Patent Publication Number: US-9410411-B2

Title: Method for inducing and further propagating formation fractures

Description:
FIELD OF THE INVENTION 
     The field of the invention is using inflatables to initiate formation fractures and further propagating the fractures with ports that are opening in gaps in or between inflatables. 
     BACKGROUND OF THE INVENTION 
     Fracturing is a performance enhancing technique where fractures are started in a variety of ways and in some cases further propagated and/or held open for ultimate production to the surface. Packers have been set in open hole as a technique to initiate fractures as described in US Publication 2011/0139456. However, this technique preferably used compression set packers and sliding sleeves 22 that were located uphole from each packer that could be selectively opened for production. Another design shown in US Publication 2011/0284229 showed a series of inflatable packers that incorporated sliding sleeves that were shifted with a shifting tool on a service string such as coiled tubing to open ports above the inflatable which fully encircled the production string. This design involved another trip in the hole to open the ports and positioning of the ports remotely from the packer since the inflatable fully surrounded the production string. 
     Other references with some relevance to the present invention include U.S. Pat. No. 2,798,560 and U.S. Pat. No. 4,655,286. 
     What is needed and offered by the present invention is a way to initiate the fractures while at the same time minimizing the distance between the frac port and the fracture initiation device. The inflatables envisioned for the present invention preferably are segmental leaving gaps in between so that the ports can be located between the preferably inflated segments that initiate propagation of the fractures. The use of such segments or lobes to initiate fracture also leaves gaps so that a cementing job can take place with the cement fully filling the annular space by flowing around the lobes. The frac ports are hydraulically operated so that an intervention string is not needed. Various sensors can be employed to transmit formation information to the surface to determine the onset of fractures. The fractures can occur through the ports opened by the sliding sleeves either in open hole without cementing or through the cement. Multiple stacks of lobes can be used with sleeve actuation devices that employ balls of progressively larger size as one way to actuate the sleeves in the order required. These and other features of the present invention will be more readily apparent to those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be found in the appended claims. 
     SUMMARY OF THE INVENTION 
     Fractures are induced from lobe shaped inflatable members disposed at different axial locations along a string with frac ports in the circumferential gaps between the lobes. The lobes are inflated by landing a ball on a seat on a sleeve that is initially shifted enough to expose a fill port on each lobe. The lobes are inflated to a pressure that initiates fractures in the formation as the lobes extend. Further raising the pressure induces the sleeve to move a second time to open frac ports. The annulus can be cemented and fracturing can penetrate the cement to further propagate the initiated fractures from lobe inflation. The process is repeated at different levels until the zone of interest is completed. Sensors can relay information by telemetry techniques as to the onset of fractures or other well conditions. The sleeve for the frac ports can be moved in a variety of ways without intervention tools. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a section view of the assembly in a run in position; 
         FIG. 2  is the view of  FIG. 1  with the lobes extended; 
         FIG. 3  is the view of  FIG. 2  with the sleeve shifted to open access ports between the lobes for fracture extension; 
         FIG. 4  shows a hydraulically operated inner sleeve in a run in position where ports to the lobes and to the formation are both closed; 
         FIG. 5  shows the first movement of the sleeve of  FIG. 4  to allow access to the lobes to inflate them; 
         FIG. 6  is the view of  FIG. 5  with the sleeve shifted a second time to open the ports to the formation; 
         FIG. 6 a    is a section view through  FIG. 6  showing the ports to the formation open; 
         FIG. 7  is and end view of the inner sleeve with the ports to the lobes and the formation closed; 
         FIG. 8  is an axial section view of the assembly shown in  FIG. 7 ; 
         FIG. 9  is an external view of two adjacent lobes showing the port for formation access between the lobes; and 
         FIG. 10  is an alternative embodiment to  FIG. 9  with the formation port surrounded by the lobe. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  illustrates the main components of the assembly. A mandrel  10  has ports  12  disposed between inflatable lobes  14 . A sliding sleeve  16  isolates internal passage  18  from the lobes  14  and ports  12  for run in. The sleeve  16  is preferably operated without well intervention such as by applied pressure from the surface of the open borehole  20  that is preferably horizontal for the deployment of the illustrated assembly. The method features opening access to the lobes  14  through ports  22  as shown in  FIG. 2 . This is accomplished with an initial translation of the sleeve  16  that is accomplished without well intervention. In  FIG. 2  the lobes  14  are inflated and in contact with the borehole  20  wall so that fractures  24  are initiated as pressure inside the lobes  14  is increased. Instruments  26  sense the onset of fracture formation and through known telemetry techniques transmit the information to the surface to alert surface personnel to take steps to move sleeve  16  so that ports  12  can be opened for propagating the fracture started by inflation of the lobes  14 . This is shown in  FIG. 3  where the ports  12  are open and fluid exits those ports very near the location where the fractures  24  started on expansion of lobes  14 . The flow represented by arrow  26  increases the initial fractures  24  as represented by  28 . 
       FIG. 4  illustrates the sequence of movement of sleeve  16  to first allow inflation of lobes  14  by opening ports  22 . One way this can be done is to drop a ball  30  on seat  32  and build pressure to break shear pins  34 . The sleeve  16  moves to the right to expose ports  22  so that lobes  14  can inflate. Seat  32  is eventually stopped at shoulder  36 . Slot  38  on the exterior of sleeve  16  allows initial movement of sleeve  16  without breaking shear pin  40  which stops the sleeve  16  with only ports  22  open. After the fractures  24  are initiated the shear pin  34  is sheared and pressure is further built up to further move the sleeve  16  to open the ports  12  so that the fractures  24  can be further propagated as shown at  28 . The seat  32  is captured by shoulder  36 . The second movement of sleeve  16  opens the ports  12  as the shear pin  40  is broken ultimately allowing the stop/lock  42  to capture the sleeve  16  in the position where ports  22  and  12  are all open. 
     Other ways to get the ports open without intervention are contemplated. For example a j-slot tied to a ball landed on a seat can be employed so that the first pressure cycle opens ports  22  and the second pressure cycle opens ports  12 . Progressively larger balls can be used to address multiple axially spaced locations for otherwise identical assemblies so that an entire desired zone can be fractured. The ability to manage each assembly in turn without running an intervention string into the borehole speeds up the process so as to reduce rig time and associated costs. 
       FIGS. 5 and 6  schematically illustrate the dual movement of sleeve  16  to initially open the ports  22  and then to open the ports  12 . Ports  12  are circumferentially rotated from the lobes  14  so that they provide direct access to the formation at the borehole wall  20  as shown in  FIG. 6 a   .  FIGS. 7 and 8  are similar to  FIGS. 1 and 4  and are somewhat schematic for the run in position taking note that the ports  12  are not literally under a lobe  14  but offset from ports  22  that are used to extend the lobes  14 . 
       FIG. 9  shows an elongated lobe  14  layout with the ports  12  located between upper ends  44  and lower ends  46  of the lobes  14 . This puts the ports  12  as close as possible to the initiated fractures  24  started by lobe  14  inflation, as shown in  FIG. 2 . In  FIG. 10  the lobe  14  surrounds the port  12  so that the flow to enhance the initiated fractures  24  comes out right at the initiation location caused by inflation of the lobes  14 . 
     Those skilled in the art will appreciate that the mandrel  10  can be part of a production string that can be left in open hole for production or can be cemented with lobes  14  expanded and the pressure of fluid through ports  12  will work its way through the cemented surrounding annulus to operate in the above described manner. The spacing of the lobes allows cement to pass around them when inflated. Later when the cement is set up removal of pressure internally at passage  18  allows the lobes to collapse to provide greater access to the ports  12  for production. Optionally the sliding sleeve can have screened openings that align with ports  12  after fracture enhancement to allow screening of production or injection flow, depending on the intended application. Preferably the cement is added with the lobes inflated but not to the degree that the fractures initiate. Rather, the lobes are further inflated after cementing to initiate the fractures with the wall ports opening to propagate the fractures. The lobe can be deflated by the frac fluid pumped through the wall ports. 
     The lobes can have a variety of shapes that are designed to contact the borehole wall to initiate fractures. The lobes can be inflatables or shapes that are compressed to contact the borehole wall to initiate fractures using an actuation method that requires no intervention. For example pressure can trigger selective pistons in a desired sequence controlled by such elements as rupture discs. Gaps between lobes allow cement to pass in cementing situations and allow location of frac ports to enhance the initiated fractures to be right at or very close to the initiated fractures by locating such frac ports between lobes or allowing lobes to surround the frac outlets. 
     The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: