Patent Publication Number: US-7591312-B2

Title: Completion method for fracturing and gravel packing

Description:
FIELD OF THE INVENTION 
   The field of the invention is completion techniques and more particularly those that involve gravel packing and fracturing with a means of preventing proppant flow back and/or formation solids production such as a screen assembly in position. 
   BACKGROUND OF THE INVENTION 
   Fracturing involves high flow rates and pressures to open up a formation using specialized fluids for the task. Typically after enough fluid volume at high enough pressure to fracture the formation is pumped, proppant is then added to the fracture fluid to enter the fractures just made and hold them open for subsequent production. In some applications, a screen assembly is introduced or is already in the well when the fracturing occurs. The fracturing process then transitions into a gravel packing process to allow proppant to fill the screen/casing annulus thus completing the gravel pack portion of a frac packed completion. When the proppant is introduced below an isolation packer for a given interval in a zone, it crosses over into the annulus surrounding the screens so that it can enter the fractures as well as fill the annular space around the screen assembly before production. The proppant is delivered into the fractures at high pressures and injection rates. The pump rates are reduced and circulation allowed to occur in order to fill the annulus between the screen and casing to complete the gravel pack. 
   In the past, fracturing and gravel packing of very long zones or multiple zones, whether in open hole or in cased hole typically required intermediate isolation packers to subdivide the interval into smaller zones to focus the fracturing or the gravel packing into such subdivided zones. This was time consuming and expensive because it required more packers, generally more trips in the well bore to facilitate equipment placement, and forced the same operation to be repeated numerous times to properly prepare an entire interval for subsequent production. 
   What is needed and provided by the present invention is a way to gravel pack the entire screened interval in a single operation in cased or open hole and then still have the ability to isolate intervals within a gravel packed zone for fracturing in a desired order through selectively opened ports in a liner. Another need addressed by the invention uses telescoping members that can be extended so that an annular space can be bridged by them while a liner is cemented, for example. Some of the telescoping members can be subsequently used for production. Some telescoping members in a liner can be associated with a valve and selectively opened in any desired order for a fracturing operation localized to the region around the telescoping members with its associated valve being opened. Production can then take place through the telescoping members with screens built into them while the other telescoping members that were used for fracturing have their associated valves closed. 
   Telescoping members have been in use to provide formation access after an annular space is cemented. These members have been equipped with either rupture discs or some other blocking material that can disappear such as by chemical interaction to open up a passage for flow after extension and cementing of the surrounding annulus. A good example of this is U.S. Pat. No. 5,829,520 as well as the various Zandmer patents cited in that patent. Gravel packing with zone isolation already in place in combination with bypass tubes to let the gravel get past such set barriers is shown in U.S. Pat. No. 5,588,487. 
   The preferred embodiment of the present invention will illustrate exemplary concepts of completions involving cementing and fracturing with a possible use of gravel packing in a procedure that optimizes the completion to allow it to get done faster and in a more cost effective manner. These and other advantages will become more readily apparent from a review of the description of the preferred embodiment and the associated drawings while recognizing that the appended claims define the full scope of the invention. 
