riser and conductor engineering
Exploring VarietyWhy analyze Conductors & Risers?
- Weather limits
Determine an operating condition or envelope
- Guide reactions
- High pressure risers
- Connectors & couplings
Design or select components
- Should vortex suppression strakes be fitted?
- How many centralisers are necessary?
- Should we plan for disconnection?
Determine a need
- Safety critical - Mission critical
Reduce risk or uncertainty
- Limiting jackup offset
- Running a template
- Reduce the conductor size or grade
Where optimisation might save time or money offshore
- High currents off Trinidad
- 30 metre waves in the North Sea
- At the limit of jackup water depth
In difficult environments
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
- Slot recovery
- 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)
Methods of producing from a well
- Drilling unit on platform
- Jackup (MODU)
- Floating vessel: Semi-sub, Drill ship
Tools to drill, workover or abandon a well
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
- Extreme event: storm loads
- Non-linear: radial gaps, soil springs
- Strength & stability Vortex induced vibration (VIV) review
- Likelihood of VIV
- Need strakes?
- Fatigue damage
Static & dynamic structural analysis
- Driving Fatigue damage > Life
- Wellhead growth
- Casing loads & pre-tensions
- Hanger lift-off
- 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
Special types of analysis
- 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
- Subsea protection structures
- Lifting frames & other temporary installation structures
Required Input Data: Standard
- Water Depth
- Deck and Guide Elevations
- Surface Equipment Weights
- Interface Between Rig and Platform
- Wave Height
- Wave Period
- Current Profile
- Corrosion Limits
- Marine Growth
- Pipe Diameters
- Casing Tensions
- Setting Depths
Casing and Tubing Data
- Capacities (Axial + Bending)