WO2017173374A1

WO2017173374A1 - Method and apparatus for hydraulic fracturing

Info

Publication number: WO2017173374A1
Application number: PCT/US2017/025561
Authority: WO
Inventors: Thomas G. Roesner
Original assignee: Cameron International Corporation
Priority date: 2016-04-01
Filing date: 2017-03-31
Publication date: 2017-10-05

Abstract

A method for fracking a well includes inserting a downhole tool into the well via a conveyance string through a wellhead assembly having a wellhead bore. The method also includes surrounding, at least partially, the conveyance string with a sleeve that at least extends below a portion of an inlet of the wellhead assembly, wherein the inlet intersects the wellhead bore. The method further includes injecting pressurized fluid into the well via the inlet of the wellhead assembly while inserting the downhole tool into well. The method further includes injecting pressurized fluid into the well via the inlet of the wellhead assembly while retrieving the downhole tool from the well. The sleeve located within the wellhead assembly may protect the conveyance string from the introduction of the fluid at the inlet of the wellhead assembly.

Description

METHOD AND

APPARATUS FOR HYDRAULIC FRACTURING

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from and the benefit of U.S. Provisional Application No. 62/317,094, filed April 1, 2016, entitled "METHOD AND

APPARATUS FOR HYDRAULIC FRACTURING," which is hereby incorporated by reference herein in its entirety for all purposes.

BACKGROUND

[0002] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0003] To meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in finding and extracting hydrocarbons (like oil and natural gas) and other subterranean resources from the earth. Particularly, once a desired subterranean reservoir containing hydrocarbons is discovered, drilling and production systems are often employed to drill and complete a well and to access and extract those hydrocarbons, which are typically found within a particular strata or layer of the earth's surface. These systems may be located onshore or offshore depending on the hydrocarbon reservoir's location.

[0004] Hydraulic fracturing or "fracking" is a process for improving reservoir yield. In short, fracking comprises injecting a stimulant (often a water and sand proppant slurry) at high pressure into the well and reservoir. The pressurized proppant creates fissures (fractures) within the formation defining the reservoir, stimulating the flow of subterranean hydrocarbons up through the well and, ultimately, to the surface for collection.

[0005] A single well may be "fracked" at multiple locations or stages. One type of multi-stage fracking is called "plug-and-perf " fracking— in which a series of consecutively installed plugs segregate the well into isolated zones, and a perforating gun perforates the well in each zone, giving the well access to the reservoir. For example, once a well is drilled and the production casing is cemented in place, a perforating gun carrying a plug is lowered into the well via a wireline. Firing the gun sets the plug in the well and then perforates the production casing and surrounding cement, providing a flow path from the reservoir into the well. The wireline and perforating gun are then completely removed from the well. Following that, fracking proppant pumped down at high pressure into the well flows into the reservoir through the perforations punched into the well, to fracture the reservoir. Once fracking of a stage is complete, the process is repeated by plugging and perforating the next stage, which is at a higher location in the well.

[0006] Installation and complete removal of the perforating gun can be a time consuming process, both of which are completed before the introduction of proppant for each stage begins.

