Abstract: As a wellbore is extended into a formation, hydrostatic and hydrodynamic pressures change due to variations in drilling mud weight, fluid density, etc. Strain gauges downhole measure forces experienced by drilling equipment also experience strain due to hydrostatic and hydrodynamic pressures. In order to measure strain due to drilling, hydrostatic and hydrodynamic pressure contributions are removed from strain measurement by removal of a pressure-effect offset, which zeroes or tares the strain measurements. Values of the pressure-effect offset can also be monitored to check that strain measurements are accurately zeroed or to monitor wellbore operations and conditions.

Abstract: As a wellbore is extended into a formation, hydrostatic and hydrodynamic pressures change due to variations in drilling mud weight, fluid density, etc. Strain gauges downhole measure forces experienced by drilling equipment. During drilling, a strain gauge measures strain applied between the drill string and the formation. When off bottom, the strain gauge measures forces experienced by the drill string other than drilling forces. A pressure calculator converts off bottom strain gauge measurements into measurements of hydrostatic pressure for periods without fluid flow (i.e., when drilling motors are paused) and into measurements of hydrodynamic pressure for periods with fluid flow (i.e., when mud motors are operating). The pressure calculator correlates strain measurements (usually in voltages) to pressure based on a predetermined relationship for a given wellbore geometry (e.g., hole diameter, drill bit diameter, drill pipe diameter, etc.).

Abstract: The disclosure provides a method which includes transmitting signals over a time period between a downhole location and a surface location during drilling of a wellbore; recording the time of each signal at the surface using a surface clock and the time of each signal downhole using a downhole clock; and correcting the downhole measurements using the recorded times.

Abstract: The disclosure provides a method which includes transmitting signals over a time period between a downhole location and a surface location during drilling of a wellbore; recording the time of each signal at the surface using a surface clock and the time of each signal downhole using a downhole clock; and correcting the downhole measurements using the recorded times.