montara & plover formations, page-120

Hi SE

Firstly that part of the NW Shelf is criss-crossed by faults, commonly termed as Horst & Grabben. Horst been a high & Grabben being a low/valley. These are created by regional tectonic forces mainly tensile or compressive that cause either up/downward displacement.

Simply put, imagine a biscuit, now apply inward pressure from both ends. This will snap into slices. Similarly, if u have a rock column like the Plover & Nome sands that have had pressure applied in a upward or downward manner, the sands will b displaced upwards & downwards depending on the direction the force is coming from (in this case from below). The correlated Crux logs illustrate this very well as the formation comes in higher in one well & lower in another.

From the topo map, the contours clearly indicate that there is a valley, caused by the major faultline, running between the Crux & Auriga well.

IMO, Crux field is a classic combination trap i.e. Structural & stratigraphic as the HC bearing rocks are isolated or separated by fault lines. One could anticipate the GWC 2b lower then the gas bearing strata at Auriga. As for the Plover & Montara sands they could come in thinner or thicker.

Read page 14 onwards on this report, shows seismic reflection for Crux wells, thankfully no faults seen in this single block so Crux gas is safe. I'd anticipate this for Libra & Auriga as well.

http://www.nt.gov.au/d/Minerals_Energy/Content/File/pdf/annual_report_2007.pdf

The question is are Libra & Auriga connected or are these blocks separated by fault & are hosting the P/M/N sandstones?

cheers