REAMER ROLLER CONE BIT WITH STEPPED REAMER CUTTER PROFILE

Abstract

A bottom hole assembly including a pilot bit for initially forming an unconfined inner sidewall of a wellbore and a reamer tool above the pilot bit and comprising a first cutter ring to expand the unconfined inner sidewall, and a second cutter ring located above and outwardly of the first cutter ring to expand the unconfined inner sidewall as expanded by the first cutter ring. The reamer tool may further comprise a third cutter ring located above and outwardly of the second cutter ring to expand the unconfined inner sidewall as expanded by the second cutter ring. The first cutter ring may be located on a first roller cone, the second cutter ring may be located on a second roller cone, and the third cutter ring may be located on a third roller cone.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

None.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The inventions disclosed and taught herein relate generally to drilling assemblies for drilling wellbores into earth formations; and more specifically related to reamer tools for such drilling assemblies.

2. Description of the Related Art

U.S. Pat. No. 4,106,577 discloses a “hydromechanical drilling tool which combines a high pressure water jet drill with a conventional roller cone type of drilling bit. The high pressure jet serves as a tap drill for cutting a relatively small diameter hole in advance of the conventional bit. Auxiliary laterally projecting jets also serve to partially cut rock and to remove debris from in front of the bit teeth thereby reducing significantly the thrust loading for driving the bit.”

U.S. Pat. No. 4,141,421 discloses “an under reamer tool for enlarging, scraping or smoothing a well bore. The tool is attached to a conventional drill string above a conventional bit and involves cutting elements that have retractable cutters arranged for extension from the tool to engage the well bore wall, each cutter, when the drill string is turned, being urged outwardly by centrifugal force until it engages the well bore wall, continued turning thereafter, pulling that cutter into its extended cutting attitude, reaming the wall to the desired diameter, cutter retraction involving ceasing turning the drill string and the pulling of the drill string and connected tool from the well bore. During that pulling should the cutter contact a shoe or first reduction of the well bore casing or the wall thereof, it will be urged into a stowed attitude recessed within the tool body, the under reamer tool of the present invention also incorporating scouring openings provided in the tool body opposite to the cutter storage areas to pass liquid or air therethrough from the drill string to purge and clean that area within the tool body, allowing the cutter to travel freely therein.”

U.S. Pat. No. 5,497,842 discloses a “reaming apparatus for enlarging a borehole, including a tubular body having one or more longitudinally and generally radially extending blades circumferentially spaced thereabout. Each of the blades carries highly exposed cutting elements, on the order of fifty percent exposure, on its profile substantially all the way to the gage. At least one of the blades is a primary blade for cutting the full or drill diameter of the borehole, while one or more others of the blades may be secondary blades which extend a lesser radial distance from the body than the primary blade. A secondary blade initially shares a large portion of the cutting load with the primary blade while the borehole size is in transition between a smaller, pass through diameter and drill diameter. It functions to enhance the rapidity of the transition while balancing side reaction forces, and reduces vibration and borehole eccentricity. After drill diameter is reached, cutting elements on the secondary blade continue to share the cutting load over the radial distance they extend from the body.”

U.S. Pat. No. 6,439,326 discloses a “drill bit including a roller cone and fixed cutters positioned external to the roller cone and radially from the bit axis of rotation. The roller cone is located so that a drill diameter of the cone is substantially concentric with an axis of rotation of the bit. The fixed cutters can be made of tungsten carbide, polycrystalline diamond, boron nitride, or any other superhard material. The fixed cutters are positioned to either maintain the hole diameter drilled by the roller cone or to drill a larger diameter hole than the hole drilled by the roller cone. The single roller cone may be located in the center of a multi-cone bit arrangement or in the center of a PDC bit to assist in drilling the center of a wellbore. The single roller cone may be used to form a bi-center bit in combination with a reaming section. The single roller cone may also be located on an independent sub that is removably attached to the bit body.”

U.S. Pat. No. 6,729,418 discloses a “back reaming tool is disclosed which includes a tool body adapted to be coupled to a drill string, and at least one roller cone rotatably mounted to a leg and having cutting elements disposed thereon. The leg is removably coupled to the tool body. The at least one roller cone is open at only one axial end thereof.”

