Simon Manser, BP Exploration for Hydro14

Using Close Range Photogrammetry to meet Offshore Platform Construction and Installation Requirements

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Clair Phase II Project - “Clair Ridge”

• UKCS West of Shetland - water depth 141

metres • Two fixed steel platforms DP & QU • Jacket installation in 2013, topsides

2015. • 168Te pre-drill template installed at DP

location (2011) • DP Jacket fitted over template, using

docking piles

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Photogrammetry – • Delivering 3D spatial models from 2D photos MEEX – Metrology in Extreme Environments • Accuracy:

• Achievable -1:5000 • Quoted - 1:2000

MEEX – Equipment • Surface Photogrammetry acquired using: • Canon EOS 5D Mark II“Full Frame” (21mpix) • Two lenses, 17-40mm & 70-200mm • Subsea Photogrammetry acquired using: • Kongsberg OE14-208 ROV mounted camera (5mpix) • Equivalent to 38-140mm

Fit Esic Photogrammetry

Kongsberg OE14-208

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Fit Esic Processing Methodology

Free Bundle Adjustment – Minimal Control • Requires 20 images for initial free bundle adjustment

• Uses a combination of triangulation and resection

• Minimum of one scale bar to be visible in approximately 10% of the images to determine the camera parameters

• Adjustment is reliant on Epipolar Geometry

• Model globally expanded using regular free bundle adjustments with self calibration

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Subsea Installation Positioning Tolerances

• Template - As-Built Requirement: • Template orientation: ±0.5° • Global template location: ±0.5m • Template level: ±0.1° Installation & as-built achieved using: • Wideband LBL array • CDL ring laser gyros & mini-tilt package • Digi-quartz leveling Template as-built used for photogrammetric model orientation

• Docking Piles - As-Built Requirement : • Pile verticality: ±0.1° • Pile separation: ±50mm As-built results derived using:

• Fit Esic “MeeX” close range photogrammetry • Verification by LBL & attitude sensor

Temporary Pile Docking Guides

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Introducing…

• Pile Measurement 1) Formation of best fit plane using collinear equations

2) Define the intersecting line between two planes (plane geometry)

Subsea Photogrammetric Docking Pile Computation

Image 1 Image 2

Edge of Pile

(from image 2)

Line of Intersection

Determining Pile Centre 3) Combining multiple lines of intersection with tangential plane equations

Image 1 Image 2

Pile

Tangential Plane

TOP VIEW

Line of Intersection

• MEEX global model point accuracy (2-sigma): 6.9mm • Docking pile angular uncertainty: 0.06º and 0.09º respectively

Subsea Results – Photogrammetry QA

COMPANY METHOD DP1 Verticality

DP1 Lean Direction

DP2 Verticality

DP2 Lean Direction

DP1 – DP2 Separation

Fit Esic Photogrammetry 0.52° 247.42°(G) 0.96° 326.36°(G) 27.946

FSL (UK) Cruciform + LBL 0.72° 256.95°(G) 0.96° 334.19°(G) 27.933

BP Cruciform + LBL 0.77° 257.23°(G) 0.96° 334.30°(G) 27.926

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DP1 DP2

Jacket Topside Dimensional Control

• Jacket Installation Positioning (HMC/DOF) • DP Jacket installed over existing piles.

• QU installed relative to DP

• Photogrammetry Scope of Work (Fit Esic)

The scope of work was to:

• Survey the flange/nozzle connections for pre-fabrication of hook up spools

• Confirm leg ovality at cut level for primary and secondary stab-in cones (6 in total)

Using existing imagery Fit Esic also delivered:

• The verticality and orientation of the Jacket

• The planarity of the leg cuts

• The leg separation post installation

• The leg cut elevation

• The location (surface and seabed) of QU relative to DP

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Model Processing: Defining the Z-plane for verticality

• All leg cuts (12 in total) processed with existing imagery to define Z reference plane • Retrospective process that is not possible using traditional dimensional control techniques

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Introducing… Model Processing: Creating & Orientating the Models

The Process

1) Define the CRS 2) Create a surface model 3) Orientate the surface model 4) Merge the surface model with the jacket

yard as-built model

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Model Processing: Jacket Verticality Results

DP Platform DOF (UK) HMC Fit Esic Pitch 0.25º 0.09º 0.08º

Roll -0.32º -0.03º -0.05º

QU Platform DOF (UK) HMC Fit Esic Pitch 0.05º 0.01º 0.05º

Roll -0.03º -0.01º -0.05º

• DOF (UK) results derived from Octans HPR sensor • HMC results derived from optical level

Verticality Results

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Surface Photogrammetric Model Accuracy

Relative Model – Initial Scope of Work Model Final Model Accuracy (mm) at 2 Sigma

QU 2.2 DP Tower West 0.5 DP Tower East 1.4

Model Best Fit RMS error (mm) QU 2.4

DP Tower West 4.6 DP Tower East 2.6

Global Model – Retrospective Processing for Additional Scope of Work

Relative free bundle adjustment

Relative model best fitted to global control

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Clair Phase II Project - “Lessons Learned”

Primary Benefits (MEEX Close Range Photogrammetry)

• Efficient – fast acquisition resulting in significant time saving • Safe - reduced HSSE exposure • Flexible - ancillary data provides retrospective processing capability without re-

mobilising to the field. Primary Constraint • Processing time - suitable when results are required within 2-4 weeks.

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