Gyro Technology
Transcript of Gyro Technology
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Early Survey Technology
PHOTO MECHANICAL DEVICES – 1930’s
A camera unit takes a picture of acompass card. The plumb bob positionchanges depending on the inclination
and direction.
Adaptations led to the ability to takemultiple camera shots.
The multishot survey was born.
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1930’S
Surface Oriented to “known” foresight
Free Gyro
Drift Error: 0.5° - 2.5° degrees/ 15 minutes
Accuracy Limitation
1° - ? degrees Azimuth
Operator Dependent
Error: 1° - ? degree
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North Seeking Rate Gyro
MWD
LWD
GWD
Modern Day
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Survey
Systems
Magnetic Gyroscopic
FilmPlum Bob
Electronic
OR / SS MS
Free Gyro Rate Gyro
Film SRGNorth
SeekingInertial
OR / SS
MS / STMWD
InclinationOnly
OR = Orientation SS = Single-Shot MS = Multi -Shot ST = Steering Tool SRG = Surface Readout Gyro
MWD = Measurement Whi le Drill ing
Available Survey Technology
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Accuracy Vs. Speed
Camera TypeGyros
Surface ReadingGyros
North SeekingGyros
DropGyros
InertialNavigation
S p e e d o f O p e r a t i o n
Accuracy
MWD
AdvancedMWD
Continuous
Gyros
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Accuracy Vs. Survivability
LaserGyros
Spinning MassGyros
MEMSGyros
S u r v i v a b i l i t
y
Accuracy
Fiber OpticGyros
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MEMS Gyro’s
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Earths Magnetic Field
• Datum moving (diurnally & general drift)• Solar effects• Local anomalies (SPE 56699)• Magnetic drilling environment
(Drill pipe, casing, mud - SPE71400)
Earths Rotational Field
• North referencing gyros• Detects earths rotational ‘rate’
• Does not vary• Perfect reference
Earths Gravity Field
• Latitude correction equation (RGF30)
Survey Sensor Datum’s
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It can be observed that thishorizontal component of the Earths spin vector is always pointing togeographic North,i.e. it is a perfect True North reference.
Earths rotational rate = (360°/24hr)+(360°/365.25dys/24hr)=15.041 degs/hr. This isconstant for any position on the globe and can be defined as consisting of ahorizontal and vertical component. However, these individual components are notconstant and are dependant on the Latitude.
The horizontal component (Eh) = 15.041 x Cosine Lat. (Houston 29.83°N, Eh = 13.05)
It is the accurate measurement of the horizontalearth rate vector that is the basis for all North
Seeking gyroscopes. In gyro compass mode thetool is held stationary at each required surveydepth and the survey data is calculatedindependently at each point. This method iscommonly referred to, as Gyro Compassing.
North Seeking Theory
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9700 9750 9800 9850 9900 9950 10000 10050 10100 10150 10200
-8850
-8845
-8840
-8835
-8830
-8825
-8820
-8815
-8810
19.3 ft
BB-509
RGS-ALC LWD
T V D
Measured Depth
Depth Error
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9500 9600 9700 9800 9900 10000 10100 10200 10300 10400 10500 10600 10700 10800 10900 11000
87.6
87.8
88.0
88.2
88.4
88.6
88.8
89.0
89.2
89.4
89.6
89.8
90.0
RGS-CT 1FT INTERVALS MWD
IS-123 LATERAL AA
I n c l i n a t i o n
Measured Depth
Continuous Gyro
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S
MD (ft)
I N C L
( d e g r e e s
)
Plan Curve Rate = 5.0 deg/100ftPDM Rate = 10.0ROT Rate = 0.0Slide Offset = 0ft
DD Type “A”Example
10,400 10,450 10,500 10,550 10,65010,600 10,700 10,750 10,800 10,850 10,90080
85
90
95
100
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Gyroscope Sensors
L ≈ ωmr²
Floated
Dynamically Tuned
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Common Gyro Surveying Modes
Mode North-Seeking Continuous
PropertiesMeasured
Earth Rotation VectorGravity Vector
Cross-Axis Tool Rotation
ApplicationsgyroMWD/GWDDrop SurveysContinuous Init
High Speed Surveying(Wireline, Drop)Continuous gyroTF
Considerations Tool must be very stillto collec t a survey
Faster running speeds arebetter, as drift errors are time-dependent.
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Gyro Instrument QA Since the quality of a gyro instrument is a critical factor in
collecting a successful survey, the instrument calibration processmust be tightly correlated to the Instrument Performance model.
Sensor Manufacture
Sensor Installation
Factory Calibration
Field Calibration
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In-Run Quality Control
Gyrocompass• Inclination QC is generally the same as with
MWD systems• Comparison against theoretical ERH is the
primary QC measure• Additional measures include gyro output
stability and gyro bias stability.Continuous Surveying•
Zero-velocity drift checks are used tocompensate for bias, mass unbalance, andEarth Rate effects
• QC measures ensure that drift variation
matches predicted values
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Basic Gyrocompass Processing
Raw
•Raw Gyro Rates (GX1, GX2, GY1, GY2)
•Raw Accelerations (AX1, AX2, AY1, AY2)
•Tens to hundreds of readings in each position
Mid
•Gyro Bias (QC Term) (G-Bias X and G-Bias Y)
•Gyro and Accel Phases (tan-1(G Y/GX))
•Gyro and Accel Stability/Noise
Done
•Inclination (normal)
•Azimuth (Gphase – Aphase)
•ERh (G Amplitude)
Data is collected by sampling cross axis rotation rate and
acceleration, at positions 180 degrees apart.
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Running Considerations
1. CASING SURVEYS WITH PROPER RUNNING GEAR PROVIDE THE BEST DIRECTIONAL MEASUREMENT
2. USE OF A CCLOR GAMMA-RAY FOR WIRELINE CORRELATION ENSURES MEASURED DEPTH ACCURACY
3. PRE-AND-POST JOB FIELD CALIBRATIONS MONITOR MASS UNBALANCE PERFORMANCE
4. DROP SURVEYS SAVE TIME BY ENABLING SURVEYS WHILE TRIPPING
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10 Questions
1. HOW ARE YOUR GYROS CALIBRATED, AND HOW OFTEN?
2. HOW DO YOU KNOW THEY NEED CALIBRATION?
3. WHAT ARE YOUR QA/QC MEASURES
4. DOES YOUR GYRO MEASURE EARTH RATE, AND WHAT SHOULD IT BE?
5. HOW DO YOU KNOW YOUR TOOL WAS WORKING PROPERLY ON LOCATION?
6. WHAT IS THE EXPERIENCE LEVEL OF YOUR SURVEYORS?
7. WHAT IS THE ACCURACY OF YOUR SURVEY TOOL?
8. DO YOU HAVE AN ISCWSA ERROR MODEL FOR YOUR SURVEY TOOL?
9. HOW DO YOU VALIDATE YOUR ERROR MODEL?
10.WHERE DO YOUR SENSORS COME FROM?