U.S. Pat. No. 7,090,034 discloses “a reamer (100) having at least one journal body (110) and at least one toroidal cutter body (116). The toroidal cutter body (116) has a maximum diameter (MD), an outer perimeter (OP) and a plurality of cutting elements (112, 145, 149) on the cutting surface (118). The toroidal cutter body is rotatably attached to the journal (110). When in the installed position, the axis of rotation (RA) of the at least one toroidal cutter body (116) intersects the longitudinal axis of the drill string at an acute angle.”

The inventions disclosed and taught herein are directed to an improved system for drilling and expanding wellbores into earth formations.

BRIEF SUMMARY OF THE INVENTION

In one embodiment, the present invention comprises a bottom hole assembly including a pilot bit for initially forming an unconfined inner sidewall of a wellbore and a reamer tool above the pilot bit, the reamer tool comprising a first cutter ring configured to expand the unconfined inner sidewall of the wellbore, and a second cutter ring located above and outwardly of the first cutter ring and configured to expand the unconfined inner sidewall as expanded by the first cutter ring. The reamer tool may further comprise a third cutter ring located above and outwardly of the second cutter ring and configured to expand the unconfined inner sidewall as expanded by the second cutter ring. The first cutter ring may be located on a first roller cone, the second cutter ring may be located on a second roller cone, and the third cutter ring may be located on a third roller cone. The reamer tool may further comprise a fourth cutter ring located on the first roller cone above and outwardly of the third cutter ring and configured to expand the unconfined inner sidewall as expanded by the third cutter ring, a fifth cutter ring located on the second roller cone above and outwardly of the fourth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fourth cutter ring, and a sixth cutter ring located on the third roller cone above and outwardly of the fourth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fifth cutter ring. Each roller cone may include three cutter rows, wherein successive cutter rows are located above and outwardly of previous cutter rows such that each cutter row engages the wellbore in such a manner as to incrementally expand the wellbore outwardly. In one embodiment, the wellbore is defined by an unconfined inner sidewall and successive cutter rows are located above and outwardly of previous cutter rows such that each cutter row engages the wellbore in such a manner as to incrementally expand the unconfined inner sidewall outwardly.

In another embodiment, the present invention includes a reamer tool for expanding a wellbore in an earth formation, the reamer comprising a first roller cone having a first cutter ring configured to expand an unconfined inner sidewall of the wellbore and a second roller cone having a second cutter ring located above and outwardly of the first cutter ring and configured to expand the unconfined inner sidewall of the wellbore as expanded by the first cutter ring. The reamer tool may further comprise a third roller cone having a third cutter ring located above and outwardly of the second cutter ring and configured to expand the unconfined inner sidewall as expanded by the second cutter ring. The reamer tool may further comprise a fourth cutter ring located on the first roller cone above and outwardly of the third cutter ring and configured to expand the unconfined inner sidewall as expanded by the third cutter ring. The reamer tool may further comprise a fifth cutter ring located on the second roller cone above and outwardly of the fourth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fourth cutter ring. The reamer tool may further comprise a sixth cutter ring located on the third roller cone above and outwardly of the fifth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fifth cutter ring.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a simplified embodiment of a bottomhole assembly utilizing certain aspects of the present inventions;

FIG. 2 illustrates a close-up view of a simplified embodiment of a roller cone reamer tool in operation expanding a wellbore, shown with multiple roller cones and cutters overlain;

FIG. 3 illustrates a particular embodiment of a roller cone utilizing certain aspects of the present inventions;

FIG. 4 illustrates another particular embodiment of a roller cone utilizing certain aspects of the present inventions;

FIG. 5 illustrates another particular embodiment of a roller cone utilizing certain aspects of the present inventions;

FIG. 6 illustrates another particular embodiment of a roller cone utilizing certain aspects of the present inventions;

FIG. 7 illustrates a composite view of the roller cones of FIGS. 3-6 overlain; and

FIG. 8 illustrates another close-up view of a simplified embodiment of a roller cone reamer tool in operation expanding a wellbore, shown with multiple roller cones and cutters overlain.

