10 years of implied metrology - ths...gyro headings and depth loops • observations are grouped...
TRANSCRIPT
10 Years of Implied Metrology
Stewart Cannon
4D Nav
• Green Canyon Area of Gulf of Mexico
• 150 miles south of New Orleans
• First oil 2007 • Oil and Gas
exported via Caesar and Cleopatra pipeline systems
• Two producing drill centers, DC1 & DC3.
• Production and Quarters (PQ) platform 2 miles south of DC1
• Water depth ranges from 1600m at DC3 to 2100m at the PQ.
• PQ processes 200,000 barrels/day
DC 1
• DC1 - 5 manifolds, 5 PLEMs and 11 trees all installed on 36 inch foundation piles.
• 300m along its north south axis
• Permanently installed tripods for LBL positioning
DC 3
• DC3 - 2 manifolds, 1 PLEM and 3 trees, also installed on foundation piles
• Permanently installed tripods for LBL positioning at each drill centre
• 4 additional wells planned
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Pre-Fabricated Jumper Metrology
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Pre-Fabricated Jumper Metrology
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Pre-Fabricated Jumper Metrology
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Pre-Fabricated Jumper Metrology - Offshore
X,Y,Z Pitch Roll Heading
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Pre-Fabricated Jumper Metrology – fabrication yard
• Perform dimensional control survey of structure to be landed on the foundation pile.
• Determine XYZ coordinates of jumper hubs, hub pitch and hub roll relative to the point where the structure interfaces with the subsea pile
• Additional receptacles installed on the structure provide additional datum points when structures are installed subsea.
Install Structure
Metrology
Issue Metrology Drawings
Isometric Drawings
Fabrication
Pressure Test
Load Out & Transport to Field
Install Jumper
Well Start Up
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Pre-Fabricated Jumper Metrology
• 3 to 4 weeks from metrology to jumper load out
• Critical path to well start up
Install Structure
Install Jumper
Issue Metrology Drawings
Isometric Drawings
Fabrication
Pressure Test
Load Out & Transport to
Field
Install Jumper
Well Start Up
14
Pre-Fabricated Jumper Metrology
• Perform metrology to subsea foundation piles
1st Oil accelerated 4 weeks
Metrology calculator software developed to allow data to be viewed and analyzed plus provide an input to real-time software
Dimensional Control Data
Baselines
Depth Loops
Inclinations
Gyro Data
Metrology Calculator
RigNav
Quality Control
Forensic Analysis
Data Model Piles and Tripods • Model includes piles,
tripods, structures, metrology tools and hubs/receptacles
• Piles and Wellheads are fixed to the seabed and may be keyed
• Tripods may have different positions at different times to accommodate movement
Data Model Structures and Hubs
• Structures sit on piles or mudmats, may be keyed or able to rotate and have hubs and receptacles
• Hubs and receptacles are defined by coordinates and attitudes in a structure based system
• Metrology tools sit on piles or hubs and have receptacles
Data Model Jumpers
• Jumpers connect one hub to another
• Coordinates and attitude of both hubs computed
• Implied metrology developed from the hub-to-hub relationship
• Vertical profile of jumper added for 3D viewing and clearance calculations
Data Model: Observations • Observations include
baselines, attitudes, gyro headings and depth loops
• Observations are grouped into data sets and campaigns
• Observed data imported into MC to eliminate transcription errors
• Observations collected over 10 years
Metrology Calculator was subsequently used to perform a complete adjustment with no scale factor using all the baselines Some pile-to-wellhead baselines were collected but not used in the initial adjustment As piles and wellheads were installed baselines were collected to tripods Initial calibration was done with Mk 4 Compatts and WF and adjusted using a scale factor DC 1 was much better for implied metrology as the longer distances make sound velocity the dominant error source DC 1 spaced about 250m and DC 3 about 500m with 8 tripods at each site Tripods set to form a near-field array and an initial calibration was performed with the existing well set at the fiduciary point
Network adjustment solution based on land techniques used Reduced by pro-rating the misclosure by the amount of time spent on a segment of a loop to correct for tide Depth loops measured between piles Paroscientific pressure sensor used to measure depth loops Initially used Pressure Sensor on Compatts for Depths but not reliable enough
Heading was measured on slotted piles Observations were collected on different quadrants and reduced to attitude and heading of the pile and offsets between the stab and inclinometer Metrology tools used for mechanical interface between Compatt stab and top of pile or wellhead Gyro or Inclinometer Compatt data collected on each pile or wellhead Piles were keyed and wellheads were not so trees had to be landed with a precise tolerance Pile and wellhead heading and attitude determination required to compute real-world coordinates of hubs and receptacles
• Heading measured in multiple
quadrants
• C-O of slots measured with DC
survey
• Meridian Convergence computed
