Malampaya DCP DESIGN FOR THE RELAXATION OF SEABED PREPARATION TOLERANCES EMMA STEER ARUP

Background Malampaya field, offshore Palawan, Philippines Malampaya gas to power project - Shell, Chevron, PNOC Shell operators Existing platform at site Shallow Water Platform (SWP) concrete gravity structure installed in 2000 Supplies gas to four power stations providing ~45% of Luzon s power needs Source: malampaya.com

Depletion Compression Platform Field requires depletion compression to continue operating effectively i.e. for future expected decrease in well pressure Depletion Compression Platform DCP Maintain flow of gas to shore at acceptable rate to end of field life Topside equipment (above deck): 3500 5000t, +/- 2m COG variation

ACE Platform Range 5-140m water depth range Up to 15,000te topsides equipment payload (equivalent to 30,000te integrated deck) Wellhead / Minimum Facilities Platforms Drilling / Workover & Production

DCP Key Project Drivers Form suited to local construction capability steel No special transport vessel resident in the region Selfinstalling Ground conditions gravity based foundation Resists typhoon and earthquake events Safety

DCP Key Structural Elements Four 21 x 19 x 4m stiffened hexagonal pad footings linked by horizontal truss Four Φ 3.8m stiffened cylindrical legs 62 x 42 x 7.5m stiffened rectangular barge

Geotechnical Aspects In-Situ Ground Conditions 0.5 6m of carbonate sand (partially cemented) 3 15m of reef limestone 35m of calcarenite Relatively poor cyclic characteristics of insitu soil Remove and replace approach Material sourced locally

Geotechnical Aspects Challenge: Eliminate dedicated scour protection layer i.e. size seabed preparation to resist scour

Soil-Structure Interaction Develop a solution to accommodate platform installation on an undulating seabed Globally accommodate differential vertical levels in the prepared seabed at footing locations Perform plastic analysis to assess local behavior of the structure for a range of potential seabed undulations Relax tolerances for undulation shape and location resulting in reduced installation time

Seabed Preparation Contractor Consultation

Mound Squash Bounding Shapes Legend 2:1 radius to height ratio 10:1 radius to height ratio

Mound Squash cont.

Pad Footing Design Four individual hexagonal pad footings, integral with leg Six compartments Filled with iron ore slurry to provide weight Connected by pin ended horizontal truss to accommodate relative levels during installation and allow lateral load share

Pad Footing Design Prepared seabed includes possibility for local mounds of finite stiffness Mound squash loads quantified associated pressure/contact area Local mounds apply high localised pressure to underside of base Base stiffened to resist

Pad Footing Design Tubular leg Vertical T- stiffeners on bulkheads Bottom Plate Horizontal T- stiffeners on external walls Vertical propping columns between top and bottom plate Concentric T-stiffeners Radial T-stiffeners

Critical Load Cases Environmental and seismic in-place loading 10,000 year Abnormal Level Earthquake (ALE) Identify possible mound types Steep mounds (1:2 slope) Small gradual mounds (1:10 slope, up to 100mm) Large gradual mounds (1:10 slope, 100-300mm height) One or two discrete mounds most critical

Local Equilibrium Axial N* Moment M* Shear V* Uniform lateral pressure from seismic inertia Ballast applied as distributed pressure load Equivalent mound reaction applied as distributed pressure over squash area Lever arm determined from moment equilibrium

Design Cases Case 1: Single mound Case 2: Two mounds (opposite edges) Case 1: Single mound Case 2: Two mounds (opposite edges) Case 3: Two mounds (near edge) Case 1: Single Mound Case 2: Two mounds (opposite edge) Case 3: Two mounds (near edge) Case 2: Two mounds (opposite edges) Case 3: Two mounds (near edge)

Mound Parameters 300mm height, 10H:1V Mound located away from edge of footing Vertical load and area halved for mound at edge Limit max pressure based on complete squash load VERTICAL FORCE (KN) DISPLACEMENT (MM) AREA (M 2 ) PRESSURE (KPA) 2506 60 5.655 443.1 8640 120 11.310 763.9 17928 180 16.965 1056.8 29437 240 22.619 1301.4 46027 300 28.274 1627.9

Load in-line with bulkhead Mound Parameters y x Squashed mound footprint ase A - load in line with bulkhead Case B - load perpendicular to face Squashed mound footprint Load in-line with bulkhead y x y x Squashed mound footprint ase B - load perpendicular to face Squashed mound footprint Load perpendicular to face Case A: Load in-line with bulkhead y Case B: Load perpendicular to face x

Structural Analysis Linear analysis in DNV SESAM Non-linear analysis in Strand7 Plate - 2D quad-8 shell elements Stiffeners beam elements Fixed boundary conditions at tubular leg

Structural Analysis Strength - Von Mises stress

Structural Analysis Plastic behaviour acceptable Plastic strain limits from ISO 19902 and API-RP-2A Base plate 5% Compact stiffener flange/web 5% Non-compact stiffener flange/web 1%

Structural Analysis Buckling assessment of stiffened plates and girders using GeniE PULS (Part 2 DNV-RP-201) Longitudinally stiffened panels Local elastic buckling and nonlinear post-buckling behaviour Define initial imperfections to account for permanent plastic set GeniE GeniE 'sub-panel ' Secondary Stiffener stiffener Longitudinally Stiffened Stiffened Panel Panel Primary Girder girder Transverse direction direction Axial Axial/longitudinal / Longitudinal direction direction Girder Assessment being checked for primary girder

Offshore Work Seabed Preparation In-situ material removed within nominated footprint Backfilled with rock fill material Local surface tolerances achieved

Offshore Work Seabed Preparation

As-built Prepared Seabed

As-built Prepared Seabed South-East Pad Footing South-West Pad Footing

Offshore Work Prepared Seabed

Offshore Work - DCP Installation DCP successfully installed February 2015 Self-installing system performed as anticipated Barge jacked into position within 2 days, allowing rapid access to commence weld-out Source: Shell Philippines Exploration B.V.

Questions? Source: Shell Philippines Exploration B.V.