   SUMMARY OF THE INVENTION 
   In one embodiment telescoping members are extended to bridge an annular gap either before or after it is cemented. Some of the telescoping members have screens and others have flow passages that can be selectively opened with associated valves to frac an interval in any order desired. The valves are then closed after the frac job and the other telescoping members are made to allow screened flow from the fractured formation. In another embodiment an interval to be gravel packed and fractured has a series of screens and selectively opened valves on a bottom hole assembly such as a liner. One or more external packers are provided. The entire interval is gravel packed at one time followed by packer actuation and then selective opening of ports to conduct a fracture operation in any of the zones defined by the set packers and in any desired order. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a section view of a bottom hole assembly in position in an open hole; 
       FIG. 2  is the view of  FIG. 1  with the telescoping members extended; 
       FIG. 3  is the view of  FIG. 2  with the annulus cemented; 
       FIG. 4  is the view of  FIG. 3  with a sliding sleeve opened to one of the telescoping members to allow fracturing to take place through it; 
       FIG. 5  shows the sliding sleeve valve of  FIG. 4  in the closed position before the piston is telescoped; 
       FIG. 6  is the view of  FIG. 5  with the sliding sleeve valve open and the piston telescoped out; 
       FIG. 7  is a split view showing the telescoping piston in more detail with a barrier intact on the left and the barrier ruptured with the piston extended on the right; 
       FIG. 8  shows a cased and cemented and perforated wellbore; 
       FIG. 9  is the view of  FIG. 8  showing a bottom hole assembly in position that includes screens and ports with valves and an external packer in the unset position; 
       FIG. 10  is the view of  FIG. 9  with the entire interval gravel packed and the packer then set; 
       FIG. 11  is the view of  FIG. 10  with one of the valved ports open for a frac job; and 
       FIG. 12  is an alternative to  FIG. 9  showing the bottom hole assembly in an open hole application as opposed to a cased hole. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows an open hole  10  with a surface string  12  supporting a liner  14  through a running tool  16 . String  12  extends through the running tool  16  to form an inner string  18  within the liner  14 . Inner string  18  terminates in a seal bore  20  located at the lower end  22  of the liner  14 . Liner  14  features telescoping members  24  and  26  shown in an alternating pattern although other patterns are possible as are different spacing and different total counts. The members  24  are preferably initially sealed with a material that can later be removed to expose a flow passage that contains a screen  28  or equivalent device to hold back solids when the formation is put onto production. Members  26  are shown in more detail in  FIG. 5 . There they are in the retracted position for run in so as not to significantly extend beyond outer surface  30 . Within the liner  14  in a recess  32  is located a slide valve  34  with seals  36  and  38  to selectively block access to passage  40  in member  26 .  FIG. 6  illustrates the open position of slide valve  34 . In this position, pressure within the liner  14  make members  24  and  26  extend radially. On reason this happens is shown in the split view of  FIG. 7 . Even after the initial opening of valves  34  with a shifting tool (not shown) each of their passages  40  is still covered such as with a rupture disc or equivalent removable barrier that can be removed with pressure or by other techniques such as chemical reaction or temperature exposure over time, for example. The other portion of  FIG. 7  shows the member  26  with passage  40  clear for flow and the obstruction member  42  disabled. The design of the telescoping members will not be explored in great detail as they are known devices whose application is described in U.S. Pat. No. 5,829,520 and the patents to Zandmer cited therein. 
   Now referring back to  FIG. 2 , the valves  34  shown in  FIG. 6  are in the open position to allow access to members  26  when the liner  14  is pressurized. The hanger  44  is set to support the liner  14 . There is always pressure access from within the liner  14  to members  24  although their passages are internally obstructed, initially, to allow pressure to telescope them out to the borehole wall  10 . Seal bore  20  can be part of a float shoe of a type known in the art to allow cement  46  to be pumped into annulus  48  and keep it from coming back into liner  14  through a check valve, not shown. After the cement  46  is pumped, the string  12  is raised and pressure is applied to pressurize the liner  14  internally and to telescope out all the members  24  and  26 . At this point the fact that flow passages  28  and  40  are obstructed allows the members to respond to internal pressure in the liner  14  and telescope out radially. Upon getting extension of members  24  and  26  the obstructions in passages  40  can be removed by pressure, chemicals, temperature exposure or other ways to allow access past the cement  46  and into the formation  50  that surrounds the cement  46 . 
     FIG. 4  shows one valve  34  then moved into the open position to allow flow from within the liner  14  through the member  26  that now has an opened passage to the formation  50 . The valves  34  can be opened in any order so as to allow fracturing through members  26  in any order with the members  24  extended but not open at passages  28  so as to allow pressure developed in liner  14  to be directed to the member or members  26  with an associated valve  34  in the open position. When the fracturing through the desired members  26  is completed, the valves  34  are all put in the closed position and the passages  28  in members  24  are ready to be opened. This can be accomplished by pressure, chemicals or time exposure to temperature or other ways so as to expose the passages  28  that preferably include a screen device to hold back some of the solids that may be produced when production begins through members  28 . 
