METHOD AND APPARATUS FOR STEERING A DRILL STRING AND REAMING WELL BORE SURFACES NEARER THE CENTER OF DRIFT

Abstract

A steerable well bore drilling device and method are disclosed. The steerable well bore drilling device comprises a drill string, a bit coupled to the drill string, a drilling motor within the drill string and driving the bit, and a pair of eccentric reamers coupled to the drill string and positioned between the bit and the motor.

Description

BACKGROUND

1. Field of the Invention

The invention is directed to methods and devices for drilling well bores, specifically, the invention is directed to methods and devices for increasing the drift diameter and improving the quality of a well bore.

2. Background of the Invention

Horizontal, directional, S curve, and most vertical wells are drilled with a bit driven by a bent housing downhole mud/air motor, which can be orientated to build or drop angle and can turn right or left. The drill string is orientated to point the bent housing mud/air motor in the desired direction. This is commonly called “sliding”. Sliding forces the drill bit to navigate along the desired path, with the rest of the drill string to following.

Repeated correcting of the direction of the well bore causes micro-ledging and “doglegs,” inducing friction and drag between the well bore and the bottom hole assembly and drill string. This undesired friction causes several negatives on the drilling process, including but not limited to: increasing torque and drag, ineffective weighting on bit transfer, eccentric wearing on the drill string and bottom hole assembly (BHA), increasing the number of days to drill the well, drill string failures, limiting the distance the well bore can be extended, and issues related to inserting the production string into the well bore.

When a dogleg, spiraled path, or tortuous path is cut by a drill bit, the relatively unobstructed passageway following the center of the well bore may yield a smaller diameter than the well bore itself. This relatively unobstructed passageway is sometimes referred to as the “drift” and the nominal diameter of the passageway is sometimes referred to as the “drift diameter”. The “drift” of a passageway is generally formed by well bore surfaces forming the inside radii of curves along the path of the well bore. Passage of pipe or tools through the relatively unobstructed drift of the well bore is sometimes referred to as “drift” or “drifting”.

In general, to address these difficulties the drift diameter has been enlarged with conventional reaming techniques by enlarging the diameter of the entire well bore. Such reaming has been completed as an additional step, after drilling of the well bore is completed. Doing so has been necessary to avoid unacceptable increases in torque and drag during drilling. Such additional reaming runs add considerable expense and time to completion of the well. Moreover, conventional reaming techniques frequently do not improve the well bore, but instead simply enlarge certain areas of the well bore.

During directional drilling of well bores, existing steering methods include a physical bend or elbow in the drill string, requiring a flex-shaft or jointed shaft, and do not condition the bore. Additionally, one of the problems in steerable drilling is that the elbow of current bent-motors moves around impacting the well bore when drilling straight. These vibrations negatively impact the drill bit and various electronic sensors in the BHA. Rotational vibrations also come from the bit due to stick-slip behavior.

Accordingly, a need exists for a reamer that reduces the torque and drag on the drill string and produces closer to drift well bore. A need also exists for a reamer capable of enlarging the diameter of the well bore drift passageway, without needing to enlarge the diameter of the entire well bore. Additionally, there is a need for a method of steering a BHA during drilling that eliminates vibrations.

SUMMARY OF THE INVENTION

The present invention overcomes the problems and disadvantages associated with current strategies, designs and provides new tools and methods of drilling well bores.

One embodiment of the invention is directed to a steerable well bore drilling device. The device comprises a drill string, a bit coupled to the drill string, a drilling motor within the drill string and driving the bit, and a pair of eccentric reamers coupled to the drill string and positioned between the bit and the motor.

Preferably, the pair of eccentric reamers are diametrically opposed about the drill string. In a preferred embodiment, each eccentric reamer comprises multiple sets of cutting elements. Preferably, each set of cutting elements are arranged along a spiral path along the surface of each eccentric reamer. The eccentric reamers are preferably identical. The drilling device preferably further comprises a drive shaft coupling the bit to the drilling motor, wherein the drive shaft passes through the pair of eccentric reamers.

