Abstract:
A device useful for conducting lateral or transverse excavating operations within a wellbore comprising a rotating drill bit with jet nozzles on a flexible arm. The arm can retract within the housing of the device during deployment within the wellbore, and can be extended from within the housing in order to conduct excavation operations. A fluid pressure source for providing ultra high pressure to the jet nozzles can be included with the device within the wellbore. The device includes a launch mechanism that supports the arm during the extended position and a positioning gear to aid during the extension and retraction phases of operation of the device.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates generally to the field of excavation of subterranean formations. More specifically, the present invention relates to a method and apparatus of excavating using a self-contained system disposable within a wellbore. The present invention involves a method and apparatus for excavating using ultra-high pressure fluids. Though the subject invention has many uses, one of its primary uses is to perforate a well and/or stimulate production in that well.  
         [0003]     2. Description of Related Art  
         [0004]     Wellbores for use in subterranean extraction of hydrocarbons generally comprise a primary section running in a substantial vertical direction along its length. Secondary wellbores may be formed from the primary wellbore into the subterranean rock formation surrounding the primary wellbore. The secondary wellbores are usually formed to enhance the hydrocarbon production of the primary wellbore and can be excavated just after formation of the primary wellbore. Alternatively, secondary wellbores can be made after the primary wellbore has been in use for some time. Typically the secondary wellbores have a smaller diameter than that of the primary wellbores and are often formed in a substantially horizontal orientation.  
         [0005]     In order to excavate a secondary wellbore, numerous devices have been developed for lateral or horizontal drilling within a primary wellbore. Many of these devices include a means for diverting a drill bit from a vertical to a horizontal direction. These means include shoes or whipstocks that are disposed within the wellbore for deflecting the drilling means into the formation surrounding the primary wellbore. Deflecting the drilling means can enable the formation of a secondary wellbore that extends from the primary wellbore into the surrounding formation. Examples of these devices can be found in Buckman, U.S. Pat. No. 6,263,984, McLeod et al., U.S. Pat. No. 6,189,629, Trueman et al., U.S. Pat. No. 6,470,978, Hathaway U.S. Pat. No. 5,553,680, Landers, U.S. Pat. No. 6,125,949, Wilkes, Jr. et al., U.S. Pat. No. 5,255,750, McCune et al., U.S. Pat. No. 2,778,603, Bull et al., U.S. Pat. No. 3,958,649, and Johnson, U.S. Pat. No. 5,944,123. One of the drawbacks of utilizing a diverting means within the wellbore however is that the extra step of adding such means within the wellbore can have a significant impact on the expense of such a drilling operation.  
         [0006]     Other devices for forming secondary wellbores include mechanical/hydraulic devices for urging a drill bit through well casing, mechanical locators, and a tubing bending apparatus. Examples of these devices can be found in Mazorow et al., U.S. Pat. No. 6,578,636, Gipson, U.S. Pat. No. 5,439,066, Allarie et al., U.S. Pat. No. 6,167,968, and Sallwasser et al., U.S. Pat. No. 5,687,806. Shortcomings of the mechanical drilling devices include the limited dimensions of any secondary wellbores that may be formed with these devices. Drawbacks of excavating devices having mechanical locators and/or tubing bending include the diminished drilling rate capabilities of those devices. Therefore, there exists a need for a device and method for excavating secondary wellbores, where the excavation process can be performed in a single step and without the need for positioning diverting devices within a wellbore previous to excavating. There also exists a need for a device that can efficiently produce secondary wellbores at an acceptable rate of operation.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     The present invention includes an excavation system for use in a wellbore comprising an arm extendable into a substantially horizontal position within the wellbore, a pressurized fluid source in fluid communication with the arm, a mechanically rotating source, and a jet nozzle disposed on the end of the arm. The pressurized fluid source is disposed within the wellbore. The jet nozzle has an exit adapted to form a fluid jet suitable for excavating and further adapted to rotate in response to the rotating source. The present invention can also comprise a positioning mechanism in cooperation with the arm. The excavation system of the present invention can further comprise a gear formed for mechanical cooperation with the arm. A drill bit can also be included with the excavation system. A motor can be connected to the pressurized fluid source capable of driving the pressurized fluid source, where the motor can be an electric motor or a mud motor. The pressurized fluid source can be a crankshaft pump, a wobble pump, a swashplate pump, an intensifier, or any combination of these. A wireline can be used to suspend the excavation system within the wellbore. Preferably the arm is flexible and can be articulated. Also, the excavation system can be at least partially submerged in fluid within the wellbore.  
