# US 9,435,649 B2 · Method and system for azimuth measurements using a gyroscope unit

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- Number: US 9,435,649 B2
- Document ID: US9435649B2
- Status: Granted
- Kind: B2
- Application number: 13/249,140
- Filed: 2011-09-29
- Published: 2012-04-05
- Granted: 2016-09-06
- Earliest claimed: 2010-10-05
- Assignees: Schlumberger Technology Corporation
- Applicants: Shigeru Sato; Juei Igarashi
- Inventors: Shigeru Sato; Juei Igarashi
- Web page: https://patentgrep.com/patent/US9435649B2

## CPC

- G01C 21/188: {for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems}
- G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S)

## 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.

## Claims

### Claim 1

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.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the two earth rate components are measured by a single gyroscope rotatable to align an input axis to each of two axes orthogonal to each other.

### Claim 3 (depends on 2)

The method according to claim 2, wherein one of the two earth rate components is measured by a first gyroscope with an input axis aligned to a first axis and the other earth rate component is measured by a second gyroscope with an input axis aligned to a second axis orthogonal to the first axis.

### Claim 4 (depends on 3)

The method according to claim 3, wherein the gyroscope unit comprises one or two MEMS-type gyroscopes.

### Claim 5

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.

### Claim 6 (depends on 5)

The system according to claim 5, wherein the gyroscope unit comprises a single gyroscope rotatable to align an input axis to each of two axes orthogonal to each other.

### Claim 7 (depends on 5)

The system according to claim 5, wherein the gyroscope unit comprises a first gyroscope with an input axis aligned to a first axis and a second gyroscope with an input axis aligned to a second axis orthogonal to the first axis.

### Claim 8 (depends on 5)

The system according to claim 5, wherein the gyroscope unit comprises one or two MEMS-type gyroscopes.