WO2014113315A1

WO2014113315A1 - Casing drilling assembly

Info

Publication number: WO2014113315A1
Application number: PCT/US2014/011249
Authority: WO
Inventors: Trevor D. KETTELS
Original assignee: National Oilwell Varco LP
Current assignee: National Oilwell Varco LP
Priority date: 2013-01-18
Filing date: 2014-01-13
Publication date: 2014-07-24
Anticipated expiration: 2015-07-18
Also published as: AR094504A1

Abstract

Methods and apparatus for drilling a wellbore with a casing string include coupling an outer drill bit to a casing string and aligning an inner drill bit to the outer drill bit. A retention mechanism is activated to couple the inner drill bit to the outer drill bit. The casing string is rotated so that the inner drill bit and outer drill bit rotate within a formation to form a wellbore. Once drilling is complete, the coupling device is deactivated and the inner drill bit and retention mechanism are removed from the wellbore while the outer drill bit and the casing string remain in the wellbore.

Description

CASING DRILLING ASSEMBLY

BACKGROUND

[0001] This disclosure relates generally to methods and apparatus for drilling a wellbore with a casing string. More specifically, this disclosure relates to methods and apparatus for drilling a wellbore using a dual-bodied drill bit supported by a casing string.

[0002] Conventional construction of a wellbore generally includes coupling a drilling assembly with a drill bit to a drill string. The drill string extends to the surface and provides the fluid or rotational power needed to rotate the drill bit. As the wellbore is drilled, the drill string is extended until a desired depth is reached. At selected intervals, the drill string and drilling assembly are removed from the wellbore and a casing, or liner, is inserted into the wellbore to isolate the wellbore from the surrounding formation.

[0003] Once the casing, or liner, is placed in the wellbore, the drill string and slightly smaller drilling assembly are used to drill further into the formation below the casing. Once the next interval of wellbore is drilled, the drill string and drilling assembly are again removed from the wellbore and another string of casing, or liner, is installed. This process repeats until the final depth of the wellbore is reached.

[0004] This conventional process of drilling, removing drilling equipment, and running casing can be very time consuming. For example, as the depth of a wellbore increases, the time needed to retrieve the drill string and drilling assembly from the wellbore, install a casing string, and redeploy the drilling assembly and drill string to drill ahead may be several days. Further, during the time that the drill string and drilling assembly are not deployed in the wellbore, controlling the influx of wellbore fluids into the wellbore from the formation and the stability of the open wellbore can be problematic.

[0005] To address these, and other concerns, systems and methods for drilling with casing, or liners, have been developed. In general these systems utilize a string of casing, or a liner, as the drill string onto which a drilling assembly is mounted. The casing supports the drilling assembly and provides power to the drill bit through rotation or a hydraulic connection to the surface. Once the wellbore has been drilled to a desired depth, the drilling assembly is disconnected from the casing and retrieved from the wellbore while the casing remains in place in the wellbore. [0006] Existing drilling with casing systems are often mechanically complex systems that necessitate specially adapted rig equipment and handling procedures. Thus, there is a continuing need in the art for methods and apparatus for drilling with casing that overcome these and other issues with the prior art.

BRIEF SUMMARY OF THE DISCLOSURE

[0007] Methods and apparatus for drilling a wellbore with a casing string include coupling an outer drill bit to a casing string and aligning an inner drill bit to the outer drill bit. A retention mechanism is activated to couple the inner drill bit to the outer drill bit. The casing string is rotated so that the inner drill bit and outer drill bit rotate within a formation to form a wellbore. Once drilling is complete, the coupling device is deactivated and the inner drill bit and retention mechanism are removed from the wellbore while the outer drill bit and the casing string remain in the wellbore.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a more detailed description of the embodiments of the present disclosure, reference will now be made to the accompanying drawings, wherein:

[0009] Figure 1 is a cross-sectional view of a drilling assembly.

[0010] Figure 2 is a partial view of the inner assembly of Figure 1.

[0011] Figure 3 is a partial sectional view of the outer assembly of Figure 1.

[0012] Figure 4 is an end view of the drilling assembly of Figure 1.

[0013] Figures 5A-5F illustrate a method of drilling a wellbore using the drilling assembly of Figure 1.

DETAILED DESCRIPTION

[0014] It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.

[0015] Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to." All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term "or" is intended to encompass both exclusive and inclusive cases, i.e., "A or B" is intended to be synonymous with "at least one of A and B," unless otherwise expressly specified herein.

