WO2019241456A1

WO2019241456A1 - Controlling fracture initiation from extended perforation tunnels

Info

Publication number: WO2019241456A1
Application number: PCT/US2019/036869
Authority: WO
Inventors: Dmitriy Ivanovich Potapenko; Doug Pipchuk; William BATZER; George Alan Waters; Robert Utter
Original assignee: Schlumberger Technology Corporation; Schlumberger Canada Limited; Services Petroliers Schlumberger; Schlumberger Technology B.V.
Priority date: 2018-06-13
Filing date: 2019-06-13
Publication date: 2019-12-19

Abstract

Systems and method presented herein facilitate enhanced hydrocarbon fluid production. For example, in certain embodiments, a borehole positioned proximate a stimulation zone (e.g., along or through the stimulation zone) may have at least one extended perforation tunnel extending from the borehole at least partially into the stimulation zone. In addition, each extended perforation tunnel may have at least one fracture initiation region to facilitate initiation of fractures at a desired location and/or in a desired direction during a stimulation operation in which fracturing fluid is pumped under pressure into the extended perforation tunnel.

Description

CONTROLLING FRACTURE INITIATION FROM EXTENDED

PERFORATION TUNNELS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 62/684,348, entitled“Controlling Fracture Initiation from Extended Perforation Tunnels,” filed June 13, 2018, which is hereby incorporated by reference in its entirety for all purposes.

BACKGROUND

[0002] The present disclosure generally relates to systems and methods for controlling fracture initiation and, more particularly, to systems and methods for controlling fracture initiation from extended perforation tunnels extending from wellbores.

[0003] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. 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 disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as an admission of any kind.

[0004] Wellbores are drilled through subterranean formations for the extraction of hydrocarbons. Hydraulic fracturing is an efficient way of increasing productivity of wells in oil and gas bearing formations. Hydraulic fracturing is based on pumping fracturing fluid at high pressure into the wellbore to create localized fractures in the formation to increase the production rates of hydrocarbons. The fracturing fluid may include proppant (e.g., sand, bauxite, ceramic, nut shells, etc.) to hold the fractures open after the frac pump pressure is removed, thereby permitting hydrocarbons to flow from the fractured formation into the wellbore. In carbonate reservoirs, the fracturing fluid may include hydrochloric acid and/or other chemicals intended to etch the fracture faces to improve the flow capacity of the fractures. It should be noted that, in certain embodiments, other types of fracture treatments may be utilized including, but not limited to, acid fracturing, slick water fracturing, foam fracturing, proppant-free fracturing, water or steam injection, and others.

[0005] The overall process for creating a hydraulically fractured wellbore includes two or three primary operations; a drilling operation, an optional casing operation, and hydraulic fracturing operations. Hydraulic fracturing operations were initially performed in single-stage, vertical or near-vertical wells. In later years, hydraulic fracturing operations became predominantly utilized in horizontal or near-horizontal sections of single- and multi-stage wells, such as to improve productivity of these horizontal or near-horizontal well sections.

SUMMARY

[0006] A summary of certain embodiments described herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure.

[0007] Certain embodiments of the present disclosure include a method that includes creating an extended perforation tunnel from a borehole proximate a stimulation zone so as to extend at least partially into the stimulation zone. The method also includes creating at least one fracture initiation region of the extended perforation tunnel to facilitate initiation of one or more desired fractures during a stimulation operation. The method further includes fracturing the stimulation zone by pumping fracturing fluid under pressure into and through the extended perforation tunnel.

[0008] In addition, certain embodiments of the present disclosure include a system that includes a borehole positioned proximate a stimulation zone in a formation. The system also includes an extended perforation tunnel extending from the borehole, the extended perforation tunnel being positioned at least partially in the stimulation zone, and the extended perforation tunnel having at least one fracture initiation region to facilitate initiation of fractures at a desired location and in a desired direction during a stimulation operation in which fracturing fluid is pumped under pressure into the extended perforation tunnel.

[0009] Various refinements of the features noted above may be undertaken in relation to various aspects of the present disclosure. 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. The brief summary presented above is intended to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings, in which:

[0011] FIG. l is a schematic illustration of a well system extending into a subterranean formation, in accordance with embodiments of the present disclosure;

[0012] FIG. 2 is a diagrammatic illustration showing an example of alpha and beta angles at which a given extended perforation tunnel may extend from a borehole, in accordance with embodiments of the present disclosure;

[0013] FIG. 3 is a schematic illustration of a well system having a plurality of extended perforation tunnels extending from a borehole to deliver stimulating fluid, in accordance with embodiments of the present disclosure;

[0014] FIG. 4 is a schematic sectional view of at least a portion of a radial drilling tool system, in accordance with embodiments of the present disclosure;

[0015] FIG. 5 is a schematic view of the radial drilling tool system illustrated in FIG. 4 in a different stage of operation, in accordance with embodiments of the present disclosure;

[0016] FIG. 6 is a schematic view of the radial drilling tool system illustrated in FIGS. 4 and 5 in a different stage of operation, in accordance with embodiments of the present disclosure;

[0017] FIG. 7 is a schematic sectional view of at least a portion of another example radial drilling tool system, in accordance with embodiments of the present disclosure; [0018] FIG. 8 is a three-dimensional element of a subterranean formation having X-Y-Z coordinates and being subjected to local stresses, in accordance with embodiments of the present disclosure;

[0019] FIG. 9 is a schematic view of at least a portion of an example wellbore system that includes a plurality of extended perforation tunnels, in accordance with embodiments of the present disclosure;

[0020] FIG. 10 is a schematic view illustrating an extended perforation tunnel created with fracture initiation regions to facilitate initiation of fractures at desired locations during a stimulation operation, in accordance with embodiments of the present disclosure;

[0021] FIG. 11 is a schematic view illustrating a downhole jetting tool, which may be used to create an extended perforation tunnel with desired fracture initiation regions, in accordance with embodiments of the present disclosure;

[0022] FIG. 12 is a schematic view illustrating an extended perforation tunnel having a cross- section, which provides desired fracture initiation regions, in accordance with embodiments of the present disclosure;

[0023] FIG. 13 is a schematic view illustrating an extended perforation tunnel having a cross- section, which provides desired fracture initiation regions, in accordance with embodiments of the present disclosure;

[0024] FIG. 14 is a schematic view illustrating an extended perforation tunnel having a cross- section, which provides desired fracture initiation regions, in accordance with embodiments of the present disclosure; [0025] FIG. 15 is a schematic view illustrating an extended perforation tunnel having a cross- section, which provides desired fracture initiation regions, in accordance with embodiments of the present disclosure;

[0026] FIG. 16 is a schematic view illustrating an extended perforation tunnel positioned in a stimulation zone and having a cross-section, which provides desired fracture initiation regions, in accordance with embodiments of the present disclosure;

[0027] FIG. 17 is a schematic view illustrating an extended perforation tunnel positioned in a stimulation zone and having a cross-section, which provides desired fracture initiation regions, in accordance with embodiments of the present disclosure; and

[0028] FIG. 18 is a block diagram of at least a portion of a processing device configured to execute instructions to implement the techniques described herein.

