![]() Total curvature in the wellbore consisting of a change of inclination and/or direction between two points.ĭogleg severity. A service company that supplies the special deflecting tools, BHA, survey instruments and a technical representative to perform the directional drilling aspects of the operation.ĭirection of inclination. ![]() The basic principle involved is gravity or the “plumb-bob effect.”ĭirectional drilling contractor. Utilizes the hole wall to minimize bending of the bottomhole assembly. This equipment acts to force the bit to turn the hole in direction and inclination. Utilizes bottomhole equipment which is not normally a part of the conventional drillstring to aid deviation control. Utilizes a bending moment principle to create a force on that the bit to counteract reaction forces that are tending to push the bit in a given direction. Horizontal displacement of one station from another.įulcrum technique. Drilling tools and equipment used to change the inclination and direction of the drilled wellbore.ĭeparture. The total fatigue damage caused by repeated cyclic stresses.ĭeflection tools. An area where subsurface formations are so composed or arranged that it is difficult to drill a straight hole.Ĭumulative fatigue damage. Wellbore that has been inadvertently deviated from a straight hole.Ĭrooked-hole area. The axis of the borehole over an interval length.Ĭourse bearing. Action taken with a directional jet bit to change the direction or inclination of the borehole.Ĭourse. Term used to indicate the closeness of two surveys one survey going in the hole and the second survey coming out of the hole.Ĭorrective jetting runs. An instrument to measure and record inclination.Ĭlosed traverse. Space between the outer diameter of the tool in question and the side of the drilled hole the difference in the diameter of the hole and the tool.Ĭlinograph. Rate of change (◦/100 ft) of the inclination angle in the section of the hole where the inclination from the vertical is increasing.Ĭlearance. That portion of the hole in which the angle of inclination is increased.īuildup rate. A wellbore configuration where the inclination is increased to some terminal angle of inclination and maintained at that angle to the specified target.īuildup. A sub in which a free-floating ball rolls to the low side and opens a port indicating an orientation position.īuild-and-hold wellbore. Position of the bottom of the hole with respect to some known surface location.īottomhole orientation sub (BHO). Assembly composed of the drill bit, stabilizers, reamers, drill collars, subs, etc., used at the bottom of the drillstring.īottomhole location. Refers to the measurements of the inclinations, azimuths and specified depths of the stations through a section of borehole.īottom-hole assembly (BHA). Refers to the azimuth in which the borehole is heading.īorehole directional survey. Refers to stabilization of the downhole assembly near the bit a stabilized bit is forced to rotate around its own axis.īorehole direction. Drill bit with one large-sized jet nozzle, used for jet deflection.īit stabilization. One of the connecting threads in machined at an angle to the axis of the body of the sub.īig-eyed bit. Sub used on top of a downhole motor to give a non straight bottom assembly. Torque on a drill string causing a twisting of the string.īent sub. Direction of a course measured in a clockwise direction from 0◦ to 360◦ also called bearing.īack-torque. Stratifiedor antisotropic formations are assumed to posses different drill abilities parallel and normal to the bedding planes with the result that the bit does not drill in the direction of the resultant force. The azimuth change through which the drillstring must be turned to offset the twist caused by the reactive torque of the downhole motor.Īnisotrospic formation theory. The angle, in degrees, taken at one at several points of variation from the vertical as revealed by a deviation survey, sometimes called the inclination or angle of deviation.Īngle of twist. The most frequently used terms listed below.Īngle of inclination (angle of drift). The glossary of terms used in directional drilling has been developed by the API Subcommittee on Controlled Deviation Drilling under the jurisdiction of the American Petroleum Institute Production Department’s Executive Committee on Drilling and Production Practice.
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