and applied
• All heading observations reduced to
one quadrant and averaged
• Also possible to compute headings
with observations to at least two
receptacles or hubs on a structure
Heading Calculation
Dimensional Control • Locations and attitudes
of hubs and receptacles surveyed into a structure-oriented coordinate system for structures and metrology brackets
• Orientation of key surveyed precisely
Dimensional Control • Coordinates entered
into MC
• .dwg outline of structure and 3D model also entered
• Report and page number referenced in MC for easy access
Implied Metrology • Given position and
attitude of two hubs we can determine the metrology between them
• In the case of trees the wellheads were not slotted so they had to be placed within a couple of degrees of planned heading
• Jumpers were pre-fabricated
A total of 14 observation campaigns were conducted at DC 3 over 7 years A total of 27 observation campaigns were conducted at DC1 over 9 years with each campaign typically having multiple baseline data sets Most measurements were observed with Mk 5 Compatts and all adjustments were done without a scale factor Issues with initial manifold headings required collection of baselines and a network solution for heading and position to check gyro observations Multi-path from measuring baselines through structures was observed and it became evident that the tripods should have been higher Checks around the network were made as infrastructure was installed or if high residuals were seen during a measurement campaign Baselines were generally observed between hubs to confirm implied metrology prior to jumper installation
Compatt Transducer to Receptacle Reduction
• The position of interest is the receptacle and not the transducer
• The Compatt may be mounted on a metrology bracket due to accessibility issues
• These calculations were added as part of the network adjustment
• Network adjustments were performed
using all available data to QC results
• Incorporates all dimensional control and
holds lever arms fixed
• Network adjustment considered all
baselines and headings
• Used tripod model that allowed for tripod
movement through time
• Combined solution for position and
heading of structures
• Cascaded calculation technique was
developed that feeds output from attitude
calculations to depth network calculation
to network adjustment
Horizontal Network Adjustment
Baseline Measurements • 1028 Baselines
• Weighted by standard deviation which combined detection accuracy and sound velocity accuracy
• All residuals for baselines less than 30m were less that 2cm
1 4 9 19
55
168
279
218
169
74
21 5 4 1
0
50
100
150
200
250
300
-12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 More
FREQ
UEN
CY
BIN
Baselines (cm)
Frequency
Gyro Measurements • 67 heading
measurements in slotted piles and receptacles
• Heading was computed by a weighted combination or baselines and gyro measurements
• Larger spread than anticipated indicates accuracy expectations not met
• Analysis showed this to be due to a combination of mechanical and procedural issues
3
0
1 1
2
4
3
5
7
9
5
6
9
5
3
2
0 0
1
0 0 0
1
2
3
4
5
6
7
8
9
10
FREQ
UEN
CY
BIN
Heading Residuals
Frequency
Vertical Network Adjustment
• Used least squares techniques developed for land differential level networks
• Provides redundancy and an indication of accuracy via residuals
• Observations were the differential depth between two points after misclosure was distributed
• All depth loop segments used the same weighting
Depth Loop Measurements
• 611 Depth Loop segments
• Most residuals within 2cm
• There were some cases of depth loops between the same two points measured at different times having a difference of 15cm
• Could have been caused by pile settlement
0 3
15
30
101
180
150
83
28
15
5 0
0
20
40
60
80
100
120
140
160
180
200
-10 -8 -6 -4 -2 0 2 4 6 8 10 More
FREQ
UEN
CY
BIN
Depth Loops (cm)
Frequency
• Headings of four structures measured by gyro were determined to be in error by over two degrees by using baselines to compute independent headings
• A tripod was suspected of moving several times due to high baseline residuals. Analysis determined it was a combination of one movement and multipath.
• Initial observations used a scale factor and subsequent data sets didn’t. With the site at the border of UTM zone there was a noticeable difference in the tripod coordinates.
• Sound velocity issues were noted in some data sets when a velocimeter was used instead of a CTD
Forensic Metrology
RigNav: Real-time Application for Rig Safety
• The positions, headings and attitudes derived from the metrology are used to generate 3D scenes describing the fields in detail
• Used by Drilling group to monitor spatial relations between BOP and the infrastructure
• DROP model used to predict landing spot for dropped objects
Metrology Calculator
RigNav real-time software
Positions, attitudes and
headings 3D Models
RigNav: Vertical Clearance Planning
RigNav: Vertical Clearance Monitoring
Commercialization of Technology • Metrology Calculator
developed into a commercial job-oriented software package called Connect in partnership with Sonardyne
• Planning tools to generate steps for metrology process
• In addition to calculations collects all data in real-time