Abstract:
A top down cementing tool operates with either mechanical manipulation or hydraulically. Rotation of the liner during cementing is enabled. A first bore is open for circulation during running in of the liner. In the hydraulic version, pressuring up on a dropped ball in the first bore opens cement packer setting ports and aligns crossover ports from the first bore to the annulus below the cementing packer and displaced fluid return ports to the annulus above the cementing packer. Pressuring up on a trailing wiper plug in the first bore opens the second bore so that pressuring on a seated ball in the second bore opens access to unsetting the cementing packer and launching the ball in the second bore for liner hanger setting and release of the running tool. The alternative embodiment gets the same result but with string manipulation for some of the realignments.

Description:
FIELD OF THE INVENTION 
     The field of the invention is top down cementing and more particularly with fluid displacement by the cement through a crossover with the ability to rotate the liner while cementing and further provisions for setting a liner hanger and release of a running tool from the cemented liner. 
     BACKGROUND OF THE INVENTION 
     Traditional liner cementing involves delivery of cement through a liner that is hung off casing with the cement going through a cement shoe at the lower end of the liner and back around in the annular space around the suspended liner. Fluid is displaced by the advancing cement through the liner hanger. At the time of fluid displacement with cement, the seal on the liner hanger is not set and there are gaps between the anchor slips through which the displaced fluid moves. After the cement is delivered a trailing wiper plug is released to clear the liner of excess cement. The cement shoe has a check valve to prevent return of the cement. The seal on the liner hanger is then set and the liner running tool is released and pulled out of the hole. The shoe can be milled or drilled out and more hole can then be drilled and the process can be repeated. 
     In some situations there can be doubt that the cement is adequately distributed using this method and an alternative technique for cement placement is desired. This is particularly beneficial when a formation is particularly weak which can result in significant fluid loses due to low fracking gradients. In a top down delivery of cement the operating pressures to which the formation is exposed are far less than the traditional bottom up cementing which can be beneficial in minimizing impact on the formation and ultimately getting a higher production rate from the formation when the well is put into production. 
     While there has been talk in the industry of doing top down cementing as a concept there have been no disclosed tools that would successfully and reliably accomplish such a cementing method. At best, schematic drawings for the flow of cement and return flows are illustrated in discrete passages with no clear details of how such tools get reconfigured for the various positions needed to actually accomplish top down cementing. Some examples of this are U.S. Pat. No. 8,387,693 FIG. 117 and the associated discussion in one paragraph in the specification and US 2010/0155067 that mentions ports such as  44  and seal bores in a passing reference to top down cementing with little detail as to how the tool is reconfigured for running in and then cementing and no details how to accomplish any associated tasks such as rotation while cementing, setting a liner hanger and releasing a running tool or how to structure a crossover tool and reconfigure such a tool between cement placement and the need to set a liner hanger/packer after cementing. 
     A top down cementing tool operates with either mechanical manipulation or hydraulically with rotation of the liner during cementing enabled. A first bore is open for circulation during running in of the liner. In the hydraulic version, pressuring up on a dropped ball in the first bore opens cement packer setting ports and aligns crossover ports from the first bore to the annulus below the cementing packer and displaced fluid return ports to the annulus above the cementing packer. Pressuring up on a trailing wiper plug in the first bore opens the second bore so that pressuring on a seated ball in the second bore opens access to unsetting the cementing packer and launching the ball in the second bore for liner hanger setting and release of the running tool. The alternative embodiment gets the same result but with string manipulation for some of the realignments. 
     Embodiments are presented that operate hydraulically and mechanically to get the same result. In either case, rotation of the liner during cementing is enabled. Those skilled in the art will better understand additional aspects of the present invention from a review of the detailed description of the preferred embodiments and the associated drawings while recognizing that the full scope of the invention can be found in the appended claims. 