SUMMARY

[0007] Certain aspects of some embodiments disclosed herein are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below. [0008] Embodiments of the present disclosure generally relate to apparatus and methods for retrieving a downhole tool via a conveyance string during a fracking operation. For example, in one embodiment, a plug-and-perf assembly may be retrieved via a conveyance string (e.g., a wireline, coiled tubing, segmented tubing, coated wireline, or the like) concurrently with the fracking proppant (e.g., a fluid, which may include water, chemicals, and/ or a proppant, such as sand or ceramics) being pumped into the well. The conveyance string may be partially shielded from the proppant by a sleeve (e.g., annular sleeve) disposed inside a goathead (e.g., frac head) receiving the pressurized proppant. That is, the conveyance string extending vertically through the goathead may be damaged by proppant entering the goathead in at least a partial horizontal direction. The sleeve, however, shields the conveyance string from this pressurized proppant, limiting damage to the conveyance string while it remains in the well as the proppant is injected. Advantageously, this is believed to reduce the operating time for performing a fracking operation (e.g., multi-stage or single-stage fracking operation), as the proppant can be injected while the perforating gun and conveyance string are being "pulled-out-of-hole" and/ or reset for the next stage. While certain embodiments are discussed with reference to a fracking proppant to facilitate discussion, as noted above, it should be appreciated that the system and method may be used with any type of fluid, including any suitable well stimulation fluid with or without proppant, such as water, water with a gel or lubricant, or an acidic fluid (e.g., corrosive fluid that may increase porosity and/ or permeability of rock). For example, the sleeve may shield the conveyance string from an acidic fluid that is provided through the goathead to a location below a reservoir rock fracture gradient to avoid fracture of the rock or to a location above the reservoir rock fracture gradient to create fractures to facilitate hydrocarbon flow and extraction. For example, the sleeve may shield the conveyance string from a chemical diverter or diverting agent that may be provided through the goathead to plug or seal (e.g., temporarily block fluid flow through) existing perforations in the casing. The chemical diverter may include any suitable material that is configured to plug the existing perforations and then to degrade over time and/ or due to temperature and/ or to dissolve in water and/ or during oil production, for example. Furthermore, while certain embodiments are discussed with reference to a wireline to facilitate discussion, as noted above, it should be appreciated that the system and method may be used with any suitable conveyance string, including a wireline, a coiled tubing, a segmented tubular, a wireline coated in a friction -reducing materia! (e.g., having a pol tetrafluoroeth lene [PTFE] sheath), or the like. Furthermore, while certain embodiments are discussed with reference to multi-stage fracking to facilitate discussion, as noted above, it should be appreciated that the system and method may be used in single-stage fracking operations. Furthermore, while certain embodiments are discussed with reference to a downhole tool that includes a perforating gun to facilitate discussion, it should be appreciated that the system and method may be used with any suitable downhole tool, including sensors configured to monitor conditions within the well (e.g., pressure sensors configured to monitor pressure, temperature sensors configured to monitor temperature, image sensors configured to obtain an image of the well, and/ or any of a variety of sensors [e.g., chemical, acoustic, optical, capacitive, or the like) configured to monitor

characteristics [e.g., chemical composition, density, or the like) of fluid within the well, or the like). Thus, the disclosed system and method may use the sleeve to shield any of a variety of conveyance strings supporting any of a variety of downhole tools from any fluid that is provided through the goathead, thereby enabling use and/ or movement (e.g., insertion or withdrawal) of the downhole tool as the fluid is provided through the goathead, such as during multi-stage or single- stage fracking operations, for example.

[0009] Various refinements of the features noted above may exist in relation to various aspects of the present embodiments. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of some embodiments without limitation to the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] These and other features, aspects, and advantages of certain embodiments will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0011] FIG. 1 is a schematic diagram showing insertion of a tool during a multistage fracking operation, in accordance with one embodiment of the present disclosure;

[0012] FIG. 2 is a schematic diagram showing withdrawal of the tool of FIG. 1 during the multi-stage fracking operation, in accordance with one embodiment of the present disclosure; and

[0013] FIG. 3 is a cross-sectional schematic of an isolation sleeve inserted within a goathead to at least partially protect a wireline, in accordance with one embodiment of the present disclosure.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0014] One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0015] When introducing elements of various embodiments, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, any use of "top," "bottom," "above," "below," other directional terms, and variations of these terms is made for convenience, but does not require any particular orientation of the components.

