Abstract:
A downhole oil well tool uses impact, reciprocal drilling and an improved rotating bit or like working member, receiving both fluid pressure and weight from an elongated pipe string with a flow bore in order to drive the tool. A valve within tool housing controls fluid pressure to the working end so that the tool pressures up, then releases pressure through the working member allowing the pipe string to load the bit, creating impact. A clutch rotates the working member during drilling to prevent imprint upon the formation. A bias spring is provided to control and adjust the amount of weight on the bit independent of pipe weight.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of copending U.S. patent application Ser. No. 07/587,993, filed Sep. 25, 1990, now abandoned, which is a continuation of 07/367,341, filed Jun. 16, 1989, now U.S. Pat. No. 4,958,691, which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to downhole oil well tools run on a pipe string, including impact or jarring type downhole oil well tools, and more particularly, to a fluid operated jarring tool and related methods of operation for use in well bores and wherein the tool has a bit or working end that jars downwardly and rotates when the bit is not subject to weight of the pipe string in order to prevent imprinting on the drilling surface. 
     2. General Background 
     In downhole well operation, there is a need for jarring or impact devices. For example, in workover operations using a pipe string such as coil tubing or snubbing equipment, it is necessary to provide downward jarring impact at the bottom of the string to enable the string to pass obstructions or restrictions (such as isolation packers, liners, etc.) or otherwise enter the well perforated zone. During fishing operations or other operations, such as paraffin scraping, it is sometimes necessary to apply upward and/or downward jarring or impact forces at the bottom of the string if the fishing tool or the like becomes stuck. This problem can be greater in inclined and in horizontal wells. In horizontal wells, the method and apparatus of the present invention can be used to overcome obstructions that can include friction between the drill string and well annulus. 11, through stem 25, through bit 14 to the drilling surface. 
     In prior U.S. Pat. No. 3,946,819, naming the applicant herein as patentee, there is disclosed a fluid operated well tool adapted to deliver downward jarring forces when the tool encounters obstructions. The tool of my prior U.S. Pat. No. 3,946,819, generally includes a housing with a tubular stem member telescopically received in the housing for relative reciprocal movement between a first terminal position and a second terminal position in response to fluid pressure in the housing. The lower portion of the housing is formed to define a downwardly facing hammer and the stem member includes an upwardly facing anvil which is positioned to be struck by the hammer. The tool includes a valve assembly that is responsive to predetermined movement of the stem member toward the second terminal position to relieve fluid pressure and permit the stem member to return to the first terminal position. When the valve assembly relieves fluid pressure, the hammer moves into abrupt striking contact with the anvil. The tool of prior U.S. Pat. No. 3,946,819, is effective in providing downward repetitive blows. The tool of the &#39;819 patent will not produce upwardly directed blows. 
     In prior U.S. Pat. No. 4,462,471, naming the applicant herein as patentee, there is provided a bidirectional fluid operated jarring apparatus that produces jarring forces in either the upward or downward direction. The jarring apparatus was used to provide upward or downward impact forces as desired downhole without removing the tool from the well bore for modification. The device provides downward jarring forces when the tool is in compression, as when pipe weight is being applied downwardly on the tool, and produces strong upward forces when is in tension, as when the tool is being pulled upwardly. 
     In U.S. Pat. No. 4,462,471, there is disclosed a jarring or drilling mechanism that may be adapted to provide upward and downward blows. The mechanism of the &#39;471 patent includes a housing having opposed axially spaced apart hammer surfaces slidingly mounted within the housing between the anvil surfaces. A spring is provided for urging the hammer upwardly. 
     In general, the mechanism of the &#39;471 patent operates by fluid pressure acting on the valve and hammer to urge the valve and hammer axially downwardly until the downward movement of the valve is stopped, preferably by the full compression of the valve spring. When the downward movement of the valve stops, the seal between the valve and the hammer is broken and the valve moves axially upwardly. 
     The direction jarring of the mechanism of the &#39;471 patent is determined by the relationship between the fluid pressure and the strength of the spring that urges the hammer upwardly. Normally, the mechanism is adapted for upward jarring. When the valve opens, the hammer moves upwardly to strike the downwardly facing anvil surface of the housing. The mechanism can be made to deliver a downward and upward blow by increasing the fluid pressure and decreasing the strength of the spring that urges the hammer upwardly. When the mechanism is so arranged, the downward momentum of the hammer is increased such that the hammer strikes the upwardly facing anvil of the housing prior to being urged upwardly to strike the downwardly facing anvil surface. 
