Well Barrier Integrity Test Unit – BTU

Background:
In current subsea wells, testing of the well barriers is done by pressurizing sections inside the well through a service line. The service line is a physical, hydraulic connection to shore inside a subsea umbilical. The umbilical bundle consists of tubes, hoses, and cables that are wrapped in an outer protective sheath, trenched, and secured at the seabed. The accumulation of cost for manufacturing and marine operations makes the umbilical a major cost driver of deploying subsea CO₂ storage sites.

Goal:
The project seeks to develop a well Barrier Testing Unit (BTU), which enables testing and monitoring of subsea CO₂ injection well barriers in a safe and economically viable way. The BTU is located subsea and integrated into the CO₂ injection well (eVXT, electrical Vertical Xmas Tree). This novel concept eliminates the need for a service line inside the umbilical. Thus, it paves the way for the complete removal of the umbilical. Together with recent developments of all-electric well systems (eVXT) it enhances the feasibility of this approach. The BTU will be designed as a fully-electric and retrievable module. It shall be installed as part of the eVXT, one for each well.

Objectives:
· Utilize CO₂ from the injection line to perform the barrier test.
· Perform barrier tests with increased and decreased pressure to cover all potential failure modes.
· Perform rapid testing sequences to ensure integrity of all injection well valves and maximize the availability and CO₂ injection capacity of the well.
· Remove the service line from the umbilical.
· Remove emissions from hydraulic fluid to sea.
· Connect to a standard subsea tree (eVXT), control system, and electrical supply through the modification of the Flow Control Module.

Activities:
The project aims to develop a full-scale BTU prototype for functional testing and system testing on land, including:
• Development system requirements and architecture and integration into eVXT
• Component development, design, and adaption
• Manufacturing and implementation
• Demonstration and testing of a prototype.