     SUMMARY OF THE INVENTION 
     The present invention presents alternative embodiments to make top down cementing a reality. The basic interpretation of the invention switches from the conventional flow pattern to a crossed over flow pattern and then back to a conventional flow pattern. The invention uses a dual bore mandrel to allow internal flow in both the upward and downward directions during cementing. During run-in of the tool the invention has flow isolated to the Inlet bore. Both bores of the dual bore mandrel have ports. The inlet bore has ports below the packer element and the return bore has ports above the packer element. The ports on both bores are blocked from allowing flow to pass through them during the run in position. A ball will be dropped to set a cementing packer that will isolate the crossover ports for inserting the cement from those used to allow bypass for the return fluid. Manipulation of the tool through hydraulic or mechanical actuation opens the bypass ports allowing the transition from conventional flow to cross over flow. Flow rates are established at this time and then the cementing operations are performed. During cementing the tool can be rotated through the packer so a more even application of the cement occurs. At the end of the cementing operations the inlet bore is closed off by a sealing object dropped from surface and pressure can be increased to open the upper end of the return bore allowing the return a conventional flow path. Hydraulic or mechanical actuation is then performed to isolate the return ports so flow is blocked through them. Additional hydraulic or mechanical manipulation will unset the packer element allowing external bypass. Further hydraulic or mechanical actuation can then be performed to send a preloaded object from within the tool to set the liner string below and release the running tools allowing detachment and retrieval of the proposed tool. Standard cleaning operations for removing excess cement from the top of the liner can be done through the return fluid bore because the flow has been returned to conventional flow path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 a -1 e    are the hydraulic embodiment of the tool in the run in position; 
         FIGS. 2 a -2 e    are the view of  FIGS. 1 a -1 e    in the packer setting position; 
         FIGS. 3 a -3 e    are the view of  FIGS. 2 a -2 e    in the crossover flow configuration; 
         FIGS. 4 a -4 e    are the view of  FIGS. 3 a -3 e    in the unset packer configuration; 
         FIGS. 5 a -5 e    are the view of  FIGS. 4 a -4 e    in the release ball configuration for setting the liner hanger/packer below and releasing for running tool removal; 
         FIGS. 6 a - i    is an alternative embodiment in the run in position; 
         FIGS. 7 a - i    is the view of  FIGS. 6 a - i    in the packer set position; 
         FIGS. 8 a - i    is the view of  FIG. 7 a - i    in the cementing position; and 
         FIGS. 9 a - i    is the view of  FIGS. 8 a - i    in the packer release and set the liner hanger/packer position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 1 a -1 e    show the fully hydraulic embodiment of the present invention in the run in position. The top down cementing tool T sits inside the previous casing  12 . The liner and associated hanger/packer are below and are not shown. The liner hanger/packer are a known design and operate in a known manner including the setting and the release from the top down cementing tool T. 
     The major components of the tool T are a cementing packer P, an inlet bore  14 , a return bore  16 , an isolation sleeve  36 , a cement crossover port  20 , a returns crossover port  22 , a packer actuation port  24 , a packer release port  26  and a liner hanger/packer actuation ball  28 . For running in the isolation sleeve  36  has no ball  30  so that circulation is possible down inlet bore  14  to its lower end  32  where the flow can then enter the liner and come back to the surface in the annular space outside the liner. 
     When the liner is properly located generally at the lower end of the previous casing  12  the ball  30  is delivered to seat  18  as shown in  FIG. 2 e   . Pressure in bore  14  shears pin  34  and shifts sleeve  36  with ports  38  such that ports  38  align with actuation port  24  so that applied pressure moves piston  42  in the direction of arrow  44  toward the packer element  78 , after breaking shear pin  45 , to set the packer P. During shifting of sleeve  36  to align ports  38  with actuation port  24 , lower end  48  of sleeve  36  lands on upper end  50  of sleeve  52  which is in turn connected to sleeve  54  at thread  56  for tandem movement as will be later described. Sleeve  54  has the lower end  32  of the bore  14 . Sleeve  54  also has a lateral opening  58  that is misaligned with opening  60  in sleeve  62 . The lower end of sleeve  62  has a diverter plug  64  to block flow until opening  58  and opening  60  align. A travel stop  66  is in the bottom sub  68  of tool T. Openings  58  and  60  ultimately align to form bypass  61  seen in  FIG. 3 e    as sleeve  54  is driven to the travel stop  66  by additional pressure on ball  30  which breaks shear pins  80 . Sleeve  62  remains fixed to facilitate the alignment between openings  58  and  60 . 
     In the  FIG. 2  position with ports  38  aligned with actuation port  24  that is closed with thermal and pressure compensating piston  72  an isolated chamber  40  that has atmospheric or low pressure hydraulic fluid. The pressure buildup in chamber  40  moves piston  42  in direction  44  and the seal assembly  78  of the cement packer P is compressed. At this time the cement exit ports  76  are still offset from crossover ports  20  but further pressuring up after the packer P is set moves abutting sleeves  36 ,  52  and  54  to break shear pin  80 . When that occurs ports  76  move into alignment with ports  20  so that when cement is delivered to bore  14  it can exit laterally. The cement is delivered after a leading dart  70  lands on ball  30  as shown in  FIG. 3 d - e   . Ports  82  in the bore  16  have been run in aligned with housing crossover ports  22 , which is where the displaced fluid exits above the now set sealing element  78 . The rupture disc  26  is still intact so that in  FIG. 3  as the cement is delivered into bore  14  it travels to the aligned ports  76  and  20  to make a lateral exit because bore  14  is now closed with dart  70  sitting on seated ball  30  on seat  18 . This cement flow is shown by arrow  84 . At the same time heavy fluid that has been pumped in advance of the cement to help retain the cement in the annular space about the liner without entering the liner is displaced ahead of the cement into bore  16  because the cement pressure on ball  30  keeps bore  14  closed and the returning heavy fluid enters bore  16  as indicated by arrows  86 . The displaced fluid then crosses over through aligned ports  82  and  22  as indicated by arrow  88 . 
     After the predetermined volume of cement is delivered in the  FIG. 3  configuration, the next steps are to set the liner hanger/packer that is not shown and to release the tool T from the cemented liner that is also not shown. To do this, a second dart  90  lands on seat  92  at the end of the cementing operations so that the aligned ports  76  and  20  are effectively isolated from the upper end  94  of the bore  14 . Pressure is now applied to break the rupture disc  26  to open up passage  96  that leads to passage  16 . The ensuing flow into passage  96  is further impeded by the no shock sleeve  100 . A metering device  98  allows hydraulic fluid in space  101  to pass slowly so that ball or sealing object  118  does not get released early from ball seat  122 . The newly opened passage  96  allows for the pressuring up on the back end of the no shock sleeve assembly  100  which will break shear pin  108  allowing the no shock sleeve assembly  100  to be shifted until it shoulders out on travel stop  102 . Such movement opens up ports  104  as seal  106  shifts past port  104 . Pressure applied into annular passage  110  moves piston  112  in the direction of arrow  114  to release and extend the seal assembly  78  of packer P. Initial movement of the piston  112  breaks shear pins  116  allowing further movement of piston  112 . The further movement of piston  112  also releases a snap ring  113  by pulling out retaining key  117  to allow springs  115  to retract seal element  78  from contact with the previous casing  12 . Further movement of piston  112  in the direction of arrow  114  will shift port  22  to be misaligned with port  82  blocking off flow path  88 . Piston  112  will travel in the direction of arrow  114  until it shoulders out on travel stop  119 . This pressure buildup to release the cement packer P can happen because the ball  118  is still seated on frangible seat  122  through which ball  118  will ultimately pass when enough pressure is applied. Once piston  112  has shifted until it has shouldered out on travel stop  119 , the remaining hydraulic fluid left in space  101  is pushed through metering device  98  aligning ports  120  with ports  121  to increase flow bypass through the no shock sleeve assembly  100 . When ports  120  and  121  align collet  129  will latch onto shoulder  125  which locks ports  120  and  121  in alignment. With the cementing packer P unset further pressure buildup will force ball  118  through seat  122  as shown in  FIG. 5  so that the released ball  118  will land in the liner hanger/packer that is not shown for setting it in a known manner and for releasing the tool T also in the known manner. The tool T is now pulled out of the hole and excess cement can be washed out through the standard flow path through passage  96  and bore  16  from tubular to annular flow. Cement is then allowed to set up after which the hole can be extended and the process repeated with another liner or the hole can be completed and put into production. 
     Rotation of the tool T with the packer P set is enabled by bearings  121 ,  123 ,  131 , and  132  which allow all the components not fixated by the sealing effect of the seal assembly  78 , when set, to relatively rotate while the cement is delivered. Rotary seals  133  and  134  beneath packer P allow for a pressure differential across packer P while relative rotation occurs between packer P and dual bore mandrel  15 . 
