A well coring apparatus is provided with the capability for monitoring the length of the core in the inner barrel (32) of a core barrel (16) and the rate at which the core enters the inner barrel (32). The device includes a Sonic Core Monitor (78) which is disposed in the upper end of the inner barrel (32) and a piston (68) which is disposed in the lower end thereof. The Sonic Core Monitor (78) generates an ultrasonic pulse that is transmitted down to the surface of the piston (68) and reflected back up to the Sonic Core Monitor (78). The time between the transmitted and received pulse is then measured and distance determined therefrom. Both length of core and rate of core entry into the inner barrel (32) can then be determined. If the core is proceeding at too slow a rate, a valve (50) can be opened to allow drilling fluid to bypass the core barrel (16). This provides the surface operator with an indication that a jam has occurred.

The impact velocity and impact frequency of the hammer piston of a percussion rock drill are varied in incremental steps in order to find the maximum penetration rate. The frequency and impact velocity are so varied that the impact power is kept substantially constant all the time. A micro-computer is used to control the process.

The disclosure relates to a method for estimating a transit time of an element circulating in a borehole during the drilling of the borehole. The transit time is representative of a time period for the element to move from the bottom of the borehole to its exit at the surface. The method comprises measuring a plurality of drilling parameters, computing a first signal of a first indicator based on a first set of measured drilling parameters and a second signal of a second indicator based on a second set of measured drilling parameters versus time. The first indicator is representative of a first type of events happening at the bottom of the borehole and the second indicator is representative of a second type of events happening at the exit of the borehole linked to the first type of events. The method also comprises characterizing a correlation between the first and second signals and determining a shift between the first and second signals. An estimated transit time is then determined from the shift.

Methods for automatically determining off bottom drillstring torque. The methods include receiving data regarding a number of drilling parameters characterizing a wellbore drilling operation, wherein the plurality of drilling parameters include a surface torque, a drillstring rotary speed (RPM, revolutions per minute), a weight on bit (WOB), a hole depth, or a bit depth, or any combinations thereof. The surface torque is recorded as an off-bottom drillstring torque data point if: the bit depth is less than the hole depth; the RPM is within a target range; and the WOB is less than a threshold value. The off-bottom drillstring torque is calculated as a function of depth from a plurality of off-bottom drillstring torque data points.

A rotary steerable drilling system that is operable to drill vertical wellbores and automatically maintain a vertical wellbore drilling path. The system includes a control module for operating solenoid valves that control an amount of fluid pressure applied to bias pad piston/cylinders. The control module is operable to determine when the system is deviating from vertical, in what direction the system is deviating, and where the bias pads are in relation to the direction of deviation. Based on these determinations, the control module actuates the requisite bias pads by controlling the amount of fluid pressure applied to the bias pad piston/cylinders to direct the system back to the vertical drilling path.

A well-logging system may include a tool assembly to be positioned within a borehole of a subterranean formation and to store second data including a second time marker related to a first time marker. The well-logging system may include a controller above the subterranean formation. The controller may process first data including the first time marker, recover the second data, and synchronize the second data based upon the second time marker and the first time marker.

A method and apparatus for communicating incremental depth and/or other useful data of a downhole tool. The incremental depth and/or other useful data of the downhole tool being communicated by measuring at least one change in the downhole system, detecting the change downhole, and subsequently determining the incremental depth and/or other useful data of the downhole tool.

A rotary steerable drilling system (100) that is operable to drill vertical wellbores and automatically maintain a vertical wellbore drilling path. The system includes a control module (40) for operating solenoid valves that control an amount of fluid pressure applied to bias pad piston/cylinders. The control module is operable to determine when the system is deviating from vertical, in what direction the system is deviating, and where the bias pads (54) are in relation to the direction of deviation. Based on these determinations, the control module actuates the requisite bias pads by controlling the amount of fluid pressure applied to the bias pad piston/cylinders to direct the system back to the vertical drilling path.

A well-logging system may include a tool assembly to be positioned within a borehole of a subterranean formation and to store second data including a second time marker related to a first time marker. The well-logging system may include a controller above the subterranean formation. The controller may process first data including the first time marker, recover the second data, and synchronize the second data based upon the second time marker and the first time marker.