CA2328636A1 - Air drilling system - Google Patents

Abstract

Down hole Intermittently Rotatable Air Motor is placed above Air Hammer and percussive drill bit. By applying weight on the drill string Air Motor is engaged. Air Motor intermittently rotates the Air Hammer and percussive drill bit at low RPM. By lifting the drill string off bottom, thus eliminating the weight on bit Air Motor is disengaged and a free flow of the compressed air is facilitated through the Air Motor into the Air Hammer and the percussive drill bit.
In the Air Motor a closed valve is operatively moved downwards by compressed air flowing down the drill string, the valve when it attains its lower position being opened and being returned under the influence of a spring or other upwardly urging means acting on the valve to its upper position at which the valve is closed thereby to complete the cycle of operations. The valve is so continuously coupled to a torque member that the downward movement of the valve causes turning of the torque member so that during the downward movement of the valve the rotor and the Air Hammer and the drill bit are rotatably driven by the torque member but are not rotated during the upward movement of the valve. During the upward movement of the valve, the compressed air flows through the open valve and continues to energize the Air Hammer and to flow through the nozzles in the drill bit. Valve is prevented from rotating by being engaged on the outside in straight longitudinal grooves while on the inside it is engaged in angular grooves that are on the outside of the torque member.
Thrust bearing is protected from the destructive shocks caused by Air Hammer by implementing hard elastomer washers.

Description

AIR DRILLING SYSTEM
BACKGROUND OF THE INVENTION
This invention relates in general to well drilling equipment and particularly to drilling oil and gas wells with compressed air as a circulating medium.
As is well known in the art drilling with compressed air where geology of the formation permits is more economical than when drilling with drilling mud.
Major advantage is in considerable faster rate of drilling.
Typically drilling with air will employ percussive drill bit that is mounted on the bottom end of an Air Hammer. Description of the typical Air Hammer is contained in the company literature describing such devices. Few examples are the Hamerdrill from Drilltech Mission a Sandvik Company or Megadrill from Sandvik Rock Tools Inc.
Above Air Hammer are connected few drill collars and drill pipe that provides conduit for the compressed air. The whole drill string is rotated at low RPM
(15-30RPM) from surface to enable teeth of the percussive drill bit to engage undisturbed surface of the bottom hole.
This method of drilling yields high penetration rates, however, when the hole deviates from vertical it is difficult to correct straightens of the hole. Air drilling method is usually abandoned and drilling reverts to drilling methods where drilling mud is the circulation medium. In order to bring well hole to vertical a down hole assembly (DHA) consisting of the drill bit, mud motor, bent sub, drill collars and drill pipe is used. By not rotating the drill string and rotating the drill bit by the hydraulic mud motor bent sub will force the drill bit to drill at an angle until the deviation of the hole is corrected.. At that point the angle in the bent sub is eliminated or the DHA is pulled up and bent sub is removed from the drill string. Normal rotary drilling method is resumed. At this point the well is already filled with the drilling mud and it would be uneconomical to revert back to the air drilling.

