Engineering Simulation Solutions for Offshore and Subsea
Harish Radhakrishnan ANSYS Inc.
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Oil and Gas Market Overview Macro Drivers • Shifting supply side – 687.44 billion barrels of oil (bbl) in proven reserves – Depleting sources of easily accessible oil especially outside of Middle East. – Reserve degradation of the super majors – Rise of independents and national oil companies – Viability of unconventional resources • Tar sand, oil shale and coal-to-liquid, ultra-deep sea
• Increasing demand – Not sustainable at 106mb/d usage projected by 2030 – Growing global demand for automotive • Global capacity to refine crude is not expanding rapidly – Need for cleaner burning liquid fuel • Role of natural gas – Natural gas to increase by 51% from 2005-2030 to 158 Trillion cubic feet – Electricity generation from Natural gas will increase to 5.5% and 4.6% respectively in China and India – Increase production and transport of liquefied natural gas (LNG) © 2010 ANSYS, Inc. All rights reserved.
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Key Market Problems Reliable and Safe Product and Processes - Drilling and Production • Inherently complex problems – Deep-waters, high pressures – Temperature variation – Hurricane, waves, – Dense areas, combustible and hazardous products – Drilling through complex geology, long distances – Many production and processing equipment : Topside, subsea • Enormous cost – Human life – Environmental concerns – Delays and fines – Loss of capital, time and equipment © 2010 ANSYS, Inc. All rights reserved.
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ANSYS Presence Diverse Range of Applications • Oil-Water-Gas Separators • Anchor Chain Drag • Ball Valves • Boilers • Cage Valve Erosion • Cementing • Check and Chock Valves • Downhole Filter Erosion • Downhole Injectors • Drill Bit Cooling and Cuttings Removal • Drill Bit Design • Drill Bit String and Electronic • Fire Suppression
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• Flare Stacks • Fluidized Catalytic Cracker (FCC) • Furnaces • Gas Dispersion • Gas Lifts • Gas Processing • Gas Separation • Generators • Heat Exchangers • Horizontal Drilling Hydrocyclones • Jet and Pool Fires • Leaks and Seals
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• • • • • • • • • • • •
Logging While Drilling Mud Drilling Fluid Mud Sedimentation Pipe Manifolds Pumps Radial Reactor Smoke Accumulation Storage Tank Collapse Subsea Blow-out Subsea Landslide Subsea Oil Cooling Coils Vortex Induced Vibration
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Example Applications
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Global Assessment of Floaters • Remaining new Oil & Gas fields largely offshore, and in ever deeper water • One off designs • High capital investment • Failure consequences high • Extreme environmental conditions – Ultra deep water – Hurricanes • Difficult to physically prototype given the design requirements
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Global Assessment of Floaters • Many considerations – Stability – Integrity of mooring/tether systems – Dynamic positioning (station keeping) – Fatigue of moorings/risers – Wave slamming – VIM/VIV – Structural integrity – Human factors © 2010 ANSYS, Inc. All rights reserved.
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Complete Solutions • The ANSYS solution provides tools for all aspects of offshore simulation – ANSYS CFD can be used to provide input to ANSYS AQWA for viscous effects – ANSYS CFD can also be used to examine specific design issues that require better physical modeling, such as wave slamming and ride-up, sloshing – The interface to ANSYS Mechanical products provides a simple and accepted method for assessing structural adequacy of floating offshore vessels © 2010 ANSYS, Inc. All rights reserved.
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Drill Bit Analysis
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Cementing/Mudflow in Casings Some images courtesy of Halliburton
Velocity profile in an eccentric gap (left), contours of turbulent viscosity (right)
Experimental cutaway of cementing in an eccentric gap used for validation of CAE simulation.
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Gas Dispersion Some images courtesy of Kerr-McGee North Sea
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Some images courtesy of BMT
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Flare Radiation Fuel to Wind ratio 1:2
Fuel to Wind ratio 2:1
Flame shape and shroud surface temperature for two different fuel and wind ratios
Flare flow pathlines, coloured by temperature © 2010 ANSYS, Inc. All rights reserved.
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Wave\Wind Loading
Transient pressure distribution caused by ocean waves on an shallow water platform
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Some images courtesy of BP
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Application Examples Off-shore structures Static Structural Analysis
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Modal Analysis
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Harmonic Analysis
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Blast Analysis
Simulated stress on a section of LPG tanker © 2010 ANSYS, Inc. All rights reserved.
Façade Detonation Response 15
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Umbilical, Risers & Flexible Piping
Equivalent stress response of the multilayer umbilical to a 36 degrees bend © 2010 ANSYS, Inc. All rights reserved.
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Application Examples Thermo-Mechanical Analysis of Umbilicals
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Tank Sloshing Colored contours of gas, oil and water in a separation tank
Without baffles
With baffles
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Baffle stress
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Renewable Energy : Turbines Vertical Axis Marine Turbine
Axial turbine
Blade stress analysis
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Propulsion, Propeller Wakes & Cavitation
Courtesy SVA-Potsdam (Potsdam Model Basin)
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Valves, Chocks, Regulators and Pumps
Wellhead Thermal data
Subsea regulator
Surface temperature on a valve surface © 2010 ANSYS, Inc. All rights reserved.
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Flow streamline for a petroleum control valve Some images courtesy of Hydril
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Pressure Vessels Stress, deformation and fracture
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Global Design Solutions - Floaters • ANSYS AQWA is primarily for global mooring performance, but does much more – Connect /offloading /disconnect scenarios – Float-over installations – Launching installations – Lifting operations – Transportation – Failure conditions – Air gap – User definable functionality © 2010 ANSYS, Inc. All rights reserved.
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Hydrodynamic Modelling
Ship & landing craft
Floatover © 2010 ANSYS, Inc. All rights reserved.
Lifting operation – AMOG
Stinger 24
Jacket launch
Truss spar – Technip ANSYS, Inc. Proprietary
Hydrodynamic Modelling
Shielding
Cargo lowered onto vessel © 2010 ANSYS, Inc. All rights reserved.
Mooring systems
Offloading operation – SBM 25
Self-installing platform – Arup Energy
FPSO & TLP Concept ANSYS, Inc. Proprietary
AQWA-FLUENT Coupling String draw down rate – 1 m/s 15m string attached to top center of the cylinder
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Cylinder mass – 5000kg
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Fully Coupled FLUENT-AQWA • Automated coupling • FLUENT and AQWA exchange information at each time step • Multiphase VOF model with Open Channel Boundary Condition in FLUENT to include waves effects • Accurate and effective for these subsea applications
Transient FLUENT simulation with Rigid Body motion
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Drag forces/moments
Linear and angular velocities
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AQWA simulation for Global Analysis
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Animation
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Code Check
• ANSYS Heritage in Offshore Structural Analysis – ANSYS ASAS – system level analysis – ANSYS Mechanical – component level analysis • Current ANSYS Offshore Structural Analysis – ANSYS Workbench – System & Component • • • •
Design Modeler ANSYS Structural Splinter/Fatjack/Beamst Links for coupled simulations
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ANSYS Mechanical Applications
• Offshore Structures • Pipelines and Risers • Tubulars, connectors • BOPs • Pressure vessels • Seals • Hulls • Etc….
Courtesy of ACA Engineering Consultants
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Courtesy of Delta Marine Engineering Company
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Design Assessment - Introduction
• What is Design Assessment? – Enables the customer to define additional data that is associated with their model and then perform custom post processing. • Custom definition of input data, result definitions & solve + post scripts
– Without any customisation, it enables the combination of existing solutions • Static Structural • Flexible Dynamics (at a specific time)
– Predefined scripts for BEAMST and FATJACK.
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ANSYS Structural Mechanics
• ANSYS Structural analysis
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Offshore System level analysis Requirement Geometry
Oil & Gas fixed Jacket
Wind Turbine fixed Jacket
Oil & Gas Floating
DM/SCDM
DM/SCDM
DM/SCDM
Wave + Current (tubular)
ANSYS/Structural
ANSYS/Structural
ANSYS/Structural
Wave + Current (shell/solid)
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Via AQWA
Splinter
Splinter
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ANSYS/Structural via shared DLL
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FATJACK
FATJACK
FATJACK
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OSAP/nCode
BEAMST
BEAMST
BEAMST
ULS (shell/solid)
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OSAP
FSI
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Pile analysis Aeroelastic coupling Fatigue (tubular) Fatigue (shell/solid) ULS (tubular/beam)
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Tubular Coupled Wave-Structures • Coupled hydro-elastic analysis for tubular framed structures – – – – –
Fully coupled hydrodynamic loading with non-linear analysis capability Automatic computation of hydrodynamic damping Regular and irregular waves Ability to take RAO results as time history loading Tube-in-tube contact
• Wave loading for application of Morison forces (coupled for non-linear analyses) • Calculation of added mass due to marine growth • Hydrodynamic mass calculations • Buoyancy calculations, including free flooding
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ANSYS - Code Checks (FATJACK/BEAMST) • Joint Code & Member Code checks including: – – – –
AISC 10th edition working stress and 2nd edition LRFD API RP2a-WSD 21st edition working stress RP2A-LRFD 1st edition ISO 19902
• Easy-to-use code check facilities including: – – – –
Code checks on time histories Code checks on combined load cases Visualization of code checks Ability to use them in combination with ANSYS calculations
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ANSYS - Fatigue Assessments • FATJACK module offers both deterministic and spectral fatigue capabilities – for tubular frame structures subjected to waves and current or wind including wind gusts – can be used in frequency and time domain – sea states: JONSWAP, Pierson-Moskovitz, Ochi-Hubble, Scot-Weigel and Shell New Wave, or user-defined wave spectra
• FATJACK includes explicit SCF definitions – – – –
SCFJ – if crown & saddle SCF is known e.g. from empirical formulae SCFA – if SCF is known at specific locations e.g. from FE SCFB – if SCF is constant across a section SCFP – if SCF values vary with location
• Automatic (empirically derived) SCF definitions based on – Efthymiou, Wordsworth, Kuang or DS449 © 2010 ANSYS, Inc. All rights reserved.
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ANSYS - Fatigue Assessments: Rainflow counting • Reduces spectrum of varying stress into simple stress reversals • Allows the application of Miner’s rule to assess fatigue life of structure subject to complex loading • Based on ASTM E1049-85 (2005) Standard Practices for Cycle Counting in Fatigue Analysis • It is possible to use results from up to 1000 different transient dynamic analyses and loading (i.e., multi-directional wave spectra) • Uses Rainflow counting method to produce stress range histogram • Results can be combined using a probabilistic approach, output includes: • fatigue life (based on Miner´s rule) • usage factors • damage per wave (history) • stress histograms
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ULS Check in Design Assessment
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System to component analysis
• Detailed joint analysis is possible:
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Summary • ANSYS continues to offer and invest in significant capabilities for offshore applications – Significant progress in implementing key features of ASAS in ANSYS Structural Mechanics products – New Design Assessment tool enabling advanced customized post-processing, including application of ANSYS developed code checking tools and user custom capabilities (not limited to Offshore) – Separate code checking products
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Thank You
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