STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

Directional drilling is a term used for drilling methods that allow the direction of a bore extending through a subterranean earthen formation to be controlled. Complex systems are used to alter and determine the path of the wellbore in any direction. Values for inclination and magnetic north, inter alia, are measured. The sensors for detecting magnetic north are placed in non-magnetizable steels at a sufficient distance from any parts that might cause magnetic interference. Only in this way can magnetic north be detected without interference and drilling routed in the proper, i.e. predefined, direction. When using directional drilling equipment, it is advantageous for the measurements of inclination and direction to be taken as close behind the bit as possible to ensure that the wellbore is following a controlled and planned desired path. In modern rotary steerable systems, only the inclination sensor is integrated directly into the system, while the direction sensors are located in a non-magnetic sector located many meters behind the system to enable magnetic north to be detected with the required accuracy. Without appropriate corrections, integrating the direction sensors and the detection of magnetic north together with the inclination sensors in the directional drilling device would result in magnetic declination and would allow major inaccuracies in direction sensing.

BRIEF SUMMARY

An embodiment of a directional drilling device comprises a housing, a drive shaft extending through the housing, wherein a drill bit is coupled to an end of the drive shaft, a plurality of magnetic field sensors positioned in the housing and in signal communication with a control device also positioned in the housing, wherein the magnetic field sensors are configured to determine a magnetic interference declination influenced by a magnetic interference field as a magnetic interference flux density and to transmit a magnetic interference declination value corresponding to a magnetic interference flux density to the control device, and a directional control device coupled to the housing and controllable by the control device to control a position of the directional drilling device, wherein the control device is configured to generate a correction value based on the magnetic interference declination value, and wherein the correction value corresponds to a deviation of the magnetic interference flux density from a reference magnetic flux density measured at a reference standard. In some embodiments, the magnetic field sensors are configured to determine a magnetic position declination influenced by an altered alignment of the direction drilling device as a magnetic position flux density. In some embodiments, the magnetic field sensors are configured to transmit a position value corresponding to the magnetic position declination to the control device. In certain embodiments, the control device is configured to generate a correction factor corresponding to the position value for returning the directional drilling device to a predefined position. In certain embodiments, the control device is configured to store the correction value and the correction factor in a memory of the control device. In certain embodiments, the magnetic field sensors are configured to determine a plurality of the magnetic interference declinations as magnetic interference flux densities in the direction of X, Y, and Z axes. In some embodiments, the magnetic field sensors are calibrated by a homogenous magnetic field generated by a Helmholtz coil.

An embodiment of a directional drilling device comprises a housing, a drive shaft extending through the housing, wherein a drill bit is coupled to an end of the drive shaft, a plurality of magnetic field sensors positioned in the housing and in signal communication with a control device also positioned in the housing, wherein the magnetic field sensors are configured to determine a magnetic interference declination influenced by a magnetic interference field as a magnetic interference flux density and to transmit a magnetic interference declination value corresponding to the magnetic interference flux density to the control device, and wherein the magnetic field sensors are calibrated by homogenous magnetic field generated by a Helmholtz coil, and a directional control device coupled to the housing and controllable by the control device to control a position of the directional drilling device, wherein the control device is configured to generate a correction value based on the magnetic interference declination value. In some embodiments, the correction value corresponds to a deviation of the magnetic interference flux density from a reference magnetic flux density measured at a reference standard. In some embodiments, the magnetic field sensors are configured to determine a magnetic position declination influenced by an altered alignment of the direction drilling device as a magnetic position flux density. In certain embodiments, the magnetic field sensors are configured to transmit a position value corresponding to the magnetic position declination to the control device. In certain embodiments, the control device is configured to generate a correction factor corresponding to the position value for returning the directional drilling device to a predefined position. In some embodiments, the control device is configured to store the correction value and the correction factor in a memory of the control device. In some embodiments, the magnetic field sensors are configured to determine a plurality of the magnetic interference declinations as magnetic interference flux densities in the direction of X, Y, and Z axes.

An embodiment of a method for operating a directional drilling device comprises (a) determining a magnetic interference declination influenced by a magnetic interference field as a magnetic interference flux density, (b) determining a magnetic interference declination value corresponding to the magnetic interference flux density, (c) generating a correction value based on the magnetic interference declination value, wherein the correction value corresponds to a deviation of the magnetic interference flux density from a reference magnetic flux density measured at a reference standard, and (d) controlling a direction of the directional drilling device based on the correction value. In some embodiments, the method further comprises (e) transmitting the magnetic interference declination value from a plurality of magnetic field sensors of the directional drilling device to a control device of the direction drilling device, wherein the control device is configured to generate the correction value. In some embodiments, the plurality of magnetic field sensors are calibrated by a homogenous magnetic field generated by a Helmholtz coil. In certain embodiments, the method further comprises (e) determining a magnetic position declination influenced by an altered alignment of the direction drilling device as a magnetic position flux density, and (f) generating a correction factor based on the magnetic position declination for returning the directional drilling device to a predefined position. In some embodiments, the method further comprises (g) storing the correction value and the correction factor in a memory of a control device of the direction drilling device. In some embodiments, (a) comprises determining a plurality of the magnetic interference declinations as magnetic interference flux densities in the direction of X, Y, and Z axes.