Non availability of the suitable motors driven by the compressed air prevents the correction of the deviated well by the air drilling method. Existing hydraulic mud motors are not suitable to be operated by compressed air since air drilling requires very low RPM while mud motors operate at considerable higher RPM. Another draw back in using existing mud motors is that when the weight on drill bit is reduced or eliminated expansion of the compressed air would cause typical mud motor which is a positive displacement device to rotate at extremely high revolutions causing breakage of the bit teeth. This does not occurs when drilling with drilling fluids since rate of the flow will dictate revolutions per minute. The same increase of the RPM will occur if the drilling motor is not a positive displacement device but is based on the turbine design.
Result is that the air drilling method is not being used on a regular basis.
A further method of the present invention is concerned with the axial trust bearings where shock developed by the Air Hammer are cushioned by elastomer washers.
SUMMARY OF THE INVENTION.
It is a general object of the present invention to provide suitable AIR
DRILLING SYSTEM consisting of the Percussive Drill Bit, Air Hammer, Intermittently Rotatable Air Motor and Bent Sub or Drill Collars and Drill Pipe.
It is a primary object of the present invention to provide a compressed air operated motor that will not rotate at accelerated RPM when the weight on the drill bit is significantly reduced. When the weight on the drill bit is eliminated and the drill bit is lifted of bottom the Air Motor will stop rotating and the flow of the compressed air will be uninterrupted throughout the stopped Air Motor into the Air Hammer and through the drill bit into the bottom of the hole to flush rock cuttings.
When the weight on the drill bit is applied Air Motor will start to rotate intermittently at low RPM ( 10-30RPM) Further object of the invention is to provide large bypass of the compressed air through the Air Motor to allow operation at low RPM and to allow for the maximum efficiency of the Air Hammer during the down stroke, while on the upward stroke the flow of compressed air is completely unrestricted.
Additional objective is to provide intermittent rotation which will allow for the maximum efficiency of the percussive drilling by the Air Hammer where each blow will be positioned into the undisturbed formation next to the already created chips.
Further object of the invention is to provide cushioning to the thrust bearings from the shocks generated by the Air Hammer.
Accordingly, the invention in one aspect provides a down hole Intermittently Rotatable Air Motor that is mounted below the Bent Sub or Drill Collars and above the Air Hammer and percussive drill bit. It comprises an elongated hollow housing having a longitudinal axis and having an upper end and a lower end, and an air control valve which is mounted within the housing for axial movement between an upper position and a lower position. The air control valve comprises a first valve member and a second valve member movable relative to the first valve member between a closed condition of the valve in which the valve substantially prevents downward flow of compressed air through the housing and an open condition of the valve in which downward flow of compressed air is permitted through the valve, the valve being upwardly urged. The valve presents valve actuation means which on operative downward movement of the valve under the influence of compressed air there above and against the influence of the upward urging of the valve and during which the valve is in its closed condition causes actuation of the valve to its open condition when the valve attains its lower position. On the operative upward movement of the valve under the influence of the upward urging of the valve and during which the valve is in its open condition the valve actuation means causes actuation on of the valve to its closed condition.
Above the uppermost position of the valve travel there is a face on the bottom part of the male spline member that will abut the top end of the second valve member and causing it to close or substantially reduce the flow of compressed air through the valve. This telescopicaly movable member is in its downmost position when the weight on the drill bit is applied. When the weight on the drill bit is removed by lifting the whole assembly off bottom male spline member will move upward and the top end of the second valve member will not make contact with the bottom part of the telescopic member. The second valve member will now remain opened and compressed air will be free to flow downward without urging the first valve member and second valve member downwards.
A torque member is rotatably mounted within the housing and is continuously coupled to the first valve member. Helically disposed first coupling means and second coupling means engaged with the first coupling means are provided for operative rotation of the torque member in one direction during downward movement of the first valve member and operative rotation of the torque member in the opposite direction during upward movement of the first valve member. An Air Hammer with percussive drill bit mounted on it bottom most end is rotatably mounted on and it projects downwardly from the lower end of the rotor, and a one-way clutch interconnects the torque member and the Air Hammer with the percussive drill bit for drivingly coupling the torque member to the Air Hammer and drill bit only during operative rotation of the torque member in said one direction whereby the Air Hammer and the drill bit is operatively intermittently rotated. Compressed air issuing from the bottom end the Air Motor enters Air Hammer to operate down and up movement of the piston that on its lowermost position strikes top end of the percussive drill bit that is connected to the Air Hammer via a splined connection.
Additional objective of the invention is to provide extremely low RPM (10-35 RPM) to the intermittently rotated Air Hammer and Drill bit. This is achieved by designing the helical spline in the torque member not greater than 15 deg.
In accordance with the said further aspect of the present invention there are provided elastomer washers under thrust bearings to facilitate cushioning of axial shocks resulting from the operation of the Air Hammer.
It is further object of the invention to provide considerable bypass around the first valve member to allow for minimum decrease in the air pressure and provide maximum efficiency of the operation of the Air Hammer and to decrease frequency of the axial movement of the first and second valve members, thus assuring rotation at low RPM and long life of the working parts.

BRIEF DESCRIPTION OF THE VIEWS
OF DRAWINGS
FIG. 1 is a view of well Air Drilling System in accordance with a preferred embodiment of the invention when the weight on the bit is applied FIG. lAis a view of well Air DSrilling System in acordance with a preferred embodiment of the invention when the drill bit is lifted of bottom.
FIG. 2 is a longitudinal section through the upper end of the Intermittently Rotatable Air Motor showing telescopic arrangement in its uppermost position when the drill bit is off bottom.
FIG. 3 is a cross-section view taken along line 3-3 of FIG. 2 FIG. 4 is a cross-section view taken along line 4-4 of FIG. 2 FIG. 5 is a longitudinal section through the upper end of the Intermittently Rotatable Air Motor showing telescopic arrangement when the weight on bit is applied.
FIG. 6 is a longitudinal section through the first and second valve member including upper part of torque member. Second valve member is in its lowermost relative position when the flow of compressed air is closed and is in contact with the top end of the torque member.
FIG. 7 is a longitudinal section through the first and second valve member in its lovermost position and the top part of the torque member showing second valve member in its uppermost relative position thus opening the flow of compressed air through the valve.
FIG. 7A is a longitudinal section view of the torque member showing engagement of coupling means.
FIG. 8 is a longitudinal section through the first and second valve members shown in the uppermost position when top of the second valve member contacts the bottom part of the telescopic member.
S