PET ATT, ED DESCRIPTION

[0029] One or more specific embodiments of the present disclosure will be described below These described embodiments are only examples of the presently disclosed techniques.

Additionally, 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.

[0030] When introducing elements of various embodiments of the present disclosure, the articles“a,”“an,” and“the” 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. Additionally, it should be understood that references to“one embodiment” or“an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0031] As used herein, the terms“connect,”“connection,”“connected,”“in connection with,” and“connecting” are used to mean“in direct connection with” or“in connection with via one or more elements”; and the term“set” is used to mean“one element” or“more than one element.” Further, the terms“couple,”“coupling,”“coupled,”“coupled together,” and “coupled with” are used to mean“directly coupled together” or“coupled together via one or more elements.” As used herein, the terms“up” and“down,”“uphole” and“downhole”, “upper” and“lower,”“top” and“bottom,” and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top (e.g., uphole or upper) point and the total depth along the drilling axis being the lowest (e.g., downhole or lower) point, whether the well (e.g., wellbore, borehole) is vertical, horizontal or slanted relative to the surface. [0032] The systems and methods described herein generally relate to enhancing hydrocarbon fluid production. For example, a well may be created in a subterranean region by drilling a borehole (e.g., a generally vertical wellbore). In certain embodiments, at least one extended perforation tunnel may be created and oriented to extend outwardly from the borehole at least a certain amount (e.g., at least 10 feet, or 3.05 meters) into a formation surrounding the borehole.

In certain embodiments, the extended perforation tunnels may be created to extend outwardly from the borehole at least 5 feet (1.5 meters), at least 10 feet (3.05 meters), at least 15 feet (4.6 meters), at least 20 feet (6.1 meters), or even substantially longer than 20 feet (6.1 meters) (e.g., up to or even greater than 1,600 feet (488 meters), as described in greater detail herein). In certain embodiments, the borehole may be oriented generally vertically and the extended perforation tunnels may extend outwardly generally horizontally. However, certain

embodiments may utilize a deviated (e.g., at least partially horizontal) borehole with extended perforation tunnels extending outwardly from the deviated borehole. Depending on the application and characteristics of the subterranean region, the extended perforation tunnels may be oriented generally horizontally, generally vertically, or at any desired orientations

therebetween.

[0033] In general, as used herein, the term“extended perforation tunnel” is intended to mean a secondary borehole that extends from a main borehole at a substantially constant angle for at least 5 feet (1.5 meters), at least 10 feet (3.05 meters), at least 15 feet (4.6 meters), at least 20 feet (6.1 meters), or even substantially longer than 20 feet (6.1 meters) (e.g., up to or even greater than 1,600 feet (488 meters), as described in greater detail herein). Conventional lateral boreholes are typically created by gradually veering from a main borehole at a continually increasing angle (i.e., such that the main borehole and the lateral borehole generally form a curved intersection between the two). In contrast, the extended perforation tunnels described herein directly extend from a main borehole at a non-zero angle (e.g., contrary to conventional lateral boreholes that extend from a main borehole at an angle that gradually increases from 0 degrees). Indeed, the non-zero angle directly formed between an extended perforation tunnel and a corresponding main borehole may be an angle substantially greater than 0 degrees, such as greater than 20 degrees, greater than 30 degrees, greater than 45 degrees, greater than 60 degrees, between 60 degrees and 90 degrees, between 70 degrees and 90 degrees, or between 80 degrees and 90 degrees, as described in greater detail herein, As such, the extended perforation tunnels described herein are not connected to a main borehole by a curved intersection, contrary to conventional lateral boreholes. Rather, the extended perforation tunnels described herein form relatively sharp transitions from their respective main boreholes. As used herein, the term “substantially constant angle” is intended to mean an angle that varies along a length of an extended perforation tunnel by no more than a very small amount, such as 5 degrees, 4 degrees, 3 degrees, 2 degrees, 1 degree, or even less.

[0034] In certain applications, the orientation of the extended perforation tunnels may be selected such that each extended perforation tunnel extends at a desired angle with respect to a direction of principal stresses in the formation. For example, in certain applications, the tunnel azimuths may be oriented in a direction of maximum horizontal stress, minimum horizontal stress, or at a desired other angle with respect to the maximum horizontal stress. Additionally, the tunnel azimuths (as well as the borehole azimuth) may be relatively constant in certain applications, but they may also vary in other applications, for example, to achieve a desired positioning with respect to a hydrocarbon bearing target zone in a formation. [0035] Once the extended perforation tunnels are created, a fracture stimulation of the extended perforation tunnels may be performed to create a network of fractures. For example, a hydraulic fracturing fluid may be pumped downhole and out through the extended perforation tunnel (or extended perforation tunnels) to create fracture networks extending from each extended perforation tunnel. The fracture networks may be created to extend laterally from each extended perforation tunnel, but they also may be created parallel with the extended perforation tunnels and/or at other desired orientations. In general, the orientation of the extended perforation tunnels ensures that the network of fractures extends through a target zone in a hydrocarbon bearing region of the formation.

[0036] As described in greater detail herein, the diameter of the extended perforation tunnels may vary according to the formation and/or other parameters of a given operation. By way of example, the extended perforation tunnels are generally smaller in diameter than a casing used along the borehole from which they extend. However, certain embodiments may utilize extended perforation tunnels equal to or larger in diameter than the borehole. The diameter of the extended perforation tunnels may be selected according to parameters of the formation and/or types of equipment used for creating the extended perforation tunnels. In addition, the resultant diameter of the extended perforation tunnels may vary depending on the particular technique used to create the extended perforation tunnels (e.g., jetting, drilling, or other suitable technique).

[0037] In certain embodiments, the borehole may be drilled at least in part in a non productive zone of the subterranean formation. The non-productive zone may be a zone that contains limited amounts of hydrocarbon fluid or is less desirable with respect to production of hydrocarbon fluid. Depending on the characteristics of the subterranean region, the borehole may be drilled in non-productive rock and/or in a region with petrophysical and geo-mechanical properties different from the properties of the target zone. For example, the borehole may be drilled in a region of the formation having a substantially higher minimum in situ stress relative to that of the target zone. It should be noted that the extended perforation tunnels may be used in many types of formations (e.g., laminated formations) to facilitate flow of fluid to the extended perforation tunnels through fracture networks even in the presence of pinch points between formation layers.