DETAILED DESCRIPTION

The Figures described above and the written description of specific structures and functions below are not presented to limit the scope of what Applicants have invented or the scope of the appended claims. Rather, the Figures and written description are provided to teach any person skilled in the art to make and use the inventions for which patent protection is sought. Those skilled in the art will appreciate that not all features of a commercial embodiment of the inventions are described or shown for the sake of clarity and understanding. Persons of skill in this art will also appreciate that the development of an actual commercial embodiment incorporating aspects of the present inventions will require numerous implementation-specific decisions to achieve the developer's ultimate goal for the commercial embodiment. Such implementation-specific decisions may include, and likely are not limited to, compliance with system-related, business-related, government-related and other constraints, which may vary by specific implementation, location and from time to time. While a developer's efforts might be complex and time-consuming in an absolute sense, such efforts would be, nevertheless, a routine undertaking for those of skill this art having benefit of this disclosure. It must be understood that the inventions disclosed and taught herein are susceptible to numerous and various modifications and alternative forms. Lastly, the use of a singular term, such as, but not limited to, “a,” is not intended as limiting of the number of items. Also, the use of relational terms, such as, but not limited to, “top,” “bottom,” “left,” “right,” “upper,” “lower,” “down,” “up,” “side,” and the like are used in the written description for clarity in specific reference to the Figures and are not intended to limit the scope of the invention or the appended claims.

Applicants have created a bottom hole assembly including a pilot bit for initially forming an unconfined inner sidewall of a wellbore and a reamer tool above the pilot bit and comprising a first cutter ring to expand the unconfined inner sidewall and a second cutter ring located above and outwardly of the first cutter ring to expand the unconfined inner sidewall as expanded by the first cutter ring. The reamer tool may further comprise a third cutter ring located above and outwardly of the second cutter ring to expand the unconfined inner sidewall as expanded by the second cutter ring. The first cutter ring may be located on a first roller cone, the second cutter ring may be located on a second roller cone, and the third cutter ring may be located on a third roller cone.

FIG. 1 is an illustration of a bottomhole assembly 10 in which the reamer tool 100 of the present invention may be employed. The bottomhole assembly may be similar to that shown and described in U.S. Pat. No. 5,497,842, incorporated herein by specific reference. The bottomhole assembly 10 may include one or more drill collars 12 suspended from a distal end of a drill string extending to the rig floor at the surface. An optional pass through stabilizer 14 may be secured to the drill collar 12. The stabilizer 14 may be sized equal to or slightly smaller than the pass through diameter of the bottomhole assembly 10, which may be defined as the smallest diameter borehole through which the assembly may move longitudinally. Another drill collar 16 (or other drill string element such as an measurement while drilling (MWD) tool housing or pony collar) may be secured to the bottom of the stabilizer 14, below which the reamer tool 100 according to the present invention is secured via a tool joint 18, which may be an American Petroleum Institute (API) joint. More specifically, in one embodiment, a 7⅝ inch API pin connector is located at the top of the reamer tool 100. Another API joint 22 is located at the bottom of the reamer tool 100. More specifically, in one embodiment, a 6⅝ inch API box connector is located at the bottom of the reamer tool 100. An upper pilot stabilizer 24, preferably secured to the reamer tool 100, is of an O.D. equal to or slightly smaller than that of a pilot bit 30 at the bottom of the assembly 10. Yet another, smaller diameter drill collar 26 may be secured to the lower end of the upper pilot stabilizer 24, followed by a lower pilot stabilizer 28 to which is secured the pilot bit 30. The pilot bit 30 may be either a rotary drag bit or a tri-cone, so-called “rock bit”. The bottomhole assembly 10 as described is exemplary only, it being appreciated by those of ordinary skill in the art that many other assemblies and variations may be employed.

