Stratigraphic potential in the Odin-Vali area, page-2

Hi VOGC

Nice piece of G&G work and thanks for sharing. As you rightly point out, Odin and Vali are shaping up as combined structural / stratigraphic plays given how large the net gas pay thicknesses are compared with the significantly smaller 4-way dip structural closure heights.

The nearby the gas fields of Crowsnest, Bow and Beckler are also combined structural / stratigraphic accumulations at the Toolachee and Patchawarra levels. These fields rely upon the drape of isolated Permian fluviatile channel systems over a plunging structural ridge (i.e. nose), or anticlinal nose with associated facies changes creating a "hose-over-nose" stratigraphic trapping geometry for gas in sandstone reservoirs. (hose = channel sand stratigraphic components, nose = ridge / anticlinal structural component.) This hose-over-nose play concept could also explain why Odin and Vali have large gas column heights exceeding the structural closures of each field. Of course, you have the have the ideal channel orientation relative to the structural nose to setup the stratigraphic component of trap.

An honours thesis by Koblet (2016) researched the palaeogeographic and depositional trends of the Patchawarra Formation over the Dullingari, Bow, Beckler, Strathmount, Odin areas. This work established the channel orientations over multiple intervals in the Patchawarra Formation. Basically Koblet’s work established that channel orientations ran roughly north – south. This orientation sets up the hose-over-nose play concept where facies changes provide up-dip lateral stratigraphic seals while the anticlinal noses / ridges provide the structural trapping component in a NW-SE direction.

Below is a hypotheticalexample of the hose-over-nose play concept on the Santos depth map at the VC50 level in the Patchawarra Formation. Of course you have this hose-over-nose play occurring at multiple levels within the Patchawarra and Toolachee.

I am hoping for a solid wireline logging result at Vali-3. Then onto the testing program.

Thanks again for your subsurface insights and contribution.



Kind regards OldGeo