No Offshore Accomodation

Crew Transfer Vessels

CTVCurrently used vessels, used as crew transfer vessels, are catamarans with 12-24 m length overall (lOA) that can allocate 12 passengers (approximately). Their wave height limit is 1.5 m, i.e. they cannot operate in the offshore environment when the waves are higher than 1.5 m. Also they can operate as far as 60 nominal miles from a base. Their economical speed isset to be approximately 20-25 knots.  Possibly future designs will improve CTV technology and allow them to be used in higher waves or to transport more than 12 people. Also, future design (e.g. Small Waterplane-Area Twin Hull (SWATH) [6])would hopefully improve stability of the vessel and so offer more comfortable transfer for technicians. Those potential changes could improve O&M activities, and so allow CTVs to be applied in more complex tasks then they are used nowadays [6].

For this solution, jack-ups still have to be chartered or bought in a spot market to repair larger replacements. Also, if travelling times are too long, then an offshore accommodation will be required.

 

Advantages

  • Fast

  • Possibility of transporting technicians and small spare parts

 

Disadvantages

  • More expensive as the distance from the shore increases

  • The working time decreases when using CTV

  • Affected by wave height (in some cases helicopter would be used instead of CTV)

  • Major repairs could not be performed

  • Due to legislation and health & safety measures smaller CTVs can carry no more than 12 passengers [7] and they cannot go further than 60 nautical miles from a base [6].

  • Vessel motion has bigger impact on technicians (higher possibility of getting sea sick)

  • Risky when weather conditions are changeable

  • Could result in wasting time and money as the distance from the shore increases