[0016] Turning now to the present figures, FIGS. 1 and 2 illustrate a fracking system 10 for a well 12, in accordance with one embodiment. In particular, FIG. 1 is a schematic diagram showing insertion of a tool 8 (e.g., downhole tool or tool assembly having a perforating gun, plug, sensors, or the like) during a multi-stage fracking operation, and FIG. 2 is a schematic diagram showing withdrawal of the tool 8 during a multi-stage fracking operation. As shown, the well 12 has a vertical leg 14 that extends to a subterranean reservoir 16 that, as illustrated, has a much greater horizontal length than vertical depth. To maximize reservoir yield, the well 12 also has a horizontal leg 18, which may extend for thousands of feet. Indeed, the well 12 may have any number of constructions depending on the geological formation, and need not be limited to directly vertical, horizontal, or linear legs.

[0017] The illustrated well 12 may be formed by drilling a wellbore and then lining that wellbore with a production casing 20 (e.g., annular casing). A layer of cement 22 is then added to seal the annular space between the exterior surface of the production casing 20 and the earthen walls of the wellbore. [0018] At the surface, an exemplary wellhead assembly 24 facilitates and controls ingress and egress to the well 12. In the illustrated embodiment, one or more spool bodies 26 (e.g., a casing head, tubing head, casing spool, or tubing spool) are provided to support various casing or tubing strings that may extend into the well 12.

[0019] The wellhead assembly 24 includes a number of components to control the insertion of fracking proppant (e.g., a fluid, which may include water, chemicals, and/ or a proppant, such as sand or ceramics) into the well 12, the components and spool bodies 26 cooperating to form a wellhead bore 25 that aligns with the entrance of the well 12. For example, a frack valve 28— which may be any number of types of valves, including ball valves, gate valves, for example— is coupled to the spool bodies 26 and can be used to isolate the well 12 from a pressurized-proppant source 29, and vice versa. The wellhead assembly 24 also includes a goathead 30 (e.g., a frac head) that can be used to merge pressurized proppant from multiple sources 29 and direct the pressurized proppant into the wellhead bore 25 and the well 12.

[0020] However, before the proppant is injected into the well 12, the well 12 may be perforated. As shown in FIG. 2, perforations 32 (e.g., holes) are punched into the casing 20 and surrounding cement 22, creating a fluid pathway between the well 12 and the reservoir 16. This can be accomplished, for example, with the tool 8, which may have a perforating gun 33 carried by a setting tool 34 and a wireline 36 (e.g., conveyance string). In the illustrated embodiment, a wireline source 38 feeds wireline 36, which may be thousands of feet long, into the well 12. The wireline 36 is a conveyance tool that can send electrical, acoustic, optical or mechanical signals to activate/ operate the attached setting tool 34 and perforating gun 33, for example. The system 10 may include a supported pulley 40 that guides the wireline 36 through a top valve 42 of the wellhead assembly 24.

[0021] In operation, the tool 8 may be lowered into the well 12, as shown by arrow 37 in FIG. 1. In some embodiments, to drive the setting tool 34 downhole into the well 12, fluid, generally just above wellbore pressure is pumped into the well 12. This carries the setting tool 34 down to a desired location in the well 12. Once the desired location is reached, the wireline 36 is prevented (e.g., blocked) from further unspooling, fixing the location of the setting tool 34 within the well 12.

[0022] At this point, a signal providing operating instructions is sent from the surface to the setting tool 34 via the wireline 36. By way of example, the signal may instruct a plug 44 (e.g., radially-expandable plug) coupled to the setting tool 34 to expand and set to seal off the well 12 below it (e.g., downstream of the plug 44). The signal may also trigger the perforating gun 33, causing explosively charged projectiles to puncture or punch through the casing 20 and surrounding cement 22, creating the perforations 32 that permit fluid to flow between the reservoir 16 and the well 12, as shown in FIG. 2.