     One of the problems with these prior art devices is the fact that during impact drilling, imprinting on the drilling surface can occur reducing or preventing penetration. The present invention rotates the working end, e.g. a drill bit, during impact drilling. With the present invention, by rotating the bit when it is not subject to weight of the pipe string, very little energy is required. As compared to rotating the bit when it is weighted, this &#34;unweighted&#34; rotation slows bit wear. Thus, impact drilling can proceed with a constant movement or rotation of the bit to prevent imprinting on the drilling surface. 
     Another problem relating to controlling the amount of the weight on a drill bit. Presently, drill pipe weight is the typical method of controlling the weight on a drill bit. In one embodiment of the present invention, a coiled spring, disk spring or other bias means is placed in the tool in such a way that a predetermined amount of force or load could be applied to the bit. This force will vary some what, increasing as the tool body moves downward. Thus, two forces of downward force can be applied to the bit. The first would be the weight of the tubing on the tool, controlled by the operator at the surface of the well, and the second would be the predetermined constant load imposed on the bit through the &#34;bias means&#34;, preferably a coil spring or disk spring. 
     During certain down hole impact drilling operations, large amounts of fluid are sometimes required to accomplish the task. For example, when acidizing or fracturing a well or when operating in a large annulus, the fluid velocity must be maintained to carry cuttings to the surface. Often nitrogen is introduced into this fluid in the form of gas, sometimes being mixed with a foaming surfactant. Nitrogen is a gas with high energy and has a very high rate of expansion. 
     Impact tools operate on a fixed volume of fluid per stroke, the higher the volume the faster the impact cycle. The impact cycle of these tools depends on the near total evacuation of the pressure in the chamber to obtain a clean blow. There is therefore a point where the amount of fluid being pumped through a tool exceeds the tool&#39;s ability to exhaust the chamber (volumetric efficiency). When this point is reached, the tool chamber will maintain a positive pressure differential and the impact will be cushioned much like the action of an automobile shock absorber. This condition is especially prevalent when a highly expansive gas such as nitrogen enters the chamber. It is therefore advantageous and desirable to devise a method that will allow one to maintain a high fluid volume while at the same time allowing the impact tool to perform at an optimum rate. 
     This is accomplished with the method and apparatus of the present invention by installing choke holes at the port or exit and laterally of the impact tool&#39;s chamber. These choke holes can be sized to pass as much fluid as desired and yet maintain the optimum fluid value for the tool&#39;s operation. The fluid volume must exceed the flow capability of the chokes before the chamber of the tool can pressure to the point of tool operation. For example, if it is established that a given tool&#39;s optimum operating fluid rate is 30 gpm but 60 gpm is required for lifting, then the choke would be designed to pass 30 gpm at the tool&#39;s optimum operating pressure. All fluid exits the tool via the center bore and out the bottom, aiding the lifting operation. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention provides an improved well tool and method of operation for use with an elongated pipe string that can load the tool transmitting impact to the tool and to the adjacent drill string. The tool includes a housing connectable to and in fluid communication with the lower end of a pipe string, and defining at least one fluid chamber therein. A tubular stem having a flow channel therethrough is telescopically received by the housing for relative reciprocal movement and sealing engagement therewith between a first &#34;pressured up&#34; unloaded and a second &#34;impact&#34; loaded position. 
     An impact receptive working member is attached to one end of the stem for relative movement therewith between the first and second positions, wherein impact is transmitted to the working member in the second impact position. The working member can be a drill bit, or a bulb shaped or &#34;light bulb&#34; bit. 
     A valve carried by the housing is operable by fluid pressure transmitted by the pipe string, and responsive to a predetermined movement of the stem with respect to the housing relieves fluid pressure in the tool housing permitting return of the stem and the housing to the first &#34;pressure up&#34; position. 
     Biasing springs disposed in the chamber bias the stem member and the housing toward the first position and bias the valve means into a closed position when the stem member and the housing are in the first &#34;pressure up&#34; position. An interface between the housing and the stem rotate the working member during relative movement of the housing and the stem. 
     In the preferred embodiment, the interface includes a clutch assembly for rotating the working member in one rotational direction and for preventing rotation of the working member in the opposite rotational direction. 
     In the preferred embodiment, the interface comprises a clutch assembly with a sleeve positioned concentrically between the housing and the stem for rotating the working member when the housing and stem move relative to one another. 