[0038] To facilitate production, at least one extended perforation tunnel may be created, which intersects the borehole and extends into a target zone (e.g., a productive zone containing hydrocarbon fluid). Often, a plurality of extended perforation tunnels may be created to extend from the borehole outwardly into the target zone to serve as extended treatment passages. The target zone may be a single region or separate distinct regions of the formation. In certain embodiments, the borehole may be entirely outside of the target zone, and a plurality of extended perforation tunnels may be created in desired directions to reach the target zone. For example, in certain embodiments, the extended perforation tunnels may be created generally horizontally, generally vertically, generally along desired angles between horizontal and vertical, in generally opposed directions with respect to each other, or at other orientations with respect to each other. In other embodiments, however, the borehole may extend into or through the target zone.

[0039] As described in greater detail herein, the well stimulation may include hydraulic fracturing of the stimulation zone or zones. During hydraulic fracturing, a fracturing fluid may be pumped down through the borehole and out through the plurality of extended perforation tunnels. In general, the fracturing fluid is forced under pressure from the extended perforation tunnels out into the surrounding subterranean formation (e.g., into the surrounding hydrocarbon bearing target zone) to fracture the surrounding subterranean formation. For example, the surrounding subterranean formation may be fractured at a plurality of stimulation zones within the overall target zone.

[0040] It should be noted that, in certain embodiments, the fracturing fluid also may comprise propping agent for providing fracture conductivity after fracture closure. In certain embodiments, the fracturing fluid may comprise acid such as hydrochloric acid, acetic acid, citric acid, hydrofluoric acid, other acids, or mixtures thereof. The fracturing of the stimulation zones within the target zone enhances production of hydrocarbon fluid from the target zone to the wellbore and ultimately to the surface. The target zone may be a productive zone of the subterranean region containing desired hydrocarbon fluid (e.g., oil and/or gas).

[0041] In addition, the embodiments described herein provide systems and methods for promoting production of well fluid from a wellbore or borehole. For example, the embodiments described herein include providing or performing an operation in a borehole positioned proximate to a stimulation zone (e.g., along or through the stimulation zone). At least one extended perforation tunnel having a length of greater than 10 feet (3.05 meters) is oriented to extend from the borehole at least partially in the stimulation zone. In addition, in certain embodiments, each extended perforation tunnel may include at least one hydraulic fracture initiation region to facilitate initiation of hydraulic fractures at a desired location during a fracture stimulation operation in which fracturing fluid is pumped under pressure into the extended perforation tunnel. In addition, in certain embodiments, orientation of the extended perforation tunnel in the formation may be used to control the angle between the direction of fracture propagation and the extended perforation tunnel. In a non-limiting example, aligning an extended perforation tunnel with maximum horizontal stress facilitates creation of a hydraulic fracture(s) initiated and propagating along the extended perforation tunnel.

[0042] Turning now to the drawings, FIG. 1 is a schematic illustration of a well system 10 extending into a subterranean formation 12. The well system 10 enables a methodology for enhancing recovery of hydrocarbon fluid (e.g., oil and/or gas) from a well. In certain embodiments, a borehole 14 (e.g., a generally vertical wellbore) is drilled down into the subterranean formation 12. In certain embodiments, the borehole 14 may be drilled into or may be drilled outside of a target zone 16 (or target zones 16) containing, for example, a hydrocarbon fluid 18.

[0043] In the illustrated embodiment, the borehole 14 is a generally vertical wellbore extending downwardly from a surface 20. However, certain operations may create deviations in the borehole 14 (e.g., a lateral section of the borehole 14) to facilitate hydrocarbon recovery. In certain embodiments, the borehole 14 may be created in non-productive rock of the formation 12 and/or in a zone with petrophysical and/or geomechanical properties different from the properties found in the target zone or zones 16.

[0044] At least one extended perforation tunnel 22 (e.g., a plurality of extended perforation tunnels 22, in certain embodiments) may be created to intersect the borehole 14. In the illustrated embodiment, at least two extended perforation tunnels 22 are created to intersect the borehole 14 and to extend outwardly from the borehole 14. For example, in certain

embodiments, the extended perforation tunnels 22 may be created and oriented laterally (e.g., generally horizontally) with respect to the borehole 14. Additionally, in certain embodiments, the extended perforation tunnels 22 may be oriented to extend from the borehole 14 in different directions (e.g., opposite directions) so as to extend into the desired target zone or zones 16.

[0045] With reference to FIG. 2, the extended perforation tunnel 22 is not aligned with the orientation of the borehole 14, but is created at some angle relative to the borehole 14 that is characterized by deviation from the direction of the borehole 14 (e.g., angle alpha: 0-90°) and the azimuthal tangential angle (beta 0-90°). For example, the extended perforation tunnels 22 may be oriented at desired alpha angles (e.g., deviation from the direction of the borehole 14) and beta angles (e.g., the azimuthal tangential angle) as illustrated in FIG. 2. The alpha and beta angles may range between 0° and 90° (e.g., from 45° to 90°, in certain embodiments). For example, the extended perforation tunnels 22 may be oriented from 45° to 90° relative to the direction of the borehole 14. In certain embodiments, the extended perforation tunnels 22 may be created and oriented at the alpha angle equal or close to 90° and the beta angle equal or close to 0° with respect to the borehole 14. Additionally, in certain embodiments, the extended perforation tunnels 22 may be oriented to extend from the borehole 14 in different directions (e.g., opposite directions) so as to extend into the desired zone 16. As described in greater detail herein, during a stimulation operation (e.g., a hydraulic fracturing operation), fractures are created, which extend from the extended perforation tunnels 22.

[0046] Returning now to FIG. 1, in general, the extended perforation tunnels 22 provide fluid communication with an interior of the borehole/wellbore 14 to facilitate flow of the desired hydrocarbon fluid 18 from the extended perforation tunnels 22, into borehole 14, and up through borehole 14 to, for example, a collection location at surface 20. Furthermore, in certain embodiments, the extended perforation tunnels 22 may be oriented in selected directions based on the material forming the subterranean formation 12 and/or on the location of desired target zones 16.

[0047] Depending on the characteristics of the subterranean formation 12 and the target zones 16, the extended perforation tunnels 22 may be created along various azimuths. For example, in certain embodiments, the extended perforation tunnels 22 may be created in alignment with a direction of maximum horizontal stress, represented by arrow 24, in the formation 12. However, in other embodiments, the extended perforation tunnels 22 may be created along other azimuths, such as in alignment with a direction of minimum horizontal stress in the formation 12, as represented by arrow 26.

[0048] In certain embodiments, the extended perforation tunnels 22 may be created at a desired angle or angles with respect to principal stresses when selecting azimuthal directions.

For example, in certain embodiments, the extended perforation tunnel (or extended perforation tunnels) 22 may be oriented at a desired angle with respect to the maximum horizontal stress in formation 12. It should be noted that, in certain embodiments, the azimuth and/or deviation of an individual extended perforation tunnel 22 may be constant. However, in other embodiments, the azimuth and/or deviation may vary along the individual extended perforation tunnel 22 to, for example, enable creation of the extended perforation tunnel 22 through a desired zone 16 to facilitate recovery of the hydrocarbon fluids 18.

[0049] Additionally, in certain embodiments, at least one of the extended perforation tunnels 22 may be created and oriented to take advantage of a natural fracture 28 or multiple natural fractures 28, which occur in the formation 12. The natural fracture 28 may be used as a flow conduit that facilitates flow of the hydrocarbon fluid 18 into the extended perforation tunnel (or extended perforation tunnels) 22. Once the hydrocarbon fluid 18 enters the extended perforation tunnels 22, the hydrocarbon fluid 18 is able to readily flow into the wellbore 14 for production to the surface 20 and/or other collection location.

[0050] Depending on the parameters of a given formation 12 and hydrocarbon recovery operation, the diameter and length of the extended perforation tunnels 22 also may vary. The extended perforation tunnels 22 are generally longer than the lengths of perforations created in a conventional perforation operation. In certain embodiments, the extended perforation tunnels 22 extend from the borehole 14 at least 10 feet (3.05 meters) into the formation 12 surrounding the borehole 14. However, other embodiments may utilize extended perforation tunnels 22 that extend from the borehole 14 at least 15 feet (4.6 meters) into the formation 12. Yet other embodiments may utilize extended perforation tunnels 22 that extend from the borehole 14 at least 20 feet (6.1 meters) into the formation 12. Indeed, certain embodiments may utilize extended perforation tunnels 22 substantially longer than 20 feet (6.1 meters). For example, in certain embodiments, some of the extended perforation tunnels 22 may extend from the borehole 14 at least 100 feet (30.5 meters), at least 200 feet (61 meters), between 300 feet (91 meters) and 1,600 feet (488 meters), or even more, into the formation 12.

[0051] In certain embodiments, each extended perforation tunnel 22 also has a diameter generally smaller than the diameter of borehole 14 (e.g., smaller than the diameter of a casing used to line borehole 14). With respect to diameter, in certain embodiments, the tunnel diameter may range, for example, from 0.5 inches (12.7 millimeters) to 5.0 inches (12.7 centimeters). However, in other embodiments, the tunnel diameter may be within a range of 0.5 inches (12.7 millimeters) to 10 inches (25.4 centimeters), within a range of 1 inch (25.4 millimeters) and 5 inches (12.7 centimeters), within a range of 1.5 inches (3.8 centimeters) and 3 inches (7.6 centimeters), and so forth. However, in other embodiments, the extended perforation tunnels 22 may utilize a diameter of 2 inches (5.1 centimeters) or less. However, other embodiments may utilize extended perforation tunnels 22 having a diameter of 1.5 inches (3.8 centimeters) or less. The actual lengths, diameters, and orientations of the extended perforation tunnels 22 may be adjusted according to the parameters of the formation 12, the target zones 16, and/or objectives of the hydrocarbon recovery operation.

[0052] FIG. 3 is a schematic illustration of a well system 10 having a plurality of extended perforation tunnels 22 extending from a borehole 14 to deliver stimulating fluid to stimulation zones 30 that are distributed through the target zone(s) 16. Distributing the stimulating fluid under pressure to the stimulation zones 30 creates fracture networks 32. The fracture networks 32 facilitate flow of fluid into the corresponding extended perforation tunnels 22. By way of example, the stimulation operation may include hydraulic fracturing performed to fracture the subterranean formation 12 (e.g., oil- or gas-bearing target zone 16) so as to facilitate flow of the desired fluid along the resulting fracture networks 32 and into the corresponding extended perforation tunnels 22.

[0053] If the stimulation operation is a hydraulic fracturing operation, fracturing fluid may be pumped from the surface 20 under pressure, down through wellbore 14, into the extended perforation tunnels 22, and then into the stimulation zones 30 surrounding the corresponding extended perforation tunnels 22, as indicated by arrows 34. The pressurized fracturing fluid 34 causes the formation 12 to fracture in a manner that creates the fracture networks 32 in the stimulation zones 30. In certain embodiments, the extended perforation tunnels 22/stimulation zones 30 may be fractured sequentially. For example, the fracturing operation may be performed through sequential extended perforation tunnels 22 and/or sequentially through individual extended perforation tunnels 22 to cause sequential fracturing of the stimulation zones 30 and creation of the resultant fracture networks 32.

[0054] As described in greater detail herein, the extended perforation tunnels 22 may be created via a variety of techniques, such as various jetting techniques or drilling techniques. For example, in certain embodiments, drilling equipment may be deployed down into wellbore 14 and used to create the desired number of extended perforation tunnels 22 in appropriate orientations for a given subterranean environment and production operation. However, in other embodiments, the extended perforation tunnels 22 may be created by other suitable techniques, such as jetting techniques, laser techniques, injection of reactive fluid techniques, electrical decomposition techniques, or other tunnel creation techniques. In a specific example, the extended perforation tunnels 22 may be jetted using hydraulic jetting technology similar to hydraulic jetting technologies available from Radial Drilling Services Ltd, Viper Drill of

Houston, Texas, Jett-Drill Well Services Ltd, or Fishbones AS of Stavanger, Norway.

[0055] As described in greater detail herein, the use of extended perforation tunnels 22 during the stimulation operation enables creation of the fracture networks 32 and/or control of the geometries thereof. In general, the fracture networks 32 provide fractures with an increased density, thus increasing the size of the contact area with respect to each target zone 16 containing the hydrocarbon fluid 18. This, in turn, leads to an increase in well productivity as compared to wells completed without utilizing extended perforation tunnels 22. [0056] FIGS. 4-6 are schematic sectional views of a portion of an example downhole radial drilling tool system positioned within a wellbore 14 and operable to from extended perforation tunnels 22 extending from the wellbore 14. For example, FIG. 4 illustrates a portion of a wellbore 14 including a casing 36 (which may be secured by cement 38 or installed open-hole) extending through a subterranean formation 12. In certain embodiments, a drill string 40 extending through the wellbore 14 includes a deflecting tool 42 operable to deflect or otherwise direct a drilling, cutting, or other boring device toward a sidewall of the wellbore 14 to create an extended perforation tunnel 22. In certain embodiments, the deflecting tool 42 may be rotatably oriented with respect to the wellbore 14, as indicated by arrow 44, to rotatably align or orient an outlet port 46 of the deflecting tool 42 in an intended direction (e.g., a substantially vertical direction). In certain embodiments, an axis 48 of the outlet port 46 is oriented substantially orthogonal (e.g., within 5 degrees, within 2 degrees, within 1 degree, or even closer, to exactly orthogonal) to the casing 36 through which the extended perforation tunnel 22 extends.