The bottomhole assembly 10 creates and expands a borehole, or wellbore, in an earth formation. The borehole preferably includes an initial inner sidewall 40 created by the pilot bit 30. The borehole also preferably includes a final inner sidewall 42 created by the reamer tool 100, as will be discussed in greater detail below. Between the initial inner sidewall 40 and the final inner sidewall 42, there is a working surface 44 of the reamer tool 100. In one embodiment of the reamer tool 100, this working surface 44 is a generally conical surface sloped upwardly and outwardly from the initial inner sidewall 40 to the final inner sidewall 42. As can be seen in FIG. 2 and as will be discussed in greater detail below, while the working surface 44 is generally linear, the working surface 44 is actually discontinuous and comprised of a series of steps, stepping up and outward from the initial inner sidewall 40 to the final inner sidewall 42. Where the working surface 44 meets the initial inner sidewall 40, the wellbore forms an inner corner 46. It can be seen that the initial inner sidewall 40, the final inner sidewall 42, the working surface 44, and the inner corner 46 are all unconstrained, or unconfined, toward the interior of the wellbore. As will be discussed in greater detail below, the reamer tool 100 of the present invention takes advantage of this unconfined characteristic.

In one preferred embodiment, as shown in FIG. 3, FIG. 4, FIG. 5, and FIG. 6, the reamer tool 100 includes four roller cones 102,104,106,108, each with a plurality of rings, or rows, of cutters 110. In another preferred embodiment, the reamer tool 100 includes three roller cones 102,104,106, each with a plurality of rings, rows, of cutters 110. In any case, the reamer tool 100 is expected to have between two and eight roller cones. FIG. 7 shows how, in actual use, the roller cones 102,104,106,108 effectively overlap, such that the cutters 110 of the roller cones 102,140,106,108 form a cutting profile 112, which engages and therefore effectively defines, or creates, the working surface 44 of the wellbore.

The roller cones 102,104,106,108 are angled such that the cutters 110 successively engage the earth formation upwardly and outwardly. It can be appreciated that the pilot bit 30 has initiated the borehole, or wellbore, thereby creating the initial unconfined inner sidewall 40 of the wellbore. An uppermost edge of the initial unconfined inner sidewall forms the unconfined inner corner 46a of the wellbore. Being unconfined, open to the initial inner sidewall 40 formed by the pilot bit 30 below the reamer tool 100, this inner corner 46a is less resistant to excavation. This is due to the fact that the inner corner 46a is only confined, or constrained, outwardly. In other words, the inner corner 46a is unconfined, or constrained inwardly, as the earth formation inwardly has already been removed by the pilot bit 30.

Therefore, successive rows, or rings, of the cutters 110 preferably engage the unconfined portions of the wellbore, successively expanding the wellbore outwardly. More specifically, referring also to FIG. 8, a first row 114a of cutters 110 engages the unconfined inner corner 46a of the wellbore, thereby expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the first row 114a of cutters 110 engages and excavates this unconfined inner corner 46a, the cutters 110 move the unconfined inner corner 46a downwardly. The first row 114a of cutters 110 also creates a first step 48a in the wellbore. This first step 48a begins at the unconfined inner corner 46a of the wellbore and extends outwardly therefrom. The first step 48a also extends upwardly slightly, forming a second unconfined corner 46b of the wellbore.

Next, a second row 114b of cutters 110 engages the second unconfined corner 46b of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the second row 114b of cutters 110 engages and excavates this second unconfined corner 46b, the cutters 110 move the second unconfined corner 46b downwardly. The second row 114b of cutters 110 also creates a second step 48b in the wellbore. This second step 48b begins at the second unconfined corner 46b of the wellbore and extends outwardly therefrom. The second step 48b also extends upwardly slightly, forming a third unconfined corner 46c of the wellbore.

Next, a third row 114c of cutters 110 engages the third unconfined corner 46c of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the third row 114c of cutters 110 engages and excavates this third unconfined corner 46c, the cutters 110 move the third unconfined corner 46c downwardly. The third row 114c of cutters 110 also creates a third step 48c in the wellbore. This third step 48c begins at the third unconfined corner 46c of the wellbore and extends outwardly therefrom. The third step 48c also extends upwardly slightly, forming a fourth unconfined corner 46d of the wellbore.

