The Relief Well Injection Spool (RWIS)

Add Energy and Trendsetter Engineering have combined expertise to provide market leading engineering and hardware support services to the industry’s most challenging problems in a nimble and responsive environment.

RWIS Photo

The Relief Well Injection Spool (RWIS) is a piece of specialist subsea equipment that enables operators to stop a blowout from a prolific reservoir safely and efficiently via a single relief well. This is achieved by increasing the pump rate of kill mud into the blowing well by removing the bottle-neck caused by restrictive choke and kill lines from the surface vessel to the seabed.

The RWIS has been designed and built to greatly increase the pumping capacity of a single relief well by enabling the ability to pump in excess of 200 barrels of kill mud per minute through a single relief well, four times as much kill fluid as typically achievable. A significant advance for the industry which utilizes multiple vessels as opposed to the conventional method of multiple relief wells.

The RWIS is installed on the relief well wellhead beneath the blowout preventer (BOP) to provide additional flow connections into the wellbore. Using high‐pressure flex lines, the inlets enable pumping units from separate floating vessels, in addition to the relief well rig, to deliver a high‐rate dynamic kill.

Click here to view the specifications sheet.

Watch here to see the RWIS in action

Benefits of using the RWIS:


Morten Haug Emilsen

Senior Vice President
Well Control & Blowout Support


Roger Pool

General Manager, North America
Well Control and Blowout Support



Add Energy was approached by a client, who, according to company safety guidelines, requested a blowout-contingency study for an offshore shallow gas well.

A blowout intervention for these types of wells are often faced with many challenges including a narrow depth window to build hydrostatic and frictional pressure during a dynamic kill combined with high pressure differential to balance the reservoir pressure. For a worst-case blowout scenario, using a relief well injection spool (RWIS) may ensure the ability to bring such wells under control with a single relief well.


The Add Energy well-control and flow-simulation specialist modeled the worst-case-blowout scenario using the planned wellbore schematic and predicted reservoir properties. A single relief well with an RWIS installed on its wellhead was used in the simulations to pump kill mud into the target wellbore. Several iterations were made using different kill muds and hardware configurations to achieve a successful kill.


A worst-case gas discharge of around

3 Billion SCF/Day

A dynamic kill using the RWIS to pump a heavy mud at a combined rate of

230 bpm

50 bpm down primary relief well and 180 bpm down secondary relief well connected to the RWIS
Hardware configuration was evaluated for hhp requirements, pump curves, pressure ratings, erosional velocities, fatigue limitations, system redundancy and other constraints
The study demonstrated that a prolific worst-case blowout scenario could in this case be killed with a single relief well.