FIG. 9 is a cross-section view along line 9-9 of FIG. 8 FIG. 10 is a longitudinal section through the one-way clutch in the bottom end of the torque member.
FIG. 11 is a cross-section view along line 11-11 of FIG. 10 FIG. 12 is a longitudinal section through the bottom end of the Intermittently Rotatable Air Motor.
FIG. 13 is a cross-section view along line 13-13 of FIG. 8 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1-13 a preferred embodiment of the invention is shown in detail. The Air Drilling System 20 shown on the FIG. 1 includes percussive drill bit 21, Air Hammer 22, Intermittently Rotatable Air Motor (Air Motor) 23 and bottom end of the Bent Sub 24. When drilling straight hole Bent Sub 24 is not used and the Air Motor is connected to the bottom end of the drill collar.
As shown on FIG. 1 drill bit 21 is equipped with teeth 25 and the drill bit is engaged by splined arrangement 26 with Air Hammer 22. Bottom part of the Rotor is screwedly connected to the top part of Air Hammer 22. Above rotor 27 the stationary - non rotating part of the Air Motor 23 is screwedly connected to the bottom part of the Bent Sub 24 (or drill collar). Detailed description of the Air Hammer is shown in the manufacturers literature as outlined in the Background of The Invention.
FIG.1 shows Air Drilling System 20 when the weight on the bit 21 is applied and teeth 25 are in contact with the bottom of the hole 28. On FIG. 1A is shown Air Drilling System when it is lifted off the bottom of the hole 28 and the neck 29 is exposed.
As shown on FIG. 2 bore on the top end of the male spline member 30 is equipped by female thread 31 to screwadly connect with the male thread of the bottom end of the Bent Sub 24 or drill collar. Compressed air as indicated by arrows through the bore 32 into small holes 33 and through the space 34 between the first valve member 35 and the second valve member 36. Second valve member is urged upward by spring means 37.
Cylindrical surface of the neck 29 is scraped clean from particles in the hole by wiper scraper 38. Pressure in the bore 32 is sealed from escaping around the neck 29 by seal 39, typically a polyseal type. Bottom end of the male spline telescopic member 30 is formed into a male spline 40 which is inserted into the female splined housing 41.
Wear ring 42 reduces sliding friction between male splined member 30 and inside diameter of the female splined housing 41.
Male spline member 30 is shown in a position when the weight on bit is removed and the Air Drilling System 20 is lifted of bottom 28. When the male spline member 30 is fully extended a split ring 43 contacts at 44 the bottom end of the female splined housing 41 and prevents further telescopic movement.
At this extended position top end of the second valve member 36 is prevented from contact with the bottom end 45 of the male spline member 30 thus leaving air passage 34 open to the flow of compressed air through the first valve member 35.
Female splined housing 41 is screwedly connected by a thread 46 to the Air Motor housing 47. Friction between the first valve member 35 and inside bore surface of the Air Motor housing 47 is reduced by wear ring 48.
FIG. 3 shows cross-section view along line 3-3 of FIG. 2.
FIGS shows top male spline member 30 fully inserted into the female spline housing 41 when the weight on bit 21 is applied as shown on FIG. 1A. Top end of the second valve member 36 is now forced by the bottom end 45 of the male splined member 30 to close air passage 34. Flow of compressed air is now restricted and pressure of the compressed air acting on the first and second valve members 35 and 36 will force them to move down as shown by arrow "A".