       FIGS. 6-9  is another embodiment that has some similarities to the embodiment described above but has some mandrel manipulation to assume the necessary positions for accomplishing top down cementing. It will be described in a more abbreviated manner assuming the detailed discussion above of the first embodiment has provided a general background as to the tool configuration for top down cementing. 
     A mandrel  200  supports an outer housing  202  on opposed bearings  204  and  206  so that when a cementing packer  208  is set, the mandrel  200  can rotate relatively to the outer housing  202  components held fixed by the set packer  208 . Inside the mandrel  200  is a body that defines the cementing bore  210  and the displaced fluid bore  212 . A rupture disc  214  isolates the top of bore  212  from bore  210  at junction  216 . Bore  210  has lateral openings  218  located between seals  220  and  222  for access through ports  224  and  225  to set the packer  208 . This is done by pushing up the pistons  226  and  227 , and locking the piston movement with lock ring  228  so that the sealing element  230  is against the surrounding casing  232 . Bore  210  can be pressurized by landing ball  234  on seat  236  and building pressure. At a predetermined pressure the packer  208  is set and the seat  236  moves against tubular travel stop  238  so as to release the flapper  240  that is spring loaded to rotate against a seat  242 . With flapper  240  on the seat  242  flow up bore  210  is cut off. 
     The mandrel  200  is split into two components: an axial shifting mandrel  201  and a rotary sleeve  203 . The axially shifting mandrel  201  can shift axially with respect rotary sleeve  203  but are rotationally locked by torque stinger  205  and lock block  207 . The rotary sleeve  203  portion of mandrel  200  is axially locked to the outer housing  202  through retainers  209  and  211  which support bearings  204  and  206 . The axial shifting mandrel  201  is picked up to the point of collet  248  landing in groove  250  as shown in  FIG. 8 b   . This movement raises openings  252  in bore  210  to slots  254  in the axially shifting mandrel  201  where the slots  254  were already aligned with openings  256  in the outer housing  202 . The same picking up movement of axial shifting mandrel  201  lifts openings  260  in bore  212  that are located between seals  262  and  264  into alignment with slots  266  which are already aligned with openings  268  in outer housing  202  as shown in  FIG. 8 c   . A second ball  244  is dropped on seat  246 , as shown in  FIG. 8 e    to block off any additional flow from passing by the flapper  240  and shifts seat  246  until it shoulders out on travel stop  241 . A dart  258  is landed on ball  244  prior to pumping cement. At this time, after the heavy fluid is delivered the cement can be delivered right behind the heavy fluid to exit laterally as indicated by arrow  270  keeping in mind that the second dart  272  is delivered behind the predetermined quantity of cement. This effectively closes ports  252  with dart  272  as shown in  FIG. 9 e   . The displaced fluid comes up bore  212  because flapper  240  closes off bore  210  to flow in the up-hole direction. Arrow  274  shows the crossover exit of this fluid above the seal  230  for the trip up-hole in the upper annulus above the cement packer  208 . 
