CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present document is based on and claims priority to U.S. Provisional

Application Serial No.: 61/863,163, filed August 7, 2013, which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore is drilled, various forms of well completion components may be installed to control and enhance efficiency of producing the various fluids from the reservoir. One piece of equipment which may be installed is a casing which may be deployed in a corresponding, drilled borehole. In multilateral wells, multiple casings may be run in their corresponding boreholes. The boreholes and casings are oriented to avoid interfering with each other.

SUMMARY

[0003] In general, a methodology and system are provided for facilitating running of casing strings in, for example, a multilateral well or system of wells. A conductor tube may be placed into a hole formed in a seabed. A plurality of oriented casings is deployed in the conductor tube and the oriented casings are arranged with a specific exit angle and azimuthal orientation. The orientation of each oriented casing is used to direct a corresponding drilling of a borehole and placement of a casing in the borehole in a manner which does not interfere with other boreholes and casings. [0004] However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

[0006] Figure 1 is a schematic illustration of an example of a platform used in cooperation with a plurality of conductor tubes for constructing a multilateral well, according to an embodiment of the disclosure;

[0007] Figure 2 is a schematic illustration of an example of a conductor tube having internal oriented casings, according to an embodiment of the disclosure;

[0008] Figure 3 is a schematic illustration of an example of a portion of an orientation system for orienting a plurality of oriented casings in a conductor tube, according to an embodiment of the disclosure;

[0009] Figure 4 is an illustration of an example of a conductor tube extending into a well bay of a well platform, according to an embodiment of the disclosure;

[0010] Figure 5 is an illustration of an example of a module used in forming a conductor tube with internal oriented casings, according to an embodiment of the disclosure; [0011] Figure 6 is a cross-sectional illustration of the module illustrated in Figure

5, according to an embodiment of the disclosure;

[0012] Figure 7 is a cross-sectional view of a module having dual oriented casings, according to an embodiment of the disclosure;

[0013] Figure 8 is an illustration of an example of a centralizer plate having an alignment pin which may be employed to align sequential modules, according to an embodiment of the disclosure;

[0014] Figure 9 is an illustration of an example of an alignment hole for receiving an alignment pin to align sequential modules, according to an embodiment of the disclosure;

[0015] Figure 10 is an illustration of an example of sequential alignment pins of sequential modules to ensure a desired orientation of the internal oriented casings, according to an embodiment of the disclosure;

[0016] Figure 11 is an illustration of an example of a conductor tube installed in a hole in a seabed, according to an embodiment of the disclosure;

[0017] Figure 12 is an illustration of an enlarged portion of the conductor tube illustrating check valves disposed in the internal oriented casings, according to an embodiment of the disclosure;

[0018] Figure 13 is an illustration of sequential modules of oriented casings being assembled in a desired alignment, according to an embodiment of the disclosure; and

[0019] Figure 14 is an illustration of a multilateral well in which a plurality of lateral boreholes and corresponding casings have been properly oriented in a non- interfering arrangement, according to an embodiment of the disclosure. DETAILED DESCRIPTION

[0020] In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0021] The present disclosure generally relates to a system and methodology for facilitating running of casing strings in, for example, a multilateral well or system of multilateral wells. A conductor tube may be placed into a hole formed in a seabed. A plurality of oriented casings is arranged in the conductor tube and the oriented casings have a specific exit angle and azimuthal orientation. In some embodiments, the system and methodology facilitate running of dual casing strings from a dual wellhead and through a conductor tube to achieve specific exit angles and azimuthal orientations. The orientation of each oriented casing is used to direct a corresponding drilling of a borehole and placement of a casing in the borehole in a manner which does not interfere with other boreholes and casings. The orientation enables use of a plurality of the conductor tubes in cooperation with a platform by controlling the orientation of the multiple boreholes and casings of the multilateral well.

[0022] In a specific example, a platform escape strategy is established by orienting dual casing strings from dual wellheads located along a platform. The technique enables the dual casing strings associated with each dual wellhead to be oriented and guided using prefabricated conductor hardware. The prefabricated conductor hardware, e.g. conductor tube related modules, provides control over the specific exit angle and azimuthal orientation of oriented pairs of casings disposed in corresponding conductor tubes which extend down to a seabed. [0023] Referring generally to Figure 1, an embodiment of a multilateral well system 20 is illustrated. In this embodiment, the well system 20 comprises a platform 22 having a plurality of platform slots 24 for corresponding wellheads 26. Each wellhead 26 may correspond with a lateral wellbore or a plurality of lateral wellbores accessed through oriented casings 28. In some applications, the wellheads 26 may comprise dual wellheads which each correspond with a pair of oriented casings 28 extending to lateral boreholes formed at a subsea location. In a variety of applications, the platform 22 may comprise a gravity based structure constructed for use in hydrocarbon production operations at suitable offshore locations.

[0024] In the example illustrated, numerous wellheads 26 are associated with the platform 22, and the oriented casings 28 corresponding with each wellhead 26 are oriented to avoid interference with other boreholes drilled into the subsea formation and lined with borehole casings. Each group, e.g. pair, of oriented casings 28 associated with a corresponding wellhead 26 is oriented with a specific exit angle and azimuthal orientation so as to avoid interference with the boreholes and borehole casings from other oriented casings 28 associated with other corresponding wellheads 26. The number and arrangement of platform slots 24 in a given platform 22 may vary depending on the application and may comprise, for example, 10 to 30 slots. In the specific example illustrated, platform 22 comprises 20 slots which each have a dual wellhead to create a multilateral well having, for example, 40 lateral boreholes. It should be noted, however, that the system and methodology described herein for orienting boreholes can be used both with multiple wellheads or with a single grouping of oriented casings associated with a single wellhead 26.

[0025] Referring generally to Figure 2, an example of a structure 30 for orienting boreholes 32 of lateral wells is illustrated. In this example, a conductor tube 34 extends down from platform 22 and into a hole 36 which may be drilled or otherwise formed in a seabed 38. In many applications, the conductor tube 34 is positioned in the hole 36 in a generally vertical orientation and extends upwardly to platform 22. A plurality of the oriented casings 28 is arranged within the conductor tube 34 such that the oriented casings 28 are positioned in a desired orientation. For example, the oriented casings 28 may be arranged so that lower, outlet ends 40 of the oriented casings 28 have specific exit angles and a desired azimuthal orientation, as illustrated in Figure 3. The specific exit angles and azimuthal orientations are predetermined so that the boreholes 32 formed beneath the oriented casings 28 are properly oriented to avoid interference with other boreholes of the multilateral well 20.

[0026] Depending on the application, a variety of orientation mechanisms 42 may be employed to orient the casings 28 and the corresponding outlet ends 40 with the specific, desired exit angles and azimuthal orientations. For example, various orientation mechanisms 42 may be constructed to secure the oriented casings 28 in a desired relationship and to affix the oriented casings 28 within the surrounding conductor tube 34 at the appropriate orientation. As discussed in greater detail below, the plurality of oriented casings 28 may be assembled in sequentially oriented and coupled modules to ensure that the oriented casings 28 and their corresponding lower outlet ends 40 are properly oriented for each wellhead 26.

[0027] Once the oriented casings 28 and the corresponding conductor tube 34 are properly oriented and placed in hole 36, boreholes 32 may be drilled. The drilling of boreholes 32 is at least initiated along a desired trajectory due to the exit angle and azimuthal orientation of the oriented casings 28 through which the drill string is routed. After drilling the boreholes 32, appropriate borehole casings 44 may be delivered down through oriented casings 28 and disposed in the corresponding boreholes 32. The borehole casings 44 may be cemented in place within their corresponding boreholes 32.

[0028] Referring generally to Figure 4, a specific embodiment is illustrated in which the conductor tube 34 extends down into hole 36 from a well bay 46 of platform 22. In this example, the conductor tube 34 is oriented generally vertically between the well bay 46 and the seabed 38. Additionally, this example illustrates the plurality of oriented casings 28 as comprising two oriented casings 28 positioned within conductor tube 34 and connected with wellhead 26 in the form of a dual wellhead. Depending on the application, the lengths, diameters, and configurations of the various system components may vary. In a specific example using standard pipe diameters, the hole 36 may be drilled as a 42 inch hole and the conductor tube 34 may comprise a 36 inch diameter conductor pipe. In this example, the oriented casings 28 may comprise 16 inch diameter casings and the borehole casings may comprise 13 and 3/8 inch borehole casings. However, other applications may use conductor tubes ranging from 20 to 50 inches in diameter with oriented casings ranging from 6 to 24 inches in diameter that cooperate with borehole casings from 4 to 22 inches in diameter. Additionally, it should be noted that many other diameters and sizes may be used depending on the parameters of a given application.

[0029] In some applications, the oriented casings 28 may be assembled via modules 48 which are sequentially aligned to position the oriented casings 28 so as to extend along a desired orientation and to provide the desired exit angle and azimuthal orientation. An example of module 48 is illustrated in Figures 5-7 and comprises a pair of the oriented casings 28 positioned in the surrounding conductor tube 34. Each module 48 may comprise a section of the conductor tube 34 with corresponding sections of the oriented casings 28 such that the sections of conductor tube 34 and corresponding sections of oriented casings 28 are stacked or coupled together in a specific sequence that provides the desired orientation of the internal oriented casings 28. However, the modules 48 also may be formed as sections of oriented casings 28 which are stacked within a corresponding conductor tube 34. Additionally, the modules 48 may be formed as sections of oriented casings 28 located in corresponding tubing sections which are then positioned and oriented within the surrounding conductor tube 34. Other configurations of modules 48 also may be used to provide the desired orientation of oriented casings 28 for a given application.

[0030] In the example illustrated, each module 48 comprises sections of the oriented casings 28 held within a corresponding section of the conductor tube 34 at a desired location with a plurality of plates or centralizers 50. The plates or centralizers 50 may be welded or otherwise connected along an interior of the conductor tube 34 so as to provide the desired orientation of casings 28 for a given module 48. The sequential modules 48 may be connected together by welding, friction fits, sealed insertion fits, threaded couplers, and/or by other suitable fasteners and/or fastening techniques.

Sequential modules 48 are oriented with respect to each other via suitable orientation features 52 which, in some applications, are coupled with the centralizers 50 located at the longitudinal ends of the module 48. Each module 48 also may be marked with an identifier 54, such as a number or other indicator, which ensures that the appropriate module 48 is joined with the appropriate next sequential module 48 so as to ensure the desired orientation of oriented casings 28 along the entire conductor tube 34.

[0031] As further illustrated in Figures 8 and 9, an example of orientation features

52 comprises an orientation pin 56 (see Figure 8) and a corresponding orientation opening or hole 58 (see Figure 9). In this example, the orientation pin 56 extends from one of the centralizers 50 located at a longitudinal end of one module 48 and is received by a corresponding orientation hole 58 located at a corresponding longitudinal end of the next sequential module 48. The orientation pin 56 and orientation hole 58 ensure that the oriented casings 28 of sequential modules 48 are properly aligned once the orientation pin 56 is inserted into the corresponding orientation hole 58. As further illustrated, the centralizers 50 also may be constructed with openings 60 sized for receipt of oriented casings 28.

[0032] In some applications, the sequential modules 48 are constructed to gradually rotate the orientation of the plurality, e.g. pair, of oriented casings 28 along the conductor tube 34. This gradual rotation of the orientation is illustrated schematically in Figure 10 which shows the differing angular positions of the pin 56 and openings 60 from one module 48 to the next. The overall alignment of oriented casings 28 and the desired exit angle and azimuthal orientation at lower outlet ends 40 may be achieved by coupling the appropriate modules 48 according to their indicators 54.

[0033] Referring generally to Figures 11 and 12, an embodiment of the conductor tube 34 and internal oriented casings 28 is illustrated. In this embodiment, sequential modules 48 are coupled together sequentially as illustrated in Figure 13. Additionally, the sequential modules 48 may be oriented via orientation pins 56 and corresponding orientation holes 58 located at the ends of each module 48 to ensure proper engagement of sequential modules once they are coupled together according to the identifiers 54. In this example, a check valve 62 is located in each oriented casing 28. For example, an individual check valve 62 may be positioned proximate a lower end, e.g. proximate lower outlet end 40, of each oriented casing 28. The check valves 62 are oriented to allow down flow of fluid into the hole 36, as illustrated by arrows 64, while restricting or blocking up flow of fluid into the oriented casings 28. The check valves 62 are useful in cementing operations, e.g. cementing of hole 36, while blocking unwanted upflow of cement into the oriented casings 28. It should be noted that in certain applications a check valve 62 may be omitted from one or more of the oriented casings 28. For example, one of the oriented casings 28 may be used for conducting the outward flow of cement as indicated by arrows 64 without having a check valve 62. However, the other oriented casing or casings 28 comprise the check valve(s) 62 to restrict or block the up flow of cement into the other oriented casing or casings.

[0034] In an operational example, the hole 36 is initially drilled into the seabed 38 generally below the region of platform 22. The conductor tube 34 is then dropped down into the hole 36. A plurality of oriented casings 28, e.g. two oriented casings 28, is arranged and oriented within the conductor tube 34 (see Figure 11). As discussed above, the pair of oriented casings 28 may be properly oriented within the corresponding conductor tube 34 during assembly of the conductor tube 34 and the internal oriented casings 28 via sequential modules 48 (see Figure 13). However, in other applications, the modules 48 may comprise internal modules formed separately from the conductor tube 34 and comprising sections of oriented casings 28 in combination with centralizers 50 and/or a surrounding support tube. In this latter embodiment, the internal modules 48 would be assembled and moved down through the conductor tube 34. In some applications, the modules 48 are formed with sections of conductor tube 34 and corresponding centralizers 50, and the oriented casings 28 are inserted down through openings 60 into conductor tube 34 in a manner similar to inserting straws down into a tube.

[0035] After proper placement/arrangement of the oriented casings 28 within conductor tube 34, a cementing operation may be performed by cementing down through one of the oriented casings 28. The cement flows down through the check valve 62 (see Figures 11 and 12) of the oriented casing 28 which is used for conducting the flow of cement (or down through an open, oriented casing 28 if no check valve 62 is employed in the oriented casing 28 used to deliver the cement). However, the check valves 62 collectively block up flow of the cement into the other oriented casing or casings 28. The cement flows down into hole 36 and fills the hole 36 up toward, to, or past the lower end of the conductor tube 34 depending on the specifics of a given application.

[0036] Once this initial cementing operation is completed, the boreholes 32 may be drilled. The drilling of each borehole 32 is initiated along a specific predetermined exit angle and azimuthal orientation due to the orientation of the corresponding oriented casing 28. As described above, the oriented casings 28 in each conductor tube 34 are properly oriented to provide the specific, predetermined exit angle and azimuthal orientation. The exit angles and azimuthal orientations are enabled by the appropriate construction and orientation of sections of the oriented casings 28 via assembly of the proper sequence of modules 48 (or by using other suitable orientation mechanisms 42). If check valves 62 are employed, the check valves 62 may be removed by drilling through the check valves or by other suitable removal techniques. Following drilling of the boreholes 32, borehole casings 44 are placed along the boreholes 32 and again are routed out of the corresponding oriented casings 28 with the appropriate, predetermined exit angle and azimuthal orientation. After the borehole casings 44 are properly placed in the corresponding boreholes 32, the borehole casings 44 may be cemented in place by, for example, performing a cementing operation down through one or more of the oriented casings 28. [0037] If more than one conductor tube 34 is positioned, the oriented casings 28 in each conductor tube 34 may be oriented collectively to provide unique exit angles and azimuthal orientations with respect to other oriented casings 28 associated with other conductor tubes 34. For example, certain applications employ platform 22 with multiple platform slots 24, as illustrated in Figure 1, to enable construction of a multilateral well. Each platform slot 24 is associated with the corresponding wellhead 26, e.g. a

corresponding dual wellhead, having conductor tube 34 and internal oriented casings 28 extending below the corresponding wellhead 26 to the appropriate hole 36 formed in seabed 38.

[0038] The internal oriented casings 28 associated with each platform slot 24 and corresponding wellhead 26 are uniquely oriented with respect to exit angle and azimuthal orientation with respect to the numerous other internal oriented casings 28. This enables the drilling of the multiple associated boreholes 32 and placement of the multiple corresponding borehole casings 44 in a non-interfering pattern, as illustrated in Figure 14.

[0039] As described herein, the overall multilateral well system 20 may comprise many types of systems and components for use in a variety of subterranean well applications. For example, various types of platforms 22, platform slots 24, and wellheads 26 may be employed. The number and arrangement of platform slots 24 and wellheads 26 also may change from one application to another. Additionally, the materials and configurations of the various conductor tubes 34, oriented casings 28, borehole casings 44, orienting mechanisms 42/52, and/or other components may be adjusted according to the parameters of a given application.

[0040] Additionally, the processes employed may be adjusted according to the environment and/or parameters of a given well application. For example, various techniques may be used for drilling hole 36 and boreholes 32. Similarly, a variety of equipment and techniques may be employed for performing the cementing operations both within hole 36 and along boreholes 32. A number of other and/or additional components may be used to facilitate drilling, cementing, testing, and/or production operations. Many types of configurations also may be used for modules 48 to facilitate assembly of specific sequential modules which ensure that internal oriented casings 28 provide the proper predetermined exit angle and azimuthal orientation so as to enable formation of multiple non-interfering boreholes and associated borehole casings.

[0041] Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.