the man who wasnt

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This report is on the summary of a play in the Snark dataset from the northwest coast of Australia. I have used Petrel to analyze and interpret this dataset. The Snark dataset lies within the Barrow basin which is home to many promising and producing oil fields such as Barrow Island which is the largest onshore discovery in Australia.

Figure 1. Northwest coast of Australia with red star showing location of Snark survey.

Off the coast of northwest Australia there are four basins which include the Northern Carnarvon, Offshore Canning, Browse, and Bonaparte basins. The shelf has experienced many periods of continental rifting dating back to the Cambrian around 500mya (King, 2008). Rifting during the Cambrian period resulted from the separation of the Australian and Chinese continental plates. The basin in which our Snark 3D dataset falls is the Northern Carnarvon Basin. This basin was developed during late Jurassic to early Cretaceous rifting. The base of the Cretaceous is easily distinguished in our dataset as the horizon separating the synrift Jurassic deposits from the post-rift Cretaceous. There are four main tectonic evolution phases seen in the area: 1) during the break up of Gondwana a series of intracratonic basins formed, 2) Early Jurassic extension which created the four main depocenters including the Barrow sub-basin, 3) during the Middle Jurassic there was another phase of extension which resulted in seafloor spreading, 4) the fourth and final rifting phase was followed by a period of thermal sagging (King, 2008).

Figure 2. Overview of the dataset showing orientations of inlines and crosslines

The Snark survey consists of 550 inlines and 850 crosslines. The inlines run from the southwest to the northeas...

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...prospect the Hilltop prospect since the overall area of closure appears form an anticlinal hill as seen in figure 6. There were many DHIs in the area such as the one shown in figure 7 which highlights the differing impedances of shale overlying hydrocarbon bearing sandstone. These brightspots suggest a reservoir of gas which is the expected in this region.

Figure 6. Hilltop prospect time slice

Figure 7. Inline showing brightspot DHI overlaying channel feature

I predict the Hilltop prospect to be within a hydrocarbon bearing sandstone deposited during the Cretaceous period. The prospect is most likely one of gas and not oil. A plausible source rock for this reservoir is the Dingo Claystone which is known to generate both gas and oil in the area but mainly gas (Parry, 1988). A seal is created by the Muderong Shale member of the Cretaceous (West Barrow).
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