Abstract:
A fracturing jet nozzle assembly features a series of angles nozzles on a rotatably mounted plate that operates in conjunction with a central nozzle or nozzles. The slanted nozzles are aimed into the perforation where the central nozzle is aimed directly so that the rotation of the nozzle plate from the slanted nozzles results in cyclic impacts in the perforation from where the fractures will propagate. The cyclic loading results in greater fracture formation and propagation. In another variation, relatively movable plates employing slanted nozzles rotate one plate with respect to another to get the effect of cyclic pulses of jetting fluid impingement in the perforation to enhance formation and propagation of fractures from the perforation.

Description:
FIELD OF THE INVENTION 
       [0001]    The field of the invention is nozzles used in formation fracturing and more particularly nozzles used to enhance the initiation and propagation of formation fractures by adding a feature of cyclical impingement to the initial perforation made by the nozzle assembly. 
       BACKGROUND OF THE INVENTION 
       [0002]    Fracturing in open hole is a complex subject and has been studied and written about by various authors. Whether using explosives or fluid jets one of the problems with the initiated fractures is in the way they propagate. If the propagation pattern is more tortuous as the fractures emanate from the borehole an undesirable condition called screenout can occur that can dramatically decrease the well productivity after it is put on production. 
         [0003]    Hydraulically fracturing from any borehole in any well orientation is complex because of the earth&#39;s ambient stress field operating in the area. This is complicated further because of the extreme stress concentrations that can occur along the borehole at various positions around the well. For instance, there are positions around the borehole that may be easier to create a tensile crack than other positions where extreme compressive pressures are preventing tensile failure. One way that has been suggested to minimize this condition is to use jets that create a series of fan shaped slots in the formation with the thinking that a series of coplanar cavities in the formation will result in decreased tortuosity. This concept is discussed in SPE 28761 Surjatmaadja, Abass and Brumley Elimination of Near-wellbore Tortuosities by Means of Hydrojetting (1994). Other references discus creating slots in the formation such as U.S. Pat. Nos. 7,017,665; 5,335,724; 5,494,103; 5,484,016 and U.S. Publication 2009/0107680. 
         [0004]    Other approaches oriented the jet nozzles at oblique angles to the wellbore to try to affect the way the fractures propagated. Some examples of such approaches are U.S. Pat. Nos. 7,159,660; 5,111,881; 6,938,690; 5,533,571; 5,499,678 and U.S. Publications 2008/0083531 and 2009/0283260. 
         [0005]    Other approaches involved some form of annulus pumping in conjunction with jet fracturing. Some examples of this technique are U.S. Pat. Nos. 7,278,486; 7,681,635; 7,343,974; 7,337,844; 7,237,612; 7,225,869; 6,779,607; 6,725,933; 6,719,054 and 6,662,874. 
         [0006]    Pulsing techniques have been used in jet drilling or in conventional drilling to pulse the bit nozzle flow as described in U.S. Pat. Nos. 4,819,745 and 6,626,253. Also related to these applications is SPE paper 130829-MS entitled  Hydraulic Pulsed Cavitating Jet Assisted Deep Drilling: An Approach to Improve Rate of Penetration.    
         [0007]    Jets mounted to telescoping assemblies have been suggested with the idea being that if the jet is brought closer to the formation the fracturing performance will improve. This was discussed in U.S. application Ser. No. 12/618,032 filed Nov. 13, 2009 called Open Hole Stimulation with Jet Tool and is commonly assigned to Baker Hughes Inc. In another variation of telescoping members used for fracturing the idea was to extend the telescoping members to the borehole wall and to set spaced packers in the annulus so as to avoid the need to cement and to allow production from the telescoping members after using some of them to initially fracture the formation. This was discussed in U.S. application Ser. No. 12/463944 filed May 11, 2009 and entitled Fracturing with Telescoping Members and Sealing the Annular Space and is also commonly assigned. 
         [0008]    The present invention seeks to improve the extent of the fracturing that is accomplished beyond the initial formation perforation that is initiated explosively or with a direct impingement nozzle. The concept is to cyclically bombard the perforation with a jet stream or streams. This is accomplished in several ways including rotationally mounting a spray plate with angled spray exit streams that induce the plate to rotate on its axis. A specific location within the perforation will then by cyclically impinged and then after a pause will be impinged again. Another way is a combination of a stationary and rotating plate to create pulsing jet streams that further extend fractures that initiate in a perforation or from jet impingement in a normal direction. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the specification and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims. 
