Abstract:
A method for cleaning debris from a wellbore having a top and a bottom comprising inserting cleaning tool comprising a coaxial pipe in the wellbore, pumping fluid through the cleaning tool to create a fluid flow in a direction towards the bottom of the wellbore, converting the fluid flow into rotary mechanical power, agitating the debris by cavitation with at least one vortex spinner having a plurality of spinner blades, and allowing the debris to flow towards the top of the wellbore thereby cleaning the wellbore.

Description:
FIELD OF INVENTION 
       [0001]    The present inventions relate to a cleaning apparatus and a method for cleaning debris from a wellbore. 
       BACKGROUND 
       [0002]    Formation damage is defined as a reduction in permeability around a wellbore, which is the consequence of drilling, completion, injection, attempted stimulation or production of the well. The mechanism of formation damage varies from well to well; however the transport of solids into and out of the wellbore is consistently an important factor. Drilling mud, drilling fluids drill-in fluids, fluid loss inhibitors, and other similar fluids can invade permeable formations, replacing native fluids adjacent to the wellbore. During replacement, solid particles invade the formation and reduce its permability by blocking flow channels. This blockage in the flow channels causes formation damage, which can result insignificant decreases in well productivity and resulting economic loss. 
         [0003]    A variety of techniques have been developed to remove formation damage. Acidization is probably the most commonly applied technique; however this solution may often result in corrosion of the wellbore equipment and chemical incompatibilities. Additionally large volumes of acid are very expensive and can be problematic in horizontal completions. Formation damage may also be limited somewhat by pretreating the fluids used in drilling, fracturing, and perforation; however this is not an option for correcting post-completion damage. 
         [0004]    A recent development in the area of hole cleaning is the use of the principle of cavitation for removing debris such as cuttings, pieces of rock chips, gravel, fines, asphaltenes, solids deposited to reduce fluid loss, and other particles that may interfere with the production or operation of a well. Cavitation generally refers to the formation and instantaneous collapse of innumerable tiny vapor bubbles within a fluid subjected to rapid and intense pressure changes. A liquid subjected to a low pressure (tensile stress) above a threshold ruptures and forms vaporous cavities. When the local ambient pressure at a point in the liquid falls below the liquid&#39;s vapor pressure at the local ambient temperature, the liquid can undergo a phase change, creating largely empty voids termed cavitation bubbles. 
         [0005]    Downhole cleaning via cavitation involves attaching a cavitation tool to the end of the coiled tubing, drill pipe or work string. To do so, the production or drilling must be stopped while the cleaning apparatus is run into the hole. Fluid pumped through the tool drives a mechanical process that induces cavitation, and a flare of bubbles is released. The combined effects of the flow impact, the suction effects of the decaying bubble flare, and the implosion shock waves of the cavitation are effective to mobilize and remove debris that may be trapped in the wellbore. 
       SUMMARY OF THE INVENTION 
       [0006]    The present inventions include a method for cleaning debris from a wellbore having a top and a bottom comprising inserting cleaning tool comprising a coaxial pipe in the wellbore, pumping fluid through the cleaning tool to create a fluid flow in a direction towards the bottom of the wellbore, converting the fluid flow into rotary mechanical power, agitating the debris by cavitation with at least one vortex spinner having a plurality of spinner blades, and allowing the debris to flow towards the top of the wellbore thereby cleaning the wellbore. 
         [0007]    The present inventions include an apparatus for cleaning a wellbore comprising a coaxial pipe with a first end and a second end, at least one vortex spinner operatively connectable to the coaxial pipe between the first end and the second end, and a fluid divider arranged inside the coaxial pipe. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present invention is better understood by reading the following description of non-limitative embodiments with reference to the attached drawings, wherein like parts of each of the figures are identified by the same reference characters, and which are briefly described as follows: 
           [0009]      FIG. 1  illustrates a side view of one embodiment of a cleaning tool during production. 
           [0010]      FIG. 2  illustrates a close-up side view of the one embodiment of the downhole cleaning tool. 
           [0011]      FIG. 3  illustrates a side view of another embodiment of the cleaning tool. 
           [0012]      FIG. 4  illustrates a top view of the cleaning tool. 
           [0013]      FIG. 5  illustrates a top view of the cleaning tool with a ball dropped to deactivate one of the nozzles. 
           [0014]      FIG. 6  illustrates a side view of the cleaning tool with a ball dropped to deactivate one of the nozzles. 
           [0015]      FIG. 7  illustrates a side view of another embodiment of the cleaning tool during production. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    For the purpose of this application, the terms used shall be understood as follows. The term “horizontal” or “deviated” well is used to describe an oil or gas well drilled at an angle at least 30 degrees from vertical. The term “debris” is used to mean cuttings, pieces of rock chips, gravel, fines, asphaltenes, solids deposited to reduce fluid loss, and other particles that may interfere with the production or operation of a well. 
