Method and apparatus for removing casing

A method and apparatus for removing a string of casing from a well bore. The method and apparatus include a plurality of drill bits substantially aligned with each other for drilling a plurality of holes in the string of casing. The plurality of holes can be used to lift the string in casing from the well bore via a series of incremental casing sections.

CROSS-REFERENCE TO RELATED APPLICATIONS

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REFERENCE TO A “MICROFICHE APPENDIX”

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BACKGROUND

The present invention relates generally to oil and gas wells and, more specifically, to a system for removing casing which has been placed in a well bore.

The process of drilling subterranean wells to recover oil and gas from reservoirs, consists of boring a hole in the earth down to the petroleum accumulation in the reservoir, and installing pipe from the reservoir to the surface. Casing is a protective pipe liner within the well bore that is cemented in place to ensure a pressure-tight connection to the oil and gas reservoir. The casing can be run from the rig floor as it is lowered into the well bore. After the casing has been run to the desired depth it is typically cemented within the well bore. The purpose of cementing is to seal the casing to the well bore formation.

Sometimes after a string of casing has been cemented, it must be removed for one or more reasons (such as plug and abandoning the well bore or removing the casing so that the well can be redrilled, called sidetracked, if for some reason the drill bit cannot pass through the previously installed casing or matter located downhole). This invention potentially saves several hours of drill rig time (from 2 hours to ½ hour) for removing the casing and is used for removing casing that was previously cemented in place. Removing the casing is a difficult job because of the tremendous amount of force which must be placed on the casing to pull it out of the ground. The casing was cemented in the ground generally to keep it in place. Accordingly, not only must the weight of the casing be pulled out of the well bore, but also the weight of the cement along with overcoming the frictional forces caused by the cement interacting with the sidewall of the well bore.

In prior art systems the casing was removed by incremental sections, such as forty foot increments. For an incremental section of casing, casing operators would cut the casing and manually drill two holes. The two holes were drilled on either side of the casing attempting to have them aligned with each other. After the holes had been drilled, a bar or rod would be placed through the two holes. The bar or rod would then be pulled up by the rig's top drive unit or the draw works a specified incremental amount, such as forty feet. As discussed above, in raising the casing a tremendous amount of force was required to overcome the resisting forces. After the incremental section of casing had been raised, the cutting and drilling process would start over again for the next incremental section of casing. After the various increments of casing were cut and pulled from the well bore, they would be disposed of.

In prior art systems, operators would attempt to individually and sequentially drill the two holes in each incremental section of casing. The operator would first drill one side. Depending on the thickness of the wall to be drilled, drilling would have to be intermittently stopped and all drilled material removed from the drill bit. This process would take much time and slow down the removal of the casing (such as 2 hours). Second, the operator would go around to the other side of the casing and attempt to drill a second hole opposite the first hole. Again, intermittent breaks to unclog the drill bit would be required. Sometimes, the operator got lucky and the two holes lined up, but at other times the two holes did not line up and a bar could not be inserted through both holes. When the two holes did not line up, the operator using a torch would have to chip and cut at least one of the holes to open it up so that the bar could be placed through both holes.

This process took much rig time and created a hazardous working environment when using a torch and was potentially repeated for each incremental section of casing.

While certain novel features of this invention shown and described below are pointed out in the annexed claims, the invention is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the spirit of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.”

BRIEF SUMMARY

The apparatus of the present invention solves the problems confronted in the art in a simple and straightforward manner. Provided is a method and apparatus for removing casing from a well bore. More specifically, the present invention solves the above problems by having a plurality of drills and a collar system for drilling two holes whereby the drills can be aligned with each other. Additionally, both holes can be drilled substantially simultaneously reducing drill time.

Both drills can be pneumatically powered to avoid fire risks. The drills can be mounted on a collar which is attached to the casing to be drilled. After both holes are drilled a bar can be placed through the two holes and a collar attached to the bar. The collar can be attached to the rig's top drive unit or draw works and the casing pulled an incremental amount, such as forty feet. The incremental amount pulled can vary by rig size, rig components, operator preference—and can change from pull to pull. For example, an incremental amount pulled can vary from five feet to ninety feet. After being pulled and cut, the incremental section of casing can be properly disposed of.