Next, a fourth row 114d of cutters 110 engages the fourth unconfined corner 46d of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the fourth row 114d of cutters 110 engages and excavates this fourth unconfined corner 46d, the cutters 110 move the fourth unconfined corner 46d downwardly. The fourth row 114d of cutters 110 also creates a fourth step 48d in the wellbore. This fourth step 48d begins at the fourth unconfined corner 46d of the wellbore and extends outwardly therefrom. The fourth step 48d also extends upwardly slightly, forming a fifth unconfined corner 46e of the wellbore.

Next, a fifth row 114e of cutters 110 engages the fifth unconfined corner 46e of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the fifth row 114e of cutters 110 engages and excavates this fifth unconfined corner 46e, the cutters 110 move the fifth unconfined corner 46e downwardly. The fifth row 114e of cutters 110 also creates a fifth step 48e in the wellbore. This fifth step 48e begins at the fifth unconfined corner 46e of the wellbore and extends outwardly therefrom. The fifth step 48e also extends upwardly slightly, forming a sixth unconfined corner 46f of the wellbore.

Next, a sixth row 114f of cutters 110 engages the sixth unconfined corner 46f of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the sixth row 114f of cutters 110 engages and excavates this sixth unconfined corner 46f, the cutters 110 move the sixth unconfined corner 46f downwardly. The sixth row 114f of cutters 110 also creates a sixth step 48f in the wellbore. This sixth step 48f begins at the sixth unconfined corner 46f of the wellbore and extends outwardly therefrom. The sixth step 48f also extends upwardly slightly, forming a seventh unconfined corner 46g of the wellbore.

Next, a seventh row 114g of cutters 110 engages the seventh unconfined corner 46g of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the seventh row 114g of cutters 110 engages and excavates this seventh unconfined corner 46g, the cutters 110 move the seventh unconfined corner 46g downwardly. The seventh row 114g of cutters 110 also creates a seventh step 48g in the wellbore. This seventh step 48g begins at the seventh unconfined corner 46g of the wellbore and extends outwardly therefrom. The seventh step 48g also extends upwardly slightly, forming an eighth unconfined corner 46h of the wellbore.

Next, an eighth row 114h of cutters 110 engages the eighth unconfined corner 46h of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the eighth row 114h of cutters 110 engages and excavates this eighth unconfined corner 46h, the cutters 110 move the eighth unconfined corner 46h downwardly. The eighth row 114h of cutters 110 also creates an eighth step 48h in the wellbore. This eighth step 48h begins at the eighth unconfined corner 46h of the wellbore and extends outwardly therefrom. The eighth step 48h also extends upwardly slightly, forming a ninth unconfined corner 46i of the wellbore.

Next, a ninth row 114i of cutters 110 engages the ninth unconfined corner 46i of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the ninth row 114i of cutters 110 engages and excavates this ninth unconfined corner 46i, the cutters 110 move the ninth unconfined corner 46i downwardly. The ninth row 114i of cutters 110 also creates a ninth step 48i in the wellbore. This ninth step 48i begins at the ninth unconfined corner 46i of the wellbore and extends outwardly therefrom. The ninth step 48i also extends upwardly slightly, forming a tenth unconfined corner 46j of the wellbore.

Next, a tenth row 114j of cutters 110 engages the tenth unconfined corner 46j of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the tenth row 114j of cutters 110 engages and excavates this tenth unconfined corner 46j, the cutters 110 move the tenth unconfined corner 46j downwardly. The tenth row 114j of cutters 110 also creates a tenth step 48j in the wellbore. This tenth step 48j begins at the tenth unconfined corner 46j of the wellbore and extends outwardly therefrom. The tenth step 48j also extends upwardly slightly, forming an eleventh unconfined corner 46k of the wellbore.

Next, an eleventh row 114k of cutters 110 engages the eleventh unconfined corner 46k of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the eleventh row 114k of cutters 110 engages and excavates this eleventh unconfined corner 46k, the cutters 110 move the eleventh unconfined corner 46k downwardly. The eleventh row 114k of cutters 110 also creates an eleventh step 48k in the wellbore. This eleventh step 48k begins at the eleventh unconfined corner 46k of the wellbore and extends outwardly therefrom. The eleventh step 48k also extends upwardly slightly, forming a twelfth unconfined corner 46l of the wellbore.