         [0008]     The present invention can further comprise a launch mechanism capable of pivotally changing from a first position to a second position. While in the second position the launch mechanism can provide a horizontal base capable of supporting the housing in a horizontal orientation. The horizontal excavation system can further comprise up to four conduits within the housing in fluid communication with the pressurized fluid source.  
         [0009]     The present invention can include a method of excavating within a wellbore comprising, forming an excavation system having an arm in fluid communication with a pressurized fluid source, a mechanically rotating source, and a jet nozzle. The arm is extendable into a substantially horizontal position within the wellbore and the jet nozzle is disposed on the end of the arm and has an exit adapted to receive fluid from the pressurized fluid source. Preferably the arm is flexible and can be articulated. The method further includes disposing the excavation system within the wellbore, pressurizing fluid within the wellbore by activating the pressurized fluid source, directing pressurized fluid from the pressurized fluid source to the jet nozzle via the arm, thereby producing a fluid jet exiting said jet nozzle, and urging the arm into the subterranean formation surrounding the wellbore.  
         [0010]     The method of the present invention can further include the step of attaching a wireline to the excavation system and the step of forming a drill bit on the end of said arm. The method can further comprise including a positioning mechanism with the excavation system for directing the arm into the subterranean formation surrounding the wellbore. The method can also include the step of connecting a motor to the pressurized fluid source, where the motor can be an electrical motor or a mud motor. The pressurized fluid source can be combined with an intensifier. The pressurized fluid source can be a pump such as a crankshaft pump, a wobble pump, and a swashplate pump. The method of the present invention can further involve including a launch mechanism with the excavation system. The launch mechanism is capable of pivotally changing from a first position to a second position; wherein while in the second position the launch mechanism provides a horizontal base capable of supporting the housing in a horizontal orientation.  
         [0011]     Accordingly, one of the advantages provided by the present invention is the ability to readily create excavations within a wellbore that extend lateral from the primary wellbore. Additionally, the present invention includes the capability of disposing a fluid pressure source within the wellbore thereby imparting a greater pressure to the fluid exiting the device. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0012]      FIG. 1  depicts in partial cross sectional view one embodiment of an excavation system in a retracted position.  
         [0013]      FIG. 2  illustrates in partial cross sectional view an embodiment of an excavation system in an extended position.  
         [0014]      FIG. 3  portrays a cross sectional view of an arm of an embodiment of an excavation system.  
         [0015]      FIG. 4  is a side view of an arm of one embodiment of an excavation system. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     The present invention includes a method and apparatus useful for excavating and forming subterranean wellbores, including secondary wellbores extending laterally from a primary wellbore. With reference to  FIG. 1 , one embodiment of an excavation system  20  of the present invention is shown disposed within a wellbore  12 . The embodiment of the excavation system  20  illustrated in  FIG. 1  comprises a motor  22  in mechanical cooperation with a pressurized fluid source disposed within a housing  21 . In the embodiment of the invention of  FIG. 1 , the pressurized fluid source is a pump unit  24 . At least one conduit  28  is shown connected on one end to the discharge of the pump unit  24  and on the other end to a drill bit  50 . Optionally an intensifier  26  can be included to work in cooperation with the pump unit  24  for increasing the pressure of the fluid exiting the pump unit  24 . An arm  31  is provided that houses a length of the conduit  28  and terminates at the drill bit  50 . The conduit  28  provides a fluid flow path from the discharge of the pump unit  24  or optional intensifier  26  to the drill bit  50 . The conduit  28  can be comprised of hose, flexible hose, tubing, flexible tubing, ducting, or any other suitable means of conveying a flow of pressurized fluid.  
         [0017]     The excavation system  20  is operable downhole and can be partially or wholly submerged in the fluid  15  of the wellbore  12 . The fluid  15  can be any type of liquid, including water, brine, diesel, alcohol, water-based drilling fluids, oil-based drilling fluids, and synthetic drilling fluids. In one embodiment, the fluid  15  is the fluid that already exists within the wellbore  12  prior to the operation. Accordingly, one of the many advantages of the present invention is its ability to operate with clean fluid or fluid having foreign matter disposed therein.  