       SUMMARY OF THE INVENTION 
       [0009]    A fracturing jet nozzle assembly features a series of angles nozzles on a rotatably mounted plate that operates in conjunction with a central nozzle or nozzles. The slanted nozzles are aimed into the perforation where the central nozzle is aimed directly so that the rotation of the nozzle plate from the slanted nozzles results in cyclic impacts in the perforation from where the fractures will propagate. The cyclic loading results in greater fracture formation and propagation. In another variation, relatively movable plates employing slanted nozzles rotate one plate with respect to another to get the effect of cyclic pulses of jetting fluid impingement in the perforation to enhance formation and propagation of fractures from the perforation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic view of a zone to be fractured between barriers showing the placement of the nozzle assembly of the present invention; 
           [0011]      FIG. 2  is a section view of the extended nozzle assembly that has initiated a perforation and is creating and extending fractures into the formation; 
           [0012]      FIG. 3  is a perspective view of half the rotating nozzle plate showing the straight and the tilted nozzles; 
           [0013]      FIG. 4  is a perspective view of the assembly that is telescopingly extended and showing the rotating nozzle plate at the leading end; 
           [0014]      FIG. 5  is a similar view to  FIG. 3  showing the rotating plate in perspective; 
           [0015]      FIG. 6  is an alternative embodiment shown in perspective of a half section that uses a stationary plate at a leading end and a rotating plate behind it. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]      FIG. 1  shows a zone  10  isolated by packers  12  and  14  and a string  16  spanning the packers  12  and  14  and extending to the surface where the source of pressurized fluid (not shown) is located on a rig at the well site. The assembly  18  which will be described in its various embodiments below is shown schematically as an array that extends circumferentially around the string  16  and can be in a single or multiple parallel rows or can be offset spirals at for example 90 degree spacing or the pattern can be random to secure good coverage of the jet streams in the zone  10 . It is understood that there can be other zones and those skilled in the art will further know that the packer  12  can be set after the zone  10  is fractured to allow fracturing to go on at a higher zone that is not shown. In that case the packer  12  is set after zone  10  is fractured to allow isolation of zone  10  when another zone is being fractured. 
         [0017]    The assembly  18  is shown in  FIG. 2  as a series of movable components  20  and  22  that extend from a fixed component  24  attached to the wall of the string  16 . Component  24  has a travel stop  26  that limits the outer extension of section  22 . Similarly section  22  has its travel stop  28  for section  20 . Within section  20  is a rotatably mounted plate  30  that has one or more centrally located nozzle openings  32  whose axis is on or parallel to the axis of the components  20  or  22 . At an outer periphery are a series of nozzles  34  that have their axis skewed to the axis of components  22  and  20  at an angle that directs their stream into the pocket  36  that was initiated either explosively or by the jet stream from the nozzle openings  32 .  FIG. 4  shows that the plate  30  rotates because of the skew of openings  34  in one direction represented by arrow  38 . The rotational direction can be reversed by simply flipping over the plate  30  or changing the skew angle of the openings  34  to induce rotation in the opposite direction. 
         [0018]    The skew in the openings  34  directs the jets obliquely as shown by arrows  39  to the straight jet stream  40  coming from opening or openings  32 . Additionally, because plate  30  is rotating, the same spot  41  for example does not get impacted with a constant stream but rather gets impacted cyclically as each nozzle  34  spins around and aligns with the spot  41 . As a result of this cyclic impact pattern the more fractures  42  are initiated and propagated. 
         [0019]      FIG. 5  illustrates a variation where the straight nozzles  32  are on a fixed segment denoted by dashed lines  44  and the nozzles or openings  34  that are skewed to cause rotation of the outer segment  46  that is able to rotate as its core with nozzles  32  is held fixed. The spacing of the nozzles  34  can be equal or unequal along a common circumferential line. The nozzles  34  can be in a single radial distance from the center of the plate  30  or in multiple concentric rows or in a random order on a common circumferential line or lines or other arrangements that will induce rotation of the plate  30 . The angular orientation of each nozzle  34  with respect to the axis of components  20  or  22  can be the same for all or the skew angles can vary. The axis of the nozzles  34  can intersect the axis of the components  20  or  22  or preferably not so that there is a tangential component to induce spin even if the array of nozzles is symmetrical about the center of the plate  30 . Optionally an inline mixer such as a screw shape shown schematically as  46  can be attached to the plate  30  and located within the components  20 ,  22  and  24  to further induce spinning of the plate  30  using the delivered fluid for an extra boost of rotational force beyond the reaction force of the fluid exiting the nozzles  34  at high velocity and on a skewed axis. Nozzles  32  may be optionally eliminated or themselves be oriented on a skew to the axis of components  20 ,  22  and  24 . While the use of telescoping segments  20  and  22  is preferred to get the plate  30  as close as possible to the borehole wall as shown in  FIG. 2  the assemblies  18  can also be fixed so that they do not telescope. As another option the extended position of  FIG. 2  can be locked in at full extension or at partial extension if the borehole wall is encountered before full extension takes place. Ratchets  48  and  50  can be used to prevent retraction after any extension. The velocity of the fluid being pumped through the nozzles  32  and  34  will create an extension force to reach the  FIG. 2  position from a collapsed position for run in. The plate  30  can be made entirely from a hard material such as tungsten carbide or in the alternative the nozzles can be formed with inserts in a softer plate  30  where the inserts are retained by internal flanges  52  attached to a sleeve  54  extending through the opening of the plate  30 . Alternatively as shown in  FIG. 2  the sleeve  56  can be secured in the wall that is plate  38  such as by threads or adhesives, for example. 
         [0020]      FIG. 6  shows a stationary plate  58  with openings  60  that can be oriented substantially parallel to the axis of components  20 ′,  22 ′ and  24 ′. Substantially parallel means in perfect parallel alignment to a 10 degree skew. Openings  62  are in rotatably mounted plate  64  and are similarly oriented as nozzles  34  in plate  30  described above. Preferably the openings  60  are larger than the openings  62  at face  66  of plate  64 . The same options with regard to extending as described above apply to this embodiment as described above for the preferred embodiment. An optional internal mixer similar to  46  in  FIG. 2  can also be fitted. In the  FIG. 6  embodiment the nozzles equivalent to  32  in  FIG. 2  are eliminated. The orientation of the nozzles  62  makes plate  64  spin and provides a pulsing flow through the openings  60 . Openings  60  can be large enough so that they do not act as nozzles but rather as mere openings for passage of accelerated fluid flowing through nozzles  62 . The orientation of the nozzles  62  with respect to the openings  60  is such that at any given time there is flow through the plate  64  to keep plate  64  spinning. Face  68  of plate  58  can be made of a hardened material to tolerate the erosive effects of impact of flowing fluid when the openings  62  are moving between openings  60 . The nozzle construction variations for nozzles  62  are the same as for nozzles  34 . The telescoping feature in the  FIG. 6  design is optional as in the  FIG. 2  design but a ratcheting telescoping design as shown is preferred. 
         [0021]    The rotational movement of the nozzles helps to start and propagate fractures during the fracturing procedure by building on the perforations that are there from the perforating or the substantially parallel nozzles if they are used. The pulsing impacts on the borehole wall help to break up the rock and start and extend the fractures. The use of the energy of the flowing fluid to get the turning action keeps the design simple. More elaborate designs that mechanically drive the plate with the nozzles can be used but they would be more expensive and more prone to breakage. The rotating plate can be supported on a stationary bushing made of a soft metal or plastic or composite material. In the alternative more expensive ball or roller bearings can be used. The assembly can be extendable by force of the flow through the nozzles and the extended position can be locked in with a ratchet or body lock ring or some other device that allows relative movement in a single direction. The rotating plate can be a circular disc or it can be an annular shape that surrounds a stationary core where the core has substantially parallel oriented nozzles with respect to the axis of the assembly. The assembly can be in arrays on casing with parallel rows or offset spiral patterns or random locations in a desired zone to be fractured to assure adequate fracturing. While the preferred orientation of each assembly is perpendicular to the axis of the casing in which it is mounted, the assemblies can also be secured in a skewed orientation to the casing axis in a manner where the axis of the assembly  10  either passes through the axis of the tubular  16  or is offset from it. 
         [0022]    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.