Real-time, limited orientation sensor auto-calibration
First Claim
1. A method of correcting sensor measurements obtained at a downhole tool, comprising:
- disposing the down hole tool having at least two sets of directional field sensors in a borehole, wherein the at least one of the sets of directional sensors measures the magnetic field and at least one of the sets measures the gravity field, wherein the directional sensors are orthogonal to each other, and one sensor in each set is oriented parallel to the longitudinal axis of the down hole tool;
obtaining magnetometer and accelerometer measurements at the tool from the at least two sets of field sensors;
determining a transformation variables using the magnetometer and accelerometer measurements;
transforming standard values of at least one of an earth'"'"'s magnetic field and an earth'"'"'s gravitational field into a reference frame of the tool using the determined transformation variables;
determining the residual measurement error from a difference between the magnetometer and accelerometer measurements and the transformed standard values of the earth'"'"'s magnetic field and the earth'"'"'s gravitational field;
selecting a quality level of the residual measurement error; and
applying the determined residual measurement error to the obtained measurements when the determined calibration correction errors are consistent with the selected quality level.
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Accused Products
Abstract
A system method and computer-readable medium for correcting measurements obtained by a down hole tool for residual measurement errors is disclosed. A down hole tool having at least two directional field sensors is disposed in a borehole. The at least two directional sensors are substantially orthogonal to each other and to a longitudinal axis of the down hole tool. Measurements are obtained from the at least two directional sensors during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool. Residual measurement errors are determined for the obtained measurements, and a quality level of the determined residual measurement errors selected. The determined residual measurement errors are applied to the obtained measurements when the determined residual measurement errors are consistent with the selected quality level. In various embodiments, the residual measurement errors are reduced from a first value that does not match the selected quality level to a second value that are consistent with the selected quality level.
34 Citations
24 Claims
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1. A method of correcting sensor measurements obtained at a downhole tool, comprising:
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disposing the down hole tool having at least two sets of directional field sensors in a borehole, wherein the at least one of the sets of directional sensors measures the magnetic field and at least one of the sets measures the gravity field, wherein the directional sensors are orthogonal to each other, and one sensor in each set is oriented parallel to the longitudinal axis of the down hole tool; obtaining magnetometer and accelerometer measurements at the tool from the at least two sets of field sensors; determining a transformation variables using the magnetometer and accelerometer measurements; transforming standard values of at least one of an earth'"'"'s magnetic field and an earth'"'"'s gravitational field into a reference frame of the tool using the determined transformation variables; determining the residual measurement error from a difference between the magnetometer and accelerometer measurements and the transformed standard values of the earth'"'"'s magnetic field and the earth'"'"'s gravitational field; selecting a quality level of the residual measurement error; and applying the determined residual measurement error to the obtained measurements when the determined calibration correction errors are consistent with the selected quality level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system for acquiring magnetometer and accelerometer data, comprising:
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a down hole tool conveyed on a member; at least two orthogonal tri-axial sets of magnetometers and accelerometers disposed on the down hole tool; a motor for rotating the member; a processor configured to; obtain magnetometer and accelerometer measurements from the at least two directional sensors during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool; determine a transformation variable using the magnetometer and accelerometer measurements; transform standard values of at least one of an earth'"'"'s magnetic field and an earth'"'"'s gravitational field into a reference frame of the tool using the determined transformation variables; determine a residual measurement error from a difference between the magnetometer and accelerometer measurements and the transformed standard values of the at least one of the earth'"'"'s magnetic field and the earth'"'"'s gravitational field; select a quality level of the determined residual measurement errors; and apply the residual measurement error to the obtained measurements when the residual measurement is consistent with the selected quality level. - View Dependent Claims (12, 13, 14, 15)
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16. A system for acquiring data downhole, comprising:
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a downhole tool conveyed on a rotating member; a magnetometer disposed on the downhole tool, the magnetometer including at least two directional sensors that are substantially orthogonal to each other and to a longitudinal axis of the member; and a processor configured to; obtain measurements from the at least two directional sensors during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool; determine a transformation variable using the magnetometer and accelerometer measurements; transform standard values of at least one of an earth'"'"'s magnetic field and an earth'"'"'s gravitational field into a reference frame of the tool using the determined transformation variables; and determine a residual measurement error from a difference between the magnetometer and accelerometer measurements and the transformed standard values of the at least one of the earth'"'"'s magnetic field and the earth'"'"'s gravitational field; select a quality level of the determined residual measurement error; and apply the determined residual measurement error to the obtained measurements when the determined residual measurement error are consistent with the selected quality level. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. A computer-readable medium having a set of instruction stored therein that are accessible to a processor in order to enable the processor to perform a method, the method comprising:
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receiving measurements from at least two directional field sensors in a borehole, wherein the at least two directional sensors are substantially orthogonal to each other and to a longitudinal axis of the down hole tool during rotation of the tool by at least 360 degrees around the longitudinal axis of the tool, wherein the at least two directional field sensors include a magnetometer and an accelerometer; obtaining magnetometer and accelerometer measurements at the tool using the at least two directional field sensors; determining a transformation variables using the magnetometer and accelerometer measurements; transforming standard values of at least one of an earth'"'"'s magnetic field and an earth'"'"'s gravitational field into a reference frame of the tool using the determined transformation variables; determining a residual measurement error from a difference between the magnetometer and accelerometer measurements and the transformed standard values of the earth'"'"'s magnetic field and the earth'"'"'s gravitational field; selecting a quality level of the determined residual measurement error; and applying the determined residual measurement error to the obtained measurements when the determined residual measurement error are consistent with the selected quality level.
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Specification