This invention pertains to a serial element of a drill string usable for adjustably deflecting the centerline of the associated drill string. The sub is designed to be adjustable by operating personnel on the drilling site.
The majority of drilling activities, in the petroleum industry, experience the need to either maintain a vertical well bore or to deflect the progressing well bore from vertical to a predetermined direction.
Directional drilling normally involves down hole instruments to indicate the direction being followed by the drill bead. When errors in direction are detected steps have to be taken to correct the progressing well bore direction. Direction includes deflection from vertical and the azimuth relative to earth. Correction usually involves lateral influence on the drill head. Lateral influence can be applied by several processes but bending the drill string some distance above the drill head seems, at present, to be most reliable. Bending, or deflecting, the drill string has been done by apparatus down hole and controlled by down-link commands from the surface. Such apparatus tends to be complex and not entirely reliable. Reliability is decreased by the apparatus presence down hole, in the hostile environment, and remaining ready to act after hours of drilling activity. Rigidity and durability is demanded of the drill string, near the drill head, and that leaves little radial room in the drill string bore for apparatus. The bore of the drill string has to conduct drilling fluid as well as provide space for apparatus. Designers of down-hole deflection controls have little space in which to fit apparatus required to exert a powerful influence upon drill strings conducting many tons of axial force upon a drill head. There is a need for deflecting apparatus that can be adjusted for deflecting the drill string yet provide a drill string serial element that is rigid and devoid of moving parts while down hole. If the apparatus cannot be adjusted while down hole, it should be adjustable at the rig site by simple processes.
It is an object of the invention to provide an adjusting sub that can be adjusted by simple rotation of opposite ends of the housing, each end relative to the other.
It is another object of the invention to provide an adjusting sub that can be tightened together for use by applying rig tongs to the sub.
It is yet another object of the invention to provide and adjusting sub that will not cause the tightening torque to derange the adjusted setting.
To achieve the objectives, the novel adjustably bendable sub is to be used as a serial element of a drill string in use. The housing includes two cylindrical bodies joined by a threaded box and pin connection that is tilted relative to the housing general centerline, when the sub is in a straight configuration, an amount one-half the maximum amount of deflection inherent in the design. When the sub is deflected the two bodies have independent center lines, or axes. When one body is rotated relative to the other, one body centerline moves to describe a cone with one line on the cone lying along the center line of the other. That one line is needed to accomplish the straight configuration. The amount of bend is a function of the amount one body is rotated relative to the other, all useful bend angles being accomplishable in one half turn of one body relative to the other, starting from the straight configuration.
Tool joint connections and a bore through the sub provide means to install the sub as a serial element in the drill string for drilling, with the usual mud flow down the string bore.
To secure the sub in the selected configuration an indicator ring is rotationally secured, and axially movable on the outer periphery of one body, preferably by keys or splines. On the same body a sleeve is threadedly secured for axial movement along the threads by tongs usable on the sleeve outer surface, which is about the same outer diameter as the sub. The sleeve on one body axially advances to secure the indicator ring against the face of the other body.
The sub can be used with either end up, but in the preferred orientation the upper body has a tilted threaded box which receives the similarly tilted threaded pin end of the lower body. When the lower body is rotated in the tilted threaded connection relative to the upper body the center line of the lower body describes the cone relative to the center line of the upper body. The centerline of each body is also the centerline of the connected drill string element. When the sub is bent, the related drill string is bent.
The upper body has a lower plane face that is perpendicular to the center line of the threads in the tilted box and pin connection. The sleeve threadedly secured on the lower body has an upper plane face that is perpendicular to the center line of the lower body. The opposed faces then are planes that have an angular relationship equal to the amount of tilt of the box and pin thread axes. To provide a rigid structure of the combined parts of the sub, the indicator ring is captured between the upper body and the sleeve. The ring has opposite plane faces that describe planes with an angular relationship equal to the angle of tilt of the box and pin connection. The indicator ring, being keyed or splined to the lower body, maintains opposed face planes that solidly contact the upper body and the sleeve. When the sleeve is torqued up to capture the indicator ring, the assembly is about as rigid as the related drill string when set at any adjusted angle.
These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from a consideration of this specification, including the attached claims and appended drawings