[0023] In certain traditional systems, the wireline 36 and the setting tool 34 undergo a "pull-out-of-hole" operation— i.e., the wireline 36 and setting tool 34 are retrieved (e.g., fully removed or withdrawn) out of the well 12— after formation of the perforations 32 and before fracking proppant is introduced into the well 12. But retrieval can be a time consuming process, as there may be thousands of feet of wireline 36 in the well 12. In such traditional systems, once the wireline 36 and setting tool 34 are retrieved, fracking proppant is pressurized at the source 29, sent to the goathead 30, and directed into the well 12 and through the perforations 32 to create fissures 46 in the formation. In such traditional systems, the process (i.e., inserting the tool 8, placing the plug 44, creating the perforations 32, completely retrieving the tool 8, and subsequently providing the proppant) may then be repeated for each stage (e.g., location within the well 12). However, the plug 44 is set and perforations 32 are punched at a higher point in the well 12 each time— the more recently set plug 44 isolating the previously fracked section or stage below it. [0024] The exemplary embodiment, however, facilitates withdrawal or retrieval of the wireline 36 and the setting tool 34, as shown by arrow 45 in FIG. 2, concurrently (e.g., simultaneously or at the same time) with injection of fracking proppant into the well 12, as shown by arrow 47 in FIG. 2. For example, the wireline 36 and the setting tool 34 are pumped (e.g., driven), typically at a relatively low pressure, down to the desired location, and a signal is sent to fire the perforating gun

33 and to set the plug 44. However, the fracking proppant may be injected into the well 12 before the pull-out-of-hole operation for the wireline 36 and the setting tool

34 is complete— that is, while the setting tool 34 and the wireline 36 are still in the well 12 (e.g., positioned within and/or moving within the well 12). In some embodiments, as shown in FIG. 2, respective plugs 44 may be set and respective perforations 32 may be created at multiple stages using the disclosed techniques. This is believed to save considerable time and reduce the cost of operating equipment and/or personnel necessary to complete the fracking operation (e.g., single-stage or multi-stage fracking operation).

[0025] FIG. 3 illustrates an exemplary device that facilitates this concurrent operation. Specifically, FIG. 3 illustrates an embodiment of a goathead assembly 31 having the goathead 30 with a series of inlets 48 that receive pressurized proppant from the proppant source 29. The illustrated inlets 48 are arranged at a 45^° angle (e.g., relative to a central or axial axis of the wellhead bore 25), but other

arrangements, including completely horizontal arrangements (e.g., perpendicular to a central or axial axis of the wellhead bore 25), are envisaged. The inlets 48 provide passageways for the pressurized proppant to enter the wellhead bore 25 of the wellhead assembly 24. As shown, the goathead assembly 31 also includes an adapter spool 27 and connectors 35 that are configured to couple to conduits that extend to the proppant source 29.

[0026] Pressurized proppant exiting the inlets 48 to go downhole into the well 12 impact an isolation sleeve 50 (e.g., annular sleeve) surrounding (e.g., circumferentially surrounding) at least a portion of the wireline 36. This protects the wireline 36 from the abrasive turbulence caused by the insertion of the proppant into the goathead 30— abrasive turbulence which increases the chances of shearing or otherwise damaging the wireline 36. The wireline 36 is exposed to the proppant below this isolation sleeve 50; however, it is believed that this proppant will have a more laminar flow and, thus, be less likely to damage the wireline 36. Indeed, the proppant exiting the inlets 48 is at a relatively high-velocity. By shielding the wireline 36 from the proppant as it introduced into the wellhead bore 25, the wireline 36 can remain in the well 12 and be retrieved while fracking proppant is injected into the well 12.

[0027] Retrieval of the wireline 36 concurrent with injecting of fracking proppant is believed to provide a number of advantages. For example, it reduces the time between when the perforations 32 are made and fracking proppant is injected into the well 12, decreasing the likelihood of unwanted perforation closure that could damage the well 12. It also increases the number of fracking stages that can be completed in a day, which can reduce the number of days necessary for the fracking operations and, in turn, reduce the operating costs for performing the fracking. Put simply, it allows the injection of fracking proppant into the well 12 at a relatively short time after a given stage of the well 12 has been plugged and perforated.