In a preferred embodiment, the drilling device further comprises a measure while drilling device adapted to control the rotational position of the pair of eccentric reamers about the drill string to steer the drill string. Preferably, the pair of eccentric reamers are coupled to the drill string at a predetermined separation corresponding to a curvature of the well bore. Preferably, the pair of eccentric reamers extend from the drill string a predetermined distance corresponding to a curvature of the well bore. The pair of eccentric reamers preferably provide a steering force when the drill string is sliding and condition the well bore when the drill string is rotating.

Another embodiment of the invention is directed to a method of drilling a well bore. The method comprises the steps of coupling a bit to a drill string, coupling a drilling motor positioned within the drill string to the bit, coupling a pair of eccentric reamers to the drill string, wherein the pair of eccentric reamers are positioned between the bit and the motor, drilling the well bore, steering the bit by sliding the drill string within the well bore, and reaming the well bore by rotating the drill string.

In a preferred embodiment, the pair of eccentric reamers are diametrically opposed about the drill string. Preferably, each eccentric reamer comprises multiple sets of cutting elements. Each set of cutting elements are preferably arranged along a spiral path along the surface of each eccentric reamer. Preferably, the eccentric reamers are identical. In a preferred embodiment, the bit is coupled to the drilling motor by a drive shaft that passes through the pair of eccentric reamers.

Preferably, the method further comprises controlling the rotational position of the pair of eccentric reamers about the drill string to steer the drill string with a measure while drilling device. In a preferred embodiment, the method further comprises separating the pair of eccentric reamers along the drill string at a predetermined distance corresponding to a curvature of the well bore. Preferably, the pair of eccentric reamers extend from the drill string a predetermined distance corresponding to a curvature of the well bore. Preferably, the steering step and the reaming step occur at separate times.

Other embodiments and advantages of the invention are set forth in part in the description, which follows, and in part, may be obvious from this description, or may be learned from the practice of the invention.

DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail by way of example only and with reference to the attached drawing, in which:

FIG. 1 is a cross-section elevation of a horizontal well bore.

FIG. 2 is a magnification of the down-hole portion of a top reamer.

FIG. 3 illustrates the layout of cutting elements along a down-hole portion of the bottom reamer.

FIGS. 4 and 5 illustrate the location and arrangement of cutting elements on another embodiment of a reamer.

FIG. 6 is an embodiment of a reamer having four sets of cutting elements.

FIG. 7 illustrates the arrangement of cutting elements on each of four blades.

FIG. 8 illustrates the eccentricities of a reamer.

FIG. 9A-B illustrate an embodiment of the placement of the reamers to steer a drill bit.

DESCRIPTION OF THE INVENTION

As embodied and broadly described, the disclosures herein provide detailed embodiments of the invention. However, the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Therefore, there is no intent that specific structural and functional details should be limiting, but rather the intention is that they provide a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention.

A problem in the art capable of being solved by the embodiments of the present invention is increasing the drift diameter of a well bore. It has been surprisingly discovered that providing diametrically opposed reamers allows for improved reaming of well bores compared to conventional reamers. This is accomplished, in one embodiment, by cutting away material primarily forming surfaces nearer the center of the drift. Doing so reduces applied power, applied torque and resulting drag compared to conventional reamers that cut into all surfaces of the well bore.

FIG. 1 depicts a cross-sectional view of a horizontal well bore containing a reamer. The reamer has a bottom eccentric reamer and a top eccentric reamer. The top and bottom eccentric reamers are preferably of a similar construction and are preferably diametrically opposed (i.e. at an angular displacement of approximately 180°)on the drill string. However other angular displacements can be used, for example, 120°, 150°, 210°, or 240°. The diametrically opposed positioning causes the cutting elements of each of the top and bottom reamers to face approximately opposite directions. The reamers are spaced apart and positioned to run behind the bottom hole assembly (BHA). In one embodiment, for example, the eccentric reamers are positioned within a range of approximately 100 to 150 feet from the BHA. Although two reamers are shown, a single reamer or a larger number of reamers could be used in the alternative.