     After port  252  has effectively been closed off, rupture disc  214  is broken with applied pressure and the axial shifting mandrel  201  is lifted to take collet  248  out of groove  250  until travel stop  276  is engaged as shown in  FIG. 9 . Several processes take place during this lifting of the axial shifting mandrel  201 . First, the lower ports  252  and  254  are misaligned closing off flow to below the packer. At the same time, the upper ports  260  and  266  are misaligned closing off flow above the packer. At the same time the mandrel assembly  301  gets rotationally locked to the rotary sleeve  203  by the engagement of tooth pattern  304  to respective pattern  306  with  306  held by drag blocks  308 . Furthermore there is a lower travel stop  300  that limits the downward movement of the mandrel assembly  301  with respect to the axial shifting mandrel  201 . It should also be noted that lifting the axial shifting mandrel  201  disengages a mandrel spline  302  at the bottom end of the mandrel assembly  301  to permit the relative rotation of the axial shifting mandrel  201  with respect to the mandrel assembly  301  for ejection of ball  280  through opening  278  described later. Furthermore, picking up the axial shifting mandrel  201 , as shown in  FIG. 9 , also rotationally releases the axial shifting mandrel  201  from the rotary sleeve  203  by disengaging the rotational lock between the torque stinger  205  and lock block  207 . With additional pickup, the packer  208  is released, seen in  FIG. 9 , by breaking a shear ring  310  that defeats the collet thread  229  to physically extend the packer  208  in a known manner. Once the packer  208  is released the setting of the liner hanger and packer can take place. The preferred way to set the liner hanger/packer is by release of dart or ball  286 . The same pickup force that engaged lower travel stop  300  undermines support for flappers  288  and  290  by respectively aligning grooves  292  and  294  momentarily as the relative movement occurs. When flappers  288  and  290  have been removed from the darts path it can then be pumped down to set the liner tools below. It should be noted that in the run in position of  FIG. 6  there is a bypass around the dart  286  from entrance  296  to exit  298  as shown in  FIG. 6 h   . The same pick up that released the flappers  288  and  290  also moves outlet hole  278  up to ball  280  that is still held out of bore  281  by a retainer  282 . There is a cam surface  284  which when rotated against ball  280  can push ball  280  through the retainer  282  so it can drop to the liner hanger/packer that is not shown for its operation with applied pressure on the seated ball  280 . The setting of the liner hanger/packer that is not shown also allows the release of the tool for pulling out of the hole. 
     Those skilled in the art will appreciate that the embodiments of the present invention to enable top down cementing. The tool is run down with circulation enabled for location of the liner. The cementing bore is isolated at the top from the displaced fluid bore and running in an object into the cementing bore allows pressuring up to set the cement packer. Further manipulation aligns the cement crossover exit ports to ports leading out of the tool below the set cement packer. At this time the fluid return ports through the tool body from the return bore are already aligned or are being aligned. At the same time a dart is dropped on the ball used to set the packer and cement can be delivered with displaced fluid crossing over from the other bore at a location above the packer that is set to an upper annulus. The cementing crossover ports are then blocked with a second dart so that built up pressure can break a rupture disc and open up the return bore at the top of the cementing bore that is now closed. As the rupture disc breaks a sleeve with a metering device and a seated ball move in tandem. This movement exposes a packer release port leading to a release cylinder. Pressuring on the cylinder actuates the movement that releases a spring housing to extend the packer to retract the seal. The shifting of the cylinder also closes off the crossover port for returns from the displaced fluid bore. With lateral openings from the displaced fluids bore closed, pressuring on the ball in the displaced fluids bore launches this ball through its seat to the liner hanger packer that is not shown so that the liner hanger can be set and the top down cementing tool can be released and pulled out of the hole. 
     In the alternative embodiment of  FIGS. 6-9  the tool is open for circulation during running in. A ball is dropped on a seat and pressured on to sets the packer. Additional pressure is applied to release a flapper that prevents up-hole flow in the cementing bore. A pickup force aligns the cement crossover exit ports from the cementing bore with the displaced fluid crossover exit ports already in alignment. A ball and dart are landed and cement is pumped through the cement bore and out of the tool and displaced fluids cross over above the set cementing packer. A second dart then blocks the cement crossover exit ports and pressuring up on the cement bore then breaks a rupture disc to open the displaced fluid bore for flow in the down-hole direction. A pickup force allows the releases of a dart to set the line hanger packer that is not shown and release the tops down cementing tool in a known manner. As a backup a ball can be cammed out of a hole with relative rotation of adjacent housing components after aligning an exit port for the ball with the picking up. The picking up also closes the crossover exit port to allow pressuring up on the dart to deliver the dart to the liner hanger packer. 
     In either case, rotation during cementing is enabled. Top down cementing is made possible by setting a cement packer and opening a cement crossover port below the set cement packer so that cement can be delivered in a down-hole direction and returns are blocked from the cement bore and come up and crossover an adjacent bore that has an initially closed upper end and a displaced fluid exit port above the set packer and below the closed upper end for the displaced fluid bore. The displaced fluid bore is then opened after cementing and lateral ports in both bores are isolated and the cement packer is unset while a ball or dart is released through the displaced fluid bore with the cement bore isolated to pressure from above. The liner hanger packer is set and the running tools are released and the top down cementing tool is pulled out of the hole. 
     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: