CHOKING ORIFICE COLLAR FOR CASING FLOATATION OPERATIONS

[0001] The present disclosure relates generally to wellbore operations, and more particularly, to the use of a choking orifice collar in a casing string floatation system to reduce the rate of fluid flow into the floatation subassembly during deactivation.

[0002] It may be beneficial to drill some wellbores to great depths. In horizontal and deviated wellbores, running the casing to these extended depths may result in increasing friction between the wellbore walls and the casing string. As the total depth increases, the influence of the drag on the casing string in the horizontal or lateral section of the wellbore may become so great that the drag impedes further progress of the casing string in the wellbore. Floatation of the casing string may reduce the drag on the casing string and allow the total depth of the casing string in the horizontal wellbore to be extended. Floatation of the casing string may be accomplished with a floatation subassembly. A floatation subassembly is a section of the casing string comprising a buoyancy chamber that is used to make a portion of the casing string buoyant. When the casing has landed at total depth, the floatation subassembly may be deactivated resulting in an internal pressure change within the casing string. This change in internal pressure may have a negative impact on some associated casing tools that may be sensitive to sudden pressure shifts.

[0003] The use of floatation subassemblies is an important part of certain wellbore operations. The present disclosure provides improved casing strings that utilize choking orifice collars to reduce the rate of fluid flow into the floatation subassembly during deactivation.

[0008] The illustrated figures are only exemplary and are not intended to assert or imply any limitation with regard to the environment, architecture, design, or process in which different examples may be implemented.

[0009] The present disclosure relates generally to wellbore operations, and more particularly, to the use of a choking orifice collar in a casing string floatation system to reduce the rate of fluid flow into the floatation subassembly during deactivation.

[0010] In the following detailed description of several illustrative examples, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific examples that may be practiced. These examples are described in sufficient detail to enable those skilled in the art to practice them, and it is to be understood that other examples may be utilized, and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the spirit or scope of the disclosed examples. To avoid detail not necessary to enable those skilled in the art to practice the examples described herein, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the illustrative examples are defined only by the appended claims.

[0011] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the present specification and associated claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the examples of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. It should be noted that when “about” is at the beginning of a numerical list, “about” modifies each number of the numerical list. Further, in some numerical listings of ranges some lower limits listed may be greater than some upper limits listed. One skilled in the art will recognize that the selected subset will require the selection of an upper limit in excess of the selected lower limit.

[0012] In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” Unless otherwise indicated, as used throughout this document, “or” does not require mutual exclusivity.

[0013] The terms “uphole” and “downhole” may be used to refer to the location of various components relative to the bottom or end of a well. For example, a first component described as uphole from a second component may be further away from the end of the well than the second component. Similarly, a first component described as being downhole from a second component may be located closer to the end of the well than the second component.

[0014] The terms “upstream” and “downstream” may be used to refer to the location of various components relative to one another in regards to the flow of a sample through said components. For example, a first component described as upstream from a second component will encounter a sample before the downstream second component encounters the sample. Similarly, a first component described as being downstream from a second component will encounter the sample after the upstream second component encounters the sample.

[0015] The present disclosure relates generally to wellbore operations, and more particularly, to the use of a choking orifice collar in a casing string floatation system to reduce the rate of fluid flow into the floatation subassembly during deactivation. Advantageously, the casing string floatation system disclosed herein may be used to extend the total depth for casing insertion in a horizontal wellbore while pressure-sensitive casing tools are present. The casing string floatation system utilizes a choking orifice collar within the casing string to provide a temporary choke along the interior length of the casing string. The choking orifice collar is a collar which chokes the fluid flow through the casing string by forcing it through an orifice having a reduced diameter relative to the interior diameter of the casing string. When the floatation subassembly is deactivated, the rate of fluid flow into the floatation subassembly is reduced as the choking orifice collar chokes the volume of fluid that can flow through its orifice. This reduction in fluid flow dampens the shift in pressure in the casing string that is induced by the deactivation of the floatation subassembly. As a further advantage, multiple choking orifice collars may be used as needed to provide increased choking of the flowing fluid in the casing string. An additional advantage is that the multiple choking orifice collars may be placed along the interior of the casing string at key location to choke the fluid flow in the locations deemed most important for dampening the impact of a pressure shift on associated casing tools. As a still further advantage, the orifice of the choking orifice collars may be shaped and sized to provide a tailored reduction in the flow rate of the fluid along the length of the casing string. Additionally, after the deactivation of the floatation subassembly, the choking orifice collars are configurable to be removed from the interior of the casing string to restore the full inner diameter of the casing string along its length. Moreover, the casing string floatation system may be used in conjunction with a variety of casing tools including liners, liner hangers, wiper plugs, cementing collars, annular packers and other casing tools that may be actuated by or sensitive to shifts in a casing string's internal pressure. One other advantage is that the choking orifice collars may be used with a variety of existing casing strings and wellbore equipment.

[0016] The casing string floatation system comprises a casing string extending from the surface into the wellbore. The casing string comprises a plurality of casing joints which are coupled together using couplings such as coupling pipe or any other suitable equipment for linking the coupling joints in a string. The casing string further comprises a casing shoe disposed at the bottom or downhole terminal end of the casing string to guide the casing string as it is run into the wellbore. The casing string also comprises a floatation subassembly disposed uphole of the casing shoe and generally extending along a length of the horizontal or lateral portion of the wellbore. In some examples, the floatation subassembly may be disposed proximate or even adjacent to the casing shoe. The floatation subassembly comprises at least one casing joint that functions as a buoyant chamber and may be filled with air or a fluid with a sufficiently low density to float this portion of the casing string in the wellbore. Floatation of a portion of the casing string may reduce drag on the casing string as it is pushed to its total depth in the wellbore. When the casing string has run to its total depth, the buoyant chamber of the floatation subassembly is filled with a fluid to deactivate the floatation subassembly such that the casing string is no longer floated in the horizontal portion of the wellbore.

[0017] The casing string floatation system further comprises a removable plug disposed within the interior of the casing string. The removable plug defines the uphole terminal end of the floatation subassembly such that casing string portion downhole of the plug comprises the buoyant chamber of the floatation subassembly, and which is sealed off from the casing string portion uphole of the removable plug. The casing string portions uphole of the removable plug may be filled with a fluid different from the air or low-density fluid in the buoyant chamber. This fluid may be a brine or any such fluid sufficient for adding weight to the vertical portion of the casing string to assist in driving the casing string into the horizontal portion of the wellbore. When the casing string reaches its total depth, the floatation subassembly is deactivated. The removable plug is removed to allow fluid flow into the floatation subassembly. Generally, the removable plug is made of a frangible material such as glass or ceramic and is fractured by applying hydraulic pressure to the uphole side of the removable plug with the fluid present in the casing string portion that is uphole of the removable plug. Pumps or other methods of increasing hydraulic pressure in the casing string may be used to increase the internal hydraulic pressure in the casing string to a degree sufficient to fracture the frangible removable plug. When the removable plug is fractured, the fluid then floods into the buoyant chamber of the floatation subassembly to deactivate the floatation subassembly. In order to fill the casing string with fluid when the floatation subassembly is opened, additional fluid may be introduced into the casing string from the surface to assist in flooding and deactivating the floatation subassembly.

[0018] The choking orifice collar is disposed in the interior of one of the casing joints of the casing string. As used herein, the term “casing string” also refers to any and all portions of the tubing string above and below any systems such as liner hangers. These string portions above the liner hanger are sometimes referred to as the landing string and may comprise drill pipe or other conduits. The string portions below liner hangers are referred to as liners. It is to be understood that the use of the term “casing string” is inclusive of these conduits that are uphole and downhole of liner hangers or similar apparatus as well as all portions of casing strings that do not contain liner hangers or liners. Moreover, the use of the term “casing joint” is used to refer to any subsection of any portion of the casing string, which are coupled together to form the string. Advantageously, the choking orifice collars are sized to fit into the inner diameter of a casing joint and may be different sizes to accommodate the differing inner diameters of different casing joints. The choking orifice collar has an orifice or opening with a diameter smaller than the inner diameter of the casing joint in which the choking orifice collar is disposed. As the orifice is smaller than the inner diameter of the casing joint, fluid flow through the choking orifice collar is choked such that the volume of fluid flow is reduced through the orifice relative to the volume of fluid capable of flowing through the casing joint. This reduction in fluid volume slows the rate of fluid flowing through the casing string to the downhole floatation subassembly when it is deactivated. When the floatation subassembly is deactivated and flow into the buoyant chamber is allowed, the fluid residing in the portion of the casing string uphole of the buoyant chamber will flood into the buoyant chamber and shift the hydraulic pressure in the casing string. Additionally, fluid may be pumped into the casing string from the surface to flood the buoyant chamber of the floatation subassembly. The introduction of additional fluid may also shift the hydraulic pressure in the casing string. The choking orifice collar chokes this fluid as it flows downstream into the buoyant chamber and reduces the suddenness of the pressure shift from the removal of the removable plug and the flooding of the buoyant chamber. The choking orifice collar produces a slower deactivation of the floatation subassembly and a gradual shift in the hydraulic pressure for portions of the casing string. This gradual shift in the hydraulic pressure may be important for reducing the possibility of pressure-sensitive casing tools from being damaged, prematurely released, or prematurely activated.

[0019] The choking orifice collar may be positioned in the interior of the casing string to dampen the shift in hydraulic pressure. The location of the choking orifice collar may be any location in the casing string deemed most important for reducing the impact on associated casing tools. For example, the choking orifice collar may be positioned in a liner suspended downhole of the liner hanger. In alternative examples, the choking orifice collar(s) may be positioned downhole and/or uphole of an annular packer, wiper plug, cementing collar, valves such as liner top squeeze cementing valves, a high-circulation subassemblies, drill pipe swivels, wellbore cleanout tools, and the like. In some optional examples, a choking orifice collar may be positioned within the interior of the floatation subassembly, for example, within the buoyant chamber. In some optional examples, multiple choking orifice collars may be used as needed to provide increased choking of the flowing fluid in the casing string. The multiple choking orifice collars may be located at multiple points in the interior of the casing string and may be positioned to optimize their dampening effect along the interior of the casing string. The choking orifice collars may also be modified and tailored to provide a desired reduction in the flow rate of the fluid flowing through the orifice. For example, the orifice of the choking orifice collars may be shaped and sized to shift the flow rate of the flowing fluid along the length of the casing string. Multiple choking orifice collars within the casing string may have different sizes and/or shaped orifices so that the flow rate of the fluid within the casing string is shifted at different location. This tailored adjustment in the flow rate may be important for increasing or decreasing the flow of the fluid at specific points in the casing string relative to the locations of any associated casing tools in or on the casing string.

[0020] The choking orifice collars may be inserted into the casing string at the surface before inserting into the wellbore. Alternatively, the choking orifice collars may be inserted into the casing string while the casing string is run into the wellbore or after the casing string has reached its total depth but before the deactivation of the floatation subassembly. The choking orifice collars may be installed in any sufficient manner including wedging into place, threading into place, fixing into place with adhesives, and the like. The choking orifice collars may be composed of any suitable material. Examples of the material may include, but are not limited to, glass, ceramic, sand/salt matrix, composite, phenolic plastic, or any combination of materials. Additionally, after the deactivation of the floatation subassembly, the choking orifice collars are configurable to be removed from the interior of the casing string to restore the full inner diameter of the casing string. The choking orifice collars may be made of a frangible material such as glass, ceramic, composite, phenolic plastic, or any combination of materials that may be fractured by the introduction of a projectile into the casing string such as a ball or dart. The projectile may be pumped in the casing sting to seal the orifice of the choking orifice collar such that the building hydraulic pressure may then fracture the choking orifice collar. The fractured pieces of the choking orifice collar may then flow out of the casing string. In alternative examples, the choking orifice collar may comprise a dissolvable material, such as a sand/salt matrix, polymer-based solids, metallics, composites, or any combination of materials which may dissolve in the fluid present in the casing string (e.g., a brine) or from a subsequently introduced fluid such as an acid. The choking orifice collar may be coated with a material to delay dissolution such that the choking orifice collar does not dissolve until after the deactivation of the floatation subassembly. The coating material may be a polymeric material or any suitable material with a sufficiently slow rate of dissolution.

[0021] The casing string floatation system may also comprise a casing tool. Examples of the casing tool include a liner hanger, wiper plug such as a liner wiper plug, a cement collar, a packer such as an annular packer, setting tool, and the like. The casing tool may be any tool that is sensitive to a shift in the interior pressure of the casing string. A casing tool is sensitive to a pressure shift if it may be damaged, prematurely actuated, prematurely released, or otherwise negatively impacted by the shift in pressure induced by the deactivation of the floatation subassembly. For example, some casing tools may be prematurely actuated directly from the sudden pressure shift. Alternatively, some casing tools may be prematurely actuated by or released from the setting tool if the setting tool is sensitive to the sudden pressure shift. The choking orifice collars may be positioned to dampen a sudden pressure shift in the interior of the casing string and slow the change in the hydraulic pressure within the casing string. This dampening may prevent damage to a casing tool or its premature actuation or release. The casing tools may be disposed at any location in or on the casing string and may be uphole or downhole of the floatation subassembly.

[0022] FIG. 1A is a cross-section illustration of an example casing string floatation system, generally 5, as disposed in a wellbore 10. Casing string 15 is inserted into wellbore 10 from the surface and descends first through the vertical portion 20 of the wellbore 10 and then into horizontal portion 25. The casing string 15 is composed of a plurality of casing joints coupled together but is generally a tubular conduit descending from the surface. The casing string 15 comprises a floatation subassembly 30 and a casing shoe 35 disposed in the horizontal portion 25 of the wellbore 10 as the casing string 15 is run to its total depth. The casing shoe 35 guides the casing string 15 as it is run downhole. The floatation subassembly 30 comprises a buoyant chamber 40 which is sealed by a removable plug 45. The buoyant chamber 40 allows for the floatation of a portion of the casing string 15 while it is run into the horizontal portion 25 of the wellbore 10 to reduce the drag on the casing string 15. Uphole of the removable plug 45, the interior of the casing string 15 is filled with fluid, such as a brine, to add weight to the casing string 15 and assist in moving it to its total depth.

[0023] A choking orifice collar 50 has been positioned below casing tool 55, illustrated as a liner hanger. The liner hanger suspends a liner which forms another section of the casing string 15. The choking orifice collar 50 comprises an orifice 60 which allows fluid flow from the surface to descend further downhole but restricts the rate of flow of this fluid by reducing the volume that may flow through the orifice 60.

[0024] FIG. 1B is a cross-section illustration of the example casing string floatation system 5 as illustrated in FIG. 1A after the removal of the removable plug (illustrated in FIG. 1A as 45). The removable plug shown in FIG. 1A may be removed by increasing the hydraulic pressure of the fluid in the portion of the casing string 15 uphole of the removable plug 45 until the frangible removable plug 45 is fractured. The fluid may then flow into the buoyant chamber 40 to fill it, resulting in the deactivation of the floatation subassembly 30. The opening of the buoyant chamber 40 to the fluid in the casing string 15 may result in a pressure shift in the casing string 15. To dampen this pressure shift, the choking orifice collar 50 reduces the rate of fluid flow downhole by forcing the fluid through the orifice 60. As the pressure shift is dampened, the impact to casing tool 55 disposed uphole of the choking orifice collar 50 may be reduced.

[0025] After the deactivation of the floatation subassembly 40, the choking orifice collar 50 may be removed through the introduction of a projectile to fracture the choking orifice collar 50 or through dissolution of the choking orifice collar 50. Once removed, the inner diameter of the casing string 15 at the former location of the choking orifice collar 50 is restored and fluid flow through this area is no longer restricted. If a casing tool 55 has not yet been actuated or released, it may be actuated or released as desired upon removal of the choking orifice collar 50. In the illustrated example, the liner was already suspended from the liner hanger; and the choking orifice collar may minimize issues with these components. Other associated casing tools 55 such as liner wiper plugs which may be present and may also benefit from the dampening of the pressure shift provided by the choking orifice collar 50.

[0026] It should be clearly understood that the example system illustrated by FIGS. 1A and 1B is merely a general application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited in any manner to the details of FIGS. 1A and 1B as described herein.

[0027] FIG. 2 is a perspective illustration of an example portion of a casing string 100. Casing string 100 comprises a casing joint 105 having a choking orifice collar 110 positioned in the interior. Choking orifice collar 110 was positioned in the casing joint 105 by being wedged into position. Orifice 115 is illustrated as being circular but may be any shape, for example, oval, square, triangular, hexagonal, octagonal, and the like. As discussed above, orifice 115 reduces the volume of fluid that can flow through the orifice relative to the section of the casing joint 105 uphole of the choking orifice collar 110. The choking orifice collar 110 may be frangible and may be removed with a projectile to seal prior to induced shattering. Alternatively, the choking orifice collar 110 may be removed by dissolution using the hydraulic fluid present in the casing string 100 or another introduced fluid.

[0028] It should be clearly understood that the example system illustrated by FIG. 2 is merely a general application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited in any manner to the details of FIG. 2 as described herein.

[0029] Provided is a casing string floatation system in accordance with the disclosure and the illustrated FIGs. An example casing string floatation system comprises a casing string, a removable plug, a choking orifice collar, and a casing tool. The casing string is disposed in a wellbore. The casing string comprises a plurality of casing joints coupled together, a casing shoe disposed at a bottom of the casing string, and a floatation subassembly comprising a buoyant chamber and disposed uphole of the casing shoe. The removable plug is disposed in the casing string and defines an uphole end of the floatation subassembly. The choking orifice collar is disposed in a casing joint. The choking orifice collar comprises an orifice having a diameter smaller than an inner diameter of the casing joint in which the choking orifice collar is disposed, and the choking orifice collar is configurable to be removed from the casing joint. The casing tool is disposed within or on the casing string and is uphole or downhole of the flotation subassembly. The casing tool is configured to actuate from an application of pressure to the casing tool.

[0030] Additionally or alternatively, the casing string floatation system may include one or more of the following features individually or in combination. The casing tool may be a wiper plug, cementing collar, setting tool, packer, valve, high-circulation subassembly, drill pipe swivel, or wellbore cleanout tool. The casing string may further comprise a liner hanger disposed uphole of the floatation subassembly. The choking orifice collar may be disposed uphole of the floatation subassembly and either uphole or downhole of the liner hanger. The casing string floatation system may further comprise a plurality of choking orifice collars. At least two of the choking orifice collars in the plurality may have an orifice of a different diameter from one another. The choking orifice collar may be disposed uphole of the floatation subassembly. The choking orifice collar may be composed of glass or ceramic. The casing string floatation system may further comprise a projectile configured to contact the choking orifice collar. The choking orifice collar may be dissolvable in a fluid introduced into the casing string.

[0031] Provided are methods for using a casing string floatation system in accordance with the disclosure and the illustrated FIGs. An example method comprises introducing a casing string floatation system into a wellbore. The casing string floatation system comprises a casing string, a removable plug, a choking orifice collar, and a casing tool. The casing string is disposed in a wellbore. The casing string comprises a plurality of casing joints coupled together, a casing shoe disposed at a bottom of the casing string, and a floatation subassembly comprising a buoyant chamber and disposed uphole of the casing shoe. The removable plug is disposed in the casing string and defines an uphole end of the floatation subassembly. The choking orifice collar is disposed in a casing joint. The choking orifice collar comprises an orifice having a diameter smaller than an inner diameter of the casing joint in which the choking orifice collar is disposed, and the choking orifice collar is configurable to be removed from the casing joint. The casing tool is disposed within or on the casing string and is uphole or downhole of the flotation subassembly. The casing tool is configured to actuate from an application of pressure to the casing tool. The method further comprises removing the removable plug, flowing a fluid into the floatation subassembly, and choking the flow of the fluid with the choking orifice collar such that a rate of the fluid flow into the floatation subassembly is reduced.

[0032] Additionally or alternatively, the method may include one or more of the following features individually or in combination. The method may further comprise removing the choking orifice collar from the casing string. The choking orifice collar may be removed after contacting the choking orifice collar with a projectile introduced into the casing string. The casing tool may be actuated after the removal of the choking orifice collar. The casing tool may not be actuated during the flowing of the fluid into the floatation subassembly. The casing tool may be a wiper plug, cementing collar, setting tool, packer, valve, high-circulation subassembly, drill pipe swivel, or wellbore cleanout tool. The casing string may further comprise a liner hanger disposed uphole of the floatation subassembly. The choking orifice collar may be disposed uphole of the floatation subassembly and either uphole or downhole of the liner hanger. The casing string floatation system may further comprise a plurality of choking orifice collars. At least two of the choking orifice collars in the plurality may have an orifice of a different diameter from one another. The choking orifice collar may be disposed uphole of the floatation subassembly. The choking orifice collar may be composed of glass or ceramic. The casing string floatation system may further comprise a projectile configured to contact the choking orifice collar. The choking orifice collar may be dissolvable in a fluid introduced into the casing string.

[0033] The preceding description provides various examples of the systems and methods of use disclosed herein which may contain different method steps and alternative combinations of components. It should be understood that, although individual examples may be discussed herein, the present disclosure covers all combinations of the disclosed examples, including, without limitation, the different component combinations, method step combinations, and properties of the system. It should be understood that the compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps. The systems and methods can also “consist essentially of or ”consist of the various components and steps. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces.

[0034] For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited. In the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values even if not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0035] One or more illustrative examples incorporating the examples disclosed herein are presented. Not all features of a physical implementation are described or shown in this application for the sake of clarity. Therefore, the disclosed systems and methods are well adapted to attain the ends and advantages mentioned, as well as those that are inherent therein. The particular examples disclosed above are illustrative only, as the teachings of the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown other than as described in the claims below. It is therefore evident that the particular illustrative examples disclosed above may be altered, combined, or modified, and all such variations are considered within the scope of the present disclosure. The systems and methods illustratively disclosed herein may suitably be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein.

[0036] Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the following claims.