When first and second valve members 35 and 36 move downwards a bypass of the flow of the compressed air will be established as shown on FIG.6 and on FIG. 4 through passage 49 and holes 50 and 50A. By allowing large volume of the compressed air to flow through the Air Motor 23 frequency of the up and down movement of the Valve members 35 and 36 will be reduced. This will assure operation of the Air Hammer at maximum efficiency.
As shown on FIG. 6 the valve members 35 and 36 are now approaching their lowermost position. Bottom end 51 of the second valve member 36 is contacting top end of the torque member 52. Further downward travel of the second valve member 36 is prevented, however, first valve member 35 is not restricted in its further travel downwards as shown by arrow B. When first valve member 35 reaches its lowest position as shown on FIG. 7 air passage 34 is now opened and compressed air can flow freely. Spring 37 will keep second valve member 36 in its uppermost position (open). Compressed air will flow through air passage 34, holes 50, holes 53 and into the bore 54 of the torque member 52.
Second valve member 36 is restricted from traveling upward by a cage 55 which is secured by a retaining ring 56. In order to reduce sliding friction of the shaft of the second valve member 36 a bushing 57 is pressed into the central portion of the first valve member 35.
As shown on FIG. 7 on the bottom end of the first valve member 35 is coupling means 58 which consist of a rollers 59 that are engaged into the straight longitudinal grooves 60 cut into the inside of torque member housing 61 as shown on FIG. 9. Rollers 59 are rotatably inserted over pins 62 which are inserted into the bottom part of the first valve member 35. On pins 62 are mounted rollers 63 which are inserted into the helical grooves 64 cut on the outside diameter of the torque member 52 as shown on FIG. 7 and FIG. 7A. During the downward movement of the valve members 35 and 36 as indicated by arrow "C" roller 59 engages the straight grove 64 in the torque member housing 61 and is prevented from rotation.
Roller 63 which is prevented from rotation by the pins 62 is forcing torque member 52 to rotate clockwise as indicated by arrow "D" on FIG. 7A.
R

Spring means 65 will urge upward the first and second valve members 35 and 36 as indicated by arrow "E". During upward movement rollers 63 will force torque member 52 to rotate counterclockwise as indicated by arrow "F" on FIG. 7A.
On FIG. 8 is shown position of the second valve member 36 contacting bottom part 45 of the male spline member 30 at its uppermost position. Flow of the compressed air is still free, however, further upward movement of the first valve member 35 which is urged upward by spring means 65 as indicated by arrow "E"
will effectively force passage 34 to be closed and passage 49 to be restricted as shown on FIG. 5. Compressed air will now move first and second valve members 35 and 36 down as indicated by arrow "C" to repeat the cycle and to force the torque member 52 to rotate clockwise and drive the drill bit 21.
Bottom end of the torque member 52 is shown in longitudinal section on FIG.
10. To prevent friction between spring means 65 and the shoulder 67 of the torque member 52 there is a ring 68 which is made from hard eleastomer that has low coefficient of friction. Torque member 52 is supported by elastomer ring 69 that has a low coefficient of friction. Torque member 52 rotates clockwise during the downward movement of the first and second valve members 35 and 36 and it rotates counterclockwise during the upward movement of the first and second valve members 35 and 36.
A one way clutch 70 allows one way clockwise rotation of the rotor 27.
During the clockwise rotation of the torque member 52 rollers 71 that are housed in the cage 72 will wedge on the tapered surface 73 as shown on FIG. 11 to lock bore 74 on the bottom end of torque member 52 and the rotor 27 to drive rotor 27 clockwise.
As shown on FIG. 10 bottom end of torque member housing 61 is screwedly connected via thread 75 to the top end of the bearing housing 76. Cavity 77 is filled wit oil. In order to prevent debris and contaminating particles into the lubricating oil there is an elastomer ring 78 that fits firmly into the internal diameter of the torque member housing 61 and slidingly over the outside diameter of the top portion of the rotor 27. Air flows through the bore 79 in the rotor 27 to enter air hammer 22.
FIG. 12 shows longitudinal section through the bottom part of the Air Motor 23 and through the rotor 27. Downward thrust from the weight of the drill string that q acts through the bearing housing 76 on the rotor 27 is supported by thrust bearings 80 and 81. Shock on bearings 80 and 81 are absorbed by elastomer rings 82 and 83.
Split ring 84 which is locked by a lock ring 85 is allowing axial thrust acting through the bearings 80 and 81 to be transferred to the rotor 27. Bearing 81 is supported by ring 86 which holds in place outer ring 87 of the radial roller bearing 88. In the bottom part of the bearing housing 76 is screwedly connected by threaded connection 89 lock nut 90. Threaded connection is secured by security nut 91 which is tightly screwed on the thread connection 89. Flow of compressed air through the threaded connection 89 is prevented by an "O" ring seal 92. Escape of the lubricating oil is prevented by a rotary seal 93. Preferred type of the rotary seal is KALSI seal which is manufactured by Kalsi Engineering, Inc.
Entry of cuttings or other contaminants from the well bore to the bottom end of the Kalsi seal 93 is prevented by an elastomer ring 94 which has low coefficient of friction. In the bore of the bottom end of rotor 27 is threaded connection 95 into which is threadedly connected top part of the Air Hammer 22.
A specific embodiment of the invention has been described by way of example. Those skilled in the art will appreciate that numerous variations and modifications may be made to this embodiment while still remaining within the spirit and scope of the invention which is set out in the appended claims.~n

Claims