     FIG. 8  shows a completion technique that starts with a cased hole  52  that has perforations at  54  and  56 . In  FIG. 9 , a bottom hole assembly  58  has a series of screens for example  60  and  62  separated from screens  64  and  66  by a barrier device than can be actuated such as a packer  68 . The number of screens and packers can be varied as can their spacing. The packer or packers used such as  68  are provided to eventually close off the annulus  70  after it is gravel packed as shown in  FIG. 10 . The assembly  58  further comprises valved ports  72  and  74  that straddle the packer  68 . Ideally, one or more valved ports should be present to provide access into the annulus  70  on either side of a packer  68  where ultimately there will be a need to fracture or produce well fluids.  FIG. 10  also shows a top packer  76  that is set in conjunction with a known crossover, not shown, to allow deposition of gravel to the entire interval below packer  76  in one operation. Tubes to allow gravel pass any sand bridges can also be used according to methods well known in the art to promote gravel distribution. Ports  72  and  74  are closed during the gravel packing of the annular space  70 . 
     FIG. 11  shows how a valve  74  can be opened while valve  72  is closed, for example. With the packer  68  already set, pressure in the assembly  58  can fracture sub zone  76  adjacent open valve  74 . The fracturing can be in any order that the valves such as  72  and  74  are operated. An anchor packer  78  can be used to close off the wellbore below the assembly  58 . 
     FIG. 12  simply illustrates that the concept of  FIGS. 9-11  can be used in open hole  80  with the same operational sequence and possibly leaving out the anchor packer  78 . 
   Those skilled in the art will now appreciate that the technique of  FIGS. 1-7  illustrates an ability to position a liner with formation access without perforation. The liner or tubular  14  can be cemented before or after extension of the members  24  and  26 . The array of members  24  and  26  allows fracturing to take place in any order that valves  34  are operated with known shifting tools or the like. While sliding sleeves are preferred for valves  34  other types that can be opened and closed when needed can be used. The option to fracture before going on production improves the production rate. The array of telescoping members allows opening of the production passages  28  that also preferably contain a screen assembly after the fracturing is completed in the desired sequence. The valves  34  are closed and the members  24  cleared for production flow through a discrete set of passages from those that were used to fracture. The passages  40  are preferably unobstructed and are made from materials that will resist high fluid velocity erosion during the fracturing operation. As previously stated, members  26  on the other hand preferably have screens in passages  28  to stop at least some produced solids from getting into the liner  14 . 
   The method described in  FIGS. 8-12  shows a completion technique that allows gravel packing an interval at once that will also be fractured in smaller increments. The presence of the set packer such as  68  in the annulus  70  can be useful in later isolation of portions of the producing zone such as for example if a portion starts to produce water. The screens in that subpart can be closed off using a schematically illustrated valve  75  and production can continue from adjacent screens without concern of axial migration of the contaminant such as water. Here again, the method allows for one gravel pack for the overall interval, an opportunity to subdivide the annulus after gravel packing with known packers followed by fracturing in any desired sequence. It should be noted that packers such as  68  are mounted on blank pipe and that during gravel deposition typically the gravel doesn&#39;t tend to pack tightly in the annulus  70  during a gravel pack. This makes it less difficult to set the packer  68  after the gravel packing is complete. The method works in cased or open hole. The method can be accomplished in a single trip when the assembly is run in with a shifting tool to operate the valves  72  or  74 . The topmost zone to be fractured can also be accessed through the crossover instead of a valved port such as  72  but the valved ports are preferred because they accommodate the higher flow rates and velocities seen during a fracturing operation. 
   The above description is illustrative of the preferred embodiment and various alternatives and is not intended to embody the broadest scope of the invention, which is determined from the claims appended below, and properly given their full scope literally and equivalently.