         [0018]     In an alternative embodiment, the wellbore  12  is filled with an etching acidic solution to accommodate the operation. In such a scenario, the acid used may be any type of acid used for stimulating well production, including hydrofluoric or hydrochloric acid at concentrations of approximately 15% by volume. Though the type of fluid used may vary greatly, those skilled in the art will appreciate that the speed and efficiency of the drilling will depend greatly upon the type and characteristics of the fluid employed. Accordingly, it may be that liquid with a highly polar molecule, such as water or brine, may provide additional drilling advantage.  
         [0019]     In the embodiment of  FIG. 1 , the motor  22  is adjacent to the pump unit  24  and an integral part of the excavation system  20 . Preferably the motor  22  is an electric motor driven by an electrical source (not shown) located at the surface above the wellbore  12 , though the electrical source could also be situated somewhere within the wellbore  12 , such as proximate to the motor  22 . Alternatively, the electrical source could comprise a battery combined with or adjacent to the motor  22 . Types of motors other than electrical, such as a mud motor, can be employed with the present invention. Optionally, the motor  22  could be placed above the surface of the wellbore  12  and connected to the pump unit  24  via a crankshaft (not shown). It is well within the capabilities of those skilled in the art to select, design, and implement types of motors that are suitable for use with the present invention.  
         [0020]     As previously noted, the excavation system  20  is at least partially submerged within wellbore fluid  15 , the pump unit  24  includes a suction side in fluid communication with the wellbore fluid  15 . During operation, the pump unit  24  receives the wellbore fluid  15  through its suction side, pressurizes the fluid, and discharges the pressurized fluid into the conduit  28 . While the discharge pressure of the pump unit  24  can vary depending on the particular application, the pump unit  24  should be capable of producing pressures sufficient to aid in subterranean excavation by lubricating the drill bit  50  and clearing away cuttings produced during excavation. The pump unit  24  can be comprised of a single fluid pressurizing device or a combination of different fluid pressurizing devices. The fluid pressurizing units that may comprise the pump unit  24  include, an intensifier, centrifugal pumps, swashplate pumps, wobble pumps, a crankshaft pump, and combinations thereof.  
         [0021]     With reference now to the arm  31  of the embodiment of the invention of  FIG. 1 , the arm  31  is comprised of a series of generally rectangular segments  32 . As seen in  FIG. 4 , each segment  32  includes a tab  39  (more preferably a pair of tabs  39  disposed on opposite and corresponding sides of the segment  32 ) extending outward from the rectangular portion of the segment  32  and overlapping a portion of the adjoining segment  32 . An aperture  41 , capable of receiving a pin  33 , is formed through each tab  39  and the portion of the segment  32  that the tab  39  overlaps. Positioning the pin  33  through the aperture  41  secures the tab  39  to the overlapped portion of the adjoining segment  32  and pivotally connects the adjacent segments  32 . Strategically positioning the tabs  39  and apertures  41  on the same side of the arm  31  results in an articulated arm  31  that can be flexed by pivoting the individual segments  32 . A drill bit  50  is provided on the free end of the arm  31 . As will be described in more detail below, flexure of the arm  31  enables the drill bit  50  to be put into a position suitable for excavation of the wellbore  12 .  
         [0022]     The excavation system  20  is suspended within a wellbore  12  via a wireline  16  to the location where excavation is desired. In the context of this application, the wireline  16 , a slickline, coil tubing and all other methods of conveyance down a wellbore are considered equivalents. Properly positioning the excavation system  20  at the desired location within the wellbore  12  is well within the capabilities of those skilled in the art. With reference now to  FIGS. 1 and 2 , the arm  31  of  FIG. 1  is in the stored or retracted position. In contrast the arm  31  as shown in  FIG. 2  is in the extended or operational position. Once it has been determined that the excavation system  20  is properly positioned, the arm  31  can be changed from the stored into the extended position.  
         [0023]     Launching the arm  31  into the operational mode involves directing or aiming the drill bit  50  towards a portion of the subterranean formation  13  where excavation is to be performed. The arm  31  is also extended outward such that the drill bit  50  exits the housing  21  into contact with the subterranean formation  13 . A launch mechanism  38  is used to aim the drill bit  50  for excavating contact within the wellbore  12 . The launch mechanism  38  comprises a base  40  pivotally connected to an actuator  48  by a shaft  44  and also pivotally connected within the housing  21  at pivot point P. Rollers  42  are provided on adjacent comers of the base  40  such that when the arm  31  is in the retracted position a single roller  42  is in contact with the arm  31 . Extension of the shaft  44  outward from the actuator  48  pivots the base  40  about pivot point P and puts each roller  42  of the launch mechanism  38  in supporting contact with the arm  31 . The presence of the rollers  42  against the arm  31  support and aim the drill bit  50  so that it is substantially aligned in the same direction of a line L connecting the rollers  42 .  
         [0024]     Although the embodiment of the invention of  FIG. 2  illustrates a drill bit  50  that is positioned substantially horizontal, the drill bit  50  can be situated at any angle lateral to the wellbore  12 . As will be appreciated by those skilled in the art, the direction of the arm  31  extending from the housing  21  can be adjusted by the changing the pivot of the base  40  about the pivot point P. A positioning mechanism comprising a gear  34  with detents  35  on its outer radius and idler pulleys ( 36  and  37 ) is provided to help guide the arm  31  as it is being retracted and extended. The detents  35  receive the pins  33  disposed on each segment  32  and help to track the arm  31  in and out of its respective retraction/extension positions, and the idler pulleys ( 36  and  37 ) ease the directional transition of the arm  31  from a substantially vertical position to substantially lateral orientation as the segments  32  pass by the gear  34 . Optionally the gear  34  can be motorized such that it can be used to drive the arm  31  into a retracted or extended position utilizing the interaction of the detents  35  and pins  33 .  
         [0025]     While aiming or directing the drill bit  50  is accomplished by use of the launch mechanism  38 , extending the arm  31  from within the housing  21  is typically performed by a drive shaft  46  disposed within the arm  31 . The drive shaft  46  is connected on one end to a drill bit driver  30  and on its other end to the drill bit  50 . The drill bit driver  30  can impart a translational up an down movement onto the drive shaft  46  that in turn pushes and pulls the drill bit  50  into and out of the housing  21 . The drill bit driver  30  also provides a rotating force onto the drive shaft  46  that is transferred by the drive shaft  46  to the drill bit  50 . Since the drive shaft  46  is disposed within the arm  31 , it must be sufficiently flexible to bend and accommodate the changing configuration of the arm  31 . In addition to being flexible, the drive shaft  46  must also possess sufficient stiffness in order to properly transfer the rotational force from the drill bit driver  30  to the drill bit  50 .  
         [0026]     In operation, the arm  31  is transferred from the retracted into an extended position by actuation of the launch mechanism  38  combined with extension of the drive shaft  46  by the drill bit driver  30 . Before the drill bit  50  contacts the subterranean formation  13  that surrounds the wellbore  12 , the motor  22  is activated and the drill bit driver  30  begins to rotate the drill bit  50 . As previously noted, activation of the motor  22  in turn drives the pump unit  24  causing it to discharge pressurized wellbore fluid  15  into the conduit  28  that carries the pressurized fluid onto the drill bit  50 . The pressurized fluid exits the drill bit  50  through nozzles (not shown) to form fluid jets  29 . Excavation within the wellbore  12  can be performed with the present invention by urging the drill bit  50  against the subterranean formation  13 . The drill bit  50  can be pushed into the formation  13  by activation of the drive shaft  46 , by operation of the gear  34 , or a combination of both actions. Excavation with the present invention is greatly enhanced by combining the fluid jets  29  exiting the drill bit  50  with the rotation of the drill bit  50 . The fluid jets  29  lubricate and wash away cuttings produced by the drill bit  50  thereby assisting excavation by the drill bit  50 , furthermore the force of the fluid jets  29  erodes away formation  13  itself. Continued erosion of the formation  13  by the present invention forms a lateral wellbore into the formation  13 , where the size and location of the lateral wellbore is adequate to drain the formation  13  of hydrocarbons entrained therein.  
         [0027]     One of the advantages of the present invention is the ability to generate fluid pressure differentials downhole within a wellbore  12  eliminating the need for surface-located pumping devices and their associated downhole piping. Eliminating the need for a surface mounted pumping system along with its associated connections further provides for a safer operation, as any failures during operation will not endanger life or the assets at the surface. Furthermore, positioning the pressure source proximate to where the fluid jets  29  are formed greatly reduces dynamic pressure losses that occur when pumping fluids downhole. Additionally, disposing the pressure source within the wellbore  12  eliminates the need for costly pressure piping to carry pressurized fluid from the surface to where it is discharged for use in excavation.  
         [0028]     The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.