Title : Data required for thorough assessment of oil/gas loading or Co2 storage monitoring
Abstract:
Through world, coastal oceans there have been extensive surveys with the application of seismic data to predict deep sediment gas hydrate loading. Over the past 10 years comparisons of seismic data and geochemistry show there is a need to combine these data for a more thorough understanding of the deep sediment gas hydrate loading. Initial observations in predicting hydrate presence with integration of seismic and geochemistry data off the mid Chilean margin suggested gas hydrate loading could be greater at a location where seismic data showed moderate gas blanking. On the Atwater Valley in the Gulf of Mexico geochemical assessment showed a region with a strong vertical rise in the BSR to be a site where gas hydrates are likely not stable as a result of salt diapir intrusions creating gas hydrate instability and higher vertical methane advection. Here we present a series of data along the eastern coast of New Zealand that include seismic profiles, geochemistry, controlled source electromagnetics, and heatflow to assess gas hydrate loading. This comparison of locations shows remarkable inconsistencies in the data sets applied to gas hydrate predictions.
Further assessment is provided with a comparison across a focus area off the coast of New Zealand that shows strong variations through comparisons of geophysical and geochemical data. The Porangahau Ridge in the Hikurangi Margin where geochemical profiles focusing anaerobic methane oxidation display moderate vertical gas migration in a region that strong seismic reflection, active heat flow, and controlled source electromagnetic data suggest deep gas hydrate loading and active fluid and gas advection. Mahia Peninsula, located further south from the Porangahau Ridge show strong similarity in geochemical and seismic data for assessment vertical methane fluxes in two different transects. However, porewater geochemical data from these transects compared to a location where seismic data indicates no gas hydrate loading are similar. Chatham Rise, a region where published seismic data was believed to contain gas hydrate loading was found to have a total absence of vertical methane migration. In this location, radiocarbon data of shallow sediment carbonate and organic carbon suggest a potential for carbon dioxide migration.
Finally, this approach applied to oil and gas assessment does provide a thorough capability to evaluate offshore deep sediment CO2 storage. This presentation will include current planning of through monitoring the fate of stored CO2 with the same data based used to assess the oil and gas loading.
