Patent Publication Number: US-2016222759-A1

Title: Toe initiator having an associated object catching seat

Description:
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/110188 filed on Jan. 30, 2015, incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     For purposes of preparing a well for the production of oil or gas, at least one perforating gun may be deployed into the well via a conveyance mechanism, such as a wireline, slickline or a coiled tubing string. The shaped charges of the perforating gun(s) are fired when the gun(s) are appropriately positioned to perforate a casing of the well and form perforating tunnels into the surrounding formation. Additional operations may be performed in the well to increase the well&#39;s permeability, such as well stimulation operations and operations that involve hydraulic fracturing. The above-described perforating and stimulation operations may be performed in multiple stages of the well. 
     The above-described operations may be performed by actuating one or more downhole tools (perforating guns, sleeve valves, and so forth) and by forming one or more fluid-diverting fluid barriers downhole in the well. 
     SUMMARY 
     The summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
     In accordance with an example implementation, a technique includes installing a tubing string having a toe initiator valve in a wellbore; and opening the toe initiator valve to establish fluid communication between an interior of the string and a region outside of the string. The technique includes using the fluid communication established by the open toe initiator valve to communicate a degradable object downhole to land in a seat of the string; and performing a downhole operation using a fluid barrier resulting from the landed object. 
     In accordance with another example implementation, a technique that is usable with a well includes opening a toe initiator valve of a tubing string; pumping a degradable object downhole to land in a seat associated with the toe initiator valve; and performing pressure testing of the string using a fluid barrier created due to the landing of the degradable object in the seat. 
     In accordance with another example implementation, an apparatus that is usable with a well includes a string, a toe initiator valve and a seat. The string is associated with a plurality of stages, and a first stage of the plurality of stages is closest to a toe end of the string. The toe initiator valve is disposed in the string near the toe end of the string and includes a radial port to communicate fluid with a region outside of the string. The seat disposed in the string between the toe end of the string and the first stage to receive an object to form a fluid barrier between the port of the toe initiator valve and the first stage. 
     In accordance with yet another example implementation, an apparatus includes a toe initiator valve to open in response to a pressure of a tubing string in which the valve is installed exceeding a pressure threshold. The toe initiator valve includes a coupler to connect the toe initiator valve to a string; at least one radial port to communicate fluid in response to the toe initiator valve being open; and a seat disposed between the coupler and the port to receive an untethered object communicated through the string. 
     Advantages and other features will become apparent from the following drawings, description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A, 1B, 1C, 1D, 1E  and IF are schematic diagrams of a well illustrating operations performed in the well using a toe initiator valve having an associated object catching seat according to an example implementation. 
         FIG. 2A  is a partial cross-sectional view of the toe initiator valve in a closed state according to an example implementation. 
         FIG. 2B  is a partial cross-sectional view of the toe initiator valve in an open state according to an example implementation. 
         FIG. 3  is a flow diagram depicting a technique to use an object catching seat of a toe initiator valve to perform a downhole operation according to an example implementation. 
         FIG. 4  is a flow diagram depicting a technique to use an object catching seat of a toe initiator valve to perform pressure testing and well stimulation operations in a well according to an example implementation. 
         FIG. 5  is a partial cross-sectional view illustrating an assembly containing an object catching seat and a toe initiator valve according to an example implementation. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth but implementations may be practiced without these specific details. Well-known circuits, structures and techniques have not been shown in detail to avoid obscuring an understanding of this description. “An implementation,” “example implementation,” “various implementations” and the like indicate implementation(s) so described may include particular features, structures, or characteristics, but not every implementation necessarily includes the particular features, structures, or characteristics. Some implementations may have some, all, or none of the features described for other implementations. “First”, “second”, “third” and the like describe a common object and indicate different instances of like objects are being referred to. Such adjectives do not imply objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. “Coupled” and “connected” and their derivatives are not synonyms. “Connected” may indicate elements are in direct physical or electrical contact with each other and “coupled” may indicate elements co-operate or interact with each other, but they may or may not be in direct physical or electrical contact. Also, while similar or same numbers may be used to designate same or similar parts in different figures, doing so does not mean all figures including similar or same numbers constitute a single or same implementation. Although terms of directional or orientation, such as “up,” “down,” “upper,” “lower,” “uphole,” “downhole,” and the like, may be used herein for purposes of simplifying the discussion of certain implementations, it is understood that these orientations and directions may not be used in accordance with further example implementations. 
