Patent Publication Number: US-9885224-B2

Title: Burst sleeve and positive indication for fracture sleeve opening

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Appl. 61/911,614, filed 4 Dec. 2013, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     In a staged fracturing operation, multiple zones of a formation need to be isolated sequentially for treatment. To achieve this, operators install a fracturing assembly down the wellbore, which typically has a top liner packer, open hole packers isolating the wellbore into zones, various sliding sleeves, and a wellbore isolation valve. When the zones do not need to be closed after opening, operators may use single shot sliding sleeves for the fracturing treatment. These types of sleeves are usually ball-actuated and lock open once actuated. Another type of sleeve is also ball-actuated, but can be shifted closed after opening. 
     Initially, operators run the fracturing assembly in the wellbore with all of the sliding sleeves closed and with the wellbore isolation valve open. Operators then deploy a setting ball to close the wellbore isolation valve. This seals off the tubing string of the assembly so the packers can be hydraulically set. At this point, operators rig up fracturing surface equipment and pump fluid down the wellbore to open a pressure actuated sleeve so a first zone can be treated. 
     As the operation continues, operates drop successively larger balls down the tubing string and pump fluid to treat the separate zones in stages. When a dropped ball meets its matching seat in a sliding sleeve, the pumped fluid forced against the seated ball shifts the sleeve open. In turn, the seated ball diverts the pumped fluid into the adjacent zone and prevents the fluid from passing to lower zones. By dropping successively increasing sized balls to actuate corresponding sleeves, operators can accurately treat each zone up the wellbore. 
       FIG. 1A  shows an example of a sliding sleeve  10  for a multi-zone fracturing system in partial cross-section in an opened state. This sliding sleeve  10  is similar to Weatherford&#39;s ZoneSelect MultiShift fracturing sliding sleeve and can be placed between isolation packers in a multi-zone completion. The sliding sleeve  10  includes a housing  20  defining a bore  25  and having upper and lower subs  22  and  24 . An inner sleeve or insert  30  can be moved within the housing&#39;s bore  25  to open or close fluid flow through the housing&#39;s flow ports  26  based on the inner sleeve  30 &#39;s position. 
     When initially run downhole, the inner sleeve  30  positions in the housing  20  in a closed state. A breakable retainer  38  initially holds the inner sleeve  30  toward the upper sub  22 , and a locking ring or dog  36  on the sleeve  30  fits into an annular slot within the housing  20 . Outer seals on the inner sleeve  30  engage the housing  20 &#39;s inner wall above and below the flow ports  26  to seal them off. 
     The inner sleeve  30  defines a bore  35  having a seat  40  fixed therein. When an appropriately sized ball lands on the seat  40 , the sliding sleeve  10  can be opened when tubing pressure is applied against the seated ball  40  to move the inner sleeve  30  open. To open the sliding sleeve  10  in a fracturing operation once the appropriate amount of proppant has been pumped into a lower formation&#39;s zone, for example, operators drop an appropriately sized ball B downhole and pump the ball B until it reaches the landing seat  40  disposed in the inner sleeve  30 . 
     Once the ball B is seated, built up pressure forces against the inner sleeve  30  in the housing  20 , shearing the breakable retainer  38  and freeing the lock ring or dog  36  from the housing&#39;s annular slot so the inner sleeve  30  can slide downward. As it slides, the inner sleeve  30  uncovers the flow ports  26  so flow can be diverted to the surrounding formation. The shear values required to open the sliding sleeves  10  can range generally from 1,000 to 4,000 psi (6.9 to 27.6 MPa). 
     Once the sleeve  10  is open, operators can then pump proppant at high pressure down the tubing string to the open sleeve  10 . The proppant and high pressure fluid flows out of the open flow ports  26  as the seated ball B prevents fluid and proppant from communicating further down the tubing string. The pressures used in the fracturing operation can reach as high as 15,000-psi. 
     After the fracturing job, the well is typically flowed clean, and the ball B is floated to the surface. Then, the ball seat  40  (and the ball B if remaining) is milled out. The ball seat  40  can be constructed from cast iron to facilitate milling, and the ball B can be composed of aluminum or a non-metallic material, such as a composite. Once milling is complete, the inner sleeve  30  can be closed or opened with a standard “B” shifting tool on the tool profiles  32  and  34  in the inner sleeve  30  so the sliding sleeve  10  can then function like any conventional sliding sleeve shifting with a “B” tool. The ability to selectively open and close the sliding sleeve  10  enables operators to isolate the particular section of the assembly. 
