Metadata Report for BODC Series Reference Number 2027204

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

Kongsberg EM 710 multibeam echosounder

The Kongsberg EM710 is a high resolution multibeam echosounder. It operates at frequencies from 70 to 100 kHz, with a maximum ping rate of 30 Hz. The EM710 features a depth range of 3m below the transducer to 2000m (1000m for the EM710S model, and 600m for the EM710RD model). The swath width is up to 5.5 times water depth, to a maximum of more than 2000m.

For more information, please see this document: https://www.bodc.ac.uk/data/documents/nodb/pdf/em710_product_specification.pdf

JC152 CHIMNEY Bathymetry: Originator's Data Processing

Sampling Strategy

Kongsberg EM710 multibeam bathymetry data were collected on board RRS James Cook cruise JC152 from 25th August to 12th September 2017. This cruise set out to map the Scanner Pockmark region in the central North Sea, and to undertake other seismic work to help scientists understand the surface and internal structure and origin of the sub-seafloor chimney structure in this region.

The data collection was funded under NERC's Characterisation of major overburden leakage pathways above sub-seafloor CO2 storage reservoirs in the North Sea (CHIMNEY) project, under grant reference NE/N016130/1. Further information is available in the cruise report.

Data Processing

Post processing of the EM710 multibeam data was undertaken using CARIS HIPS and SIPS software v10.3. A file structure was created for the cruise and two projects created. The initial lines in the work area 53, 55, 57, 59, 61, 63 where used in project JC152_patch_test to establish the attitude angular offsets for the attitude system, Attitude 2. It was decided by the science party not to enter these into the EM710 system but to have them in the CARIS vessel file so they are only applied in post processing.

Lines 53 ? 482 and 509 - 699 were then imported daily by the technician into the JC152 project. Predicted tide from NOC's POLPRED software was applied and initial cleaning was undertaken by removing some of the outer beams and removing major spikes. The scientific party then undertook additional cleaning using the swath and subset editors.

The data were exported into Geographic decimal degrees as ASCII .xyz files with longitude, latitude and depth, and submitted to BODC.

JC152 CHIMNEY Bathymetry: Processing by BODC

The multibeam bathymetry data from JC152 in the North Sea were supplied to BODC as ASCII XYZ files from the Kongsberg EM710 system. The dataset was transferred into a common format, a netCDF subset. The following table shows how the variables within the files were mapped to the appropriate BODC parameter codes:

Following transfer, the data are screened visually, using BODC's in-house visualisation software, and any spikes or instrument malfunctions are clearly labelled with quality control flags.

Project Information

Characterization of major overburden leakage pathways above sub-seafloor CO₂ storage reservoirs in the North Sea (CHIMNEY)

The NERC-funded Characterisation of Major Overburden Leakage Pathways above Sub-sea floor CO₂ Storage Reservoirs in the North Sea (CHIMNEY) project is investigating the risks of leaks from storing carbon dioxide (CO₂) under the seabed. Academics from the University of Southampton, the University of Edinburgh, and the National Oceanography Centre (NOC) are working together to understand more about the hazards involved in the storage of CO₂ in depleted oil and gas reservoirs and saline aquifers in the North Sea. The project has been designed to complement the 2017 Strategies for Environmental Monitoring of Marine Carbon Capture and Storage (STEMM-CCS) experiment.

Background

Industrial emissions of carbon dioxide (CO₂), including fossil fuel power generation, are recognised as a likely agent of global climate change and acidification of the oceans, but most economies will remain dependent on these technologies for the next few decades. Carbon dioxide Capture and Storage (CCS) has been identified as an important way of reducing the amount of CO₂ added to the atmosphere. CCS is seen as making a key contribution to reducing mankind's greenhouse gas emissions by 80-95% by 2050 and keeping climate change derived temperature increases below 2 degrees Celsius, as outlined in European Commission policy. In addition, CCS is considered an important way of reducing the cost of mitigation measures around the continued use of fossil fuels. Offshore storage of CO₂ in depleted oil and gas reservoirs and saline aquifers is the option of choice for most European nations, and there is currently one operational storage complex (Sleipner, Norway), and several other commercial scale demonstration projects are in late stages of development (e.g. ROAD-Netherlands, Peterhead and White Rose-UK), and expected to be in full operation by 2020.

A key element of CCS offshore is that there is confidence that the risks of any leakage are understood. The location and potential intensity of any possible CO₂ leakage at the seafloor are critically dependent on the distribution of fluid (dissolved and gaseous CO₂) pathways in the rocks overlying the reservoirs in which the CO₂ is stored, and on the ability of these pathways to transmit fluid (termed permeability). Recent studies of the structure of marine sedimentary rocks in the North and Norwegian Seas have revealed that near-vertical structures, which resemble chimneys or pipes, cross-cut the sedimentary sequence. These structures may be pathways for fluid flow. Natural fluids from deeper rock layers have migrated through these structures at some point in geological time. If CO₂ leaking from sub-seafloor storage reservoirs reaches the base of these structures, and if their permeability is sufficiently high, they could act as CO₂ leakage pathways towards the seafloor and overlying water column. To provide a reliable prediction of potential seafloor seep sites, the degree to which these pathways are continuous and especially their permeability needs to be better understood.

Further details are available on the CHIMNEY project page.

Participants

The following institutions are involved in the CHIMNEY project:

• National Oceanography Centre, Southampton (NOCS) - Project Principal Investigator: Professor Jonathan Bull
• University of Edinburgh
• GEOMAR - Helmholtz Centre for Ocean Research, Kiel
• Lawrence Berkeley National Laboratory
• CGG
• Applied Acoustics

Research details

Four Work Packages have been funded and are described in brief below:

• Work Package 1: Novel broad-band seismic anisotropy experiment over a North Sea chimney in order to understand its structure and origin, derive fracture geometry and topology, and ascertain if fractures are open or closed. Additional high-frequency seismic reflection imaging. 10 days of ship-time funded to supplement STEMM-CCS experiment. BODC is only likely to receive data from this work package.

• Work Package 2: Rock physics experiments on synthetic samples to constrain chimney and surrounding rock permeability.

• Work Package 3: Geochemical characterisation of chimney material and pore fluids. Core samples from the North Sea chimney will be used to assess hydraulic connectivity, water-rock reactions that affect permeability and the longevity of fluid flow, and to constrain reactive transport modelling.

• Work Package 4: Flow and reactive transport modelling to integrate outcomes of the three other WPs and do scenario modelling.

Fieldwork and data collection

Data will be collected over a chimney structure within the North Sea using a ship to make new and unusual measurements with sound waves. Several different marine sound sources will be used to make images of the chimney, using receivers at the sea surface, and also record the sound arrivals on sea bed instruments known as ocean bottom seismometers. By looking at the sound travel paths through the sub-surface from a range of directions and frequencies, information will be obtained about fractures and fluid pathways in the chimney as well as the surrounding rocks. The results will be calibrated and analysed via laboratory studies of materials (synthetic rocks) that mimic the sub-surface rocks. By understanding the propagation of sound through synthetic rocks with known fluid pathways the results of the marine experiment can be understood. A computer model of the sub-surface chimney will also be constructed combining the results of the seismic experiment, rock physics, and chemistry.

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: