Hydrocarbon Pipelines Introduction

Transportation of liquids by pipelines has been used for thousands of years. The first major exploitation and commercialization using pipelines started 150 years ago, and the building of long distance, large diameter pipelines was pioneered in the 1940’s (Hopkins, 2007). Today’s pipeline industry has originated from the oil business that brought considerable amount of profit to the energy producers and pipeline operators. In addition to be one of the most environment-friendly and the safest means for oil and natural gas transportation, pipelines have integrated in the components of national security.

Pipelines are lifelines of the global oil/gas industry, providing most convenient, eco-friendly, efficient and economical mode of transportation for oil and natural gas from upstream production to downstream refineries, power station, industries, domestic consumers and markets, crossing nations, oceans and continents. Pipelines are underground highways which may involve higher cost initially but in the longer run pipelines provide the most economic, safe and reliable means to transport products from one place to another place compared to rail, road and marine transportations.

Pipelines can be broadly bifurcated into two types based on location of installation i.e.:

  • Onshore Pipelines
    • It covers all inland cross country pipelines which are not in offshore areas.
    • It includes the main pipelines, spur lines and feeder lines, crossings/other features en route, associated despatch terminals, sectionalizing valve station, compressor stations, pump stations, intermediate terminals and receiving terminal facilities. The upstream and downstream handling storage and process facilities are excluded from the scope of onshore pipeline systems.

  • Offshore (Submarine) Pipeline
    • It covers all pipelines in offshore areas beyond the line of ordinary high water, along that portion of the coast that is in direct contact with the open seas and beyond the line marking the seaward limit of inland coastal waters.
    • It includes trunk lines, inter-field/ inter platform lines, lines from offshore terminal to Land Fall Point, crossings/ other features en-route, associated risers, subsea PLEMs, subsea isolation valves (SSIV)/ laterals and termination at land fall point as applicable. The upstream and downstream facilities at terminal ends are excluded from the scope of offshore pipelines.


This article introduces the key topics contained in the lifecycle of pipeline, such as pipeline design, procurement, installation & testing and a fundamental basic understanding of pipelines.

Any pipeline system involves following different stages:

  • Operation and Maintenance

(This article includes the brief on the first two stages only i.e. Engineering & Design and Installation, testing & commissioning of the pipelines.)
Stages of Pipeline

The design & engineering stage of the pipeline can be fragmented broadly into four major phases i.e.:

Design and engineering
Fig. Phases of Engineering and Design


    1. Establishment of preliminary requirements
    2. Identification of inlet location (Despatch Station) and outlet location (Receiving Station)
    3. Evaluation of alternatives
    4. Finalization of the concept


    1. Desktop study and preliminary selection of pipeline route
    2. Development of schematic based on Pipeline facilities, Intermediate Station
    3. Route Engineering and Route Reconnaissance by walking along the pipeline route
    4. Study of alternate routes
    5. Development of Equipment Layout
    6. Preliminary Wall thickness for pipeline
    7. Stress Analysis
    8. Hydraulic Studies & Optimization
    9. Establishment of tentative Project Cost
    10. Project Implementation Scheme
    11. Environmental Impact Assessment & Risk Analysis, if required
    12. Complete MTO of Pipeline System including stations


    1. Route Finalization - Surveys & Investigations
    2. Process Design & Pipeline Sizing
    3. Optimization Studies
    4. Preparation of Basic Engineering Design Basis
    5. Preliminary Selection of Pipes Parameters, such as Wall Thickness, Material & Grade, corrosion protection and type of coating requirement etc.
    6. Preparation of Route Maps, Layouts, Location Plan, Indicative Scope Drawings etc.
    7. Development of Implementation Schedule


    1. Preparation of Engineering Design Basis
    2. Route Engineering
    3. Engineering Analyses and Report
    4. For Onshore Pipelines
      Wall Thickness Analysis
      – Elastic Bend Radius Analysis
      – Stability Analysis for Water Bodies/ Marshy Areas
      – Horizontal directional drilling design
      Railroad/ Highway Crossing Analysis
      – Casing Pipe Analysis for Crossings
      – Seismic Design
      For Offshore (Submarine) Pipelines
      – Wall Thickness Analysis
      – On-bottom Stability
      – Free Span Analysis
      – Global Buckling Analysis – Lateral and Upheaval
      – Pipeline Expansion Analysis
      – Pipeline Crossing Analysis
    5. Preparation of Job Specifications & Job Standards
    6. Engineering for Procurement for long lead items such as:
    7. Line pipes & coatings
      – Scraper traps
      – Valves
      – Insulating joints
      – Long radius bends
      – Flow tees etc.
      – Assorted Pipes
      – Flanges and Fittings
    8. Preparation of Installation Tender
    9. Preparation of Drawings for Construction such as:
    10. For Onshore Pipelines
      – Alignment Sheets
      – Equipment Layouts
      – Crossing Drawings (such as rivers, highways, railroads, existing pipelines etc.)
      – GADs (general arrangement drawings) for Terminals etc.
      – Station Approach Drawings
      For Offshore (Submarine) Pipelines
      – Alignment Sheets
      – Overall Field Layout
      – Riser Location Drawings
      – Riser General Arrangement Drawings
      – Clamps Drawings
      – Pipeline Crossing Drawings
      – PLEM/ Subsea lateral/ Tie-in Spool detail drawings
      – Platform Approach Drawings
    11. Review of Installation Engineering and Procedures

