Project Greensand is the first CCUS project of its kind to use gas reservoirs under the North Sea for permanent carbon storage. The consortium wanted to evaluate the injection of CO2 into an existing water injection well while protecting the well’s completion string.
The consortium needed to conduct a study comprising multiple cycles of CO2 injection followed by seismic measurements to examine formation behavior. The injection string needed a unique BHA that would isolate the completion, complete the well barrier, and deliver CO2 directly to the formation at 4,300-m MD for CCUS. Transportation and storage of the liquid CO2 required the coiled tubing (CT) string to remain in the well for several months. SLB conducted meticulous contingency planning to prevent complications from hydrates, water contamination, and corrosion during this period. After detailed prejob analysis of prospective metallic and elastomeric components and multiple iterations of material upgrades, SLB recommended the world’s first deployment of CT combined with the SIMplus retrievable bridge plug and Peak Family™ flow control and well intervention tools tailored for CO2 injection.
The BHA with the SIMplus plug, pump-through check valve, and CT stinger assembly reduced operational runs by a staggering 85% compared with conventional methods. Using the CT as the injection string, more than 4,100 m3 of liquid CO2 was successfully pumped into the reservoir—with no service quality or HSE incidents.
Studying the downhole behavior of CO2 was key to successfully deploying this novel CT service. The pilot set a new precedent for using intervention technology and knowledge as an early enabler for carbon storage projects, especially in an offshore setting. Lessons learned will be used to scale up future carbon storage solutions for Project Greensand and other North Sea CCUS projects.
