riser and conductor engineering

Exploring Variety

Why analyze Conductors & Risers?

    Determine an operating condition or envelope

  • Tension
  • Weather limits

    Design or select components

  • Guide reactions
  • High pressure risers
  • Connectors & couplings

    Determine a need

  • Should vortex suppression strakes be fitted?
  • How many centralisers are necessary?
  • Should we plan for disconnection?

    Reduce risk or uncertainty

  • Safety critical - Mission critical

    Where optimisation might save time or money offshore

  • Limiting jackup offset
  • Running a template
  • Reduce the conductor size or grade

    In difficult environments

  • High currents off Trinidad
  • 30 metre waves in the North Sea
  • At the limit of jackup water depth

Novel configurations

Good engineering practice

Code compliance – “fit for purpose”

Certifying authority or government regulation


We don't just analyze the pipe - we look at the whole SYSTEM


Categorize! Where are ‘Risers’ used?

    Types of Well

  • Exploration
  • Tieback
  • Platform-Drilled
  • Subsea

    Activity

  • Drilling
  • Production
  • Side-track
  • Slot recovery
  • Work-over
  • Abandonment

    Methods of producing from a well

  • Conventional fixed structure
  • Minimum weight structure (e.g. monotower, RACP)
  • Compliant tower
  • Jackup (MOPU)
  • Floating vessel (FPSO or Semi-sub)
  • Subsea (tied back by flowline to nearby facility)

    Tools to drill, workover or abandon a well

  • Drilling unit on platform
  • Jackup (MODU)
  • Floating vessel: Semi-sub, Drill ship

Combinations = endless possibilities


In all of the cases above, conductors or risers will be needed – and may need to be analysed.


What ‘Risers’ are we interested in?

What Wells Can Be Analysed? All wells, new or old can be analysed It all depends on what you want to find out


"Seabed to surface"


    What exactly is a 'Conductor'
  • ‘Conductor’ is short for ‘Well Conductor’
  • It’s a tube…
  • This connects an offshore well…
  • With the means to work on it or use it. E.g. drilling, production, workover.
  • A conductor is a STRUCTURAL element which transfers loads into the SEABED.

    What exactly is a 'Riser'?
  • A riser is a STRUCTURAL element which connects a well to surface, and may also have to withstand pressure
  • Risers are usually, but not always, ‘single string’
  • Some configurations have both a conductor and a riser present… (e.g. a subsea well)

Types of analysis – risers & conductors

    Static & dynamic structural analysis

  • Extreme event: storm loads
  • Non-linear: radial gaps, soil springs
  • Strength & stability
  • Vortex induced vibration (VIV) review
  • Likelihood of VIV
  • Need strakes?
  • Fatigue damage

    Fatigue assessment

  • Wave
  • VIV
  • Driving Fatigue damage > Life

    Thermal analysis

  • Wellhead growth
  • Casing loads & pre-tensions
  • Hanger lift-off

    Special types of analysis

  • Trawl-board snagging
  • Ship impact
  • Docking pile assessment
  • Under-balanced drilling
  • Tree motion
  • Platform installation tolerance
  • ‘Splitter’ wells (multiple completions)
  • High pressure surface risers: Drilling BOPs, Coiled tubing Injector, Hydraulic workover units
  • Cement level sensitivity
  • Corrosion sensitivity
  • Flowline stress
  • Casing helical buckling

    Types of analysis – other tubular goods
  • Platform production risers, caissons, J-tubes
  • Pipelines, flowlines, expansion spools
  • Renewable energy - e.g. related to foundation piling

    Types of analysis – Structures
  • RACPs i.e. Rig Assembled Conductor Platforms or Fixed Wellhead Platforms
  • Templates
  • Subsea protection structures
  • Lifting frames & other temporary installation structures

Required Input Data: Standard

    Rig/platform Data

  • Water Depth
  • Deck and Guide Elevations
  • Surface Equipment Weights
  • Interface Between Rig and Platform

    Environmental Data

  • Wave Height
  • Wave Period
  • Current Profile
  • Corrosion Limits
  • Marine Growth

    Casing and Tubing Data

  • Pipe Diameters
  • Weight
  • Grade
  • Casing Tensions
  • Setting Depths

    Connector Data

  • Type
  • Capacities (Axial + Bending)

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