     In the preferred embodiment, the clutch assembly includes a tubular member having one or more spiralling and longitudinally extending slots and the slots define a track, and a corresponding number of pins (or a roller bearing mechanism) connects the housing and tubular stem together. 
     In the preferred embodiment, the interface rotates the working member at least partially when the working member is unloaded. 
     In the preferred embodiment, the working member is rotated prior to loading of the working member with the pipe string. 
     In the preferred embodiment, the tubular stem is contained within the housing and the interface sleeve is positioned concentrically between the housing and the stem. 
     In the preferred embodiment, the interface includes a tubular member having an enlarged lower end that engages the housing upon impact transmitted to the bit. 
     In the preferred embodiment, the valving means includes a tubular valve element having a fluid port therethrough, one end portion communicating with the fluid chamber and the other end portion positioned to form a fluid seal with the tubular stem for stopping fluid flow therethrough to the working member. 
     In the preferred embodiment, the tubular stem is an elongated generally cylindrical stem with a central stem flow bore or channel therethrough and the flow bore or channel is in fluid communication with the working member. 
     In one embodiment of the present invention, laterally extending &#34;choke&#34; holes are provided for adjusting the fluid volume so that the tool&#39;s optimum operating fluid rate is not exceed when operating in a well wherein large volumes of fluid or highly expansive gas such as nitrogen enters the chamber. 
     In another embodiment of the apparatus of the present invention, a minimum operating pressure is built into the tool so that the tool will function in formations wherein it does not meet substantial resistance. 
     In another embodiment, a bias means (preferably coil or disk spring) is used to control the amount of weight on the drill bit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein: 
     FIG. 1 is a sectional elevational view of the preferred embodiment of the apparatus of the present invention during impact; 
     FIG. 2 is a sectional elevational view of the preferred embodiment of the apparatus of the present invention illustrating the tool in a position with the bit in a loaded position; 
     FIG. 3 is a sectional elevational view of the preferred embodiment of the apparatus of the present invention illustrating the bit in an unloaded position with the valve opened; 
     FIG. 4 is a sectional elevational view of the preferred embodiment of the apparatus of the present invention in the impact position with the valve opened; 
     FIG. 5 is a sectional view taken along lines 5--5 of FIG. 4; 
     FIGS. 5A-5B are fragmentary views illustrating the locking cam portion of the clutch member; 
     FIG. 6 is a sectional view taken along lines 6--6 of FIG. 4; 
     FIG. 7 is an elevational view of a light bulb type bit working member as used with the preferred embodiment of the apparatus of the present invention and its method of operation. 
     FIG. 8 is a sectional, elevational view of an alternate embodiment of the apparatus of the present invention; 
     FIG. 9 is an elevational view of an alternate embodiment of the apparatus of the present invention shown in an extended position; 
     FIG. 10 is a sectional, elevational, schematic view illustrating the use of the method and apparatus of the present invention showing horizontal well drilling; and 
     FIG. 10A is another sectional view illustrating the method and apparatus of the present invention as used in horizontal well drilling. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1-4 illustrate the preferred embodiment of the apparatus of the present invention designated generally by the numeral 10. In FIGS. 1-4, there can be seen sequential sectional elevational views showing operation of the tool beginning with the post impact position (immediately prior to pressuring up) that is shown in FIG. 1 and ending with the tool impact position shown in FIG. 4. 
     Otherwise, the component parts and construction of the apparatus 10 can be seen by viewing the FIGS. 1-4 at one time. 
     The apparatus 10 includes a housing 11 having upper 11A and lower 11B end portions. The housing provides at upper end portion 11A, a longitudinally extending port 12. The upper end portion 11A of the tool body 11 can be attached for example to a running and pulling sub (not shown) which is then attached to a pipe string such as, for example, a coil tubing unit. The connection of the tool 10 to a coil tubing unit using a running and pulling sub is described generally in my prior U.S. Pat. Nos. 3,946,819 and 4,462,471 which are incorporated herein by reference. 
     The lower end portion 11B of the tool body 11 carries a working member such as drill bit 14. A central tubular section 13 of housing 11 with an annular wall 15 defines an internal fluid chamber 16. Chamber 16 communicates with port 12 at 17 so that fluid transmitted to the tool 11 through the pipe string of the coil tubing unit can be used to &#34;pressure up&#34; the tool by conveying pressurized fluid to the tool chamber 16 via port 12. 
     Fluid chamber 16 carries valving member 20, a longitudinally extending valve member having a generally X-shaped cross section such as the valving member shown in FIG. 6 of my prior U.S. Pat. No. 3,946,819. 