[0057] As illustrated in FIG. 5, in certain embodiments, after the deflecting tool 42 is positioned at an intended longitudinal (e.g., axial) location within the wellbore 14 and at an intended rotational orientation, a drilling tool 50 (e.g., a flexible casing drilling string, in certain embodiments) terminating with a drilling, milling, cutting, or other bit 52 may be deployed through the drill string 40, such as via a micro-coil or coiled tubing, to create a perforation 54 (i.e., a hole) through the casing 36. As illustrated in FIG. 6, in certain embodiments, once the perforation 54 is created, the drilling tool 50 may be retracted from the deflecting tool 42 to the surface 20 and a hydraulic jetting tool 56 (i.e., a radial jet cutting tool, in certain embodiments) terminating with a nozzle 58 may be deployed downhole through the drill string 40, such as via a micro-coil or coiled tubing, through the deflection tool 42, and into alignment with or at least partially into the perforation 54. The hydraulic jetting tool 56 may then be operated to discharge a stream 60 of pressurized water or another fluid to create an extended perforation tunnel 22. However, in certain embodiments, instead of utilizing both the drilling tool 50 and the jetting tool 56, a combinatory radial drilling tool (not shown) may be utilized to create both the casing perforation 54 and the extended perforation tunnel 22, such as to minimize or reduce the number of lifting/tripping operations.

[0058] After the extended perforation tunnel 22 is created, the deflecting tool 42 may be reoriented to create another extended perforation tunnel 22 or moved longitudinally along the wellbore 14 to a selected location (e.g., at another formation zone 16). The process may be repeated until the intended number of extended perforation tunnels 22 are created along the entire wellbore 14 or into several formation zones 16.

[0059] Although the deflecting tool 42 is illustrated as being coupled along the drill string 40, in other embodiments, the deflecting tool 42 may be deployed downhole as part of another tool string or otherwise separately from a drill string 40, such as via coiled tubing, and utilized in conjunction with the drilling tool 50 and the jetting tool 56 to create the extended perforation tunnels 22. As described in greater detail herein, stimulation (e.g., fracturing) operations may be performed after the extended perforation tunnels 22 are created. However, fracture or other stimulation treatment operations may be performed in one or more of the formation zones 16 along the wellbore 14 before creating extended perforation tunnels 22 in one or more subsequent formation zones 16.

[0060] It is to be understood that other downhole tools may be utilized to create the extended perforation tunnels 22 within the scope of the present disclosure. For example, FIG. 7 is a schematic sectional view of a portion of a laser cutting tool 62 positioned within a wellbore 14 and operable to create extended perforation tunnels 22 extending from the wellbore 14. In certain embodiments, the laser cutting tool 62 may be conveyed longitudinally along the wellbore 14 (e.g., via coiled tubing 64). After an intended longitudinal position is reached, a portion of the laser cutting tool 62 including a laser emitting port 66 (e.g., optical opening) may be rotated with respect to the wellbore 14, as indicated by arrow 68, to rotatably align or orient the laser emitting port 66 in an intended direction (e.g., a substantially vertical direction). After the intended longitudinal position and rotational orientation are established, the laser cutting tool 62 may be operated to emit a laser beam 70 to create the extended perforation tunnel 22. After the extended perforation tunnel 22 is created, the laser cutting tool 62 may be reoriented to create another extended perforation tunnel 22, or moved longitudinally along the wellbore 14 to a subsequent selected location (e.g., at another formation zone 16), and the process is repeated until the intended number of extended perforation tunnels 22 are created along the entire wellbore 14 or into several formation zones 16.

[0061] Subterranean formations containing the wellbore systems described herein are confined and under stress. FIG. 8 illustrates a three-dimensional element of a subterranean formation 12 having X-Y-Z coordinates and being subjected to local stresses. The element of subterranean formation 12 is also illustrated with a portion of an extended perforation tunnel 22 extending therethrough. As illustrated, the stresses imparted to the element of subterranean formation 12 may be divided into three principal stresses, namely, a vertical stress 72, a minimum horizontal stress 74, and maximum horizontal stress 76. These stresses 72, 74, 76 are normally compressive, anisotropic, and nonhomogeneous, which means that the stresses on the formation 12 are not equal and vary in magnitude on the basis of direction, which controls pressure operable to create and propagate a fracture, the shape and vertical extent of the fracture, the direction of the fracture, and the stresses trying to crush and/or embed a propping agent during production. A hydraulic fracture will propagate along a direction of maximum horizontal formation stress 76 or along a plane 78 (or another parallel plane) of maximum horizontal formation stress 76 (along a plane 78 perpendicular to the minimum horizontal stress 74). The direction of maximum formation stress 76 may be measured while drilling or otherwise creating a subterranean bore, for example, via an acoustic or nuclear logging while drilling tools. The resulting measurements may then be used to select directions of the wellbore 14 and the extended perforation tunnels 22 for optimal productivity.

[0062] Accordingly, as the hydraulic fractures propagate along the plane 78 of maximum horizontal formation stress 76, extended perforation tunnels 22 may be created extending along (i.e., in alignment with, in a direction of) a plane comprising the maximum horizontal formation stress 76. Such orientation of the extended perforation tunnel 22 may result in a hydraulic fracture originating at the extended perforation tunnel 22 propagating longitudinally along the extended perforation tunnel 22. As illustrated in FIG. 8, because a hydraulically-induced fracture may propagate along the plane of maximum horizontal stress 76, at least a portion of the extended perforation tunnel 22 may be created at an angle 80 with respect to the true vertical 82 such that the extended perforation tunnel 22 extends along (i.e., is aligned with, extends in a direction 84 along) the plane 78 (along the X-Y plane) and not such that the extended perforation tunnel 22 extends through, across, or diagonally to the plane 78 (along the Y-Z plane). Such orientation 84 of the extended perforation tunnel 22 may result in a hydraulic fracture propagating longitudinally along the extended perforation tunnel 22 (e.g., not diagonally across the extended perforation tunnel 22), facilitating longitudinal and, thus, optimal fluid connection between the extended perforation tunnel 22 and the fracture.

[0063] The drilling and fracturing methods described herein may facilitate substantial production and efficiency gains in hydraulic fracturing operations. For example, use of the extended perforation tunnels 22 described herein may substantially improve the efficiency of production, such as by promoting production from a greater number of sedimentary layers in the formation 12. Creating these extended perforation tunnels 22 from one or more wellbores 14 may also facilitate substantial production increase to be achieved. Moreover, the embodiments described herein permit creation of well systems 10 that include a plurality of wellbores 14, each including a corresponding plurality of extended perforation tunnels 22 resulting in production magnification.

[0064] FIG. 9 is a schematic sectional view of at least a portion of an example wellbore system 86 that includes a substantially vertical wellbore portion 88 and a plurality of extended perforation tunnels 22 extending from such substantially vertical wellbore portion 88 through a casing 36 and one or more formation zones 16 of a subterranean formation 12. As illustrated, in certain embodiments, the extended perforation tunnels 22 may extend at selected angles 90, 92 with respect to the substantially vertical wellbore portion 88 and/or a true vertical direction 94 and/or a true horizontal direction 96. For example, assuming that the wellbore system 86 is created in a three-dimensional space X-Y-Z, one or more of the extended perforation tunnels 22 may deviate or otherwise extend from the substantially vertical wellbore portion 88, along the X- Y plane and/or the Y-Z plane, at angles 92 ranging between about -45 degrees and about 45 degrees from the true horizontal 96 (between about 45 degrees and about 135 degrees with respect to the substantially vertical wellbore portion 88 and/or the true vertical 94). However, in other embodiments, angles 92 that are greater than -45 and 45 degrees from the true horizontal 96 are also within the scope of the present disclosure, resulting in extended perforation tunnels 22 that may be substantially vertical or closer to the true vertical 94 than to the true horizontal 96. Furthermore, in other embodiments, one or more of the extended perforation tunnels 22 may also extend from the substantially vertical wellbore portion 88 and/or the true vertical 94 along the X- Z plane at any angle 90 (i.e., between zero and 360 degrees) or in any azimuthal direction 98 around the substantially vertical wellbore portion 88 and/or the true vertical 94. For example, in certain embodiments, the extended perforation tunnels 22 may be created to extend from the substantially vertical wellbore portion 88 in a direction along or aligned with a plane of maximum horizontal formation stress (e.g., along direction 84 and plane 78, as illustrated in FIG. 8), which may result in a hydraulic fracture propagating longitudinally along the extended perforation tunnels 22. However, in other embodiments, the extended perforation tunnels 22 may be created to extend from the substantially vertical wellbore portion 88 in a direction that is transverse (i.e., perpendicular) to the plane of maximum horizontal formation stress, which may result in hydraulic fractures propagating transversely with respect to the extended perforation tunnels 22.

[0065] The present disclosure is further directed to enhancing hydrocarbon fluid production by controlling the formation of fracture initiation regions via the extended perforation tunnels 22 described herein. For example, in certain embodiments, production of well fluid is promoted by providing or performing an operation in a borehole 14 positioned proximate a stimulation zone 30. For example, in certain embodiments, the borehole 14 may be a vertical or a deviated (e.g., at least partially horizontal) borehole 14 positioned along or through the stimulation zone 30. In certain embodiments, at least one extended perforation tunnel 22 may be oriented to extend from the borehole 14 at least partially into the stimulation zone 30. In addition, as described in greater detail herein, in certain embodiments, each extended perforation tunnel 22 may have at least one fracture initiation region to facilitate initiation of hydraulic fractures at a desired location during a stimulation operation. For example, the stimulation operation may include pumping fracturing fluid 34 under pressure through the borehole 14 and the at least one extended perforation tunnel 22.

[0066] In addition, in certain embodiments, orientation of the at least one extended perforation tunnel 22 in the formation 12 may be used to control the angle between the direction of fracture propagation and the extended perforation tunnel 22. As a non-limiting example, in certain embodiments, aligning an extended perforation tunnel 22 with maximum horizontal stress may facilitate creation of a hydraulic fracture(s) initiated and propagating along the extended perforation tunnel 22. As such, in certain embodiments, the geometry of the extended perforating tunnels 22 in selected zones may be adjusted to facilitate fracture initiation in such zones, as described in greater detail herein. During the subsequent fracturing treatment, fracture initiation regions of the extended perforation tunnel geometry may help control the location of created fractures.

[0067] Creation of fracture initiation regions along each extended perforation tunnel 22 provides greater predictability with respect to the location and number of fractures created in the surrounding formation/stimulation zone. In general, relative unpredictability of both location and number of fractures tends to increase the risk of a fracturing operation not proceeding according to a pre-defmed plan due to, for example: high fluid losses into the formation 12; competition between created hydraulic fractures resulting in narrow fracture width or reduced number of fractures; and/or lower than planned fluid flow rate into each fracture because of a high number of fractures.

[0068] The embodiments described herein facilitate control over fracture initiation along extended perforation tunnels 22, thereby overcoming these drawbacks of conventional systems. For example, the greater control over fracture initiation reduces the operational risks, and allows for optimization of the completion program in a manner providing better zonal coverage. More specifically, the embodiments described herein are configured to adjust the geometry of the extended perforation tunnels 22 at certain locations to, for example, simplify fracture initiation at specific zones/locations.

[0069] Referring generally to FIG. 10, an example of one of the extended perforation tunnels 22 is illustrated. In the illustrated example, the extended perforation tunnel 22 is created with a plurality of fracture initiation regions 100. In certain embodiments, the fracture initiation regions 100 may have various configurations, but the illustrated example provides fracture initiation regions 100 in the form of an enlarged extended perforation tunnel diameters 102 at specific locations along the extended perforation tunnel 22.

[0070] As illustrated in FIG. 11, in certain embodiments, enlarging the diameter 102 of the extended perforation tunnel 22 at the fracture initiation regions 100 may be achieved through deployment of a jetting nozzle 104, which may be part of a bottom hole assembly 106 in certain embodiments. In certain embodiments, the jetting nozzle 104 may have a first set of jetting holes 108 oriented to create the extended perforation tunnel 22 and a second set of jetting holes 110 oriented laterally to apply a jetting action on the walls 112 of the created extended perforation tunnel 22. For example, in certain embodiments, the jetting nozzle 104 may be stopped at predefined locations along the extended perforation tunnel 22 for a longer period of time so as to create each enlarged diameter 102 via high pressure flow through jetting holes 110. In certain embodiments, the jetting nozzle 104 may be stopped to create the predefined fracture initiation regions 100 while pulling out of the extended perforation tunnel 22 after the extended perforation tunnel 22 is created. In addition, in certain embodiments, the extended perforation tunnel 22 may be enlarged in at least the tip 114 of the extended perforation tunnel 22 (see, e.g., FIG. 10).

