MEO has identified and mapped such a reservoir and seal. The candidate appears to be Maastrichtian sandstones of the Turnstone Formation encountered in the Evans Shoal-1 and 2 wells. In Evans Shoal-2 a 80 metre thick massive sandstone was revealed between 1670 and 1750 m bdf. This sandstone is termed the Turnstone Formation, which we believe is equivalent to the Lynedoch Formation and the Puffin Formation of the Ashmore Cartier region. The lowest sandstone occurs beneath a thick shale section of 60 to 80 m, which could provide a regional seal.

The seismic demonstrates NE-SW faults in the area of the Evans Shoal gas accumulation. It is evident that the faults are offsetting these sandstones and may provide potential leakage points for carbon dioxide. However, there is a large area to the southwest of over 100km˛ that appears unfaulted. The seismic suggests that the sandstone and regional seal encountered in the Evans Shoal wells may be laterally extensive. The seismic lines demonstrate the correlation of the lower Turnstone Formation sandstone.

MEO is seeking to quantify the volumes of carbon dioxide that could be disposed in the Turnstone Formation and estimate the risk that gas could escape the saline aquifer through faults. CSIRO has been engaged to review the work already conducted by our geophysicist, provide an opinion as to the technical merit of the target sandstone and any substantial problems in principle with the approach. Additionally, CSIRO will conduct reservoir modelling and volumetric calculations.

A range of CO² daily injection rates have been provided and the potential volume of CO² possible for re-injection is to be established.

While this investigation is clearly being targeted for the Tassie Shoal project and the potential for the gas producers to supply domestic gas to Darwin, the findings of the study and the expertise developed could be applied to many other projects.