     In accordance with example implementations, for purposes of completing a wellbore, a tubing string (a casing string, for example) may be run into and installed in the wellbore for purposes of lining and supporting the wellbore. At its distal, or far, end, the tubing string may include a valve called a “toe initiator valve.” The toe initiator valve has an open central passageway and radial ports, and the toe initiator valve may be remotely operated to control fluid communication through its radial ports. In general, the toe initiator valve has two states: a closed state in which the toe initiator valve blocks fluid communication through the radial ports; and a closed state in which the toe initiator valve allows fluid to be communicated through the radial ports. 
     When the tubing string is initially run into and installed in the wellbore, the toe initiator valve is in its closed state, and the interior of the tubing string may be a closed space, which means a fluid flow cannot be communicated through the tubing string. A fluid flow inside the tubing string may be used for various purposes, such as communicating stimulation fluid downhole, hydraulic fracturing, pumping tools downhole, and so forth. 
     For purposes of establishing a fluid flow inside the tubing string, the toe initiator valve is opened, which permits a fluid flow from the interior of the tubing string to a region outside of the tubing string. One way for the toe initiator valve to be opened is through the use of a well intervention operation in which a tool is run inside the tubing string to engage the valve. For example, the toe initiator valve may be constructed to be mechanically opened by a shifting tool. In this manner, a shifting tool may be run downhole inside the central passageway of the tubing string for purposes of engaging a sleeve of the valve to shift the sleeve to open the radial ports. 
     The toe initiator valve may be constructed to be opened without a well intervention. For example, the toe initiator valve may be constructed to shift a sleeve to open communication through the radial ports in response to the pressure inside the interior of the tubing string exceeding a certain activation pressure threshold. After the installation of the tubing string (after cementing of the string in place for implementations in which the tubing string is a casing, for example), a pressure test may be performed on the string (e.g., a casing pressure test may be performed). One way to allow such a pressure test to be conducted is to construct the toe initiator valve to open with pressure and have a pressure opening threshold that exceeds the pressures involved in pressure testing the tubing string. Thus, the toe initiator valve remains closed (i.e., remains in its initial state) during the pressure testing and may be subsequently opened to initiate a fluid flow by pressurizing the interior of the tubing string with a pressure higher than the pressures associated with the pressure testing. 
     In accordance with example systems and techniques that are discussed herein, a tubing string installed in a well has a toe initiator valve, which is constructed to open at a tubing pressure that is less than the maximum pressure used to pressure test the tubing string. Thus, the closed state of the toe initiator valve may not be used to seal off the interior space of the tubing string for pressure testing. Instead, the toe initiator valve has an associated object catching seat, which is constructed to receive an object to form a temporary fluid barrier to seal off the toe end of the tubing string. More specifically, in accordance with example implementation, toe initiator valve may be opened (by pressurizing the tubing string, for example) before pressure testing. To isolate the toe initiator&#39;s port(s) to allow the pressure testing to occur, the toe initiator valve has an associated object catching seat, which is used to catch an object to form a temporary fluid obstruction, or fluid barrier, uphole of the valve. The object is at least partially formed from a degradable material, which means that the fluid barrier formed from the object disappears with the passage of time. In this manner, the degradable material is constructed to remain intact and structurally sound for a certain period of time for purposes of allowing pressures uphole of the object to build up to complete the pressure testing and isolate the open port(s) of the toe initiator valve from the pressure testing. However, eventually, the degradable material degrades to an extent that removes the fluid barrier formed by the object. After this occurs, flow may be re-established inside the tubing string using the open port(s) of the toe initiator valve. Moreover, as further described herein, another object (degradable object, for example) may be deployed to land in the object catching seat to form another temporary fluid barrier for other purposes, such as, for example, diverting fluid for a subsequent well stimulation operation in the stage above the toe initiator valve. 
     In accordance with example implementations, the object catching seat is constructed to receive, or catch, an untethered object that is pumped downhole through the central passageway of the tubing string. In this context, an “untethered object” refers to an object that is communicated downhole through the passage of a tubing string along at least part of its path without the use of a conveyance line (a slickline, a wireline, a coiled tubing string, and so forth). As examples, the untethered object may be a ball (or sphere), a dart or a bar. Regardless of its particular form, the untethered object travels through the passageway of the tubing string to land in the object catching seat that is disposed above the toe initiator valve to form a corresponding fluid obstruction or fluid barrier. 