     Valve member 20 includes an upper 21 and lower 22 end portions. Lower end portion 22 can form a fluid tight seal at seat 23 with the upper end portion 26 of tubular stem 25. Coil spring 24 biases valving member 20 upwardly when the seal at seat 23 between lower end portion 22 of valve 20 and the upper end portion 26 of stem 25 is broken. Thus, 23 defines a valve seat for sealing the longitudinal flow bore 27 of stem 25. 
     The lower most end portion 28 of stem 25 carries working member 14, such as a drill bit. The central longitudinal stem flow bore 27 thus extends the full length of stem 25 communicating with the bore 29 of working member 14. When fluid flows downwardly in the tool 10 and more particularly through chamber 16 and into bore 27 of stem 25, flow can also communicate with and flow through bore 29 of working member 14, exiting the bit or working member 14, carrying away cuttings generated during drilling or like operations. The position of the tool 10 in FIG. 1 illustrates the impact position in that the housing 11 rests upon the bit 14 with the annular shoulder 11C of housing 11 resting upon the annular shoulder 32 of clutch 35. 
     The lowermost end portion of clutch member 35 is enlarged below shoulder 32. Clutch 35 allows rotation in one direction only, clockwise rotation of bit 14 in this case during operation as viewed from the top view. This rotation also tightens all threaded connections of the tool apparatus 10. 
     In FIG. 2, a &#34;pressured up&#34; position is shown. Fluid under pressure is entering chamber 16 via port 12 (see arrows 40, FIG. 2) and forces housing 11 to rise with respect to stem 25 and bit 14. When member starts its upward movement, the weight of the pipe string is supported by body During this upward travel, member 35 is unloaded and the clutch allows the member 35 to rotate counter-clockwise around stem member 25, by means of the helix slots 50 and the pins 60. 
     The lowermost shoulder 11C of housing 11 is now spaced from the upper annular shoulder 32 of clutch 35. In the position of FIG. 2, coil spring 24 has been fully compressed, and the valve member 20 can move no further in the direction of arrow 41 with respect to housing 11 because the coil spring 24 is fully compressed above by shoulder 42 of valving member 20, and below by the annular shoulder 43 of tubular section 13. Because of the presence of pressurized fluid within fluid chamber 16, housing 11 continues to rise, carrying valving member 20 with it, and away from stem 25 until the seal at seat 23 is broken. Valve 20 travels with sleeve 11, the lower end 22 of valving member 20 lifts from the upper end 26 of stem 25 breaking the seal at 23 so that fluid contained within the chamber 16 is now free to discharge via the stem longitudinal flow bore 27 (FIG. 3). 
     Diagonal or helical slot 50 of clutch sleeve 35A has rotated upon pin 60 which is connected to the tubular section 13 of housing 11 and more particularly extends from the annular wall 15 portion thereof. The pressurized fluid contained in chamber 16 exits the tool 10 via stem longitudinal bore 27 and the bore 29 of working member 14. This exiting of pressurized fluid helps clean cuttings away from the drilling area. 
     When pressure within the tool chamber 16 equalizes with external pressure, nothing is preventing the full weight of the pipe string from thrusting the housing 11 downwardly. As the housing 11 moves downwardly as shown by the arrows 44 in FIG. 3, the pin 60 travels in spiralling slot 50 of sleeve 35A causing bit or working member 14 to rotate. Clutch 35 is a single rotation directional clutch which only allows single direction rotation of the bit 14. Clutch 35 (FIG. 5) uses a plurality of small closely spaced cam members C. Such unidirectional clutch cam members C are commercially available. The cams C have flat upper and lower surfaces, and fit within recess 35A. Each cam C has a radially extending vertical surface 71 that is larger than its opposed vertical radial surface 70. Each cam has a smaller inner curved vertical surface 72 and a larger outer curved vertical surface 73. The outer curved surface thus has a locking tip 74 which binds against surface recess 35A when rotation is in one direction. However when rotation is in the opposite direction, the locking tip 74 rotates toward stem 25 so that binding is stopped and rotation permitted. 
     A feature of the present invention is that rotation of the bit thus takes place prior to loading of the bit with the housing and the pipe string. Notice in FIG. 3 that as the pin 60 moves downwardly through spiralling slot 50, rotation of the bit takes place. It is not until the lower annular shoulder 11C of housing 11 strikes the upper annular shoulder 32 of clutch 35 that the impact is transmitted from the housing 11 and the pipe string directly to the working member 14 (see FIG. 4). This second spring 24A is placed between the enlarged upper end 26 of stem 25 and shoulder 24B. A second coil spring 24A can be placed between the enlarged upper end 26 of stem 25 and shoulder 24C, to serve as the bias means for controlling load on the drill bit 14. 