     Because the zones of a formation are treated in stages with the sliding sleeves  10 , the lowermost sliding sleeve  10  has a ball seat  40  for the smallest ball size, and successively higher sleeves  10  have larger seats  40  for larger balls B. In this way, a specific sized ball B dropped in the tubing string will pass though the seats  40  of upper sleeves  10  and only locate and seal at a desired seat  40  in the tubing string. Despite the effectiveness of such an assembly, practical limitations restrict the number of balls B that can be effectively run in a single tubing string. 
       FIGS. 2A-2B  illustrates another ball-actuated sliding sleeve  10  according to the prior art. To protect the sleeve  10  during run-in, cementing in the borehole, and the like, a protective cover  27  can be disposed about the exterior of the sleeve&#39;s housing to cover the flow ports  26 . The protective cover  27  is typically composed of a composite material and prevents debris, cement, and the like from entering the sliding sleeve&#39;s flow ports  26  before the sliding sleeve  10  is opened. The exterior of the sleeve&#39;s housing  20  may have a slot  29  to accommodate the cover  27  flush with the exterior of the housing  20 . When the sliding sleeve  10  is opened, fluid pressure from the flow ports  26  readily breaks the composite protective cover  27 . 
       FIG. 3  illustrates another ball-actuated sliding sleeve  10  according to the prior art in partial cross-section. This ball-actuated sliding sleeve  10  counts balls of the same size before opening an inner sleeve  60 . To do this, the sliding sleeve  10  includes a counter  50  and a separate seat  70 . In a similar fashion to the sliding sleeve discussed above, the sliding sleeve  10  also includes a protective cover  80  to protect the sliding sleeve&#39;s flow ports  26  during run in and other operations until open. The cover  80  may also initially hold grease or other filler material in the sleeve  10  during deployment. 
     The protective cover  80 , which is shown in more detail in  FIGS. 4A-4C , is a thin sleeve and can be composed of an aluminum alloy. The protective cover  80  typically has a thickness t 1  of about 0.09-in. and has a diameter d 1  suited to fit around the outside of the housing  20 , which may have a diameter of about 5.65-in. The cover  80  includes various holes or passages  84  defined from the inside  82  to the outside  86  that allow initial fluid flow from the open flow ports  26  to pass through the cover  80 . Eventually, the flow, which may include proppant, erodes the cover  80  from around the housing  20  and flow ports  26 , allowing the sliding sleeve  10  to be used for fracturing and other treatment operations. 
     During operations deploying balls to actuate the sliding sleeves downhole to treat various zones, operators want to detect an identifiable pressure spike at surface that helps indicate that a sliding sleeve has opened downhole. Currently, the sliding sleeves attempt to create a suitable surface indication using shear screws, shear rings, and the like in the sliding sleeves. When the deployed ball lands on the seat in the sliding sleeve, fluid pressure applied against the seated ball breaks the shear screws to shift the insert open in the sliding sleeve. The pressure spike and fall off measured at the surface resulting from the build up and release of pressure that break the shear screws can be used by operators to determine that the sliding sleeve has opened. In some cases, the pressure spike is insufficient to indicate opening of the sliding sleeve. 
     The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above. 
     SUMMARY OF THE DISCLOSURE 
     As disclosed herein, a sliding sleeve opens with a deployed plug. The sliding sleeve comprises a housing defining a first bore and defining a flow port communicating the first bore outside the housing. An inner sleeve defines a second bore and is movable axially inside the first bore from a closed position to an opened position relative to the flow port. A seat disposed in the sliding sleeve engages the deployed plug. Fluid pressure applied against the seated plug shears the insert free from the housing. For example, shear pins or other temporary attachment may hold the insert in the closed position, and the build-up of fluid pressure against the seated plug can break this attachment and allow the insert to move toward the opening position. This first pressure build-up and release may give a first indication that the sleeve has opened. 
     A burst band is disposed about the exterior of the housing at the flow ports. Once the insert moves to the opened position, fluid pressure applied against the seated plug passes through the open flow ports and acts against the burst band. Eventually, the burst band, which can have a number of scores, indentations, or the like, breaks and permits flow of fluid from the flow ports to pass out of the housing. Bursting of the band and the associated build-up of pressure causing it provides a second pressure indication to operators at the surface that the sliding sleeve has opened. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a ball-actuated sliding sleeve according to the prior art in partial cross-section. 
