Patent Publication Number: US-4928776-A

Title: Deviation control tool

Description:
This invention pertains to well drilling tools used to control the deviation of a drill head from the path of the preceding well bore. More particularly, this invention pertains to apparatus used as part of the drill string to bend, or deflect, the axis of the drill string. 
     BACKGROUND 
     It is often necessary, for reasons well known to those in the drilling art, to control the course of a progressing well bore being drilled. In the past, unwanted deviation from vertical was of prime concern. More recently, well bores were directionally drilled when necessity dictated, to drill into otherwise inaccessible formations. With more sophisticated equipment, directional drilling is now practiced for convenience as well as economy. 
     For well bore deflection purposes, bending the drill string about a transverse axis fixed to the drill string can be done with rugged and reliable machinery. The related drilling practice generally requires a drilling motor below the bend or a lateral jet in the drill head. The drill string bend can be permanent in the form of a &#34;bent sub&#34; but that system is not considered suitable for straight hole drilling. Once a well bore is deflected from an original path, the &#34;reach&#34; of hole subsequently drilled usually does not require continued deflecting effort. The drill string is conventionally tripped from the hole to remove the bent sub until the next time deflection is needed. 
     There has been a recognized need for some time for the ability to change the downhole assembly from a directional configuration to a straight hole drilling configuration, and ideally to reverse the process, without tripping the drill string. This need has produced &#34;knuckle joint&#34; tools that have hinge means to accomplish the effect of a bent sub. The ideal objective of commanding the sub to accomplish the bent result by simple manipulation of drilling controls at the surface has received some effort, with some success, in recent years, and this invention is an effort to further that art. In the drilling arts, simplicity generally results in greater reliability and this invention is directed to a deflection tool of simple construction and simple controls. 
     It is an object of this invention to provide a drill string deflection tool that can be controlled by manipulation of the drilling controls at the surface to provide a straight drilling or a deflected drilling configuration of the downhole assembly. It is a further object to cause the change in configuration by axial manipulation of the drill string and to lock in the selected configuration by manipulation of drilling fluid flow controls. 
     It is another object of this invention to provide a downhole drill string deflection apparatus that can influence the resistance to the flow of drilling fluid such that the configuration of the downhole assembly will be indicated at the surface by the pressure-flow relationship of the drilling fluid circuit. 
     SUMMARY OF THE INVENTION 
     A drill string deflection tool has a body arranged to function as a segment of a drill string. The body has upper and lower portions that telescope together in a mid-section to shorten the body when axially compressed and to lengthen the body when pulled axially. 
     When the body is compressed, cam surfaces on each portion engage and cooperate to radially deflect the longitudinal axis of one portion relative to the other. A fulcrum in the telescoping mid-section, axially displaced from the cams, reacts to the radial displacement to cause an angular deflection of the axis of one portion relative to the axis of the other. 
     Transverse lock bolts are situated in the male part of the telescoping mid-section to extend radially to engage cooperating sockets in the inner wall of the female part to lock the body in the configuration that exists when fluid pressure is established. The lock bolts have piston ends in fluid communication with drilling fluid channels, that extend axially through the tool, to extend the lock bolts by drilling fluid pressure. The lock bolts are, preferably, cam shaped to cooperate with the socket shapes to urge the bolts inward when axial forces on the tool urge telescoping movement and drilling fluid pressure is low. 
     The piston ends of the lock bolts are situated to intrude radially into the drilling fluid channel to cause fluid flow resistance when the lock bolts are radially inward. The fluid resistance can be detected at the surface and gives an indication of the configuration of the tool. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1A is a side elevation view, mostly cut away, of the preferred embodiment of this invention. 
     FIG. 1B is an orthographic projection, mostly cut away, of the tool of FIG. 1A. 
     FIG. 2A is a side elevatIon view, mostly cut away, of the tool of FIG. 1A, after actuation to deflect. 
     FIG. 2B is an orthographic projection, mostly cut away, of the tool of FIG. 2A. 
     FIG. 3 is a section, taken along line 3--3, of FIG. 1B. 
    