     FIG. 7, a light bulb bit 80 is shown attached to apparatus 10 which is affixed to the lower end of a coil tubing spring, CT. The light bulb bit 80 could be used, for example, as the working member when the method of the present invention is for acidizing. Using the rotation and reciprocation of the apparatus 10 of the present invention together with a working member such as light bulb bit 80, acidizing, for example a well can be accomplished. 
     In the embodiment of FIGS. 8 and 9, the apparatus 10 is equipped with a plurality of diagonally extending choke holes 81, 82 which are installed diagonally exiting the impact tool apparatus 10 bore 27. The choke holes 81, 82 can be sized to pass as much fluid as desired from the bore 27 but yet maintain optimum fluid value for the apparatus 10 operation. The fluid volume must exceed the flow capability of the chokes 81, 82 before the bore 27 can pressure to the point of operation. For example, if it is established that a given optimum operating rate is 30 gpm, but 60 gpm is required for lifting, then the choke would be designed to pass 30 gpm at the optimum operating pressure. All fluids exit the tool via bore 27 and out the bottom, aiding in the lifting operation. 
     The embodiment of FIGS. 8 and 9 provide a second coil spring 24A that can be of a desired spring value to preload the tool with a minimum operating pressure. When penetrating horizontal bores, there will be areas where the working member 14, such as a drill bit, may not meet any substantial resistance at all. Therefore, it would be advantageous to have an operating pressure minimum set into the tool. By arranging the coil spring 24B as a bias means within the tool, the spring 24B is positioned under the enlarged upper end portion 26 of tubular stem 25 and above annular shoulder 24C. By preselecting the spring 24B compression, the spring 24B becomes a means of adjusting the operating pressure of the tool. 
     When entering a horizontal well using coil tubing for example as the drill string, it has been determined that after a certain distance of travel in the horizontal section of the well bore, the coil tubing can begin to resist any further penetration causing a friction build up whereby the tubing begins to take on a series of &#34;S&#34; or sine shapes. This in turn increases the friction by further gripping the walls of the horizontal well bore (cased or uncased). This added friction eventually causes the coil tubing to form helix shapes, firmly gripping the well bore walls and eventually bringing penetration to a complete halt. 
     With the apparatus of the present invention, the rapid reciprocation of the tool produces a vibratory effect on both the tool body and the attached drill string. The pressuring up of the tube causes the tube to expand and therefore straighten. Releasing the pressure causes the tube to relax and spring back. This utilizes the natural spring action of the tube to create vibration. The magnitude of the vibration can be intensified by adding a weighted bar between the working bit and the impact surfaces of the tool. The rate (volume) of the fluids being pumped can be controlled at the surface until the most advantageous vibration frequencies are achieved. This vibration can be utilized when penetration begins, and before the tubing begins going into an &#34;S&#34; shaped configuration, the vibration thus shaking the coil tubing and forcing it to remain &#34;laid-out&#34; or in a more relaxed, straighter configuration thus resulting in deeper penetration of the drilling. 
     By increasing the compressive force of spring 24B, the operating pressure of the tool increases respectively, thereby adding another advantage by increasing the exhaust pressure of the tool. This pressure increase allows any fluid mixture exiting the tool to do so at a higher pressure than if pumped through the coil tubing alone. As a result of this increase in pressure, the fluid being discharged can more effectively penetrate the production zone which is important for example when acidifying the well. Thus, the present invention provides a constant running, vibrating impact variable frequency apparatus that can be installed at the bottom of the drill string, coil tubing, or the like. It is possible also to install the apparatus 10 of the present invention at various intervals in the coil tubing to provide continuous vibration at desired positions along the work string. 
     In FIGS. 10 and 10A, a coil tubing unit (CTU) is designated in schematic form and a horizontal well bore HB wherein the coil tubing CT can be seen in a curved orientation within the well bore HB. In FIG. 10A, the apparatus 10 of the present invention is shown installed at the end of the coiled tubing CT and within the horizontal bore HB so that the apparatus 10 of the present invention induces a vibration into the attached coil tubing which helps maintain the coil tubing (CT) in a straightened configuration as shown in FIG. 10A. 
     Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.