     As a more specific example,  FIG. 1A  depicts a well  100  in accordance with example implementations. The well  100  includes a laterally extending wellbore  120 , which traverses one or more hydrocarbon-bearing formations. As depicted in  FIG. 1A , the wellbore  120  is lined and supported by a tubing string  130 . The tubing string  130  may be cemented to the wellbore  120  (i.e., the tubing string  130  is a casing); or the tubing string  130  may be secured to the surrounding formation(s) by packers (such wellbores typically are referred to as “open hole wellbores”). For the specific example of  FIG. 1A , the tubing string  130  is a casing that has been run into the wellbore  120 , and a cementing operation has been formed to place cement  140  in the annular region between the exterior of the casing and the wall of the wellbore  120 . 
     It is noted that although  FIG. 1A  and other figures that are discussed herein depict a laterally extending wellbore, the techniques and systems that are disclosed herein may likewise be applied to vertically extending wellbores. Moreover, in accordance with example implementations, the well  100  may contain multiple wellbores, which contain tubing strings that are similar to the illustrated tubing string  130  of  FIG. 1A . The well  100  may be a subsea well or may be a terrestrial well, depending on the particular implementation. Additionally, the well  100  may be an injection well or may be a production well. Thus, many implementations are contemplated, which are within the scope of the appended claims. 
     As depicted in  FIG. 1A , the tubing string  130  extends from a heel end  141  of a lateral segment  121  of the wellbore  120  to a toe end  143  of the segment  121 . The lateral segment  121  may be associated with multiple stages, which are isolated and stimulated separately, as further discussed herein. 
     The toe end  143  of the tubing string  130  includes a casing shoe  161  and a toe initiator valve  150 . As depicted in  FIG. 1A , the toe initiator valve  150  includes one or multiple radial ports  160 . In its open state, the toe initiator valve  150  allows fluid communication through the radial port(s)  160  to thereby allow fluid communication between the interior space of the tubing string  130  and the region outside of the tubing string  130 . Such an open state may be used for purposes of establishing a fluid flow inside the tubing string  130  after the tubing string  130  has been run into and installed in the wellbore  120 . In this regard, before the toe initiator valve  150  is opened, the interior of the tubing string  130  may be an otherwise closed system. 
       FIG. 1A  also depicts an object catching seat  151  that is associated with the tubing string  130 . As depicted in  FIG. 1A , the object catching seat  151  is disposed uphole of the toe initiator valve  150 . The object catching seat  151 , in accordance with example implementations, is a restriction or narrowing of the central passageway of the tubing string  130 . In accordance with example implementations, the object catching seat  151  is constructed to catch an untethered object that is deployed inside the central passageway of the tubing string  130 . As described further herein, depending on the particular implementation, the object catching seat  151  may be a component of the tubing string  130  separate from the toe initiator valve  150  or may be part of the valve  150 . Regardless of its form, the object catching seat  151  may be disposed in the string  130  between the port(s)  160  of the toe initiator valve  150  and the stage (of the plurality of stages) of the wellbore  120 , called the “first stage” herein, which is closest to the toe end  143  of the wellbore  120 . 
     In accordance with example implementations, the toe initiator valve  150  may be initially closed when run into the wellbore  120  with the tubing string  130 , and the toe initiator valve  150  may be constructed to be remotely operated by pressurizing the interior of the tubing string  130  to a pressure that causes the valve  150  to open the valve&#39;s port(s)  160  without the use of a well intervention. More specifically, referring to  FIG. 1B , in accordance with example implementations, for purposes of delivering the untethered object downhole, fluid communication is first established inside the central passageway of the tubing string  130 . In this manner, as shown in  FIG. 1B , fluid pressure inside the central passageway of the tubing string  130  may be increased to a pressure threshold level that causes the tubing initiator valve  150  to open, thereby permitting a flow  170  that may extend through the radial ports  160  into the region (as depicted at reference numeral  172 ) exterior to the string  130 . 
     As an example, in accordance with some implementations, the toe initiator valve  150  may be constructed to transition from its closed state to its open state in response to the tubing string pressure at the valve  150  exceeding 10,000 pounds per square inch (psi), which may be less than the maximum pressure (12,000 psi, for example) used for pressure testing the tubing string  130 . 
     Using the flow  170 , an untethered object, such as an activation sphere, or ball  174 , may be pumped downhole and land in the object catching seat  151 , as depicted in  FIG. 1C . For this state of the well  100 , the landing of the ball  174  in the seat  151  creates a downhole fluid obstruction, or fluid barrier, uphole of the toe initiator valve  150 . This fluid barrier, in turn, may be used to seal off the bottom end of the tubing string  130  to isolate the toe initiator valve  150  and allow a pressure test to be performed on the tubing string  130  without change the state of the valve  150 . 