Following activities are required to be carried out for construction of onshore pipelines:

Topographical survey & soil investigation
  • Pegging
  • Bench Marking
  • Pipeline Centerline marking
  • Profile
  • Crossing identification such as water bodies, railway lines, roads etc.
RoU grading
RoU Clearing and Grading
  • Staking
  • Monument Fencing
  • Identification of position of detours
  • Grading of access roads by dozer
  • Trenching by excavator
  • Separation of arable soil in fertile land
  • Trenching by blasting / rock breaker in rocky area
  • Protection of underground facilities
  • Pipe Handling and Transportation on trailors at site
  • Pipe placement on sand bags/ wooden blocks
Cold field bending
Cold Field Bending
  • Classification of location for bend installation
  • Bend Radius (R), equals to
  • – 40D (For pipe dia. 18” & above)
    – 30D ( For pipe dia. less than 18”)
  • Allow Pigs to pass through un-impeded
Field Welding
Field Welding
  • Weld procedure qualification
  • Welder qualification
  • Fit-up & pre-heating
  • Root pass
  • Hot pass
  • Filling passes
  • Capping
Non Destructive Testing
  • Visual inspection
  • 100 % NDT by following
  • – X-Ray
    – Automatic Ultrasonic Testing (AUT)
Field Joint Coating
Field Joint Coating
  • Procedure qualification
  • Sand Blasting
  • Pre-heating
  • Application of primer
  • Application of heat shrink sleeves
  • Post-heating
  • Trench inspection
  • Pre-padding
  • Holiday testing
  • Lowering
  • Cover check
  • OFC installation
  • Post-padding
  • Installation of warning mat
  • Backfilling
  • Crowning
Hydrostatic Testing
  • Air cleaning
  • Gauging and Pigging
  • Water-filling
  • Thermal stabilization
  • Pressure holding
  • Acceptance
Pre-commissioning & Commissioning
  • De-watering
  • Swabbing
  • Drying
  • Nitrogen/ Inert gas purging
  • Fluid charging

Following activities are required to be carried out for construction of offshore pipelines:

Pre-construction Survey
  • Verification of pre-engineering survey data
  • Firming-up of seabed preparation and intervention methodologies
  • Identification of as laid position of any stub-ends and their extremities
  • Equipemnts: Sub-bottom profiler, echo sounder, side scan SONAR, magnetometer
Pipe Handling and Transportation
Pipe Handling and Transportation
  • Inspection of pipes and its coatings
  • Repair of pipe/ coatings, if required
  • Transportation of pipes to port area
  • Loading and transportation of pipes on cargo barges
  • Unloading of pipes on pipelay barge
Anchor Handling & Barge Positioning
Anchor Handling & Barge Positioning
  • Barge positioning (considering minimum draft requirement)
  • Firming up of barge positions/ anchor locations such that no existing pipelines/ cables etc. are damaged due to anchor dropping and anchor dragging
  • Anchor handling tugs
Trenching/ Dredging
Trenching/ Dredging
  • Mechanical amphibian dredger for shore approach
  • Trenching sledge/ jetting dredger for post trenching in deeper waters
  • Rock blasting in rocky seabed
  • Weld procedure qualification
  • Welder qualification
  • Pipe end preparation, fit-up & pre-heating
  • Root pass/ Hot pass
  • Filling passes
  • Capping
Non-destructive testing
  • Visual inspection
  • 100 % NDT by Automatic Ultrasonic Testing
Field joint coating
Field joint coating
  • Procedure qualification, sand blasting, pre-heating, application of Primer, application of Heat Shrink Sleeves and post-heating
  • Holiday testing of coated portion at pipe ends
  • Filling up of HDPU foam to uniform the pipe diameter at pipe ends
Pipeline laying
Conventional pipelay methods are:
  • S-Lay (for shallow waters) – rigid pipes
  • J-Lay (for ultra deep waters) - rigid pipes
  • Reel-Lay (for rigid/flexible pipelines)
Shore Pull
Shore Pull
  • Length of shore pull based on minimum barge draft requirements
  • Firming up the requirement of number of buoyancy unit and pulling force
  • Preparation of winch foundation and Anchor block
  • Preparation of pipe string on barge
Installation of Tie-in spool
Installation of Tie-in spool
  • Metrology of as laid position of pipeline lay down head and corresponding riser end/ PLEM end
  • Fabrication of tie-in spool on barge
  • Installation of tie-in spool by derricks
Pipeline Crossing
Pipeline Crossing
  • Analysis for acceptable pipeline configuration above existing pipeline
  • Placement of pipe supports at designated locations
  • Laying of new pipeline on the pipe supports
Back-filling of trench
Back-filling of trench
  • Engineered backfilling or backfilling the excavated material in shore approach area
  • Backfilling is performed using Split Hopper Barge
Post-construction survey
Post-construction survey
  • As-laid survey
  • Free span survey (extent of unsupported span)
  • Checking of depth of cover
  • Identification of pipeline alignment; Diving survey