         [0017]    Referring to  FIG. 1 , one embodiment of downhole cleaning tool  100  is shown installed in wellbore  101  during production. Cleaning tool  100  is attached to a portion of tubing  102  and lowered into the well. In this embodiment, the cleaning tool is shown integrated with the production tubing. Alternatively the cleaning tool may be inserted into the well with a wireline, stinger, or another joint of tubing. In the embodiment shown, only one cleaning tool is depicted; however, multiple tools may be installed at various intervals along the tubing to increase cleaning efficiency. 
         [0018]    Cleaning tool  100  may be made up of coaxial pipe  103 , fluid divider  104 , and vortex spinner  105  connectable around the circumference of the coaxial pipe. Connectors  106  hold the spinner in place, decrease friction of vortex spinner  105  while rotating, and seal the fluid flow from interior pipe to outside.  FIG. 2  shows a close-up view of a portion of the downhole cleaning tool from  FIG. 1  in which connectors  106  are roller bearings, or any similar connection apparatus. Vortex spinner  105  comprises spinner housing  107 , interior spinner blades  108 , and exterior spinner blades  109 . 
         [0019]    During operation, fluid is pumped down production tubing  102  through cleaning tool  100  towards the bottom of the wellbore as represented by arrow  110 . When the fluid moves through fluid divider  104 , the pressure decrease causes the velocity of the fluid to increase. Alternatively fluid divider  104  may be removed from the design. The fluid hits interior spinner blades  108  and rotates vortex spinner  105  at a speed sufficient to induce cavitation. The interior and exterior spinner blades and may be connected to the vortex spinner in any arrangement; however, a spiral, helical, or slanted configuration is preferred. Vortex spinner  105  and exterior spinner blades  109  agitates the fluid in annulus  112  and releases debris attached to the wall of the wellbore. The fluid then may pass through the rest of the assembly. Mobilized debris may be circulated along annulus  112  (according to arrow  111 ) to the surface. 
         [0020]      FIG. 3  shows an alternative embodiment of the downhole cleaning tool. In this embodiment, nozzles  301  may be attached to vortex spinner  105  to enhance the cleaning process. The number of nozzles and angles at which the nozzles are positioned may be adjusted based on well conditions. Optionally the nozzles may be equipped with nozzles heads (not shown) to direct fluid as it exists the nozzle. Optionally the nozzles may be threaded or otherwise manufactured to direct fluid flow. When fluid is pumped down along arrow  110 , a portion may pass through nozzle  301  to agitate debris  302  and loosen it from the wellbore. The rest of the fluid continues through the tool to activate rotate the components to induce cavitation. 
         [0021]      FIG. 4  shows a top view of the embodiment of the downhole cleaning tool from  FIG. 3  in wellbore  101 . Coaxial pipe  103  is shown encircled by vortex spinner  105 . A plurality of nozzles  301  extend through vortex spinner  105 . In this embodiment, four nozzles are shown; however more could be included in a variety of arrangements. Each nozzle may be equipped with a nozzle head  402  at its end, which can be adjusted to set the angle at which fluid exists the tool. Each nozzle may be connected to a hole in the inner wall of vortex spinner  105 . Fluid breaker  403  encircles the inner wall of vortex spinner  105  beneath the holes leading to the nozzles. 
         [0022]    During operation, fluid flows across fluid divider  104  and experiences an increase in velocity. Alternatively, the fluid divider could be omitted and the vortex spinner driven with the natural velocity of the fluid. A portion of the fluid hits interior spinner blades  108  and causes coaxial pipe  103  (or is it vortex spinner  105 ?) to rotate at a specified speed. A different portion of the fluid may enter nozzles  301  and is shot against the formation to loosen debris. The rest of the fluid may continue through the tool to activate the cavitation process via vortex spinners  105 . One possible path of the fluid is shown by arrows  404 ; however, others paths are possible. 
         [0023]    When the operator no longer requires the use of one of the nozzles, controllable passageways capable of stopping fluid communication in one or all of the nozzles may be used. In one embodiment, a ball  501  may be dropped to deactivate the nozzle.  FIG. 5  shows a top view of the tool with ball  501  resting on fluid breaker  403  and blocking the hole, which leads the leftmost nozzle.  FIG. 6  shows a side view of the same scenario. Alternatively another mechanism known in the industry to block flow such as a flapper valve. Alternatively, as shown in  FIG. 7 , the vortex spinners may be removed and replaced with pipe  301  so that the tool is simplified to only include the nozzle cleaning mechanism. Any other method that achieves the effect of the controllable passageways may be used. 
         [0024]    Advantages of some embodiments of the invention may include one or more of the following:
       Allows the assembly of one or multiple fluid-driven rotary cleaning subs as needed anywhere in the completion eliminating the limitations of tools that may only be installed at the end of the tubing   Eliminates additional trips required to disassemble and insert a cleaning assembly   Reduces or eliminates backreaming   Prevents settling of drill cuttings   Increases lifetime of completion equipment and other downhole tools       
 
         [0030]    Those of skill in the art will appreciate that many modifications and variations are possible in terms of the disclosed embodiments, configurations, materials, and methods without departing from their spirit and scope. Accordingly, the scope of the claims appended hereafter and their functional equivalents should not be limited by particular embodiments described and illustrated herein, as these are merely exemplary in nature.