         FIG. 1B  illustrates a detailed view of the ball-actuated sliding sleeve of  FIG. 1A . 
         FIGS. 2A-2B  illustrates another ball-actuated sliding sleeve according to the prior art. 
         FIG. 3  illustrates yet another ball-actuated sliding sleeve according to the prior art having a protective cover. 
         FIGS. 4A-4C  illustrate perspective, end-sectional, and cross-sectional views of a protective cover according to the prior art. 
         FIGS. 5A-5B  illustrates a ball-actuated sliding sleeve in partial cross-section having a burst band according to the present disclosure. 
         FIG. 5C  graphs an example of surface indications resulting from the opening of the ball-actuated sliding sleeve having the burst band. 
         FIGS. 6A-6C  illustrate perspective, end-sectional, and cross-sectional views of an burst band according to the present disclosure. 
         FIG. 7  illustrates another ball-actuated sliding sleeve in partial cross-section having a burst band according to the present disclosure. 
         FIG. 8A  illustrate a cross-sectional view of an upper housing component for the ball-actuated sliding sleeve of  FIG. 6 . 
         FIGS. 8B-8C  illustrate cross-sectional and end-sectional views of another housing component of the ball-actuated sliding sleeve of  FIG. 6 . 
         FIG. 9A  illustrates burst calculations for a four tests on different configurations of burst bands according to the present disclosure. 
         FIG. 9B  graphs the correlation between the burst pressure of the burst bands to the diameter of the burst band. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
       FIGS. 5A-5B  illustrates a downhole tool  10  in partial cross-section having a burst band  100  according to the present disclosure. As shown, the downhole tool  10  can be a ball-actuated sliding sleeve  10 , which deploys on a tubing string in a borehole and can be used for fracture operations. The sliding sleeve  10  includes a housing  20  defining a bore  25  and having upper and lower subs  22  and  24 . An inner sleeve or insert  30  can be moved within the housing&#39;s bore  25  to open or close fluid flow through the housing&#39;s flow ports  26  based on the inner sleeve  30 &#39;s position. 
     When initially run downhole, the insert  30  positions in the housing  20  in a closed state covering the flow ports  26 . A breakable retainer  38  initially holds the insert  30  toward the upper sub  22 , and a locking ring or dog  36  on the insert  30  fits into an annular slot within the housing  20 . Outer seals on the insert  30  engage the housing  20 &#39;s inner wall above and below the flow ports  26  to seal them off. Shear pins and other known features can be used to hold the insert  30  in its closed state. 
     The insert  30  defines a bore  35  having a seat  40  fixed therein. When an appropriately sized plug (e.g., ball, dart, etc.) lands on the seat  40 , the sliding sleeve  10  can be opened when tubing pressure is applied against the seated ball  40  to move the insert  30  open. To open the sliding sleeve  10  in a fracturing operation once the appropriate amount of proppant has been pumped into a lower formation&#39;s zone, for example, operators drop an appropriately sized ball B downhole and pump the ball B until it reaches the landing seat  40  disposed in the insert  30 . 
     Once the ball B is seated, built-up pressure forces push against the insert  30  in the housing  20 , eventually shearing the breakable retainer  38  and freeing the lock ring or dog  36  from the housing&#39;s annular slot. The insert  30  can then slide downward. As it slides, the insert  30  uncovers the flow ports  26 . 
     During opening of the sliding sleeve  10 , a first surface indication can be produced when the ball B lands on the seat  40  and built-up pressure exceeds the shear value and shifts the insert  30  open. The value of this first surface indication can depend on the type of sliding sleeve  10  used, the operating pressure, shear values, and the like. The shear values required to open the insert  30  can range generally from 1,000 to 4,000 psi (6.9 to 27.6 MPa). 
     When the insert  30  moves open, applied fluid pressure diverted by the seated ball B acts against the burst band  100 . As initially discussed, the burst band  100  is disposed around the exterior of the sleeve&#39;s housing  20  and covers the flow ports  26 . Thus, the burst band  100  can provide the conventional benefits of keeping out debris from the sleeve  10  and holding in any grease or the like. 
     In addition to these conventional benefits, however, the burst band  100  produces a second surface indication as built-up pressure bursts the burst band  100 . This second surface indication is expected to produce a signature pressure spike that can be preconfigured to a desired value for an implementation. Once the burst band  100  bursts, the sliding sleeve  10  is open to the borehole, and operators at the surface detecting the signature pressure spike can determine that the sleeve  10  has opened downhole successfully. 