As shown, the drill string advances to the left as the well is drilled. Each of the reamers preferably has an outermost radius, generally in the area of its cutting elements, less than the inner radius of the well bore. However, the outermost radius of each reamer is preferably greater than the distance of the nearer surfaces from the center of drift. The top and bottom reamers preferably comprise a number of carbide or diamond cutting elements, with each cutting element preferably having a circular face generally facing the path of movement of the cutting element relative to the well bore as the pipe string rotates and advances down hole.

In FIG. 1, the bottom reamer begins to engage and cut a surface nearer the center of drift off the well bore shown. As will be appreciated, the bottom reamer, when rotated, cuts away portions of the nearer surface of the well bore, while cutting substantially less or none of the surface farther from the center of drift, generally on the opposite side of the well. The top reamer performs a similar function, reamer nearer the center of drift as the drill string advances. Each reamer is preferably spaced from the BHA and any other reamer to allow the centerline of the pipe string adjacent the reamer to be offset from the center of the well bore toward the center of drift or aligned with the center of drift.

FIG. 2 is a magnification of the down-hole portion of the top reamer as the reamer advances to begin contact with a surface of the well bore nearer the center of drift. As the reamer advances and rotates, the existing hole is widened along the surface nearer the center of drift, thereby widening the drift diameter of the hole. It will be appreciated that the drill string and reamer advance through the well bore along a path generally following the center of drift and displaced from the center of the existing hole.

FIG. 3 illustrates the layout of cutting structure along a down-hole portion of the bottom reamer illustrated in FIG. 1. Four sets of cutting elements, Sets A, B, C and D, are angularly separated about the exterior of the bottom reamer. FIG. 3 shows the position of the cutting elements of each Set as they pass the bottom-most position shown in FIG. 1 when the bottom reamer rotates. As the reamer rotates, Sets A, B, C and D pass the bottom-most position in succession. The Sets of cutting elements are arranged on a substantially circular surface having a center eccentrically displaced from the center of rotation of the drill string.

Each of the Sets of cutting elements are preferably arranged along a spiral path along the surface of the bottom reamer, with the down-hole cutting element leading as the reamer rotates (e.g., see FIG. 6). Sets A and B of the reamer cutting elements are positioned to have outermost reamers forming a 6⅛ inch diameter path when the pipe string is rotated. The cutting elements of Set B are preferably positioned to be rotated through the bottom-most point of the bottom reamer between the rotational path of the cutting elements of Set A. The cutting elements of Set C are positioned to have outermost cutting faces forming a six inch diameter when rotated, and are preferably positioned to be rotated through the bottom-most point of the bottom reamer between the rotational path of the cutting elements of Set B. The cutting elements of Set D are positioned to have outermost reamers forming a 5⅞ inch diameter when rotated, and are preferably positioned to be rotated through the bottom-most point of the bottom reamer between the rotational path of the cutting elements of Set C.

FIGS. 4 and 5 illustrate the location and arrangement of Sets 1, 2, 3 and 4 of cutting elements on another reamer embodiment. Sets 1, 2, 3 and 4 of cutting elements are each arranged to form a path of rotation having respective diameters of 5⅝ inches, 6 inches, 6⅛ inches and 6⅛ inches. FIG. 5 illustrates the relative position of each of Sets 1, 2, 3 and 4 of cutting elements. The cutting elements of Set 2 are preferably positioned to be rotated through the bottom-most point of the reamer between the rotational path of the cutting elements of Set 1. The cutting elements of Set 3 are preferably positioned to be rotated through the bottom-most point of the reamer between the rotational path of the cutting elements of Set 2. The cutting elements of Set 4 are preferably positioned to be rotated through the bottom-most point of the reamer between the rotational path of the cutting elements of Set 3.