[0071] However, enlarged extended perforation tunnel diameters 102 may be created by techniques other than jetting techniques, such as by increasing the diameter of a cutting head (e.g., drill bit) at selected fracture initiation regions 100 when utilizing drilling techniques. In addition, in certain embodiments, a reamer may be used to create the enlarged extended perforation tunnel diameters 102. For example, a drilling bottom hole assembly (BHA) may include a drill bit and a reamer, which may be activated at certain locations in the extended perforation tunnel 22 (e.g., by pumping fluid through the drilling BHA when pulling from the extended perforation tunnel 22). In other embodiments, the enlarged extended perforation tunnel diameters 102 may be created by jetting solids through the nozzle 104 (or through a drill bit) when placed at selected locations along the extended perforation tunnel 22. In other embodiments, the enlarged extended perforation tunnel diameters 102 may be created by injecting acid or other reactive chemicals within the extended perforation tunnel 22 at the selected locations. [0072] In certain embodiments, the fracture initiation regions 100 may be created by creating the extended perforation tunnel 22 or regions of the extended perforation tunnel 22 with non circular cross-sectional areas 116, as illustrated in FIGS. 12-15. The non-circular cross- sectional areas 116 may be created with angles such that the points of the angles form the fracture initiation regions 100, as illustrated by the generally rectangular shape (FIG. 12), generally triangular shape (FIG. 13), generally polygonal (e.g., hexagonal) shape (FIG. 14), and curved sections joined at points (FIG. 15).

[0073] It should be noted that each of the non-circular cross-sectional areas 116 of the fracture initiation regions 100 illustrated in FIGS. 12-15 are characterized as“generally” of the particular shape illustrated. It will be appreciated that the term“generally” is meant to convey that the actual non-circular cross-sectional areas 116 of the fracture initiation regions 100 that are created using the techniques described herein are of the particular shape illustrated, but with relatively minor variances from that particular shape, which may be expected depending on the particular techniques used (e.g., jetting, drilling, and so forth). As such, for example, when referring to shapes of the non-circular cross-sectional areas 116 of the fracture initiation regions 100 as“generally rectangular”, this is meant to convey that the intended shapes of the non circular cross-sectional areas 116 of the fracture initiation regions 100 (e.g., using the particular techniques) are rectangular, but that relatively minor variances (e.g., within 1 inch or so) from being exactly rectangular may be created.

[0074] The cross-sectional shapes 116 of the fracture initiation regions 100 illustrated in FIGS. 12-15 may be created by a variety of techniques, such as a two-step technique in which each extended perforation tunnel 22 is created using drilling or jetting methods as those described in greater detail herein (e.g., with respect to FIGS. 4-7). In certain embodiments, each extended perforation tunnel 22 or portions of the extended perforation tunnel 22 may

subsequently be shaped into the desired cross-sectional shape 116 using, for example, a reamer.

In certain embodiments, however, each extended perforation tunnel 22 may be created with the desired cross-sectional shape 116 in a single run (e.g., a single jetting run with jets oriented to create the desired cross-sectional shape 116 having points oriented in desired directions). For example, in certain embodiments, the fracture initiation regions 100 may be at the points created, and may be oriented along points of weakness in the formation 12, thus making fracture initiation from these points easier. By way of example, in certain embodiments, the non-circular cross- sections 116 of the fracture initiation regions 100 may be oriented in a specific orientation to facilitate fracturing (e.g., with an edge of a triangular cross-sectional area oriented in an upward position toward the horizon along the extended perforation tunnel 22 as but one, non-limiting, example).

[0075] In certain embodiments, the fracture initiation pressure at selected locations can be reduced by orienting the shape of the cross-sectional area 116 such that the points/fracture initiation regions 100 are oriented in a desired direction. As illustrated in FIG. 16, for example, the extended perforation tunnel 22 has a square cross-sectional shape 116 with sides oriented generally horizontally and vertically. Such orientation may work in a variety of formations 12. However, in some formations 12, the fracture initiation pressure at points/fracture initiation regions 100 may be reduced by changing the orientation of the extended perforation tunnel 22 (e.g., by rotating the extended perforation tunnel 45°, as illustrated in FIG. 17) so that at least one of the points/fracture initiation regions 100 aligns in a vertical direction. In this case, the vertical orientation of the upper and lower points/fracture initiation regions 100 may correspond with weak points of the formation 12 and, thus, may result in fracture initiation at a lower pressure. The actual degree of rotation may depend on the characteristics of a given formation 12

[0076] As described in greater detail herein, in certain embodiments, the well system 10 may be stimulated using propped hydraulic fracturing, foamed fracturing, slick water fracturing, acid fracturing, propellant fracturing, fracturing using energetic products, or other stimulation techniques based on creating pressure in at least a portion of the reservoir above the level of the fracturing or fracture initiation pressure of the given formation 12. In certain embodiments, the borehole 14 also may be completed with various types of completion equipment, and the fracturing operation may be performed by pumping fracturing fluid 34 through the completion equipment in the borehole 14. In certain embodiments, the completion techniques may include casing and completing the borehole 14 using an open hole completion, using a multi-stage fracturing completion, and/or using other types of completion equipment. In addition, in certain embodiments, various types of jetting equipment, reamers, and other devices and techniques may be used to create the desired cross-sectional shapes 116 and/or enlarged diameters 102 of extended perforation tunnels 22.

[0077] In certain embodiments, control of the creation of the extended perforation tunnels 22, as well as the creation and the shape of the fracture initiation regions 100 of the extended perforation tunnels 22 may be performed or caused to be performed by a processing device 118 executing coded instructions 120. For example, the processing device 118 may receive information from a wellsite operator and automatically generate and transmit output information to be analyzed by the wellsite operator, and/or operate or cause a change in an operational parameter of one or more pieces of the wellsite equipment described herein. FIG. 18 is a block diagram of at least a portion of a processing device 118 configured to execute instructions 120 to implement the techniques described herein (e.g., to send control signals to the equipment described herein to control the creation of the extended perforation tunnels 22, as well as to control the creation and the shape of the fracture initiation regions 100 of the extended perforation tunnels 22, among other things). The processing device 118 may form at least a portion of one or more electronic devices utilized at the wellsite or located offsite.

[0078] In certain embodiments, the processing device 118 may be in communication with various sensors, actuators, controllers, and other devices of the well system 10. The processing device 118 may be operable to receive coded instructions 120 from human operators and sensor data generated by the sensors, process the coded instructions 120 and the sensor data, and communicate control data to local controllers and/or the actuators to execute the coded instructions 120 to implement at least a portion of the techniques described herein.

[0079] In certain embodiments, the processing device 118 may be or include, for example, one or more processors, special-purpose computing devices, servers, personal computers (e.g., desktop, laptop, and/or tablet computers), personal digital assistants, smartphones, internet appliances, and/or other types of computing devices. In certain embodiments, the processing device 118 may include a processor 122, such as a general-purpose programmable processor. In certain embodiments, the processor 122 may include a local memory 124, and may execute coded instructions 120 present in the local memory 124 and/or another memory device. In certain embodiments, the processor 122 may execute, among other things, the machine-readable coded instructions 120 and/or other instructions and/or programs to implement the techniques described herein. In certain embodiments, the programs stored in the local memory 124 may include program instructions or computer program code that, when executed by the processor 122 of the processing device 118, may cause the well system 10 and/or other devices to perform the techniques described herein. In certain embodiments, the processor 122 may be, include, or be implemented by one or more processors of various types suitable to the local application environment, and may include one or more of general-purpose computers, special-purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as non-limiting examples. Of course, other processors from other families are also appropriate.