Next, a twelfth row 114l of cutters 110 engages the twelfth unconfined corner 46l of the wellbore, thereby successively expanding the initial inner sidewall 40 of the wellbore outwardly. As the bottomhole assembly 10 is lowered into the wellbore and the twelfth row 114l of cutters 110 engages and excavates this twelfth unconfined corner 46l, the cutters 110 move the twelfth unconfined corner 46l downwardly. The twelfth row 114l of cutters 110 also creates a twelfth step 48l in the wellbore. This twelfth step 48l begins at the twelfth unconfined corner 46l of the wellbore and extends outwardly therefrom. In one embodiment of the reamer tool 100, the twelfth step 48l terminates in the final inner sidewall 42 of the wellbore.

The rows 114a-114l of cutters 110 are preferably dispersed across the roller cones 102-108. In the embodiment of the reamer tool having four roller cones 102-108, each roller cones preferably has three of the rows 114a-114l of cutters 110. More specifically, in this particular embodiment, the first roller cone 102 preferably includes the first row 114a, the fifth row 114e, and the ninth row 114i of cutters 110. In this particular embodiment, the second roller cone 104 preferably includes the second row 114b, the sixth row 114f, and the tenth row 114j of cutters 110. In this particular embodiment, the third roller cone 106 preferably includes the third row 114c, the seventh row 114g, and the eleventh row 114k of cutters 110. In this particular embodiment, the fourth roller cone 108 preferably includes the fourth row 114d, the eighth row 114h, and the twelfth row 114l of cutters 110.

In the embodiment of the reamer tool having three roller cones 102-106, each roller cones preferably has four of the rows 114a-114l of cutters 110. More specifically, in this particular embodiment, the first roller cone 102 preferably includes the first row 114a, the fourth row 114d, the seventh row 114g, and the tenth row 114j of cutters 110. In this particular embodiment, the second roller cone 104 preferably includes the second row 114b, the fifth row 114e, the eighth row 114h, and the eleventh row 114k of cutters 110. In this particular embodiment, the third roller cone 106 preferably includes the third row 114c, the sixth row 114f, the ninth row 114i, and the twelfth row 114l of cutters 110.

In both embodiments, dispersing the rows 114a-114l of cutters 110 across multiple cones, provides adequate spacing between the rows 114a-114l, while still providing an overlapping cutter profile 112, thereby allowing shavings, or cuttings, to be removed by drilling fluid or other processes known in the art. In other words, the cutter profile 112 engages the working surface 44 with overlapping cutters 110, the rows 114a-114l of cutters 110 overlapping from one roller cone to the next. At the same time, however, the rows 114a-114l on any one roller cone 102-108 are adequately spaced to allow the cuttings to be removed. The dispersion, distribution, and/or spacing of the cutters 110 themselves, as well as the rows 114a-114l of cutters 110, allows the roller cones 102-108 to freely rotate without the cutters 110 coming into contact with one another.

In one embodiment of the reamer tool 100, dispersing the rows 114a-114l of cutters 110 across multiple roller cones allows the cutter profile 112 to engage the working surface 44 with overlapping cutters 110, without the cutters 110 from one roller cone meshing with the cutters 110 from another roller cone. This allows the roller cones 102,104,106,108 to rotate independently of each other. Spacing of the roller cones 102,104,106,108, themselves, around the reamer tool 100, may aid in separating the cutters 110 from different roller cones.

In any case, it can be seen that successive rows 114a-114l of cutters 110 are located above and outwardly of previous cutter rows such that each cutter row engages the wellbore in such a manner as to incrementally expand the wellbore outwardly, as the bottomhole assembly 10 is lowered into the wellbore. More specifically, successive rows 114a-114l of cutters 110 are located above and outwardly of previous cutter rows such that each cutter row engages the wellbore in such a manner as to incrementally expand the unconfined inner sidewall 40 outwardly. Still more specifically, in one embodiment, a first cutter ring, or row, 114a is configured to expand the unconfined inner sidewall 40 of the wellbore, a second cutter ring 114b is located above and outwardly of the first cutter ring 114a and configured to expand the unconfined inner sidewall 40 as expanded by the first cutter ring 114a, and a third cutter ring 114c is located above and outwardly of the second cutter ring and configured to expand the unconfined inner sidewall as expanded by the second cutter ring.