FIG. 6 is a photograph illustrating an embodiment of a reamer having four sets of cutting element, with each set arranged in a spiral orientation along a curved surface having a center eccentric with respect to the drill pipe on which the reamer is mounted. Adjacent and in front of each set of cutting elements is a flow area formed in the surface of the reamer. The flow area allow fluids, such as drilling mud for example, and cuttings to flow past the reamer and exit away from the reamer's cutting structure during operation.

The positioning and arrangement of Sets of cutting elements may be rearranged to suit particular applications. For example, the alignment of the Sets of cutting elements relative to the centerline of the drill string, and the distance between the bottom eccentric face and the top eccentric face along with the outer diameter of the reamer body can be adjusted to each application.

FIG. 7 depicts the blades of an embodiment of a reamer. The reamer is designed to side-ream the “near” side of a directionally near horizontal well bore that is crooked to straighten the crooks. As the 5.25″ body of the reamer is pulled into the “near” side of the crook the cut of the rotating reamer will be forced to rotate about the body's threaded center and cut an increasingly larger radius into just the “near” side of the crook without cutting the opposite side. This cutting action will act to straighten the crooked hole without following the original bore hole path.

FIG. 8 depicts the radial layout of an embodiment of a reamer. The tops of the PDC cutters in each of the two eccentrics of the reamer rotate about the threaded center of the tool and are placed at increasing radii starting with the No. 1 cutter at 2.750″ R. The cutters' radii increase 0.018″ ever 5 degrees through cutter No. 17, where the radii become constant at the maximum of 3.062″ which is the 6.125″ maximum diameter of the tool.

FIGS. 9A-B depict a preferred placement of the reamers 505A and 505B within a drill string 500 that allows reamers 505A-B to steer the drill bit 510 as well as condition the well bore. In a preferred embodiment of the instant invention, reamers 505A-B are positioned between drill bit 510 and drilling motor 515. However, in other embodiments, one or both of reamers 505A-B may be positioned on motor 515. Drilling motor 515 is preferably housed within drill string 500 with a straight drive 525 shaft running through reamers 505A-B and coupling drill bit 510 to motor 515, thereby allowing the drill bit 510 to rotate without the reamers 505A-B turning.

Preferably, reamers 505A-B are positioned in front of the drilling motor 515 to steer the bit 510 during a slide, or when the drill string 500 is not rotating. Lateral forces on reamers 505A-B during a slide preferably results in a lateral force on bit 510, causing the assembly to turn as it drills forward (i.e. to the right in the figures) and creating a curved bore hole. Preferably the spacing between reamer 505A and 505B as well as the distance reamers 505A-B are positioned behind drill bit 510 are matched to the bit size and the desired turn build rate. For example, larger reamers 505A-B will create a smaller diameter curve than smaller reamers 505A-B. With larger reamers 505A-B, a larger drill bit 510 will be necessary accommodate the larger reamers. Additionally, by placing the reamers further apart, a larger diameter curve can be cut.

The rotational positioning of reamers 505A-B is preferably monitored by a Measure While Drilling (MWD) device 520 positioned behind reamers 505A-B within drill string 500. MWD 520 may have GPS sensors, magnometers, thermometers, rotation sensors, accelerometers, and/or other sensors to determine at least one of the rotational speed of the drillstring, the smoothness of that rotation, the type and severity of any vibration downhole, downhole temperatures, torque and weight on bit, and mud flow volume. With the data from MWD 520 reamers 505A-B can be rotated to provide the proper direction of curvature for drilling the well bore. Additionally, the path of the well bore may be corrected, adjusted, and/or maintained based on data received from MWD 520. In other embodiments, the positioning of the drill string may be determined by calculating the twist in the drill string.

