Abstract:
A modular hydrojetting tool for fracturing well formations. The tool has a plurality of jetting modules. Each jetting module has a plurality of jetting nozzles therein. A sleeve is disposed in each jetting module except the lowermost module, and each sleeve is moveable from a first position covering the jetting nozzles in the corresponding module to a second position covering the jetting nozzles in an adjacent module. Plugs may be pumped into the tool to move each sleeve sequentially, thereby operating the jetting modules sequentially.

Description:
BACKGROUND  
       [0001]     The present invention relates to hydrojetting tools for fracturing oil and gas wells, and more particularly, to a hydrojetting tool with jetting openings which may be sequentially opened during a jetting operation.  
         [0002]     Hydraulic fracturing is often utilized to stimulate the production of hydrocarbons from subterranean formations penetrated by wellbores. In performing hydraulic fracturing treatments, a portion of the formation to be fractured is isolated using conventional packers or the like, and a fracturing fluid is pumped through the wellbore and perforations into the isolated portion of the formation to be stimulated at a rate and pressure such that fractures are formed and extended in the formation. Propping agent is suspended in the fracturing fluid to keep the fractures from closing and thereby provide conductive channels in the formation through which produced fluids can readily flow to the wellbore.  
         [0003]     One method that has been developed for such fracturing is to use a hydrojetting tool having at least one fluid jet forming nozzle. The hydrojetting tool is positioned adjacent to a formation to be fractured, and fluid is then jetted through the nozzle against the formation at a pressure sufficient to form a cavity therein. The high pressure exerted on the formation causes a microfracture to occur. Hydrojetting has been used in cased wellbores as well as uncased ones.  
         [0004]     Hydrojetting has worked well to create a controlled fracture. However, the process is limited in that the method uses a tool that inherently is limited in its ability to deliver large volumes of proppant through the orifices.  
         [0005]     A problem that can arise with hydrojetting is that the jetting nozzles can erode to an extent that they can no longer jet the fluid at a sufficient pressure to cut into the formation. With present hydrojetting tools, the tool must be retrieved from the well and refitted with new jetting nozzles. Obviously, this is a costly and time-consuming procedure. The present invention solves this problem by providing a hydrojetting tool with a series of modules, each module having at least one jetting nozzle therein. The jetting nozzles may be sequentially opened so that a new jetting nozzle is available when it is determined that the previous jetting nozzle has had too much erosion. The tool may be run into the wellbore with as many modules as necessary.  
       SUMMARY  
       [0006]     The modular hydrojetting tool of the present invention comprises a plurality of jetting modules that can be opened sequentially from the surface when desired. Each module has at least one jetting nozzle therein.  
         [0007]     The invention may be described as a hydrojetting tool for use in a well adjacent to a formation of interest, wherein the tool comprises a plurality of jetting modules, each jetting module having jetting nozzles therein adapted for jetting fluid into the formation The jetting modules may be operated sequentially.  
         [0008]     At least one of the modules has a sleeve therein moveable from a first position covering the jetting nozzles in the one module to a second position covering the jetting nozzles in an adjacent module. A plug may be pumped into engagement with the sleeve for moving it from the first position to the second position. The sleeve preferably comprises an inwardly extending mandrel adapted for engagement by the plug. The plug may be further pumped through the sleeve after moving it from the first position to the second position thereof.  
         [0009]     Stated in another way, the apparatus is a hydrojetting tool comprising a plurality of jetting modules with jetting nozzles therein adapted for jetting fluid into a well formation, and a sleeve slidably disposed in all but one of the jetting modules. Each sleeve has a first position covering the jetting nozzles in the corresponding jetting module and is moveable to a second position uncovering the jetting nozzles in the corresponding jetting module and covering the jetting nozzles in an adjacent jetting module. The sleeves may be moved sequentially such that the jetting modules may be operated sequentially.  
         [0010]     The apparatus may further comprise a plurality of plugs, wherein each plug may be pumped into engagement with a corresponding one of the sleeves for moving the corresponding sleeve from its first position to its second position.  
         [0011]     In the preferred embodiment, each sleeve comprises an upper sleeve portion which covers the jetting nozzles in the corresponding jetting module when the sleeve is in the first position, a lower sleeve portion which covers the jetting nozzles in the adjacent jetting module when the sleeve is in the second position, and an inwardly extending mandrel disposed between the upper and lower sleeve portions and adapted for engagement by the corresponding plug. The mandrels define holes therein, and the holes are progressively larger from a lowermost sleeve to an uppermost sleeve.  
         [0012]     The jetting module not having a sleeve therein is the lowermost jetting module. The lowermost jetting module may have a shoulder therein for limiting movement of the sleeve in the adjacent jetting module.  
         [0013]     Numerous objects and advantages of the present invention will become apparent to those skilled in the art when the following detailed description of the invention is read in conjunction with the drawings illustrating such embodiment. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  illustrates a modular hydrojetting tool of the present invention in position in a tool string in a deviated portion of a well.  