     When it bursts, the band  100  preferably breaks into two or more pieces that fall away from the sleeve  10 . It may be acceptable in some implementations to have the band  100  split at one location rather than breaking into pieces. In any event, if any piece remains adjacent the ports  26 , the material can be eroded away during subsequent treatment operations. 
     Once the sleeve  10  is open, operators can then pump proppant at high pressure down the tubing string to the open sleeve  10 . The proppant and high pressure fluid flows out of the open flow ports  26  as the seated ball B prevents fluid and proppant from communicating further down the tubing string. The pressures used in the fracturing operation can reach as high as 15,000-psi. 
     Preferably as shown, the burst band  100  is not connected to the internal workings of the sliding sleeve  10 . Therefore, the burst band  100  is preferably disposed on the exterior of the housing  20 , which may have an external slot  29  to accommodate the band  100 . Fluid seals  28 , such as O-rings or the like, can be disposed on the exterior of the housing  20  (and/or on the interior of the burst band  100  depending on the band&#39;s thickness). These seals  28  can contain the fluid pressure at least partially inside the sliding sleeve  10  once the insert  30  is opened. In other implementations, seals may not be used, or seals may be disposed on the band  100 . 
     The burst value or surface indication value indicative of the bursting of the burst band  100  can be much higher than traditional surface indication devices. Additionally, as shown in the graph of  FIG. 5C , two pressure spikes or surface indications may be produced during the opening of the sliding sleeve  10  downhole. In particular, the first indication results from the build-up and then release of fluid pressure applied against the seated ball B to shear the insert  30  open. Then, the second indication results from the build-up and then release of fluid pressure to burst the burst band  100  covering the flow ports  26 . At surface using pressure measurements and known pressure devices, operators can then use the dual surface indications as further confirmation that the sliding sleeve  100  has successfully opened downhole. 
     Turning now to  FIGS. 6A-6C , details of one embodiment of a burst band  100  are shown in various views. The burst band  100  is preferably composed of cast iron, although other materials could be used, including other metals or non-metallic materials. The burst band  100  can have a thickness t 2  of about 0.4-in, but the particular thickness t 2  can be configured for a particular implementation and desired burst pressure as disclosed herein. The diameter d 2  of the band  100  depends on the diameter of the sleeve&#39;s housing  20 , and in one example, the band  100  may have an inside diameter d 2  of about 5.25-in for a 5.5-in. sliding sleeve. The height of the band  100  for such a sliding sleeve may be about 3.2-in. Inside edges of the band  100  can be beveled at 15 to 30 degrees for about 0.1-in. Again, the particulars of the diameter, height, and the like of the burst band  100  can be configured for a particular implementation and desired burst pressure as disclosed herein. 
     A plurality of scores  104 , indications, slots, grooves, or the like can be defined around the burst band  100  to facilitate rupture of the band  100  caused by internal pressure applied against the inner surface  102  of the band  100 . The scores  104  can be machined or formed in appropriate ways and are preferably defined on the exterior surface  106  of the band  100 . Additionally, the scores  104  preferably run along the longitudinal axis of the band  100  from the top to the bottom to promote splitting of the band  100 . 
     The depth of the scores  104  can depend on the implementation and other factors (e.g., thickness of band  100 , material used, burst pressure desired, etc.). In general, the scores  104  may have a depth of about 0.005 to 0.015-in., and they may define V-shaped profiles with sides angled at 45-degrees. 
     Any suitable number of scores  104  may be provided on the band  100 , and four are shown in the present example. The number of scores  104  used about the circumference of the band  100  can be configured to facilitate bursting at a desired pressure and/or producing a desired number of burst pieces of the band  100 . Preferably, at least two scores  104  are provided so that the band  100  breaks into two or more pieces. In one particular arrangement, four scores  104  are defined at every 90-degrees around the circumference of the band  100 . 
     Overall, the pressure level required to burst the band  100  is configured by the thickness t 2  of the band  100 , the material of the band  100 , the diameter d 2  of the band  100 , the number of flow ports  26  exposed to the band  100 , the number of scores  104  defined, the depth of the scores  104 , and other factors. 
       FIG. 7  illustrates another downhole tool  10  in partial cross-section having a burst band  100  according to the present disclosure. This downhole tool  10  is a ball-actuated sliding sleeve that counts passage of same-sized balls before opening and is similar to the sliding sleeve disclosed in US 2013/0186644 and US 2013/0025868, which are incorporated herein by reference in their entireties. To do this counting, the sliding sleeve  10  includes a counter  50 , an insert  60 , and a separate seat  70 . The insert  60  has flow passages  66  and seals inside the housing  26 . When the insert  60  is shifted, the insert&#39;s passages  66  align with the flow ports  26  to allow fluid flow out of the sliding sleeve  10 . 
     To help operators determine opening of the sliding sleeve&#39;s insert  60  inside the housing  20 , the sliding sleeve  10  includes the burst band  100  disposed about the housing  20  around the location of the flow ports  26 . Indication of the opening of this insert  60  may come primarily by the bursting of the band  100 , since a shear pin or other temporary retainer may not hold the insert  60  closed. Yet, the pressure response from the counter  50  and/or seat  70  can be used as another indication. To help seal the burst band  100  in place, the housing  20  includes seals  28 , such as O-rings disposed around the housing  20  both above and below the flow ports  26 . Other forms of sealing can be used. 
     To facilitate assembly of the burst band  100  on the sliding sleeve  10 , the housing  20  of the sliding sleeve  10  may include separate housing components. For example,  FIG. 8A  illustrates a cross-sectional view of an upper housing component  21   a  for the ball-actuated sliding sleeve  10  of  FIG. 6 .  FIGS. 8B-8C  illustrate cross-sectional and end-sectional views of another housing component  21   b  of the ball-actuated sliding sleeve  10  of  FIG. 6 . These two housing components  21   a - b  couple together with the burst band (not shown) disposed around their junction at the location of the flow ports  26 . Both components  21   a - b  define annular slots  28  for holding O-ring seals on the exterior to engage against the inside surface of the burst band (not shown). 
     As noted above, the pressure at which the burst band  100  bursts depends on a number of factors and can be configured for a particular implementation. For example,  FIG. 9A  illustrates burst calculations for four tests on different configurations of burst bands  100  according to the present disclosure. In each of the burst test calculations, the burst bands  100  are composed of a cast iron. 
     The charts for each of the calculations show the outside and inside diameters (minimum, nominal, maximum) of the burst band  100 , ultimate tensile strength, the band&#39;s wall thickness, the ratio of the outside diameter to the wall thickness, a correction factor, and thin and thick wall based calculations. In the first test calculation (Test  1 ), the band  100  has a first thickness of about 0.188-in., and it is calculated to burst at a burst pressure ranging from about 3732 to 4258-psi, depending on the various factors. In a first test run, a burst band  100  having this first thickness and having a 0.009-in groove depth for the scores was subject to burst pressure from flow ports on a sliding sleeve. The band  100  was observed to burst at 3920-psi into two overall pieces. 
     In the second test calculation (Test  2 ), the band  100  has a second thickness of about 0.172-in., and it is calculated to burst at a burst pressure ranging from about 2479 to 2821-psi, depending on the various factors. In a second test run, a burst band having this second thickness and having a 0.025-in groove depth for the scores was observed to burst at 2608-psi into three overall pieces. 
     In the third test calculation (Test  3 ), the band  100  has a third thickness of about 0.138-in., and it is calculated to burst at a burst pressure ranging from about 1523 to 1723-psi, depending on the various factors. In a third test run, a burst band having this third thickness and having a 0.059-in groove depth for the scores was observed to burst at 1602-psi into two overall pieces. 
     In the fourth test calculation (Test  4 ), the band  100  has a fourth thickness of about 0.152-in., and it is calculated to burst at a burst pressure ranging from about 1879 to 2132-psi, depending on the various factors. In a fourth test run, a burst band having this fourth thickness and having a 0.045-in groove depth for the scores was observed to burst at 1977-psi into two overall pieces. 
     Finally,  FIG. 9B  graphs the correlation between the calculated burst pressures of the burst bands  100  to the outside diameters of the burst bands  100  for a range between 5.52-in to 5.64-in. This correlation graphs as a polynomial equation and can be used to configure the particular factors of a burst band  100  for a particular implementation and desired burst pressure. 
     The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. For example, although the present disclosure focuses on verifying the opening of a sliding sleeve, such as a fracture sleeve, opened by a deployed plug or ball, the teachings of the present disclosure can apply to any other type of downhole tool used on a tubing string, such as a pressure-actuated sleeve, a ball-actuated sleeve, a toe sleeve, a stage tool, and the like. 
     It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter. 
     In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.