Abstract:
This specification involves combining automatic fluid driven bit hammering apparatus with generic rotary drilling motor assemblies used on non-rotating drill strings to produce more effective well and earth borings.  
     The present invention incorporates the highly effective percussion drilling with the newer technology of rotary downhole fluid driven motors.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to an improved well drilling tool for use on hollow continuous non-rotating drill stings having a gaseous pressure supply therein. The invention further relates to a gas powered automatic hammering apparatus for combining with a gas powered rotary drilling motor. More specifically this invention relates to apparatus for driving the drill bit forward impulsively repeatedly simultaneously and in combination with rotary drill bit action from a generic type pneumatic drilling motor.  
         BACKGROUND OF THE INVENTION  
         [0002]    Downhole rotary fluid powered drilling motors of several types are in use today and others are being developed for drill bit rotations for application on non-rotating drill strings in oil well servicing and open hole earth borings. Also there are a number of different type percussion drills in use today mostly in water well drilling, blast hole drilling and the like but these are rotated from the surface and have proven to be very effective, especially where weight forces on the bit are limited. Because the industry is moving to increased usage of fluid powered downhole motors for bit rotations instead of surface drill string rotation and because percussion drilling has proven so effective, this invention combines the two methods of drilling in one drilling tool. An object of this invention is to provide a pneumatic hammer in combination with a gas powered rotary drilling motor.  
           [0003]    When downhole motors alone are used on continuous type coil tubing strings, weight forces on the drill bit are severely limited. Also in highly deviated or horizontal wells, drill bit penetration rates are less than desirable and often times unacceptable for the same reason. A second object of this invention therefore is to provide a device to improve drill bit formation penetration in situations where low bit weight drilling is performed and better penetration rates in all applications. Presently a number of fluid powered downhole rotary motors are in use and others are being developed for drilling with non-rotating drill strings. Among these are the Moineau progressive type on which there is highly developed art such as covered by U.S. Pat. Nos. 6,241,494 B1 and 4,676,725. Experimental and limited usage motors such as the roller rod vane type of U.S. Pat. Nos. 5,785,509, 5,833,444 and U.S. Pat. No. 6,302,666 B1 are examples of a second class of motors and examples of a third class are the geared vane and geared turbine type described in patent application Ser. No. 09/694/997 titled “Fluid Powered Rotary Drilling Assembly” by Martini filed Oct. 24. 2000. All the drilling motor types listed are considered generic as related to the apparatus described herein and each could be adapted to incorporate an automatic fluid power reciprocal bit hammering piston for improved drilling characteristics. It is therefore a third object of this invention to advance the art of well bore drilling and providing the means therefore.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention is a automatic fluid powered reciprocal mass piston percussion drilling means adapted to drive a drill bit forward in sustained repetition while being coupled with a generic fluid driven rotary motor to enhance the drilling operation and satisfies the before stated objects. Percussion drilling is a desirable method of producing well boreholes and historically has demonstrated to be very effective when combined with drill bit rotations.  
           [0005]    The reciprocal piston for hammering the bit forward is driven by fluid exhausting from the coupled generic fluid powered rotary motor and has automatic valving means with a central coacting motor output shaft for oscillating said piston and is adapted to strike a shoulder on said motor output shaft during its rotation. Pressure fluid first powers the generic rotary motor and fluid exhausted from the motor at lower pressure drives the oscillatory piston and the motor and piston in combination rotates and hammers the bit to crush and cut the earth formation being drilled while the circulating fluid continues through the bit to flush the borehole and carry the cuttings up outside the drill string to the well surface.  
           [0006]    Since the output torque and rotational speed of the generic motors varies with the particular design, operational pressure and other factors the combined percussion hammer would need to be sized, tuned and made suitable for the characteristics of each motor as well as the field application. For example a higher speed lower torque output motor would want a lighter hammer to bit impact while a higher torque lower speed motor could have a higher hammer to bit impact to better match motor parameters. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a center vertical sectional view of the lower end of a fluid powered drilling motor showing the bearing mounted rotary output shaft with drill bit, reciprocal piston and the ports and passages of the valving means.  
