In the unlikely event of a subsea well control incident, the Capping Stack is a temporary solution in order to stop an uncontrolled release of hydrocarbons to the environment while a relief well drilling operation with well kill is considered to be a permanent solution.

SWIS membership provides access to the four capping stack systems, which have been designed by the leading industry experts to provide the means to safely soft shut in the majority of anticipated worst-case flow rates.

Members are entitled to mobilise two of the four capping stacks in the event of an incident which ensures redundancy in the service for other members.

OSRL is the custodian of the equipment, storing and maintaining the capping stack systems in four international locations. 15 kpsi capping stacks are located in Brazil and Norway, and 10 kpsi capping stacks are located in Singapore and South Africa.

The units can be configured for a variety of subsea interface requirements, and can be transported by land, sea or air. Maximum depth of 12,500ft/ 3800 m and include chemical injection points for direct dispersant injection to mitigate the formation of hydrates. It is suitable for both exploration and production wells, and can safely contain, choke and cap up to 100,000 bpd flow in a controlled manner.

Logistics planning guidelines


Key facts

  • Four capping systems, including two 18 3⁄4" 15k stacks and two 7 1⁄16" 10k stacks (with ancillary equipment)
  • Transportable by sea and/or air
  • Available for a variety of international metocean conditions
  • Designed for subsea use up to 3800m water depth
  • Stored in four strategic regional locations around the world
  • Manufactured by Trendsetter Engineering

Key features

  • Flexible to handle a variety of scenarios
  • Retrievable chokes to help gain control of a flowing well
  • 15k connectors, adapter and spacer spools
  • Connects to BOP, flex joint, or top of wellhead
  • 4 x 51⁄8’’ outlets on the diverter spool
  • Diverter spool providing optimal flow path during installation and shut in 7 1⁄16” and 18 3⁄4” running tools
  • Acoustic real-time pressure and temperature data to surface
Design Pressure 10 kpsi / 15 kpsi
Design Life 20 years (storage),
6 months (flowing),
2 years (shut)
Water Depth Up to 3800m
Flow Rate
0 to 100 kbd of oil equivalents
Design Temp -2°C to 150°C (Operation),
-20°C to 40°C (Storage)
CO2 0 to 10%data
H2S 0 to 500 ppm
Injection Dispersant and Hydrate Inhibitor (150 L/min)
Outlets 4 outlets,
each with dual 51⁄8” Gate Valves
Sealing Device 10k Stack: 2 x 71⁄16”
Gate Valve (fail as is)/ 15k Stack: 2 x 183⁄4” Rams
Operation Third-Party ROV (manual and hydraulic)
Measurements Pressure and Temperature
Connectors H4 and HC 183⁄4” 15kpsi
Adapter spools H4 and HC 183⁄4” by 183⁄4”
15 kpsi API flange
Flow Control Retrievable Choke Valve on each outlet
Installation Method Drill Pipe and / or Wire Line
Transportability Air (Boeing 747-400 ERF), Land and Sea
Material NACE MR-0175 Zone 3


  • Air Freightable Capping Stack External version

  • Air Freightable Capping Stack Internal version

  • Capping Stack with Flowline Connector

  • Capping and Containment Concept (Long)

  • Capping and Containment Concept (Short)


  • Capping Stack 15k psi

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