    
     DETAILED DESCRIPTION OF DRAWINGS 
     Some details pertaining to manufacturing and maintenance utility, such as threaded connections, weld lines and the like, are omitted in the interest of clarity of points of novelty. It can be assumed that the tool is assembled as shown with final closure completed by welding. 
     In the drawings, wherein feature and caption consistency is maintained throughout, FIG. 1A shows the preferred embodiment as a segment of a drill string, in a straight configuration. The body is comprised of an upper, or first, portion 1 and a lower, or second, portion 3 telescopingly joined in mid-section 2. Telescope bore 3b accepts a reduced diameter extension of portion 1. The extension is retained in the bore by non-circular drive flat 3g which has face 3e arranged to engage face 5c of washpipe 5 which is fastened to portion 1, best shown in FIG. 1B. The overall body is at maximum length. 
     Washpipe 5 has extension 5d telescopingly received in bore 3j and is secured to portion 1 by arcuate retaining lug 5b in arcuate groove 1g. Portion 1 and washpipe 5 move axially relative to portion 3 and portion 1 can move downwardly until first cam surface 1a is stopped by second cam surface 3a. Portion 1 can rotate in the plane of the drawing of FIG. 1A about pivot axis PA seen as a point in FIG. 1A and as a line PA in FIG. 1B. The axial location of the pivot axis is determined by fulcrum 1m which is simply a diameter that closely fits the diameter of the bore 3b. Pivoting about axis PA is made possible by diameter reliefs 1f and 1e. Pivoting relative to the washpipe is accepted by cooperating arcuate sealing surfaces 1h and 5a. The center of curvature of these sealing surfaces, and lug 5b and groove 1g is axis PA. 
     Rotational drive between portions 1 and 3 is best shown by FIG. 3. Non-circular flat 1j cooperates with a mating flat on non-circular drive ledge 3g. The non-circular feature has length to accept telescoping action. 
     The upper portion 1 is locked in the straight configuration shown by upper lock bolts 4a and lower lock bolts 4b engaging upper sockets 3c and middle sockets 3d respectively. The lock bolts 4a and 4b are sealingly fitted into and slide radially in upper cross bore 1c and lower cross bore 1d respectively. The lock bolts have piston ends 4d in communication with drilling fluid channel 1k such that drilling fluid pressure in channel 1k urges the lock bolts radially outward into the sockets. The lock bolts are urged radially inward by the detent action of tapered detent head 4c and the tapered sockets when axial forces tend to telescope the body. 
     Body straightening forces are produced, after the lock bolts have been radially inward and the body is pulled to full length, by application of drilling fluid pressure to extend the tapered ends of the bolts into the tapered sockets. A deflection range of less than three degrees is planned. In cases of reluctance to straighten, due to bending forces in the hole, the drill string will be slowly rotated while drilling fluid pressure is maintained until the lock bolts are fully extended. 
     Fluid tight connection to the continuing drill string is accomplished by tool joint connections 1b and 3m. A drilling fluid channel comprising channel 1k, 5e and 3k extends through the tool. 
     FIGS. 2A and 2B show the tool in the deflected configuration. FIG. 2B is displaced somewhat upward from the normal position of an orthographic projection. The tool joints have been described and are not further shown. 
     Portion 1 has been pushed downward, cam surface 1a has cooperated with cam surface 3a to urge the two portions in opposite radial directions. The relative radial movement has operated, in conjunction with fulcrum 1m, to produce an angular deflection of the axis of the lower portion relative to the axis of the upper portion. 
     With the body telescoped to minimum length, lock bolts 4b are aligned with lower sockets 3f and are shown radially extended by drilling fluid pressure. With the cam surfaces engaged, the overall body is rigid. Lock bolts 4a are not needed for rigidity and serve a signal function when radially inward as shown. 
     In conjunction with channel 1k, the lock bolt piston ends comprise a valve means to resist drilling fluid flow therein. The resistance is responsive to configuration of the tool. In FIGS. 1A and 1B, the piston ends of the lock bolts do not protrude into channel 1k and this minimum resistance is indicative of the straight configuration after the lock bolts have extended. In FIGS. 2A and 2B, only the lower lock bolts move radially outward, lock bolts 4a intrude into channel 1k and produce a drilling fluid flow resistance related to the deflected (bent or directional) configuration. A condition not shown will exist when the tool is between the two axial extreme positions shown. No lock bolt will be aligned with a socket and all will protrude into and cause additional flow resistance in channel 1k. This maximum resistance will indicate a transition condition. This simple signal valve means will indicate at the earth surface the configuration of the tool downhole by influencing the drilling fluid flow rate to pressure ratio at the standpipe. 
     The tool has been described with an upper end and a lower end for descriptive convenience. In use, either and may be used upward in the drill string. 
     The lock bolts have been arranged for detent forces to provide the bias to move them radially inward for change of tool configuration. This is preferred to prevent unwanted changes in the tool configuration each time drilling fluid pressure is reduced below a certain amount. The lock bolts can obviously be spring biased inward by features well known in the machine construction art. 
     From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the method and apparatus. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. 
     As many possible embodiments may be made of the apparatus and method of this invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.