         [0015]      FIGS. 2A and 2B  show a cross-sectional view of the modular hydrojetting tool. 
     
    
     DESCRIPTION  
       [0016]     Referring now to the drawings, and particularly to  FIG. 1 , a modular hydrojetting tool of the present invention is shown and generally designated by the numeral  10 . Hydrojetting tool  10  is positioned in a wellbore  12  on a tubing string  14 . Wellbore  12  is shown as a deviated wellbore that penetrates a subterranean formation  16 . Wellbore  12  includes a substantially vertical portion  18  which extends to the surface and a substantially horizontal portion  20  which extends into formation  16 . It will be understood by those skilled in the art that hydrojetting tool  10  may be used in virtually any type of wellbore and is not intended to be limited to use in deviated wells.  
         [0017]     Additional tools may be run with hydrojetting tool  10  as desired. For example, but not by way of limitation, a centralizer  22  may be run to keep hydrojetting tool  10  in a central position within wellbore  12 . Other tools could also be run with hydrojetting tool  10  but are not shown for simplicity.  
         [0018]     Referring now to  FIGS. 2A and 2B , the details of hydrojetting tool  10  will be discussed. Hydrojetting tool  10  comprises a plurality of jetting modules. In the illustrated embodiment, there are a first module  24 , a second module  26  and a third module  28 . First module  24  is the lowermost module. Second module  26  is above first module  24 , and third module  28  is above second module  26 . As will be further described herein, any number of modules can be included in hydrojetting tool  10 , and the invention is not intended to be limited to the three shown.  
         [0019]     Hydrojetting tool  10  has a housing  30  which includes an upper adapter  32  connected to tubing string  14  in a known manner. Housing  30  also includes a first module housing  34  which is the outer portion of first module  24 , a second module housing  36  which is the outer portion of second module  26 , and a third module housing  38  which is the outer portion of third module  28 . First module housing  34  is attached to second module housing  36  by a threaded connection  40 . Second module housing  36  is attached to third module housing  38  by a threaded connection  42 . Third module housing  38  is attached to upper adapter  32  by threaded connection  44 .  
         [0020]     First module housing  34  of first module  24  defines a bore  46  therein with an inwardly extending shoulder  48  at the lower end thereof. Above shoulder  48 , a plurality of openings  50  are defined in first module housing  34 . A first jetting nozzle  52  is disposed in each opening  50 . Each of first jetting nozzles  52  defines an orifice  54  therein. First jetting nozzles  52  may be replaceable.  
         [0021]     Hydrojetting tool  10  has a central opening  56  therethrough. In the configuration of hydrojetting tool  10  as it is run into wellbore  12 , first jetting nozzles  52  are in communication with central opening  56 .  
         [0022]     Second module housing  36  of second module  26  defines a bore  58  therein. A second module sleeve  60  is slidably disposed in bore  58 . Second module sleeve  60  has an inwardly extending mandrel  62  therein with a hole  64  therethrough. Extending upwardly from mandrel  62  is an upper sleeve portion  66 , and extending downwardly from mandrel  62  is a lower sleeve portion  68 . Second module sleeve  60  is initially held in second module housing  36  by a shear pin  69 .  
         [0023]     Above mandrel  62  a plurality of openings  70  are defined in second module housing  36 . A second jetting nozzle  72  is disposed in each opening  70 . Each of second jetting nozzles  72  defines an orifice  74  therein. Second jetting nozzles  72  may be replaceable. In the configuration of hydrojetting tool  10  as it is run into wellbore  12 , second jetting nozzles  72  are covered by upper sleeve portion  66  of second module sleeve  60  so that second jetting nozzles  72  are not in communication with central opening  56 . This is a first position of second module sleeve  60 .  
         [0024]     Third module  28  is substantially identical to second module  26 . Third module housing  38  of third module  28  defines a bore  76  therein. A third module sleeve  78  is slidably disposed in bore  76 . Third module sleeve  78  has an inwardly extending mandrel  80  therein with a hole  82  therethrough. Hole  82  in third module sleeve  78  is larger than hole  64  in second module sleeve  60 . Extending upwardly from mandrel  80  is an upper sleeve portion  84 , and extending downwardly from the mandrel  80  is a lower sleeve portion  86 . Third module sleeve  78  is initially held in third module housing  38  by a shear pin  87 .  
         [0025]     Above mandrel  80 , a plurality of openings  88  are defined in third module housing  38 . A third jetting nozzle  90  is disposed in each opening  88 . Each of third jetting nozzles  90  defines an orifice  92  therein. Third jetting nozzles  90  may be replaceable. In the configuration of hydrojetting tool  10  as it is run into wellbore  12 , third jetting nozzles  90  are covered by upper sleeve portion  84  of third module sleeve  78  so that third jetting nozzles  90  are not in communication with central opening  56 . This is a first position of third module sleeve  78 .  
