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

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1 Using Close Range Photogrammetry to meet Offshore Platform Construction and Installation Requirements Simon Manser, BP Exploration for Hydro14

2 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 Te pre-drill template installed at DP location (2011) DP Jacket fitted over template, using docking piles

3 Fit Esic Photogrammetry 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 & mm Subsea Photogrammetry acquired using: Kongsberg OE ROV mounted camera (5mpix) Equivalent to mm Kongsberg OE14-208

4 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

5 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

6 Introducing Subsea Photogrammetric Docking Pile Computation Pile Measurement 1) Formation of best fit plane using collinear equations 2) Define the intersecting line between two planes (plane geometry) Edge of Pile (from image 2) Image 1 Image 2 Determining Pile Centre 3) Combining multiple lines of intersection with tangential plane equations Pile TOP VIEW Line of Intersection Tangential Plane Image 1 Line of Intersection Image 2

7 Subsea Results Photogrammetry QA DP1 DP2 COMPANY METHOD DP1 Verticality DP1 Lean Direction DP2 Verticality DP2 Lean Direction DP1 DP2 Separation Fit Esic Photogrammetry (G) (G) FSL (UK) Cruciform + LBL (G) (G) BP Cruciform + LBL (G) (G) MEEX global model point accuracy (2-sigma): 6.9mm Docking pile angular uncertainty: 0.06º and 0.09º respectively

8 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

9 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

10 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

11 Model Processing: Jacket Verticality Results 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

12 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 Relative free bundle adjustment Global Model Retrospective Processing for Additional Scope of Work Model Best Fit RMS error (mm) QU 2.4 DP Tower West 4.6 DP Tower East 2.6 Relative model best fitted to global control

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