[0028] The isolation sleeve 50 may be a separate, retrievable piece (e.g., coupled to and/ or held in place relative to the goathead 30 via fasteners, threads, flanges, or the like), or it may be integrated into the goathead 30 (e.g., integrally formed with the goathead 30, thereby forming a one-piece structure), or other spool body that is the inlet for the fracking proppant. It should be appreciated that the isolation sleeve 50 and the goathead 30 may have any of a variety of configurations that enable the isolation sleeve 50 to block contact between the proppant flowing into the wellhead bore 25 and the wireline 36 and/ or to facilitate injection of fluid to drive the downhole tool 8 into the well 12 and/ or injection of the proppant while the wireline 36 is positioned within and/ or moves through the wellhead bore 25. [0029] While the aspects of the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. But it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.

Claims

1. A method for fracking a well, comprising: inserting a downhole tool into the well via a conveyance string through a wellhead assembly having a wellhead bore; surrounding, at least partially, the conveyance string with a sleeve that at least extends below a portion of an inlet of the wellhead assembly, wherein the inlet intersects the wellhead bore; and injecting a first pressurized fluid into the well via the inlet of the wellhead assembly while retrieving the downhole tool from the well.

2. The method of claim 1, wherein the inlet comprises a non-vertical inlet relative to a central axis of the wellhead bore.

3. The method of claim 1, comprising inserting the downhole tool to a desired location within the well while injecting a second pressurized fluid into the well via the inlet.

4. The method of claim 1, comprising inserting the downhole tool to a desired location within the well and injecting a second pressurized fluid into the well while the downhole tool is stationary at the desired location.

5. The method of claim 1, wherein the sleeve is an annular sleeve that circumferentially surrounds the conveyance string.

6. The method of claim 1, wherein the sleeve is coupled to the wellhead assembly.

7. The method of claim 1, wherein the sleeve is integrally formed with the wellhead assembly.

8. The method of claim 1, comprising perforating a casing that lines the well at multiple stages using the downhole tool.

9. The method of claim 1, wherein retrieving the downhole tool from the well comprises moving the downhole tool from a first position within the well proximate to a formation from which a resource is extracted to a second position within the well proximate to the wellhead assembly.

10. A method for fracking a well, comprising: inserting a downhole tool into the well via a conveyance string through a wellhead assembly having a wellhead bore; surrounding, at least partially, the conveyance string with an annular sleeve that at extends axially across an inlet of the wellhead assembly; and injecting pressurized fluid into the wellhead bore via the inlet of the wellhead assembly while the downhole tool is positioned within the well.

11. The method of claim 10, wherein the inlet comprises a non-vertical inlet relative to a central axis of the wellhead bore.

12. The method of claim 10, comprising injecting the pressurized fluid into the wellhead bore via the inlet while the downhole tool is moving through the well.

13. The method of claim 10, comprising injecting the pressurized fluid into the wellhead bore via the inlet while the downhole tool is stationary within the well.

14. The method of claim 10, wherein the annular sleeve is coupled to the wellhead assembly.

15. The method of claim 10, wherein pressurized fluid comprises a fracking proppant, a diverting agent, or any combination thereof.

16. The method of claim 10, comprising perforating a casing that lines the well at multiple stages using the downhole tool.

17. A system for fracking a well, comprising: a wellhead assembly comprising a goathead configured to receive pressurized fluid, the goathead comprising an inlet and a wellhead bore that are non-parallel to one another; an isolation sleeve located in the wellhead bore, wherein the isolation sleeve extends below at least a top portion of the inlet where the inlet and wellhead bore intersect; and a wireline coupled to a downhole tool and configured to move within the wellhead bore as pressurized fluid flows into the wellhead bore via the inlet.

18. The system of claim 17, wherein the isolation sleeve is configured to block contact between wireline and the pressurized fluid exiting the inlet into the wellhead bore.

19. The system of claim 17, wherein the downhole tool comprises a perforating gun that is configured to perforate a casing that lines the well, a sensor that is configured to monitor a condition of the well, or a combination thereof.

20. The system of claim 17, wherein the sleeve is an annular sleeve that circumferentially surrounds the conveyance string.