Front-End Subsea Pipeline Conceptual Engineering Study

Jee determined the size and routes of subsea three pipelines required to develop three gas fields outside the UK, using the local national design code.

These are two 323.8 mm (12in) by 33 km and 21 km long lines containing untreated well fluids, and a 404.6 mm (16in) by 17 km long export gas line.

This preliminary front-end engineering design (FEED) study used preliminary reservoir and platform process information to determine the diameter, wall thicknesses and concrete weight coating for the three lines linking one manned two and normally-unmanned platforms to deliver the export gas to a tie-in on an existing line to shore. 

The investigation examined the stability of the seabed sediments in the area, the need for trenching and likelihood of self burial.

At the client’s request, the bulk of the conceptual study was completed within the first three weeks, with further clarification of the design in the following few weeks.

The front-end engineering conceptual design study also included

• development of the Basis of Design (BoD) document including determination of seabed sediments, metocean data and abstracted flow regime (temperature and pressures)
  
• optimisation of diameters for flows over life of the fields
  
• determination of the temperature gradient envelopes of the lines and expansion potential in the buried and unburied state
  
• optimisation of the diameter of the lines throughout the life of the development
  
• slugging flow in the flowlines and risers, determined using PipeSim software
  
• suitability of carbon steel and determination of the required corrosion allowance
  
• report the legal requirement for buried lines
  
• determination of the magnitude of trawling interaction loads that could be applied to surface lines
  
• recommendation of concrete thickness for installation using S-lay and the revised steel thickness for reel-lay barge.  This ensures the pipelines will remain stable during installation and operation
  
• determine propensity for lateral buckling and minimum burial cover to prevent upheaval buckling

All case studies

• Trenching study for flexible pipeline subject to trawl gear interaction
• Wye piece verification
• Front-End Subsea Pipeline Conceptual Engineering Study
• Deep water pipelay capability spreadsheet
• Upheaval Buckling Analysis of a Flexible Pipeline
• Stability analysis of subsea gas pipelines using PRCI Level 2 stability analysis software
• Preparation of MathCAD sheets for pipeline stability analysis
• Goldeneye Third-Party Verification
• Overtrawling of large diameter pipeline trials JIP
• Recommended procedures and methods for design of subsea flanges
• Steady state FEA thermal analysis of a flexible pipeline in ANSYS
• Review of the Upheaval Buckling Analysis of a Pipe in Pipe System
• Investigation of data flow to foreign fishermen
• Pig impact at riser bends
• Analysis and tests of response of subsea equipment to acoustic vibrations
• Optimisation of fins on pipeline riser fairings using CFD
• Rock dump stability study
• Offshore support on pipeline inspection survey
• Pipeline design and installation procedure verification
• Study of fishing in the Gulf of Gabes
• Evaluation of the thermal properties of pipe sections and pipeline components
• Pipeline installation pull analysis
• Overtrawling capability of subsea protective structures
• Bundle towhead over-trawling – Scale model tests
• Thermal finite element analysis of a trenched umbilical
• Mattress placement study
• Pipeline stability assessment using PRCI Level 2 and Level 3 analysis tools
• Engineering critical assessment to BS 7910:2005
• Colombo harbour development
• Fishing interaction study
• Re-assessment of overtrawlability
• North Sea field development study
• Finite element analysis of mechanical connectors
• Flange leak investigation
• Spares and repairs
• Development of pipeline design sheets in MathCad
• Overtrawling of protection structures and umbilicals
• Riser ESDV leakage rate study
• Fatigue analysis of a riser in Orcaflex
• Support to BP Subsea and Pipelines Team
• Pipeline 4001 - Girth weld defect assessment
• Historical condition and lifetime prediction for Amethyst, Wollaston and Whittle
• Trawling risk assessment
• Assessment of pig run times
• Comparitive assessment of decommissioning options
• Assessment of current/ historical status of riser and bypass pipework
• Assessment of thermowell vibration fatigue due to vortex-induced vibration (VIV)
• Validation of water injection pipelines
• Defect assessment
• Unbilical stability assessment
• Technical authority and decommissioning support
• Major accident prevention document (MAPD) review and update
• General pipeline support
• Assessment of Pipeline Spares surrently held, future Spares and preservation requirements
• Creation of Technical Assessment summary sheets for North Sea pipelines
• Span and buckling assessment
• Overtrawlability trials of subsea structure
• Structural overtrawling trials
• Bend restrictor analysis
• Buoyancy module analysis
• FEA of an internally-lined pipe
• FEA of an internally-lined pipe Stage 2
• Fishing interaction
• Prediction of riser bend damage
• Pipeline decommissioning
• Fatigue analysis
• SNS decommission studies
• Riser ESDV leakage rate study
• Non-trenching study
• Span assessment and solution development
• Pipeline contingency plan
• Umbilical stability assessment
• Integrity under new flow conditions