         [0008]    [0008]FIG. 2 is a cross sectional view taken at line  2 - 2  of FIG. 1  
         [0009]    [0009]FIG. 3 is a cross sectional view taken at line  3 - 3  of FIG. 1  
         [0010]    [0010]FIG. 4 is a cross sectional view taken at line  4 - 4  of FIG. 1  
     
    
     DETAILED DESCRIPTION  
       [0011]    This specification covers an automatic bit hammering apparatus as part of a gaseous fluid powered generic well drilling motor assembly. It is incorporated to increase the rate of drill bit penetration. It has been proven many times that impacting a drill bit during rotation will make the drilling operation more effective. The motor assembly, operable from the fluid supplied through the drill string, may be of one of the variations of moineau types, geared vane, geared turbine type or other having an axial downward extending output shaft for coupling with this apparatus. The pressure fluid would first power the rotation of the motor and secondly power subject hammering apparatus—each being operable from differential pressure across them—each consuming a portion of the pressure energy supplied. The gaseous pressure fluid commonly used in the oil field is nitrogen and supplied to the motor assembly through the drill sting at high pressure. The first significant pressure drop would power the primemover of the motor for a rotary torque output while the second significant pressure drop would supply the percussion hammer for impacting the bit. Both differential pressure drops are well within common oil field pressure capabilities even at very deep well depths. A motorized percussion hammer as described herein would be very advantageous for increased drill bit penetration especially when used on non-rotating coil tubing drill strings where very limited weight force can be applied to the drill bit.  
         [0012]    The preferred embodiment of the percussion hammer  5  for fluid motor  4  (not shown) consists of housing  6 , bearing mounted rotary shaft  7  with drill bit  8 , reciprocal piston  9  and automatic valving means  10 .  
         [0013]    The housing is made up of barrel  11 , bottom sub  12 , middle sub  13  and sleeve  14  all in fixed relation. Sleeve  14  is close fitted to inside of barrel  11  and has extended lugs  15  on both ends to fit in recesses  16  of bottom sub  12  and middle sub  13 . Bottom sub  12  has suitable bearings for shaft  7 , means for locking shaft  7  and is threadably attached to barrel  11 .  
         [0014]    Shaft  7  is bearing mounted on its upper end in middle sub  13  and on its lower end in bottom sub  12  and is adapted for limited axial freedom of movement during rotation. On its upper end  15 , shaft  7  has a coupling  30  for transferring rotary torque from motor  4  and isolating the motor from the axial movements of shaft  7 . Coupling  30  may be internally splined to slip fit with shaft end  15  or be of a number of other types that allow longitudinal shaft displacements. Also shaft  7  has a stepped impact receiving shoulder  17  intermediate its ends, fluid passageway  18  extending from the upper end to cross ports  20 , fluid passageway  19  extending upward from the lower end to intersect with cross ports  21  and  22  and a thread-on shouldered nut  31  near its upper end for retaining the shaft in the assembly.  
         [0015]    Piston  9  is close slip fit with sleeve  14  on its outside diameter and close slip fit sealed with shaft  7  on its inside diameter, has end space chamber  28  above the piston, end space chamber  29  below the piston and is adapted for fluid driven axial oscillation by valving means  10 . The lower end of piston  9  has surface  23  for impacting shoulder  17  of shaft  7  on each piston cycle. Piston  9  has a first upper internal recess  24  and a fluid passageway  25  to the lower end of the piston and chamber  29 , and a second internal recess  26  with fluid passageway  27  communicating with the upper end of piston  9  and chamber  28 .  
         [0016]    The valving means  10  for piston  9  reciprocation consists of shaft  7  ports  20 ,  21  and  22  and piston  9  internal recesses  24  and  26  as well as piston end surface  23  and are arranged such that automatic piston oscillation is achieved.  
         [0017]    The piston  9  cycle start and end position is shown in FIG. 1 where at the end of its down stroke strikes the shaft  7  shoulder  17  for inertial energy transfer and the valving means  10  ports and passages are aligned for pressure charging chamber  29  for accelerating the piston upward and for exhausting chamber  28  above the piston. As piston  9  travels upward it reaches a position where valving  10  exhausts fluid from chamber  29  through port  22  and simultaneous pressurizes chamber  28  above piston  9  as recesses pass ports to reverse piston travel with a compressible cushion of gas trapped in chamber  28 . On piston down stroke, valving  10  further charges chamber  28  for added piston acceleration. Near the end of piston  9  down stroke, valving means  10  through recesses  26  and ports  21  exhausts fluid from chamber  28  and through recesses  24  and ports  20  pressurizes chamber  29  for immediate, piston acceleration upward after the piston  9  surface  23  strikes shaft  7  shoulder  17  for a percussive blow that is transferred to bit  8  to end one piston cycle. Piston  9  cycle frequency may vary from high to low depending on supply pressure from the motor primemover exhaust fluid. Screws  32  in bottom sub  12  are provided to be adjusted inwardly in shaft  7  recesses  33  to lock said shaft for changing bits.  
         [0018]    The foregoing description of the invention is explanatory thereof and various changes in size, shape and materials as well as the details of the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention.