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© 2010 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary © 2010 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary

Engineering Simulation

Solutions for Offshore

and Subsea

Harish Radhakrishnan

ANSYS Inc.

© 2010 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary

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)


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


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

• 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

• 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


Example

Applications


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


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


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


Drill Bit Analysis


Cementing/Mudflow in Casings

Experimental cutaway of cementing in an eccentric gap used for validation of CAE simulation.

Velocity profile in an eccentric gap (left), contours of turbulent viscosity (right)

Some images courtesy of Halliburton


Gas Dispersion

Some images courtesy of BMT

Some images courtesy of Kerr-McGee North Sea


Flare Radiation

Flare flow pathlines,

coloured by

temperature

Flame shape and shroud surface

temperature for two different fuel

and wind ratios

Fuel to

Wind ratio

1:2

Fuel to

Wind ratio

2:1


Wave\Wind Loading

Transient pressure distribution caused by ocean waves on an shallow water platform

Some images courtesy of BP


Application Examples

Off-shore structures

Modal Analysis Harmonic Analysis Static Structural Analysis


Blast Analysis

Simulated

stress on a

section of

LPG tanker

Façade

Detonation

Response


Umbilical, Risers & Flexible

Piping

Equivalent stress response of the multi-

layer umbilical to a 36 degrees bend


Application Examples

Thermo-Mechanical Analysis of

Umbilicals


Tank Sloshing

Without baffles

Colored contours of

gas, oil and water

in a separation tank

Baffle stress With baffles


Renewable Energy : Turbines

Vertical Axis

Marine Turbine

Axial turbine

Blade

stress

analysis


Propulsion, Propeller Wakes & Cavitation

Courtesy SVA-Potsdam (Potsdam

Model Basin)


Valves, Chocks, Regulators and Pumps

Flow streamline

for a petroleum

control valve

Subsea regulator

Surface temperature

on a valve surface

Some images courtesy of Hydril

Wellhead

Thermal

data


Pressure Vessels

Stress, deformation

and fracture


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


Ship & landing craft Jacket launch Lifting operation – AMOG

Truss spar – Technip Floatover Stinger

Hydrodynamic Modelling


Shielding Mooring systems

FPSO & TLP Concept

Self-installing platform

– Arup Energy

Cargo lowered

onto vessel

Offloading operation – SBM

Hydrodynamic Modelling


AQWA-FLUENT Coupling

15m string attached to top center of the cylinder

String draw down rate – 1 m/s

Cylinder mass – 5000kg


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

AQWA simulation for Global Analysis

Drag forces/moments

Linear and angular velocities


Animation


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


ANSYS Mechanical Applications

• Offshore Structures • Pipelines and Risers • Tubulars, connectors • BOPs • Pressure vessels • Seals • Hulls • Etc….

Courtesy of Delta Marine Engineering Company Courtesy of ACA Engineering Consultants


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.


ANSYS Structural Mechanics

• ANSYS Structural analysis


Offshore System level analysis

Requirement Oil & Gas fixed Jacket

Wind Turbine fixed Jacket

Oil & Gas Floating

Geometry DM/SCDM DM/SCDM DM/SCDM

Wave + Current (tubular)

ANSYS/Structural ANSYS/Structural

ANSYS/Structural

Wave + Current (shell/solid)

- - Via AQWA

Pile analysis Splinter Splinter -

Aeroelastic coupling

- ANSYS/Structural via shared DLL

-

Fatigue (tubular) FATJACK FATJACK FATJACK

Fatigue (shell/solid)

- - OSAP/nCode

ULS (tubular/beam)

BEAMST BEAMST BEAMST

ULS (shell/solid) - - OSAP

FSI - - -


• 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

Tubular Coupled Wave-Structures

• 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


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


• 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

ANSYS

- Fatigue Assessments


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


ULS Check in Design Assessment


System to component analysis

• Detailed joint analysis is possible:


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


Thank You

engineering simulation solutions for offshore and · pdf fileengineering simulation solutions...

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