Overview of SURF Systems and Analysis Overview of SURF Systems & Analysis Presenter: Tarun Rewari...

Overview of SURF Systems and Analysis

Overview of SURF Systems & Analysis

Presenter: Tarun Rewari

Director – Aryatech Marine &

Offshore

Software: OrcaFlex

What does SURF mean?S Subsea constructionU UmbilicalsR RisersF Flowlines

presentation introduction

Aryatech Marine & Offshore Services


Define a deepwater system



Define a ‘Deepwater System’

Deepwater marine system

Floater system

Whatever we call it (and plenty of definitions), these systems are not rigidly connected to seabed. They have a ‘floater’ with ‘lines’ between floater and seabed

‘deepwater’ marine systems



Define a ‘Deepwater System’

Though clearly important and linked, this presentation focuses on the design and analysis of SURF systems

Floater

Reservoir

SURF




Water Depth

Floater systems range in water depth: 10m <> 2000m




Design Life

There are a variety of time frames (though no rigid distinction):

• Permanent systems (life of field, ≈25 years)

• Temporary systems (temp operations, few months)

• Installation (construction / decommissioning, few hours, maybe a day)

Analyses and main components are similar.

Main differences: env. return periods, acceptance criteria




Main System Components



Main Components

• Floaters SURF top end boundary condition with various functions. (FPSOs, Semi-submersibles, TLPs, SPARs, offloading shuttles, drilling, installation /

decommissioning)

• Moorings multi-component wire, chain, polyester used to keep floater on-station. (spread, turret, SPMs, ‘jetty’, catenary, taut, hawsers)

• Risers dynamic pipe (or pipe assembly), to transfer production or injection fluids, control fluids or lift gas between seafloor and floater. (SCR, TTR, flexible, hybrids, export systems (incl. hoses), flexible jumpers)

main system components



Main Components

• Umbilicals Assembly of hydraulic hoses used to control subsea structures from a host. Loaded statically and dynamically. (power, control, chemical injection, hydraulic fluids, etc)

• Flowlines static flexible pipe on seafloor for transportation of production or injection fluids. (Generally infield, linking subsea structures, or to a production facility. 100’s m < length < several km)

• Jumper short pipe connecting flowlines and (flexible or rigid) subsea structures or close subsea

structures. Loaded statically &dynamically




Main Components

• Installation lower to seabed (‘payloads’, anchors, etc)

lay flow- & pipelines (J-, S- & reel-lay)

pre-lay risers & mooringsvessel hook-upfloatoverheavy liftpipelay vessels, barges

• Also recovery for repairs and re-installation, and decommissioning for permanent removal




Main Components

• Other parts: bend stiffenerstapered stress jointsmid-water arches (MWAs)

riser towers, riser tethersanchorscranes / winches / tensioner systems payloads (PLETs, PLEMs, BOPs, etc)

J-tubesstingers & rollersmoonpoolsbuoyancy modules & clump weightsdrag chains




Main Components – ‘flexibles’TLP Turret moored FPSO

SPM

Semi-submersible

transfer lines

jumpers

flowlines

risers

buoyant ‘steep’ wave

mid-water arch

riser tower

export lines




Main Components – ‘rigid lines’




Main Components - installation

•Colin Lewis to supply some nice OrcaFlex screenshots of some of the components on the previous slide.

FloatoverJacket launch

S-lay

Pull-in Lower to seabed

Recovery / re-installation

Load transfer




Main Analysis Steps



Main Analysis Steps

High level main systems design loop

In principle a strong feedback loop, though in practice, analysis does not often reflect this

Floater

Moorings

SURF

Installation

Both Concept Selection and main Engineering Design

main analysis steps



Main Analysis Steps

For floater, moorings, SURF and installation, some or all of the following required:

main analysis steps

Static load screening

VIVanalysis

Extremedynamics

Interference analysis

Fatigue

Concept design

Acceptabledesign

Installation



Concept / FEED

• Main considerations:– costs

– regulatory issues

– existing infrastructure

– floater availability

– environment

– reservoir characteristics

• Initial evaluation often done through proprietary scenario simulators to evaluate production from different options

main analysis steps



Acceptance Criteria

for ‘lines’



Acceptance Criteria

Once analysis completed, results are then assessed against various acceptance criteria:

• Internal loads (components, buckling, utilisation, end loads)

• Interference (clearances with other items)

• Fatigue (predicted vs. life of field)

Above to be checked for all systems (moorings, SURF and installation), though some detailed checks may not apply to all

acceptance criteria, rules & regs



• Philosophy varies from code to code• Focus on two different methods for structural design

– Working Stress Design (WSD)

– Limit State Design/Load and Resistance Factored Design (LRFD)

Design Philosophy




There are many different codes covering several applications:

• Dynamic Systems Codes

• Codes specific to Rigid Risers

• Codes specific to Flexibles (umbilicals, risers, hoses)

• Codes specific to Mooring (incl. anchors)

• Codes specific to Installation (including pipelay, heavy lift, etc)

Codes in Common Use




Floater Types



Hull Forms

Permanent:

But must also remember wide variety of ‘temporary’ floaters associated with field construction, repair and decommissioning – installation vessels, barges, offloading vessel, pipelay, crane lift, transportation

floater types



Existing GoM Floaters

floater types



Free floating hull – many variants

– catenary or taut moorings

– anchors

– vertical or catenary risers

Semi-submersible Hull

XY

Z700 ft

OrcaFlex 8.5b: messabout2.dat (modified 11:48 AM on 4/20/2002 by OrcaFlex 7.5a) (azimuth=230; elevation=0) Statics Complete

floater types

Pontoons

Columns

Bracings



• Ballasted hull keeps tendons in tension

• Tension minimises heave

• Inverted pendulum

• Springing / ringing & setdown

Tension Leg Platform (TLP)

floater types



• Vertical column floater

• First spars had solid hull

• 2nd generation truss hull

• 3rd generation cell hull

• Mooring similar to semi-sub

• VIM & 2nd order vertical motions

SPARs

VIV strakes

floater types



Shipshape Hull

Conventional spreadmoor

Single point mooring outside of hull

Single point mooringcontained in hull

floater types



• Deck Mating as fixed platform – but with moving hull

• Spar – Loadout and Tow / Upending

• Shipshape – towed

• Semisub/TLP – heavy lift vessel

Hull Installation

floater types



Mooring & Anchoring Systems



• Re-cap on main types– catenary or taut

– spread or single point (weathervaning)

– temporary or permanent

• Mooring line – seabed end termination is a fixed location

– vessel end termination moves with vessel

– weight controlled thru materials (chain, wire rope, synthetic rope)

– accessories (links, eyes, shackles, sockets, fairleads, winches, stoppers)

• Anchor types– drag embedment

– suction caisson

Mooring Systems

mooring & anchoring



Catenary vs. Taut Mooring

Catenary– heavy in deep water

– line horizontal at seabed

– anchor subject to horizontal forces

– restoring forces by line weight

Taut leg – line non-horizontal at seabed

– anchor sees non-horizontal forces

– restoring forces by line elasticity

– smaller footprint than catenary mooring

mooring & anchoring



Anchor Types

• Deadweight (gravity base)

• Piling (driven)

• Drag embedment anchors

• Suction anchors

• Vertically loaded anchors (VLA)

• Suction Embedded Plate Anchor (SEPLA)

75 ft

mooring & anchoring



Additional Mooring Components

• Buoys– may be in-line or attached to the line

– provide buoyancy to reduced load on platform

– add compliance to a mooring line

– generally kept below surface to avoid additional wave loading

• Sinker weights and Deadman– additional clump weights added to lines

– weight line down (invert catenary)

– sinker weights in water column

– dead man on seabed – similar to gravity base anchor

mooring & anchoring



Mooring Design Codes

• Most common– API RP2SK – Rules for Station Keeping (mooring line and anchors)

– API RP2SM – Synthetic mooring lines

– DNV-RP-E301 – Position Mooring

• Additional for anchors– DNV-RP-E303 – Design and Installation of Suction Anchors In Clay

– DNV-RP-E302 - Design and Installation of Plate Anchors in Clay

– DNV-RP-E301 - Design And Installation Of Fluke Anchors In Clay

• Codes apply different factors of safety for– distinguish between permanent vs. mobile mooring

– intact and damaged condition

– quasi-static vs. dynamic analysis

mooring & anchoring



Anchor Proof Test

• For the analysis– mooring line analysis gives loads at seabed fixed point

– demonstrate anchor can achieve a prescribed load

• For the installation– vessel pull on mooring line for period of time

– demonstrates that anchor can take intended loads

mooring & anchoring



Risers



Riser Systems

• Transportation of production hydrocarbons and other fluids between seabed and floater

– oil/gas – import or export, reinjection

– water – export, injection

• Drilling and work over operations (may also contain hydraulic lines or electrical lines)

• Can be bundle (several lines in one carrier pipe)

• Can be a pipe-in-pipe

• May be added to a facility after initial installation (eg, tieback from new wells)

riser systems



Common Configurations

JumperJumper

CVARCVAR

Catenary,Catenary,Free HangingFree Hanging

DrillingDrillingRiserRiser

MooringMooringlineslines

RisersRisersArraysArrays

FPSO,FPSO,Barge ...Barge ...

Catenary,Catenary,Lazy-waveLazy-wave

Flexible,Flexible,Steep-SSteep-S

TankerTanker

TLPTLP

LFSdeep

riser systems



Riser Systems – pros & cons

riser systems



Umbilicals



Umbilical Applications

• Transfer hydraulic and electrical power

• Data logging (electrical or fiber optic)

• Chemicals for well control (methanol)

• Transfer between floater and seabed

• Transfer between wells and manifolds

umbilicals


OrcaFlex - Latest Developments

OrcaFlex User Group, Aberdeen, 2003www.orcina.com Slide 47 of 4

Tarun Rewari

Director - Aryatech Marine & Offshore

www.aryatech.net

Overview of SURF Systems and Analysis Overview of SURF Systems & Analysis Presenter: Tarun Rewari...

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