Abstract: A measurement system detects a downhole drilling variable in relation to the rotational orientation of a drill string during drilling. The system includes a downhole reference signal generator and a downhole variable signal generator. The reference signal generator is coupled downhole to the drill string for generating a downhole reference (DR) signal indicative of the angular relationship between the angular orientation of a lower portion of the drill string about its axis and a directional reference, such as gravity or the earth's magnetic field. The downhole variable signal generator detects downhole parameters and generates a downhole variable (DV) signal representative of a downhole parameter of interest during drilling, such as the bending moment applied to the lower portion of the drill string.

Abstract: In accordance with an illustrative embodiment of the present invention, a new and improved weight-on-bit and/or torque measuring apparatus for use in making measurements-while-drilling includes a tubular housing adapted to be attached in the drill string above the bit, the housing having diametrically opposed, radially directed holes that are enclosed to provide a sealed chamber isolated from ambient well fluids. The holes have peripheral wall surfaces to which are attached sensors that measure strain induced by axial and/or torsional loading of the housing. The strain sensors are attached to the walls at locations to be substantially insensitive to strains induced by temperature gradients, and an internal sleeve is utilized in combination with pressure equalization to eliminate spurious stresses in the region of the holes caused by pressure differences inside and outside the housing.

Abstract: A measurement system detects a downhole drilling variable in relation to the rotational orientation of a drill string during drilling. The system includes a downhole reference signal generator and a downhole variable signal generator. The reference signal generator is coupled downhole to the drill string for generating a downhole reference (DR) signal indicative of the angular relationship between the drill string and a directional reference, such as gravity or the earth's magnetic field. The downhole variable signal generator detects downhole parameters and generates a downhole variable (DV) signal representative of a downhole parameter of interest during drilling. The DV signal and the DR signals are thereupon processed, either downhole or uphole depending in part on the telemetry system employed. The system is especially adapted for indicating the resultant lateral force applied to the drill string at the drill bit during drilling which is useful in projecting the probable drilling direction.

Abstract: In accordance with an illustrative embodiment of the present invention, a shock limiting apparatus for mounting an instrumentality in a drill collar comprises piston and cylinder means subject to hydrostatic well fluid pressure for preventing longitudinal movement of the instrumentality within the drill collar unless a predetermined level of deceleration is exceeded, and a combination of hydraulic damping and Coulomb friction means for dissipating kinetic energy of the instrumentality in a substantially uniform manner when applied deceleration exceeds said predetermined level.

Abstract: In accordance with an illustrative embodiment of the present invention, apparatus for use in measuring weight-on-bit downhole during a drilling operation includes tubular telescoping members having resilient means reacting therebetween whereby relative longitudinal movement of the members is functionally relative to axial loading of a drill bit, sensor means mounted on one member and connected by linkage means to the other member for sensing the amount of relative movement, and means providing an elastic discontinuity in said linkage means for substantially isolating said sensor means from vibratory movement of said other member due to the cutting action of the bit.