[0016] Referring initially to Figure 1, drilling assembly 100 is formed from an inner assembly 300 disposed within an outer assembly 200. Outer assembly 200 includes an outer drill bit 210 coupled to a casing string 220. As shown separately in Figure 2, inner assembly 300 comprises an inner drill bit 310 that is coupled via tubular body 320 to an instrumentation sub 330, a coupling device 340, and a fishing neck 350. In certain embodiments, instrumentation sub 330, coupling device 340, and fishing neck 350 may be coupled directly to each other and to the inner drill bit 310, making the tubular body 320 integral to the inner assembly 300. One or more ports 322, provide fluid communication between the inner bore of the inner assembly 300 and the annulus between the inner assembly 300 and the outer assembly 200. Ports 322 allow drilling fluid into the inner drilling assembly 300 from the casing and provide a pressure balance across the coupling device 340.

[0017] Inner drill bit 310 includes a cutting structure 312 mounted to the face 313 of the inner drill bit 310. The cutting structure 312 may be hardened inserts, diamond cutters, carbide cutters, or other hardened structures arranged into blades 318 or other configurations to facilitate forming a wellbore. Although not shown, the face 313 of the inner drill bit 310 may include nozzles that expel drilling fluid onto the face 313 to clean and cool the cutting structure 312 and circulate formation cuttings up through the wellbore. As can be seen in Figure 4, inner drill bit 310 and outer drill bit 210 fit together to form a full gauge drill bit. The blades 318 on the inner drill bit 310 may be configured to align with blades 212 formed on the outer drill bit 210.

[0018] To properly align the inner assembly 300 with the outer assembly 200, inner drill bit 310 includes one or more splines 314 formed integrally with or coupled to an outer surface 315. Splines 314 interface with corresponding grooves 214 (see Figure 3) formed in outer assembly 200 and serve to rotationally lock the inner assembly 300 to the outer assembly 200. Splines 314 and grooves 214 may be any configuration that is suitable to transmit torque between the inner assembly 300 and the outer assembly 200 but not axially constrain the inner assembly 300 relative to the outer assembly 200.

[0019] Instrumentation sub 330 may be coupled to inner drill bit 310 via a tubular body 320 or may be coupled directly to the inner drill bit 310. Instrumentation sub 330 may include any desired downhole sensors or communication systems suitable for relaying information to and/or from the surface. In one example, instrumentation sub 310 may provide real time well inclination measurements by transmitting data to the surface during each connection made in the drilling string, such as NOV's FLODRIFT tool. In other embodiments, inner assembly 300 may not include an instrumentation sub 330. In certain embodiments, a portion of the casing string 220 may be constructed from a composite (i.e. non-metallic) material that allows for further communication between the surface and the instrumentation sub 330.

[0020] Coupling device 340 serves to selectively couple the inner assembly 300 to the outer assembly 200. Coupling device 340 may be a packer-type system that allows the inner assembly 300 to be coupled to the outer assembly 200 without any reliance on mechanical locking devices or latch profiles formed in the outer assembly 200. In certain embodiments, the coupling device 340 may be similar to an inflatable packer that relies on hydraulic pressure to expand a resilient member into contact with the inner wall of the outer assembly 200.

[0021] One example of the use of drilling assembly 100 to form a wellbore is illustrated in Figures 5A-5F. In certain embodiments, inner assembly 300 is coupled to outer assembly 200 either at the rig or prior to the equipment being sent to the rig. As previously discussed, inner assembly 300 is coupled to the outer assembly 200 by inserting the inner assembly 300 into the outer assembly 200 until the inner drill bit 310 is mated with the outer drill bit 210, is coupled to a casing string 220. Once the inner drill bit 310 and the outer drill bit 210 are engaged, the coupling device 340 is activated to engage the inner surface of the casing string 220 and fix the axial position of the inner assembly 300 relative to the outer assembly 200.

[0022] Referring initially to Figure 5 A, the drilling assembly 100, including casing string 220, and run into a wellbore 400. The casing string 220 is supported and rotated by the drilling rig as it is lowered into the wellbore 400. Drilling fluid is pumped down through the casing string 220 and enters the inner drilling assembly 300 through ports 322 above the coupling device 340. The drilling fluid exits the drilling assembly 100 through nozzles in the inner drill bit 310 and is circulated back up the wellbore 400 through the annulus 410 to the drilling rig.

