Which platform type is fixed to the seabed and uses jackets and piles?

• A. Concrete gravity platform
• B. Semisubmersible
• C. Steel-Jacket platform
• D. Floating drillship

Answer: (C)

Fixed offshore platforms that use a lattice frame anchored to the seabed rely on steel jackets and piles. A steel-jacket platform consists of a tall steel lattice jacket driven or drilled into the seabed with piles, and the topside facilities sit on the jacket, providing a rigid, fixed base. This contrasts with floating systems that stay buoyant and are kept in place by mooring or dynamic positioning.

The other options don’t fit because a concrete gravity platform stays in place due to its weight, not jackets and piles; a semisubmersible is designed to float (usually moored) rather than be fixed to the seabed; and a floating drillship is a mobile vessel that remains afloat rather than being anchored by jackets.