1. Field of the Invention
The invention relates generally to devices and methods for conducting liner drilling and subsequent completion of the drilled section by securing the liner into place by anchoring and cementing.
2. Description of the Related Art
In its basic form, a wellbore is drilled using a drill bit that is attached to a drill string fashioned of drill pipe. When the wellbore is drilled to an original desired depth, the drill string and bit are removed from the hole. Then steel casing is inserted into the borehole and cemented in place as a protective tubular sheath to prevent collapse of the borehole wall. The term “casing,” as used herein will refer to those protective sheaths that extend along a portion of the wellbore all the way to the surface. The well can then be drilled to deeper depths in successively smaller diameter intervals below the original depth. These lower intervals are then lined with wellbore liners. As used herein, the term “liner” will refer to those protective sheaths that extend along a portion of the wellbore, but do not extend all the way to the surface.
In addition to traditional drilling using drill strings made up of drill pipe, techniques have been developed recently for casing drilling and liner drilling. In casing drilling, the bottom hole assembly containing the drill bit is threaded to a section of casing and, after drilling, the casing is hung at the top of the wellbore. Liner drilling is a similar concept. In liner drilling, the liner to be cemented in serves as a part of the drilling string while traditional drill pipe usually forms the upper part of the drill string. The bit can be attached to the liner and the liner then rotated within the borehole. Alternatively, a mud motor is attached to liner and the mud motor is used to turn the bit while the liner remains stationary. When liner drilling is completed, the drill pipe portion of the drill string is detached from the liner and withdrawn from the wellbore. The liner portion of the drilling string remains in the borehole, set on the bottom of the hole and is later cemented into place. The bit and mud motor are also left in the hole.
A significant problem with this conventional liner drilling process is that the liner can deform by bending or corkscrewing under its own weight when set down on bottom. This is especially true of very long liners. If the liner is cemented in this condition, it will be permanently deformed and perhaps be unusable for passing large diameter tools through. For this reason, a number of “one-trip” liner drilling arrangements have been developed that incorporate liner hangers into the drilling string on the upper end of the liner so that the liner can be anchored to the pre-existing casing after cementing. An example of a “one-trip” liner drilling system is described in U.S. Pat. No. 5,497,840, issued to Hudson.
A major problem with “one trip” liner drilling systems is their ability to return drill cuttings to the surface of the wellbore. The liner portion of the drill string has a much greater diameter than traditional drill pipe. As a result, the annulus surrounding the liner portion is quite small, leaving little room for pumped down drilling mud and generated cuttings to return to the surface of the well. While this problem is inherent to the process of liner drilling, it is made substantially worse by the presence of any exterior components that extend outwardly into the annulus beyond the diameter of the liner. Thus, externally mounted hangers or packers, that might be used to hang the liner in tension from the casing or liner above could not be run in with the liner during the drilling operation without destroying the ability to drill and remove cuttings effectively during drilling. Thus, there is a need to be able to conduct liner drilling with minimal exterior components to allow annular bypass of returning drilling mud and cuttings.
The present invention addresses the problems of the prior art.
The invention provides improved methods and systems for conducting liner drilling and subsequent completion of the drilled section by cementing and anchoring the liner into place. The methods and systems of the present invention prevent the liner from being cemented in in a bent or corkscrewed configuration. Additionally, the systems and methods of the present invention minimize the number of exterior components associated with the liner during drilling so as to allow relatively unrestricted return of drilling mud and cuttings.
In accordance with preferred embodiments of the invention, a liner is drilled into a wellbore below original depth using a running tool. A liner setting sleeve having a substantially smooth exterior is affixed to the top of the liner, thereby permitting substantially unrestricted annular bypass and minimal exterior mechanical complexity during drilling. Once the target depth has been reached, the liner is set on the bottom of the hole and the liner setting tool is released from the liner. The running string is then withdrawn from the hole. Next, a liner hanger/packer assembly is run into the hole. The liner hanger/packer assembly has a latch-in seal assembly to latch into the liner setting sleeve. Once, latched, the liner is lifted off the bottom of the hole. A liner packer is then set to hang the liner in tension. Thereafter, the liner may be anchored to the casing above and cemented into place within the wellbore in a substantially straight and true condition.
For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:
The liner drilling system 20 also includes a length of running string formed of drill pipe 42 that extends downwardly from the drilling rig 22 and is secured to the liner setting sleeve 34 and PBR 40 at its lower end.
After the completion of cementing, the drill string running tool 55 is then removed from the latching liner hanger assembly 54. This is usually accomplished by rotating the drill string running tool 55 to unthread the hanger assembly 54 and then withdrawing the running tool 55 from the wellbore 10.
Those of skill in the art will recognize that the methods and systems of the present invention provide a number of advantages over conventional liner drilling and placing systems. First, they help ensure that the liner 32 will not be deformed from compression bending or corkscrewing at the time that it is cemented in or anchored to the casing 18. As a result, there will be fewer subsequent problems with running large diameter tools through the liner 32 at a later point in development of the wellbore 10. Additionally, the liner drilling process is made more effective because there is a minimum complication of the annulus 50 during the drilling phase. There are no external packers or slips associated with the liner 32 during the drilling phase, and therefore, the cuttings and mud can more easily reach the surface 12.
Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.
This application claims the priority of U.S. Provisional Patent Application Ser. No. 60/700,555 filed Jul. 19, 2005.
Number | Date | Country | |
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60700555 | Jul 2005 | US |