Drillship vs Semi

[coldduck]

Ive been browsing the specs for all these new build rigs lately and it has me wondering;why so many drillships compared to dp semis'? I am not a rig guy by any means but it appears to me from looking at the specs online, that the semis are very comparable to drillships in drilling depth, operating weather, and several other parameters. I might be wrong but to me they seem like they might be an even more stable drilling platform. Can any of you guys that switched over to the drilling side, explain to me the disparity between the orders for drillships and semis' Thanks

[c.captain]

for starters

semisubmersible advantages:
-low heave/motions
-lower cost to build
-less total kW required for DP station keeping
-can be easily utilized as moored rig if operator chooses


drillship advantages
-higher total variable deck load
-stability better
-more space on deck
-ability to mob to new global regions quickly without tow/heavy lift
-better suited to dual activity derrick
-BOP can be carried closer to waterline
-more tank space available for all liquids

what am I missing capt Lee and orniphope?

[Capt. Lee]

I would say that overall station keeping is better and more forgiving to weather situations on a semi vs drillship.

Since most have 8 thrusters there is more redundancy on station keeping.

[coldduck]

Thanks! Those are exactly the kind of answers I was looking for, and from a few of the guys I thought could answer them.

[El Segundo]

Drillships have a lot more stairs.