw-shaped bit. Linear motion of the cylinder is converted to a pivoting of the bit in a radial direction by a deflector. In a preferred embodiment, the linear actuator is a hydraulic piston-cylinder assembly and the deflector is an inclined surface. Operation of the actuator in a first direction drives the bit into the inclined deflection surface, which causes the bit to pivot and protract radially outward of the tool housing to perforate the wall of a pipe. Operation of the actuator in the opposite direction pulls the bit back into the tool housing so that the perforator tool can be easily moved with a well casing.
The invention is described in detail hereinafter on the basis of the embodiments represented in the accompanying figures, in which:
Preferably, perforator tool 100 is hydraulically powered, in which case conduit 30 consists of a pair of hydraulic hoses—one for fluid supply and the other for fluid return. However, electric, pneumatic, or other mechanical power may be used in place of hydraulic power as appropriate.
A local source of hydraulic power, such as a gasoline engine driving a hydraulic pump, may be included with drawworks unit 12 for powering tool 100 via hoses 30. Alternatively, hydraulic power may be provided by skid steer vehicle 14, from a power take-off (PTO) unit, for example.
Tool 100 is generally cylindrically shaped and has an outer diameter to allow tool 100 to pass freely through casing 52 when its perforating claw is fully retracted. However, the dimensions of tool 100 are such that when its perforating claw 102 is fully protracted, its width exceeds the inner diameter of casing 52. For example, for a six inch well bore, tool 100 preferably has housing 104 with about a 4-5 inch outer diameter. When fully protracted, claw 102 extends about 2-3 inches beyond housing 104.
The dimension of tool housing 104 is preferably small enough to allow tool 100 to be easily passed through most well bores. However, well bores are often serpentine in nature, and they can become somewhat crushed and oblong in certain locations. If tool 100 becomes lodged when lowering it, claw 102 can be repeatedly cycled between fully-retracted and half-protracted positions. Each cycle causes the claw to engage the well casing and pull tool downward slightly. Repetitive cycling tends to “walk” tool 100 below problematic spots in the well bore.
Referring now to
Hydraulic cylinder assembly 130 has a generally square profile, although a cylinder assembly with a circular profile may be used as well. Cylinder assembly 130 is dimensioned to fit snugly within upper housing 112, with the rod end 134 abutting the upper surface of base plate 114. Cylinder assembly 130 includes four bores 136 formed through its longitudinal length, which are spaced at ninety degree intervals about the centerline of piston rod 132 and at the same spacing as threaded holes 118 of base plate 114. Cylinder assembly 130 includes inlet and outlet fluid ports 138, 139, and upper housing 112 includes one or more recesses, slots or openings 113 that are positioned so that ports 138 and 139 can be accessed.
Upper tool assembly 100 includes an end cap 140. End cap 140 is preferably formed of steel plate and has a generally circular shape that is dimensioned to fit snugly within upper housing 112. End cap 140 includes four holes 142 spaced ninety degrees about its center at the same spacing as cylinder assembly bores 136 and threaded base plate holes 118. End cap 140 also preferably includes a padeye 144 for securing downhole tool 100 to chain or wire rope 28 with a shackle 29 (
Finally, upper tool assembly 110 includes a claw assembly 150, which preferably includes a perforating bit 102 pivotally mounted to a ‘U’-shaped clevis or gudgeon 152, with a pintle, pin or bolt 154, for example. Bit 102 may be journaled to gudgeon 152 with a ball bearing assembly, or the like, if desired. Clevis or gudgeon 152 is adapted to be connected to the end of piston rod 132. Preferably, a threaded connection is used, which allows fine length adjustment of upper tool assembly 110.
Perforating bit 102 is a planar member having the general shape of an apostrophe or claw. The larger round end of claw 102 defines a crosshead 156 and includes a hole formed therethrough for receiving bolt 154. The distal end of claw 102 forms a sharp tip 157. A convex side 158 and a concave side 159 are defined between tip 157 and crosshead 156.
Upper tool assembly 110 is assembled as follows: Bores 136 of cylinder assembly 130 are aligned with threaded holes 118 of base plate 114, and cylinder assembly 130 is inserted into upper housing 112 until its rod end 134 rests on base plate 114 with piston rod 132 extending through hole 116. Next, end cap 140 is oriented so that holes 142 align with bores 136 and is inserted into upper housing 112 above cylinder assembly 130. The longitudinal dimension of upper housing 112 and cylinder assembly 130 are such that end cap 140 fits flush with the upper end of upper housing 112 and snuggly encases cylinder assembly 130. Four threaded fasteners 148 are passed through holes 142 in end cap 140 and bores 136 in cylinder 130. Fasteners 148 are threaded into holes 118 in base plate 114. Finally, claw assembly 150 is connected by threading or otherwise attaching gudgeon 152 to piston rod 132.
