Quantifying Intraformational Seal in a Coal-Rich Sedimentary System

Abstract

The Gippsland Basin, situated in Bass Strait, Australia, contains excellent potential CO2 storage sites in a nearshore zone where there is optimum development of reservoir and seal units. A particular focus for the CarbonNet project is intraformational seals of the Middle Eocene (and older) Traralgon sequence in this nearshore zone. The seals are a combination of conventional shale seals (including seat earths) and coal beds. Thick units of coal with interbedded shale function are proven to contain oil and gas accumulations for millions of years in the local area and display pressure and salinity evidence of seal behaviour between different subsurface aquifers. 3D seismic mapping of the seal units demonstrates that they are continuous across wide areas, but that there are local minor faults and fractures. Studies of shale and coal properties, fault geometries, and interactions with the low-permeability units and varied lithologies demonstrate that the Traralgon sequence contains valid seals for large columns of CO2 and will store CO2 for extended periods before final dissolution into meteoric offshore aquifers.

Keywords: Site characterisation and selection, GHGT-14, Seal, 3D seismic, CO2, CO2 Storage, Gippsland Basin, Coal, CO2 column, MICP, Shale Gouge, Fault interactions, Meteoric aquifer, offshore aquifer, Dissolution