Advantages and Disadvantages of Tender Assist Drilling, Jack-Up, and Semi-Submersible

Asked by ChemKB 6 years, 6 months ago | 1 Answers

Advantages and Disadvantages of Tender Assist Drilling (TAD), Jack-Up, and Semi-Submersible Drilling Units (SSDU)

1 Answer

sabdullayev 6 years, 6 months ago




Tender Assist Drilling (TAD)

  • Nonproprietary design
  • Simple hull form
  • Low cost hull fabrication
  • Could be fabricated in many yards
  • Large number of suppliers resulting in a competitive cost
  • Large decks where the Drilling Equipment Set is stored and transported
  • Large rig-up crane
  • Provide accommodations and construction facilities
  •  Weight sensitive
  • Susceptible to the adverse weather conditions
  • Limitation of availability of suitable deepwater installation vessels
  • Not suitable for deepwater


  • Mobile , easier to move than other units
  • Stable when installed
  • Low initial cost
  • Leasable with lower daily rate
  • No mooring required
  • Wells and risers are of conventional type.
  • Sensitive for the weather windows for placement (jacking up or down)
  • Seafloor scour
  • Limited to areas where soil permits satisfactory support of the legs
  • No storage capability
  • Blowout can cause collapse of platform due to wall fluidization
  • Rack Phase Differential

Semi–Submersible Drilling Units (SSDU)

  • Achieve better motion response and be easily positioned over a well template for drilling.
  • Allow large number of flexible risers
  • Large deck area
  • High initial and operating costs
  • Pipeline infrastructure or other means is required to export processed oil
  • Longer time to construct than jack-up
  • Limited deck load (low reserve buoyancy)
  • Structural fatigue
  • Expensive to move long distances
  • Limited dry-docking facilities available
  • Difficult to handle mooring systems and land BOP stack and riser in rough seas