In
The operation of downhole perforator tool 100 is described with reference to
Referring to
To retract claw 102, pressurized fluid is pumped into lower port 139, which raises piston 133, piston rod 132, gudgeon 152, and claw crosshead 156. When raised, claw 102 pivots about bolt 154 and retracts into housing 104.
Although an embodiment using a single claw-shaped bit is described herein, multiple bits may be used as appropriate within the scope of the invention. Similarly, although the means for deflecting the puncturing bit is described as an inclined surface, alternative deflectors may be used, such as a bellcrank, for example, within the scope of the invention.
The Abstract of the disclosure is written solely for providing the United States Patent and Trademark Office and the public at large with a way by which to determine quickly from a cursory reading the nature and gist of the technical disclosure, and it represents solely a preferred embodiment and is not indicative of the nature of the invention as a whole.
While some embodiments of the invention have been illustrated in detail, the invention is not limited to the embodiments shown; modifications and adaptations of the above embodiment may occur to those skilled in the art. Such modifications and adaptations are in the spirit and scope of the invention as set forth herein:
Claims
1. A tool (100) for perforating a pipe (52) from the interior of the pipe, said tool defining a longitudinal axis, the tool comprising:
- an actuator (130) operable to reciprocate a gudgeon (152); and
- a bit (102) having a first end (156) pivotally coupled to said gudgeon and a second end (157) defining a claw;
- whereby movement of said gudgeon in a first direction causes pivotal protraction of said claw outward from said axis.
2. The tool of claim 1 wherein:
- said first end of said bit defines a crosshead that is journaled to said gudgeon.
3. The tool of claim 1 further comprising:
- a deflector (162) disposed at a fixed distance from said actuator;
- whereby linear movement of said gudgeon in said first direction is converted by said deflector to pivotal protraction of said claw radially outward from said axis.
4. The tool of claim 1 further comprising:
- a housing (104) enclosing said actuator and said gudgeon, said housing having an opening (166);
- whereby translation of said gudgeon by said actuator in said first direction forcibly protracts said claw through said opening a distance beyond said housing, and translation of said gudgeon by said actuator in a second direction opposite to said first direction retracts said claw into said housing.
5. The tool of claim 1 further comprising:
- a generally cylindrical housing (104) enclosing said actuator and said gudgeon, said housing being centered about said axis and having top and bottom ends (140, 162), said bottom end (162) of said housing being inclined at an acute angle with respect to said axis;
- whereby translation of said gudgeon by said actuator toward said bottom end of said housing causes said bit to contact and deflect off an inclined interior surface of said bottom end for pivoting said bit about said gudgeon.
6. The tool of claim 1 wherein:
- said actuator is a cylinder-piston assembly.
7. The tool of claim 1 wherein:
- said claw of said bit is generally planar having first and second parallel sides, a third convex side (158) and a fourth concave side (159).
8. The tool of claim 1 wherein:
- only a single bit is present.
9. The tool of claim 1 further comprising:
- a drawworks (12) carrying a tension member (28),
- said housing (104) carried by said tension member; and
- a vehicle (14) carrying said drawworks and providing power to said actuator.
10. A method for perforating a pipe comprising the steps of:
- inserting a linear actuator (130) into said pipe (52);
- activating said actuator in a first direction to move a gudgeon (152) and a bit (102) attached to said actuator; and
- pivoting said bit so that a distal pointed end (150) of said bit is protracted through the wall of said pipe.
11. The method of claim 10 further comprising the step of:
- activating said actuator in a second direction to retract said bit from said wall of said pipe.
12. The method of claim 10 further comprising the step of:
- pivoting said bit by a deflector (162).
13. The method of claim 12 wherein:
- said deflector is an inclined surface.
14. The method of claim 13 wherein:
- said bit has a convex edge (158); and
- said inclined surface has a concave groove (168);
- whereby a contact force of said convex edge against said concave groove acts to pivot said bit.
Type: Application
Filed: Apr 6, 2010
Publication Date: Oct 6, 2011
Applicant:
Inventors: WILLIAM R. JOHNSTON (Crosby, TX), James D. Hayes (Crosby, TX)
Application Number: 12/755,110
International Classification: E21B 43/11 (20060101); E21B 29/00 (20060101);