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US 9,435,649 B2Granted
Method and system for azimuth measurements using a gyroscope unit
AssigneeSchlumberger Technology Corporation
InventorsShigeru Sato, Juei Igarashi
Life of this patent
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Abstract
Methods and systems for azimuth measurements using a gyroscope unit are disclosed. The method includes acquiring a ratio value between two earth rate components orthogonal to each other by using the gyroscope unit at a measuring position; acquiring three gravity vector components orthogonal to each other at the measuring position; and determining an azimuth with respect to a reference axis predetermined in the gyroscope unit, based on the ratio value, the three gravity vector components and a geodetic latitude of the measuring position.
Claims8
A method for determining an azimuth measurement of a downhole wellsite system using a gyroscope unit, comprising:
- acquiring a ratio value between two earth rate components orthogonal to each other by using the gyroscope unit at a downhole measuring position;
- acquiring three gravity vector components orthogonal to each other at the downhole measuring position;
- determining an azimuth with respect to a reference axis predetermined in the gyroscope unit, based on the ratio value, the three gravity vector components and a geodetic latitude of the downhole measuring position;
- and
- using the azimuth for a wellbore survey, or navigation of the wellsite system from the downhole measuring position;
- wherein the azimuth is determined by using:
- σ
- =
-
- ±
- δ
- ±
- ɛ
-
- (
- λ
- )
- =
-
- ±
- arccos
- (
- G
- z
-
- Ω
- x
- ′
- (
- 1
- -
- G
- x
- 2
- )
-
- (
- G
- z
- 2
- +
- (
- G
- x
-
- Ω
- x
- ′
- +
- G
- y
-
- Ω
- y
- ′
- )
- 2
- )
- )
- ±
-
- arccos
- (
- (
- G
- y
-
- Ω
- x
- ′
- -
- G
- x
-
- Ω
- y
- ′
- )
- 2
- -
- cos
-
- (
- λ
- )
- 2
- cos
-
- (
- λ
- )
- 2
-
- [
- (
- G
- y
-
- Ω
- x
- ′
- -
- G
- x
-
- Ω
- y
- ′
- )
- 2
- -
- 1
- ]
- )
- where X-axis and Y-axis of an orthogonal coordinates system are defined for measuring the two earth rate components, the X-axis is set as the reference axis, δ represents an angle between the projection of X-axis onto the horizontal plane and a fourth intersection line between the earth rate plane and the horizontal plane, ε represents an angle between the third intersection line and the fourth intersection line, σ represents the azimuth, Ω′x, and Ω′y and represent components along the X-axis and the Y-axis of the normalized earth rate projection vector on an XY-plane as the measurement coordinate plane, Gx, Gy and Gz represent the normalized gravity vector components, and λ represents the geodetic latitude having a plus value in the Northern Hemisphere and a minus value in the Southern Hemisphere,
- wherein the azimuth is further determined by using one of equations (30-1) - (30-8) listed in Table I, based on conditions for selecting an azimuth formula with respect to a normal Ω unit vector PΩ of the earth rate plane, a unit gravity vector G, a unit vector LO—dof the fourth intersection line, and a unit vector X′ of the X-axis projected onto the horizontal plane.
113 more elements
A system for determining an azimuth measurement of a downhole wellsite system, comprising:
- a housing;
- a gyroscope unit including one or two gyroscopes;
- three orthogonal axis accelerometers;
- a data processing unit;
- and
- a power supply unit,
- wherein the data processing unit comprises a computer having a processor and a memory, and
- wherein the memory stores a program having instructions for:
- acquiring a ratio value between two earth rate components orthogonal to each other by using the gyroscope unit at a downhole measuring position;
- acquiring three gravity vector components orthogonal to each other at the downhole measuring position;
- determining an azimuth with respect to a reference axis predetermined in the gyroscope unit, based on the ratio value, the three gravity vector components and a geodetic latitude of the downhole measuring position;
- and
- using the azimuth for a wellbore survey, or navigation of the wellsite system from the downhole measuring position;
- wherein the azimuth is determined by using:
- σ
- =
-
- ±
- δ
- ±
- ɛ
-
- (
- λ
- )
- =
-
- ±
- arccos
- (
- G
- z
-
- Ω
- x
- ′
- (
- 1
- -
- G
- x
- 2
- )
-
- (
- G
- z
- 2
- +
- (
- G
- x
-
- Ω
- x
- ′
- +
- G
- y
-
- Ω
- y
- ′
- )
- 2
- )
- )
- ±
-
- arccos
- (
- (
- G
- y
-
- Ω
- x
- ′
- -
- G
- x
-
- Ω
- y
-
- ′
- )
- 2
- -
- cos
-
- (
- λ
- )
- 2
- cos
-
- (
- λ
- )
- 2
-
- [
- (
- G
- y
-
- Ω
- x
- ′
- -
- G
- x
-
- Ω
- y
- ′
- )
- 2
- -
- 1
- ]
- )
- where X-axis and Y-axis of an orthogonal coordinates system are defined for measuring the two earth rate components, the X-axis is set as the reference axis, §represents an angle between the projection of X-axis onto the horizontal plane and a fourth intersection line between the earth rate plane and the horizontal plane, ε represents an angle between the third intersection line and the fourth intersection line, σ represents the azimuth, Ω′x, and Ω′y represent components along the X-axis and the Y-axis of the normalized earth rate projection vector on an XY-plane as the measurement coordinate plane, Gx, Gy and Gz, represent the normalized gravity vector components, and λ, represents the geodetic latitude having a plus value in the Northern Hemisphere and a minus value in the Southern Hemisphere,
- wherein the azimuth is determined by using one of equations (30-1) - (30-8) listed in Table I, based on conditions for selecting an azimuth formula with respect to a normal unit vector PΩ of the earth rate plane, a unit gravity vector G, a unit vector LO—d of the fourth intersection line, and a unit vector X′ of the X-axis projected onto the horizontal plane.
122 more elements
Dependencies are inferred from the claim text.