[0023] Once the drilling assembly 100 has reached a target depth, a fishing tool 530 is run into the casing string 220 on wireline 540 and engages the fishing neck 350 on the upper end of the inner drilling assembly 300. The coupling device 340 is then released, such as by shearing a pin or other method, so that it disengages the casing string 220 and the inner drilling assembly 300 can be retrieved via the wireline 540, as is shown in Figures 5B-5D.

[0024] Referring now to Figures 5E and 5F, once the inner drilling assembly 300 is retrieved to the surface, a cementation plug 500 is pumped through the casing string 220 and engages the outer drilling assembly 200 at or near the outer drill bit 210. The cementation plug 500 is pumped into the casing string 220 along with cement 520 and a wiper plug 510. After the cementation plug 500 lands in the outer drilling assembly 200, a valve opens allowing the cement 520 to enter the wellbore annulus 410. Continued pumping of the wiper plug 510 pushes the cement 520 into the annulus 410 until the wiper plug 510 contacts the cementation plug 500.

[0025] Once cemented in place, the cementation plug 500 and wiper plug 510 are drilled or milled out and a smaller diameter drilling assembly (not shown), or other drilling system, is run through the now cemented casing string 220 to drill further into the wellbore 400. Thus, the use of drilling system 100 as described above allows wellbore 400 to be drilled with a casing string 220 that can be cemented in place one at a desired depth. This reduces the total time needed to drill the wellbore 400 by reducing tripping time and potential problems that occur during tripping and while running casing.

[0026] While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and description. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the disclosure to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure.

Claims

What is claimed is:

1. A drilling assembly comprising:

an outer drill bit coupled to a casing string;

an inner drill bit disposed within the outer drill bit; and

a coupling device coupled to the inner drill bit and operable to selectively engage an inner diameter of the casing string.

2. The drilling assembly of claim I, wherein the inner drill bit further comprises a cutting structure including blades.

3. The drilling assembly of claim 2, wherein the outer drill bit further comprises a cutting structure including blades that align with the blades of cutting structure of the inner drill bit.

4. The drilling assembly of claim I, further including splines disposed on the inner drill bit that engage with grooves disposed on outer drill bit.

5. The drilling assembly of claim 1, wherein the coupling device comprises a resilient member that engages the casing string when expanded.

6. The drilling assembly of claim 5, wherein the resilient member is expanded by hydraulic pressure.

7. The drilling assembly of claim 1, further comprising an instrumentation sub coupled to the inner drill bit.

8. A drilling assembly comprising:

an inner assembly having an inner drill bit and a coupling device; and

an outer assembly having an outer drill bit coupled to a casing string, wherein torque is transmitted between the inner assembly and the outer assembly independently of the coupling device.

9. The drilling assembly of claim 8, wherein the inner drill bit further comprises a cutting structure including blades.

10. The drilling assembly of claim 9, wherein the outer drill bit further comprises a cutting structure including blades that align with the blades of cutting structure of the inner drill bit.

11. The drilling assembly of claim 8, further including splines disposed on the inner drill bit that engage with grooves disposed on outer drill bit that transfer torque between the inner assembly and the outer assembly.

12. The drilling assembly of claim 8, wherein the coupling device comprises a resilient member that engages the casing string when expanded.

13. The drilling assembly of claim 12, wherein the resilient member is expanded by hydraulic pressure.

14. The drilling assembly of claim 8, further comprising an instrumentation sub coupled to the inner drill bit.

15. A method of drilling a wellbore comprising:

coupling an outer drill bit to a casing string to form an outer assembly;

disposing an inner assembly within the outer assembly such that an inner drill bit is axially aligned with the outer drill bit;

activating a coupling device so as to axially couple the inner drill bit to the outer drill bit;

rotating the casing string so that the inner drill bit and outer drill bit rotate within a formation to form a wellbore;

deactivating the coupling device; and

removing the inner drill bit from the wellbore while the outer drill bit and the casing string remain in the wellbore.

16. The method of claim 15, wherein torque is transmitted between the outer assembly and the inner assembly independently of the coupling device.

17. The method of claim 15, wherein the coupling device comprises a resilient member that engages the casing string when expanded.

18. The method of claim 17, wherein the resilient member is expanded by hydraulic pressure.

19. The method of claim 15, further comprising operating an instrumentation sub that is coupled to the inner assembly to communicate with the surface.

20. The method of claim 15, further comprising cementing the casing string into the wellbore.