[0080] In certain embodiments, the processor 122 may be in communication with a main memory 126, such as may include a volatile memory 128 and a non-volatile memory 130, perhaps via a bus 132 and/or other communication means. In certain embodiments, the volatile memory 128 may be, include, or be implemented by random access memory (RAM), static random access memory (SRAM), synchronous dynamic random access memory (SDRAM), dynamic random access memory (DRAM), RAMBUS dynamic random access memory

(RDRAM), and/or other types of random access memory devices. In certain embodiments, the non-volatile memory 130 may be, include, or be implemented by read-only memory, flash memory, and/or other types of memory devices. In certain embodiments, one or more memory controllers (not shown) may control access to the volatile memory 128 and/or non-volatile memory 130. [0081] In certain embodiments, the processing device 118 may also include an interface circuit 134, which may be, include, or be implemented by various types of standard interfaces, such as an Ethernet interface, a universal serial bus (USB), a third generation input/output (3GIO) interface, a wireless interface, a cellular interface, and/or a satellite interface, among others. In certain embodiments, the interface circuit 134 may also include a graphics driver card. In certain embodiments, the interface circuit 134 may also include a communication device, such as a modem or network interface card to facilitate exchange of data with external computing devices via a network (e.g., Ethernet connection, digital subscriber line (DSL), telephone line, coaxial cable, cellular telephone system, satellite, etc.). In certain embodiments, one or more of the local controllers, the sensors, and the actuators of the well system 10 may be connected with the processing device 118 via the interface circuit 134, such as may facilitate communication between the processing device 118 and the local controllers, the sensors, and/or the actuators.

[0082] In certain embodiments, one or more input devices 136 may also be connected to the interface circuit 134. In certain embodiments, the input devices 136 may permit the human operators to enter the coded instructions 120, such as control commands, processing routines, operational settings and set-points. In certain embodiments, the input devices 136 may be, include, or be implemented by a keyboard, a mouse, a joystick, a touchscreen, a track-pad, a trackball, an isopoint, and/or a voice recognition system, among other examples. In certain embodiments, one or more output devices 138 may also be connected to the interface circuit 134. In certain embodiments, the output devices 138 may be, include, or be implemented by video output devices (e.g., an LCD, an LED display, a CRT display, a touchscreen, etc.), printers, and/or speakers, among other examples. In certain embodiments, the processing device 118 may also communicate with one or more mass storage devices 140 and/or a removable storage medium 142, such as may be or include floppy disk drives, hard drive disks, compact disk (CD) drives, digital versatile disk (DVD) drives, and/or USB and/or other flash drives, among other examples.

[0083] In certain embodiments, the coded instructions 120 may be stored in the mass storage device 140, the local memory 124, and/or the removable storage medium 142. Thus, the processing device 118 may be implemented in accordance with hardware (perhaps implemented in one or more chips including an integrated circuit, such as an ASIC), or may be implemented as software or firmware for execution by the processor 122. In the case of firmware or software, the implementation may be provided as a computer program product including a non-transitory, computer-readable medium or storage structure embodying computer program code (i.e., software or firmware) thereon for execution by the processor 122. In certain embodiments, the coded instructions 120 may include program instructions or computer program code that, when executed by the processor 122, may perform the processes and/or operations described herein.

[0084] The specific embodiments described above have been illustrated by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.

Claims

1. A method, comprising:

creating an extended perforation tunnel from a borehole proximate a stimulation zone so as to extend at least partially into the stimulation zone;

creating at least one fracture initiation region of the extended perforation tunnel to facilitate initiation of one or more desired fractures during a stimulation operation; and

fracturing the stimulation zone by pumping fracturing fluid under pressure into and through the extended perforation tunnel.

2. The method of claim 1, wherein creating the at least one fracture initiation region of the extended perforation tunnel comprises creating a plurality of enlarged diameter fracture initiation regions.

3. The method of claim 2, comprising creating the plurality of enlarged diameter fracture initiation regions using jetting techniques.

4. The method of claim 3, comprising creating the plurality of enlarged diameter fracture initiation regions by injecting using solids-containing fluids.

5. The method of claim 2, comprising creating the plurality of enlarged diameter fracture initiation regions by enlarging a diameter of a drill bit or using a reamer.

6. The method of claim 2, comprising creating the plurality of enlarged diameter fracture initiation regions after creating the extended perforation tunnel.

7. The method of claim 2, wherein the plurality of enlarged diameter fracture initiation regions comprises at least one enlarged diameter fracture initiation region having a noncircular cross-sectional shape.

8. The method of claim 7, wherein the non-circular cross-sectional shape is a generally rectangular cross-sectional shape, a generally triangular cross-sectional shape, or a generally polygonal cross-sectional shape.

9. The method of claim 7, wherein the non-circular cross-sectional shape comprises curved sections joined at points.

10. The method of claim 1, wherein fracturing the stimulation zone comprises pumping the fracturing fluid under pressure through completion equipment deployed in the borehole.

1 1. The method of claim 1 , wherein fracturing the stimulation zone comprises pumping the fracturing fluid under pressure through the borehole alone.

12. A system, comprising:

a borehole positioned proximate a stimulation zone in a formation; and an extended perforation tunnel extending from the borehole, the extended perforation tunnel being positioned at least partially in the stimulation zone, and the extended perforation tunnel having at least one fracture initiation region to facilitate initiation of fractures at a desired location and in a desired direction during a stimulation operation in which fracturing fluid is pumped under pressure into the extended perforation tunnel.

13. The system of claim 12, wherein the at least one fracture initiation region comprises a zone of the extended perforation tunnel with an enlarged tunnel diameter.

14. The system of claim 12, wherein the at least one fracture initiation region comprises a zone of the extended perforation tunnel with a non-circular cross-sectional shape of the extended perforation tunnel.

15. The system of claim 14, wherein the at least one fracture initiation region comprises a zone of the extended perforation tunnel with a generally rectangular cross-sectional shape of the extended perforation tunnel, a generally triangular cross-sectional shape of the extended perforation tunnel, or a generally polygonal cross-sectional shape of the extended perforation tunnel.

16. The system of claim 14, wherein the at least one fracture initiation region comprises a zone of the extended perforation tunnel with a non-circular cross-sectional shape of the extended perforation tunnel having points oriented along weak regions of the formation.

17. The system of claim 12, wherein the at least one fracture initiation region is created using jetting techniques.

18. The system of claim 12, wherein the at least one fracture initiation region is created by enlarging a diameter of a drill bit or using a reamer.