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Integrated geophysical data to advance ENI’s CCS projects

  • Two landmark decarbonisation schemes in the North and South of UK, using new and existing infrastructure, Hydrogen and CCS for large scale industrial decarbonisation.
  • Very complex operating environments representative of ‘CCS hub environments’.
  • Shearwater and XOCEAN partner to provide multi-disciplinary, fully-integrated data solution.
Background

The HyNet North West project is the UK’s foremost industrial decarbonisation project using hydrogen and carbon capture and storage (CCS) to reduce carbon emissions in industry, homes and transport across northwest England and north Wales. The project will store captured CO in the depleted Hamilton and Lennox gas fields in the Irish Sea operated by Eni UK. It will also integrate existing natural gas plants with CCS activities to produce low carbon hydrogen for supply to industry, transport and electricity generation in the region. Delivered by a multi-partner consortium, Eni UK, will develop and operate the onshore to offshore transportation and storage of CO.

Meanwhile, Bacton Thames Net Zero (BTNZ), an initiative launched by Eni UK, involves more than 10 entities working together to substantially decarbonise power and industrial processes in Norfolk, and Thames Estuary, near London. The plan is to capture, transport and store at least 10Mtpa of carbon dioxide emitted from these regions into the Hewett depleted gas field operated by ENI, off the coast of North Norfolk.

The challenge – data to delineate shallow geophysical targets in extremely complex operational contexts

The task was to acquire high-quality, high resolution data, in an extremely complex operational context, to help Eni delineate shallow geophysical targets in multiple identified storage sites. Both Liverpool Bay and Hewett presented a challenge representative of many CCS hub locations globally. The target sites, generally depleted fields, tend to be close to shore in water depths of 10m and shallower. Geophysical imaging for CCS requires focus on the shallow overburden geology with high-resolution parameters for site characterisation and pre-injection imaging, and a future-proofed baseline monitor survey. The data to mitigate CO containment risk has to be acquired as efficiently as possible. Additional time constraints added to the complexity of both projects.

The solution – integrated bathy-morphological, hybrid seismic surveys 

The integrated data approach allows for contiguous imaging of the seabed, that would have otherwise been prevented if limited to any one single approach. The areas closest to the shoreline in Liverpool bay, for example, had post-critical angles that prevented imaging of the seabed. However, this lack of information was easily recovered both from the sub-bottom profiler data and from the ocean bottom node survey. Additionally, the integration of the data sets resulted in more effective processing and imaging of the targets and deep reservoirs.

For the Liverpool Bay, we used the Shearwater Bly towed streamer technology to maximise efficiencies, and then used a bespoke node solution in the shallowest sections to ensure full data imaging requirements could be delivered. This hybrid approach demonstrates. Shearwater’s versatility and operational excellence.

Bathymetric data was essential for safe navigation and de-risking the area geophysically and geomorphologically. Shearwater partnered with XOCEAN using their innovative carbon neutral unmanned surface vessels to provide multiple data measurements in an operationally efficient and safe manner. These data measurements, including Multi Beam EchoSounder, Sub Bottom Profiler and Sound Velocity Profiles, provided an integrated data solution to deliver more effective processing and imaging of the targets and deep reservoirs.

We were able to leverage a high tidal range to acquire data from the Lennox field with the SW Bly as shallow as 7m – shallower than the vessel’s minimum operating depth. We needed the SW Bly on location at high tide, and clear otherwise. Placing a seismic vessel with towed equipment at a specific location at a specific time would typically see significant standby time waiting for ideal conditions. The acquisition strategy was able to further exploit a low tide operating limit for the southern part of the Hamilton field, which was in water depths of 15-20m. This limit was set by the Liverpool Port Authority to allow commercial shipping access to the port during high tide.

We were able to acquire Lennox on high tide, Hamilton South on low tide and Hamilton North efficiently while waiting for the next Lennox high tide. The detailed planning added to an already challenging area featuring multiple windfarms, obstructions within the survey area, fishing community engagement, several other stakeholders and high tidal currents. And all to a tight permit deadline.

The bathymetry to enable the safe acquisition of both Hamilton and Lennox was acquired on a condensed timeline which needed Shearwater and XOCEAN to quickly develop a close relationship to provide the right data in the right place in time for Shearwater to establish an acquisition plan.

The Hewett field off the coast of Norfolk was an equally complex and challenging environment with additional hurdles. For Hewett we used the Shearwater Amundsen towed steamer multi component technology in very shallow water up to just 10m, with four obstructions to acquire around. The coverage gaps were further minimised by innovative close-pass lines in between the platforms, with the remaining gaps infilled using deployed nodes from the Shearwater Vespucci. Coverage around the platforms was critical for site characterisation and pre-injection.

To add to the complex operating environment, the survey started late in the North Sea season, with weather standby increased. We were able to make the most of every good weather opportunity to maximise production, with minimal technical downtime. This was achieved by significant investment prior to the survey to ensure all in-sea equipment was fully operational. Additional de-noise and de-multiple stages were added to the fast-track processing to verify high quality data in a challenging environment.

Success of the project once again needed a co-ordinated effort with XOCEAN which provided crucial updated water bottom bathymetry, allowing safe navigation along the 10m contour. Simultaneous operations with rig decommissioning, fishing activity and strong tidal currents up to 3.0 knots also meant the crews of the SW Amundsen and Vespucci had to have a strong plan, with contingency built in for flexibility.

Success of the project once again needed a co-ordinated effort with XOCEAN which provided crucial updated water bottom bathymetry, allowing safe navigation along the 10m contour. Simultaneous operations with rig decommissioning, fishing activity and strong tidal currents up to 3.0 knots also meant the crews of the SW Amundsen and Vespucci had to have a strong plan, with contingency built in for flexibility.

The result – high quality data acquired safely and efficiently and delivering on technical expectations

Significant data uplift showed the benefit of a modern high resolution data set .

The acquired surveys will be fundamental to guarantee a successful and safe execution of a key client’s carbon capture and storage projects. The combination of shallow waters (30-2m), the huge variation of the mean sea level linked to the tides (8-9m) and the shallow geophysical targets together with the presence of numerous oil and gas infrastructures, wind farms and naval traffic make such offshore acquisition campaigns unique in their operational complexity.

The successful project deliveries led to Shearwater and XOCEAN formalising a collaboration partnership promoting the value of the integrated data approach demonstrated on the ENI projects. This approach provides clients with a fully-integrated, multi-disciplinary data solution combining modern high resolution towed streamer and OBN 3D seismic data with bathymetric multi-beam echo sounder and sub-bottom profiler.

Carbon capture and storage is a strategic focus for Shearwater, and we are developing a fit for purpose acquisition toolkit specifically for this growing market. Shearwater and XOCEAN have successfully demonstrated the integrated data solution that maximised efficiency, minimised cost and exposure, all against the backdrop of a challenging environment and shifting project timelines.