In this First Break article from October 2024, Roya Dehghan-Niri, Åsmund Sjøen Pedersen, Mark Thompson, Anne-Kari Furre, Harald Westerdahl (Equinor Energy AS), Sandrine David and Tone Holm-Trudeng (TGS) present the results from a series of 2D and 3D mini-streamer operations across the Sleipner CO2 storage site, which are assessed and compared with conventional streamer seismic.
Introduction
CCS technology has a vital role to play in mitigating climate change. The technology consists of capturing CO2 at the source, such as power plants or factories, and storing it in underground formations. In recent years there has been a significant development in the deployment of large-scale CCS projects, demonstrating a growing recognition of the technology’s ability to address climate change. However, the adoption of CCS needs a strong business case to be successful. To improve the business case, the technology, including monitoring cost, would benefit from becoming more mature and cost-effective. Monitoring is an essential part of the technology to ensure conformance and containment of the stored CO2. Conformance monitoring involves demonstrating that the CCS system operates within the required legal and regulatory standards. The monitoring of conformance helps to minimise environmental and safety risks, which could otherwise have negative implications for public perception, operational efficiency, and legal compliance.
Containment monitoring ensures that the CO2 injected into subsurface formations remains securely stored within the storage complex, with minimal environmental risk. Therefore,
through regular monitoring, the integrity of the storage facility is assessed and any potential leaks or escape points that could compromise the effectiveness of the CCS system are identified. In addition, regular monitoring helps to identify potential gaps in performance and assists in making informed decisions to improve the operational efficiency and prevent environmental and safety risks.
To date time-lapse seismic, using conventional seismic streamers, has been the main technology used to image and monitor the subsurface in offshore CO2 storage sites (Furre et al., 2017). Here, we show how we have investigated mini streamers or Extended High Resolution (XHR) seismic as a potentially more flexible and cost-efficient solution for CCS monitoring.
While conventional streamer acquisition is characterised by a multitude of seismic streamers that are several kilometres in length, XHR uses significantly shorter streamers with a length typically ranging from tens to a few hundreds of metres.
Figure 1 - Illustration of different application scenarios for the XHR technology. Scenario 1 is similar to the deep-water GOM tests, Scenario 2 is similar to the Barents Sea experiment. Scenario 3 is the one that was investigated through this research and scenario 4 is left for further research.
Originally mini streamers were deployed successfully in the Barents Sea to map the Håkon Mosby Mud Volcano (Berndt et al., 2006) and later their use was demonstrated for time-lapse purposes in the Gulf of Mexico (GoM) to monitor two injection wells in a reservoir at 800-1200 m depth in 2500 to 3000 m water depth (Hatchell et al., 2019). In both cases, the targets were located above the first water bottom multiple. However, the potential for using this technology to monitor deeper targets in shallow water depth where the target falls below the first water bottom multiple was unclear. Figure 1 illustrates different scenarios for the application of the mini-streamers.
Read the full article here.