SYSTEM AND METHOD FOR THE CALIBRATION OF AZIMUTHAL RESISTIVITY LOGGING TOOLS
First Claim
1. A method for calibrating an azimuthally sensitive resistivity tool having at least one transmitter and at least one receiver, at least one of the transmitter and receiver comprising a dipole moment tilted or transverse to a longitudinal axis of the tool, the method comprising:
- a) disposing the tool horizontally above the earth surface at a predetermined height, and recording measurements made by the at least one receiver while rotating the tool about the longitudinal axis from an angle of 0 degrees through 360 degrees;
b) fitting the recorded measurements with a sinusoidal curve, and determining a mean value of the measurements and an angle θ
corresponding to a direction of the dipole moment when the recorded measurement is at the mean value;
c) placing a calibration loop having a first selected impedance along the tool and setting an azimuthal angle of a normal to a plane of the calibration loop to the angle θ
;
d) recording measurements of a component of voltage induced in the receiver related to a distance to a resistivity boundary, and subtracting the mean value from the recorded measurements;
e) changing the first selected impedance to a second selected impedance and repeating the recording measurements of the first voltage component induced; and
e) determining correction parameters for the first voltage component induced using the recorded measurements made using the first selected impedance and the second selected impedance.
1 Assignment
0 Petitions
Accused Products
Abstract
A system and method for the calibration of downhole azimuthally sensitive resistivity tools is disclosed. The system and method can eliminate and/or compensate for the measurement errors due to the electronic circuit, the mechanical structure, etc., of the tool. The system and method also can validate the measurement accuracy. The downhole azimuthal resistivity logging tool can be, but not limited to, the LWD azimuthal resistivity tools with coil(s) oriented in the directions other than the tool axis. In one embodiment, the system is constructed by the azimuthal resistivity tool, a tilted calibration loop made of conductive wire; an external resistor; and an external inductor. Some other method embodiment comprises an azimuthal resistivity tool, a semicircular conductive wire connected with a conductivity rectangular wire, and the external resistor and inductor. Although this disclosure is primarily intended for azimuthal resistivity Logging-While-Drilling (LWD) or Measuring-While-Drilling (MWD) tools, the disclosure is also applicable to wireline and any other possibly equipment.
2 Citations
13 Claims
-
1. A method for calibrating an azimuthally sensitive resistivity tool having at least one transmitter and at least one receiver, at least one of the transmitter and receiver comprising a dipole moment tilted or transverse to a longitudinal axis of the tool, the method comprising:
-
a) disposing the tool horizontally above the earth surface at a predetermined height, and recording measurements made by the at least one receiver while rotating the tool about the longitudinal axis from an angle of 0 degrees through 360 degrees; b) fitting the recorded measurements with a sinusoidal curve, and determining a mean value of the measurements and an angle θ
corresponding to a direction of the dipole moment when the recorded measurement is at the mean value;c) placing a calibration loop having a first selected impedance along the tool and setting an azimuthal angle of a normal to a plane of the calibration loop to the angle θ
;d) recording measurements of a component of voltage induced in the receiver related to a distance to a resistivity boundary, and subtracting the mean value from the recorded measurements; e) changing the first selected impedance to a second selected impedance and repeating the recording measurements of the first voltage component induced; and e) determining correction parameters for the first voltage component induced using the recorded measurements made using the first selected impedance and the second selected impedance. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
-
Specification