         [0026]     First, second and third jetting nozzles  52 ,  72  and  90  are illustrated as being oriented substantially perpendicular to a central axis of hydrojetting tool  10  and wellbore  12 . However, if so desired, any or all of the first, second and third jetting nozzles  52 ,  72  and  90  could be positioned at a different angle so that fractures may be initiated at such angles.  
       Operation of the Invention  
       [0027]     In operation, modular hydrojetting tool  10  is run into wellbore  12  on tubing string  14  in a conventional manner. As already indicated, other tools, such as centralizer  22  may also be run on tubing string  14  as needed. Hydrojetting tool  10  is positioned at the desired location within formation  16 .  
         [0028]     As previously discussed herein, hydrojetting tool  10  is initially in a configuration in which first jetting nozzles  52  are open and in communication with central opening  56 , and second and third jetting nozzles  72  and  90  are closed and covered by second and third module sleeves  60  and  78 , respectively, which are in the first positions thereof.  
         [0029]     Jetting fluid is pumped down tubing string  14  and jetted out first jetting nozzles  52  to begin initiation of fractures  94  in formation  16  and then propagation of propped fractures. As the fracture propagates, fluid rate is increased and injection via the annulus between tubing string  14  and wellbore  12  is initiated and established. Bemouli&#39;s principle allows the hydraulic fracture to remain isolated at the point of the jetting, and proppant fluid is pumped in the flow via tubing string  14  and through first jetting nozzles  52 . This proppant increases the erosion process of first jetting nozzles  52 , and the pressure due to the nozzle diameter starts to decrease and can be detected at the surface.  
         [0030]     When the operator determines when or if first jetting nozzles  52  have eroded or “washed” out too much for effective further jetting, a plug  96  is dropped into tubing string  14  and pumped down into hydrojetting tool  10 . Plug  96  has a plurality of wipers  98  to engage the inner surface of tubing string  14  and has a nose  100  on a lower end. Plug  96  is adapted to pass through hole  82  in third module sleeve  78  and to engage mandrel  62  on second module sleeve  60 . Nose  100  is adapted to fit in hole  64  in second module sleeve  60 . After plug  96  thus engages second module sleeve  60 , further pressure applied will force plug  96  to shear shear pin  69  and move second module sleeve  60  downwardly until it contacts shoulder  48  in first module housing  34 . This is a second position of second module sleeve  60 . When second module sleeve  60  moves to this second position, it covers and closes first jetting nozzles  52  and uncovers and thus opens second jetting nozzles  72  to communication with central opening  56 .  
         [0031]     Further jetting with second jetting nozzles  72  may then be carried out to form additional fractures  102 .  
         [0032]     When or if it is determined that second jetting nozzles  72  have incurred too much erosion, then another trip plug  104  is dropped into tubing string  14  and pumped down into hydrojetting tool  10 . Plug  104  has a plurality of wipers  106  to engage the inner surface of tubing string  14  and has a nose  108  on a lower end. Plug  104  is adapted to engage mandrel  80  on third module sleeve  78 . Nose  108  is adapted to fit in hole  82  in third module sleeve  78 . After plug  104  thus engages third module sleeve  78 , further pressure applied will force plug  104  to shear shear pin  87  and move third module sleeve  78  downwardly until it contacts the upper end of second module sleeve  60 . This is a second position of third module sleeve  78 . When third module sleeve  78  moves to this second position, it covers and recloses second jetting nozzles  72  and uncovers and thus opens third jetting nozzles  90  to communication with central opening  56 .  
         [0033]     Further jetting with third jetting nozzles  90  may then be carried out to form additional fractures  110 .  
         [0034]     While three modules have been shown herein for hydrojetting tool  10 , those skilled in the art will see that additional modules could also be used as necessary to carry on jetting of formation  16  until the desired amount of fluid is flowed out formation  16 . The above-described procedure would simply be repeated for each module. It is important to note that each succeeding trip plug must be larger than the previous one so that the plug and mandrel systems match and the next series of jetting nozzles are opened and used as desired.  
         [0035]     First module housing  34  has been illustrated herein as having central opening  56  continue below shoulder  48  so that fluid can be flowed through hydrojetting tool  10  to any other tools therebelow and also to allow full circulation of fluid through tubing string  14  and hydrojetting tool  10  as required. Plugs  96  and  104  may be configured so that they can be pumped on through hydrojetting tool  10  by the application of additional pressure thereon to provide for such further fluid flow or circulation. If this flow is not necessary, a lower end of first module housing  34  is simply closed.  
         [0036]     It will be seen, therefore, that the modular hydrojetting tool of the present invention is well adapted to carry out the ends and advantages mentioned as well as those inherent therein. While a presently preferred embodiment has been shown for the purposes of this disclosure, numerous changes in the arrangement and construction of the parts and steps in the method of use may be made by those skilled in the art. All such changes are encompassed within the scope and spirit of the appended claims.