     The ball  174 , in accordance with example implementations, contains one or multiple degradable material. Depending on the particular implementation, the ball  174  may contain one or multiple non-degradable materials, may be solid, may be hollow, may be formed from interlocking pieces, and so forth. Regardless of its particular form, the ball  174  is constructed to initially provide a structural integrity that permits a fluid column uphole of the ball  174  to be pressurized (pressurized to perform pressure testing of the tubing string  130 , for example) and subsequently degrade in a relatively short interval of time (one week, a few weeks, a month, less than six months, and so forth), as compared to the degradation rates of other equipment in the well (the tubing string  130 , for example). The degradation of the ball  174  allows the ball to leave or exit the object catching seat  151  after this relatively short interval of time. For example, the object catching seat  150  may have a diameter that is sized to catch a ball having a minimum outer diameter, and the ball  174  may dissolve over the relatively short interval of time so that the ball&#39;s outer diameter reduces below the minimum outer diameter. As another example, the ball  174  may be constructed to degrade until the ball  174  collapses, thereby allowing the ball to pass through the seat  150 . 
     In accordance with some implementations, after the fluid barrier is formed (and confirmed via a surface pressure measurement, for example), the pressure of the tubing string  130  may be monitored until a pressure drop occurs, indicating that the fluid barrier (and ball) has been removed. Thus, some degree of waiting may occur before operations that rely on fluid communication through the toe initiator valve  150  may resume, in accordance with example implementations. 
     After the ball  174  degrades and the fluid barrier is removed, other operations may then be performed in the well  100 , which rely on communicating fluid through the toe initiator valve  150 . For example, referring to  FIG. 1D , flow may be re-established in the tubing string  130 , and a perforating gun assembly  180  may be pumped downhole on a wireline  181  to a region of the lateral segment  121  above the toe initiator valve  150 . The perforating gun assembly  180  may then be activated to fire its perforating charges. This produces corresponding perforating jets, which perforate the wall of the tubing string  130  and form corresponding perforation tunnels  190 , which extend into the surrounding formation, as depicted in  FIG. 1E . In this state, the well  100  now has fluid communication with the surrounding formation to permit a well stimulation operation to be performed in the first stage above the toe initiator valve  150 . For this to occur, another untethered object, such as a degradable ball  192 , may be pumped downhole to once land in the object catching seat  151 , as illustrated in  FIG. 1F . This once again creates a fluid barrier that may be used to divert fluid uphole of the ball  192  for purposes of diverting the stimulation fluid into the stage associated with the perforation tunnels  190 . 
       FIG. 2A  depicts a partial cross-sectional view of the toe initiator valve  150 , in accordance with example implementations. It is noted that  FIG. 2A  depicts an upper cross-sectional view of the toe initiator valve  150  about a longitudinal axis  201  of the string  130 , with it being understood that the lower cross-section of the valve  150  generally mirrors the depicted upper cross-section about the longitudinal axis  201 . 
     The toe initiator valve  150  includes a tubular housing  200 , which includes the radial ports  160 . The housing circumscribes a sleeve  210 , which translates along the longitudinal axis  201  to open and close (the state shown in  FIG. 2A ) fluid communication through the port(s)  160 . For the example implementation of  FIG. 2A , at its uphole end  207 , the toe initiator valve  150  includes an upper coupling interface,  204  to couple the housing  200  to the portion of the tubing string  130 , which is uphole of the valve  150 . In general, the upper coupling interface  204  may include threads  206  formed in the housing  200 . As also shown in  FIG. 2A , below the threads  204 , the toe initiator valve  150  may, in accordance with example implementations, include the object catching seat  151 , which is, for this implementation, formed by an upset, or shoulder, of the housing  200 . 
       FIG. 2A  depicts the toe initiator valve  150  in its closed state. In this state, an internal sleeve  210  of the toe initiator valve  150  blocks fluid communication through the radial port(s)  160 . It is noted that the various seals between the sleeve  210  and the housing  204  are not depicted in  FIG. 2A . In general, the toe initiator valve  150  may include one or multiple rupture discs  220  that are in communication with an atmospheric chamber (not shown) of the toe initiator valve  150 . When the pressure inside the tubing string  130  increases above a pressure threshold established by the ruptured disc  220 , the ruptured disc  220  ruptures to communicate pressure inside the tubing string  130  to the valves atmospheric chamber. This pressure imbalance, in turn, operates a piston of the sleeve  210  (not shown) to shift the sleeve  210  open to form an open state for the toe initiator valve  150 , as depicted in  FIG. 2B . As shown in  FIG. 2B , for this state, fluid communication is open through the radial ports  160 . 
     Referring to  FIG. 3 , thus, in accordance with example implementations, a technique  300  includes installing (block  304 ) a string having a toe initiator valve in a wellbore and opening (block  308 ) the toe initiator valve to establish fluid communication between the interior of the string and the region outside the string. In accordance with example implementations, the toe initiator valve may be opened by pressuring the tubing string  130  to a pressure that meets or exceeds a pressure activation threshold of the toe initiator valve, and this pressure activation threshold may be less than the maximum pressure used to pressure test the tubing string  130 . Pursuant to the technique  300 , fluid communication established by the open toe initiator valve is used (block  312 ) to pump a degradable object downhole to land in a seat of the string. A downhole operation that uses the fluid barrier resulting from the landed object may then be performed (block  316 ). As examples, this downhole operation may be a well stimulation operation, a pressure test, and so forth. 
     More specifically, in accordance with example implementations, a technique  400  that is depicted in  FIG. 4  may be performed. Pursuant to the technique  400 , a toe initiator valve is opened (block  402 ) to establish a fluid flow, and a degradable object is pumped downhole in the tubing string pursuant to block  404  to land in a seat that is associated with the toe initiator valve. Pressure testing of the string may then be performed (block  408 ) using the fluid barrier formed by the degradable object landing on a seat associated with the toe initiator valve. Pursuant to the technique  400 , a first stage well stimulation operation using a flow through the now opened toe initiator valve may be performed, pursuant to block  412 . Subsequently, a perforating gun assembly may be pumped downhole inside the tubing string to perforate the string for a second stage well stimulation operation, pursuant to block  416 . The perforating guns may then be retrieved (block  420 ), and another degradable object may be pumped downhole in the tubing string to land in the seat associated with the toe initiator valve, pursuant to block  424 . The technique  400  includes performing (block  428 ) the second stage well stimulation operation that uses the fluid barrier formed from the second degradable object landing in the seat. 
     In accordance with example implementations, one or more components of the degradable object (such as balls  174  and  192  that are described herein) may contain a material or materials, which allow at least part of the object to degrade (dissolve, structurally deteriorate, and so forth) by well fluid or another fluid, which is introduced into the tubing string passageway. As an example, the material(s) for the object may be the same or similar to the materials disclosed in the following patents, which have an assignee in common with the present application and are hereby each incorporated by reference: U.S. Pat. No. 7,775,279, entitled, “DEBRIS-FREE PERFORATING APPARATUS AND TECHNIQUE,” which issued on Aug. 17, 2010; and U.S. Patent No. 8,211,247, entitled, “DEGRADABLE COMPOSITIONS, APPARATUS COMPOSITIONS COMPRISING SAME, AND METHOD OF USE,” which issued on Jul. 3, 2012. 
     In this context, degradable material is a material that degrades at a significantly faster rate than other materials or components (the tubing string  130 , for example) of the downhole well equipment. For example, in accordance with some implementations, dissolvable or degradable material(s) may degrade at sufficiently fast rate to allow the fluid barrier to disappear (due to the material degradation) after a relatively short period of time (a period less than one year, a period less than six months, or a period of less than ten weeks, as just a few examples). In this manner, the fluid barrier maintains its structural integrity for a sufficient time to allow the downhole operation(s) that rely on the fluid barrier to be performed, while disappearing shortly thereafter to allow other operations to proceed in the well, which rely on access through the portion of the tubing string, which contained the fluid barrier. 
     Other implementations are contemplated, which are within the scope of the appended claims. For example, referring to  FIG. 5 , in accordance with further implementations, the seat  151  may be part of a tool or component that is separate from the toe initiator valve  150 . In this manner, as shown in  FIG. 5 , the seat  151  may be form from an inner should or upset  510 , of the tubing string  130  and is disposed uphole of the toe initiator valve  150 , i.e., disposed uphole of the upper threaded coupler  204  of the valve  150 . As example, for these implementations, the toe initiator valve  150  may be the KickStart rupture disc valve, available from Schlumberger. 
     While the present techniques have been described with respect to a number of embodiments, it will be appreciated that numerous modifications and variations may be applicable therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the scope of the present techniques.