Preferably, once the slide is complete and the drill string begins rotating, reamers 505A and 505B continue to ream and condition the bore hole as described herein. Preferably, the bore conditioning action benefits all of the drill string components that follow reamers 505A-B by clearing rough spots and tight spots in the well bore. Additionally, the cutting structures on reamers 505A-B preferably take rotational vibrations that come from the bit and motor and transmit them to the well bore as cutting action. The drill string between reamers 505A-B and the surface is preferably protected from those vibrations. By putting the steering reamers 505A-B between the motor and bit, vibrations from both bent-motors and the drill bit are addressed and the greatest possible amount of the drill string is protected.

Other embodiments and uses of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. All references cited herein, including all publications, U.S. and foreign patents and patent applications, are specifically and entirely incorporated by reference. It is intended that the specification and examples be considered exemplary only with the true scope and spirit of the invention indicated by the following claims. Furthermore, the term “comprising of” includes the terms “consisting of” and “consisting essentially of.”

Claims

1. A steerable well bore drilling device, comprising: a drill string;a bit coupled to the drill string;a drilling motor within the drill string and driving the bit; anda pair of eccentric reamers coupled to the drill string and positioned between the bit and the motor.

2. The steerable well bore drilling device of claim 1, wherein the pair of eccentric reamers are diametrically opposed about the drill string.

3. The steerable well bore drilling device of claim 2, wherein each eccentric reamer comprises multiple sets of cutting elements.

4. The steerable well bore drilling device of claim 3, wherein each set of cutting elements are arranged along a spiral path along the surface of each eccentric reamer.

5. The steerable well bore drilling device of claim 1, wherein the eccentric reamers are identical.

6. The steerable well bore drilling device of claim 1, further comprising a drive shaft coupling the bit to the drilling motor, wherein the drive shaft passes through the pair of eccentric reamers.

7. The steerable well bore drilling device of claim 1, further comprising a measure while drilling device adapted to control the rotational position of the pair of eccentric reamers about the drill string to steer the drill string.

8. The steerable well bore drilling device of claim 1, wherein the pair of eccentric reamers are coupled to the drill string at a predetermined separation corresponding to a curvature of the well bore.

9. The steerable well bore drilling device of claim 1, wherein the pair of eccentric reamers extend from the drill string a predetermined distance corresponding to a curvature of the well bore.

10. The steerable well bore drilling device of claim 1, wherein the pair of eccentric reamers provide a steering force when the drill string is sliding and condition the well bore when the drill string is rotating.

11. A method of drilling a well bore, comprising: coupling a bit to a drill string;coupling a drilling motor positioned within the drill string to the bit;coupling a pair of eccentric reamers to the drill string, wherein the pair of eccentric reamers are positioned between the bit and the motor;drilling the well bore;steering the bit by sliding the drill string within the well bore; andreaming the well bore by rotating the drill string.

12. The method of claim 11, wherein the pair of eccentric reamers are diametrically opposed about the drill string.

13. The method of claim 12, wherein each eccentric reamer comprises multiple sets of cutting elements.

14. The method of claim 13, wherein each set of cutting elements are arranged along a spiral path along the surface of each eccentric reamer.

15. The method of claim 11, wherein the eccentric reamers are identical.

16. The method of claim 11, wherein the bit is coupled to the drilling motor by a drive shaft that passes through the pair of eccentric reamers.

17. The method of claim 11, further comprising controlling the rotational position of the pair of eccentric reamers about the drill string to steer the drill string with a measure while drilling device.

18. The method of claim 11, further comprising separating the pair of eccentric reamers along the drill string at a predetermined distance corresponding to a curvature of the well bore.

19. The method of claim 11, wherein the pair of eccentric reamers extend from the drill string a predetermined distance corresponding to a curvature of the well bore.

20. The method of claim 11, wherein steering step and the reaming step occur at separate times.