Drill bits can be sized to allow the bits to go completely through very thick portions of casing with cement layers attached thereon—drilling to the casing's interior without periodically cleaning/emptying the drill bits. Additionally, during the drilling process, the bits can be lubricated with fluid, such as by water, to prevent sparks and cooling thereby allowing drilling to continue all the way through the cement and casing thickness without stopping for cooling down/cleaning out periods.

The present invention provides a more efficient operation significantly improving the speed and safety of removing casing from a well bore.

These and other objects, features, and advantages of the present invention will become apparent from the drawings, the descriptions given herein, and the appended claims. The drawings constitute a part of this specification and include exemplary embodiments to the invention, which may be embodied in various forms.

DETAILED DESCRIPTION

Detailed descriptions of one or more preferred embodiments are provided herein.

It will be understood that such terms as “up,” “down,” “vertical” and the like are made with reference to the drawings and/or the earth and that the devices may not be arranged in such positions at all times depending on variations in operation, transportation, and the like. As well, the drawings are intended to describe the concepts of the invention so that the presently preferred embodiments of the invention will be plainly disclosed to one of skill in the art but are not intended to be manufacturing level drawings or renditions of final products and may include simplified conceptual views as desired for easier and quicker understanding or explanation of the invention.

FIG. 1is a perspective view of a preferred embodiment of recovery system10shown attached to casing20. Casing20, comprising upper and lower sections30,40, had previously been cemented in well bore45and is to be removed. Casing20can be removed in incremental sections (such as in forty foot increments) and can be pulled up in incremental sections from well bore45in the direction of arrow420, by using traveling block470and bar460combined with fitting/shackle480(not shown).

For the first section of casing20to be removed, a cut line35can be made using a casing cutting tool36and the upper incremental section of casing31above the cut line35can then be removed. Before making cut line35and below cut line35, slips for rig50can be connected to casing20for holding lower section40of casing20and preventing it from dropping down well bore45.

Preferably, after making cut line35, recovery system10can be connected to the remaining portion of casing20to create to holes for raising and removing another incremental section of casing20. Recovery system10can be connected prior to making cut line35, but doing so may interfere with the cutting operation. Recovery system10can be attached to casing20by clamp80. Using handles or cranks150and390, drills120and270drill into casing20in the direction of arrows400,410and along centerline430creating openings440and450(FIG. 3). Casing20, comprising upper and lower sections30,40, can be partially pulled up from well bore45in the direction of arrow420, by using traveling block470and bar460combined with fitting/shackle480(not shown). Slips for rig50can again be connected to casing20and used to hold lower section40after casing20is cut. Below the slips a new cut line35can be made and another incremental section31of casing20(above the new cut line35) can be removed.

Recovery system10can again be attached to casing20by clamp80. Using handles or cranks150and390, drills120and270drill into casing20in the direction of arrows400,410and along centerline430creating openings440and450(FIG. 3). Bar460combined with fitting480(not shown) can then be installed in the new holes440,450. Another incremental section of casing20, comprising upper and lower sections30,40, can again be pulled up from well bore45in the direction of arrow420, by using traveling block470and bar460combined with fitting/shackle480(not shown). Slips for rig50can be connected to casing20and used to hold lower section40after casing20is cut. Above the slips a new cut line35can be made and the incremental casing section above the new cut line35can be removed. For making new holes recovery system10can again be attached to casing20.

The process can be repeated until the entire length of casing20is pulled from well bore45via incremental sections31. Well bore45can then be further worked, such as by sidetracking or plugging and abandoning.

As a casing cutting tool36, a Guillotine saw is preferably used. A casing cutting saw can also be used, but may create increase risks when making cut35.

FIG. 2is a perspective view of the recovery system10shown inFIG. 1.

Recovery system10can be comprised of body220, body360, and clamp30. Body360can be constructed substantially similar to body220. During drilling operations clamp80can be used to position drills120,270on either side of casing20. Recovery system10can be supported by legs225and365standing on rig floor60of rig50.

Clamp80can be comprised of first portion90and second portion100. First and second portions90,100can be detachably connected by a plurality of fasteners110. First portion90can be connected to lower portion223and can comprise connector plates91,92. Second portion100can be connected to lower portion363and can comprise connector plates101,102. Clamp80can be sized based on the diameter of casing20to be removed. First and second portions90,100can also be removably connected to lower portions223,363(e.g., by fasteners) and a plurality of first and second portions90,100can be included to address different size casings20. Alternatively, different sized clamps80can be provided to address different size casings20. Any conventionally available fastening method can be used in place of fasteners110. For example, first and second portions90,100can be pivotally connected on one side with a locking bracket on the other. A plurality of bolted fasteners110is preferred to accommodate variations in diameter of casing20.

FIG. 2is a perspective view of recovery system10showing bodies220and360which include drills120and260. Body360can be constructed substantially similar to body220and therefore only body220will be described in detail.

Drill120can be comprised of motor130, shaft140, and drill bit180. Motor130is preferably pneumatically powered to minimize the risk of explosion. Depth181of drill bit180can be sized to at least accommodate the thickness of wall of casing20and any other obstructions which must be cut through (such as cement lining). Diameter of drill bit180(which can be similar to diameter321of drill bit320) can be sized to accommodate the lifting apparatus (e.g., bar460and fitting/shackle480) which is to be inserted through casing20, such as bar460as shown inFIG. 3. Drill bit180can be any conventionally available drill bit and can also include a pilot bit190to ease initial drilling of wall of casing20. Drill bit180can include priming drill bit190attached to the center of bit180. Drill bit180attaches to shaft140and shaft140attaches to130.

Lower portion223can support an ambulatory system for drill120linearly moving drill120in the directions of arrows400. Drill120can be attached to base230via motor130. Base230can move linearly with respect to lower portion223. Base230can be threadably connected to drive shaft240and track along length of lower portion223. Turning crank250in the direction of arrow425can move base230in a longitudinal direction of arrow400toward the center of clamp80. Turning crank250in the opposite direction can move base230in the opposite direction. Guides241,242can be used to guide base230when linearly moving on lower portion223.

Before attaching recovery system10to casing20, body150is attached to mounting rack300. Clamp160was sized for the particular diameter of casing20. First portion170is removed from clamp160. Recovery system10is placed against casing20aligning hole185approximately at the location where casing20is ultimately to be cut. Mounting bracket310is placed against the wall of casing20. Second portion180of clamp160should also mount against the wall of casing20. Chain360is wrapped around casing20, arms370and connected to connectors380. First portion170of clamp160is attached to second portion180via fasteners190. Liner200will make a fluid tight seal with wall of casing20. Recovery system10can then be connected to pump30and recovery tank120through hoses134and135.

After being connected to casing20, motor130can be started rotating shaft140and rill bit200. As shown inFIG. 1, crank250can be rotated in the direction of arrow45causing base230and drill120to move toward the center of casing20. Priming drill bit190will first contact wall of casing20(or cement layer25) making a priming hole and steadying the drilling by drill bit180. Drill bit180will continue through the wall of casing20(and through cement layer25) creating an opening440the size of drill bit180(seeFIG. 3). The portion of the wall of casing20(and cement layer25) which is cut out will be contained in the interior of drill bit180. Crank250is then turned in the opposite direction of arrow425causing drill bit180move in the opposite direction. As stated above the operation of drill260and crank390is substantially similar to drill120and crank250(and will not be specifically described). However, it should be noted that drill260and crank390can be operated simultaneously or separately with drill120and crank250.

After holes440,450are drilled, recovery system10is removed from casing20(such as by releasing fasteners110) and an apparatus, such as bar460, can be placed between holes440,450. A incremental section of casing20, comprising upper section30and lower section40, can then be pulled up, such as by using traveling block470. A similar process is performed for the next incremental section of casing20, and continued until each incremental section of casing has been pulled from well bore45. After complete removal of casing20, further work on well bore45can be performed, such as sidetracking or plugging and abandoning.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof, and it will be appreciated by those skilled in the art, that various changes in the size, shape and materials, the use of mechanical equivalents, as well as in the details of the illustrated construction or combinations of features of the various elements may be made without departing from the spirit of the invention.

The following is a list of reference numerals:

It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention set forth in the appended claims. The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.