Other and further embodiments utilizing one or more aspects of the inventions described above can be devised without departing from the spirit of Applicant's invention. For example, just as more or fewer roller cones may be used, more or fewer rows of cutters can be used on each roller cone. While the roller cones are described as having equal numbers of rows of cutters, roller cones having different numbers of rows of cutters could be used in some embodiments. Further, in some embodiments, one or more of the cutter rings, may be embodied as a cutter disk, a serrated disk, a row or ring of milled and hardfaced teeth, and/or a row of tungsten carbide inserts.

Additionally, or alternatively, in one embodiment, each outer-most row of cutters, or cutter ring, on each roller cone 102,104,106,108 combine to contribute to the final inner sidewall 42 of the wellbore. For example, in an embodiment with four roller cones 102,104,106,108, the ninth row 114i of cutters 110 on the first roller cone 102, the tenth row 114j of cutters 110 on the second roller cone 104, the eleventh row 114k of cutters 110 on the third roller cone 106, and the twelfth row 114l of cutters 110 on the fourth roller cone 108 all contribute to the final inner sidewall 42 of the wellbore. In this case, the ninth row 114i of cutters 110 may be longer and/or otherwise configured differently from the twelfth row 114l of cutters 110. In other embodiments, one, two, three, or more outer-most cutter rings contribute to the final inner sidewall 42 of the wellbore. In any case, by having multiple cutter rings contribute, this provides a smoother, more uniform, and more consistently sized and shaped final inner sidewall 42.

The order of steps can occur in a variety of sequences unless otherwise specifically limited. The various steps described herein can be combined with other steps, interlineated with the stated steps, and/or split into multiple steps. Similarly, elements have been described functionally and can be embodied as separate components or can be combined into components having multiple functions. Finally, the various methods and embodiments of the reamer tool 100 can be included in combination with each other to produce variations of the disclosed methods and embodiments. Discussion of singular elements can include plural elements and vice-versa. For example, in some embodiments, rather than one of each individual cone 102,104,106,108 described above, there may be two, spaced at approximately 180 degrees, three spaced at approximately 120 degrees, four spaced at approximately 90 degrees, or more, for each cone described above. More specifically, there may be two or more first roller cones, configured and performing as described above, but spaced 180 degrees across the reamer tool 100.

As discussed above, it is anticipated that the roller cones will be substantially uniformly spaced around the reamer tool 100. However, in one embodiment, four roller cones are spaced at 90 degrees, 90 degrees, 100 degrees, and 80 degrees, on center. Therefore, the roller cones may be offset five, ten, fifteen, or twenty degrees, or some included range, off otherwise uniform spacing. This spacing applies to embodiments having singular and/or multiple individual first, second, third, and/or fourth roller cones 102,104,106,108.

The inventions have been described in the context of preferred and other embodiments and not every embodiment of the invention has been described. Obvious modifications and alterations to the described embodiments are available to those of ordinary skill in the art. The disclosed and undisclosed embodiments are not intended to limit or restrict the scope or applicability of the invention conceived of by the Applicants, but rather, in conformity with the patent laws, Applicants intend to fully protect all such modifications and improvements that come within the scope or range of equivalent of the following claims.

Claims

1. A reamer tool for expanding a wellbore in an earth formation, the reamer tool comprising:

a first roller cone having a first cutter ring configured to expand an unconfined inner sidewall of the wellbore; and

a second roller cone having a second cutter ring located above and outwardly of the first cutter ring and configured to expand the unconfined inner sidewall of the wellbore as expanded by the first cutter ring.

2. The reamer tool as set forth in claim 1, further comprising a third roller cone having a third cutter ring located above and outwardly of the second cutter ring and configured to expand the unconfined inner sidewall as expanded by the second cutter ring.

3. The reamer tool as set forth in claim 2, further comprising a fourth cutter ring located on the first roller cone above and outwardly of the third cutter ring and configured to expand the unconfined inner sidewall as expanded by the third cutter ring.

4. The reamer tool as set forth in claim 3, further comprising a fifth cutter ring located on the second roller cone above and outwardly of the fourth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fourth cutter ring.

5. The reamer tool as set forth in claim 4, further comprising a sixth cutter ring located on the third roller cone above and outwardly of the fifth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fifth cutter ring.

6. A bottom hole assembly comprising:

a pilot bit for initially forming an unconfined inner sidewall of a wellbore; and

a reamer tool above the pilot bit, the reamer tool including a first cutter ring configured to expand the unconfined inner sidewall of the wellbore, a second cutter ring located above and outwardly of the first cutter ring and configured to expand the unconfined inner sidewall as expanded by the first cutter ring, and a third cutter ring located above and outwardly of the second cutter ring and configured to expand the unconfined inner sidewall as expanded by the second cutter ring.

7. The bottom hole assembly as set forth in claim 6, the reamer tool further comprising first, second and third roller cones.

8. The bottom hole assembly as set forth in claim 7, wherein the first cutter ring is located on the first roller cone, the second cutter ring located on the second roller cone, and the third cutter ring is located on the third roller cone.

9. The bottom hole assembly as set forth in claim 8, further comprising

a fourth cutter ring located on the first roller cone above and outwardly of the third cutter ring and configured to expand the unconfined inner sidewall as expanded by the third cutter ring;

a fifth cutter ring located on the second roller cone above and outwardly of the fourth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fourth cutter ring; and

a sixth cutter ring located on the third roller cone above and outwardly of the fourth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fifth cutter ring.

10. The bottom hole assembly as set forth in claim 9, wherein each roller cone includes at least three cutter rows, wherein successive cutter rows are located above and outwardly of previous cutter rows such that each cutter row engages the wellbore in such a manner as to incrementally expand the wellbore outwardly.

11. The bottom hole assembly as set forth in claim 9, wherein the wellbore is defined by an unconfined inner sidewall and successive cutter rows are located above and outwardly of previous cutter rows such that each cutter row engages the wellbore in such a manner as to incrementally expand the unconfined inner sidewall outwardly.

12. A method of expanding a wellbore using a reamer tool comprising a plurality of cutter rows mounted on a plurality of roller cones, the method comprising the steps of:

engaging, with a first cutter row on a first roller cone, an unconfined inner sidewall of the wellbore, thereby expanding the wellbore outwardly; and

engaging, with a second cutter row located on a second roller cone above and outwardly of the first cutter row, the unconfined inner sidewall of the wellbore as expanded by the first cutter row, thereby further expanding the wellbore outwardly.

13. The method as set forth in claim 12, further including the step of engaging, with a third cutter row located on a third roller cone above and outwardly of the second cutter row, the unconfined inner sidewall of the wellbore as expanded by the second cutter row, thereby further expanding the wellbore outwardly.

14. The method as set forth in claim 13, further including the steps of

engaging, with a fourth cutter row located on the first roller cone above and outwardly of the third cutter row, the unconfined inner sidewall of the wellbore as expanded by the third cutter row;

engaging, with a fifth cutter row located on the second roller cone above and outwardly of the fourth cutter row, the unconfined inner sidewall of the wellbore as expanded by the fourth cutter row; and

engaging, with a sixth cutter row located on the third roller cone above and outwardly of the fifth cutter row, the unconfined inner sidewall of the wellbore as expanded by the fifth cutter row.

15. The method as set forth in claim 12, wherein the reamer expands the wellbore outwardly from the unconfined inner sidewall of the wellbore and the reamer tool is lowered in the wellbore.

16. The method as set forth in claim 12, wherein the wellbore is defined by an initial inner sidewall formed by a pilot bit below the reamer tool, a first step formed by the first cutter row adjacent the initial inner sidewall, a second step formed by the second cutter row above and outward of the first step, and a final inner sidewall formed by the reamer tool.