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Outline:

Name: Beetaloo Basin

Location: Northern Australia

Contractors/Interested Parties: (4) Falcon Oil & Gas, PetroHunter Energy, Origin Energy, Dugan Production Co.

Type: Combination well; Shales, Porous Sandstones, Gas

Sparked Interest: 2007

Brief Summary:

The Beetaloo Basin sits in Northern Australia and sits South the major Northern City of Darwin. This city harbors major processing plants for the hydrocarbon basins sitting onshore and offshore residing around the city. The Beetaloo basin is considered an active Hydrocarbon system, and there are sections of the basin which contain many sections of oil and gas layers within the basin thousands and thousands of meters.()

The Beetaloo Basin stratigraphy consists of interesting areas which date back over 1400 Million Years Ago (Mya). Peak oil generation stopped around 200 million years ago. The basin began as an early rift basin which later became an aborted rift basin. After this, sediment laid on top and became a compressional basin.

There are two thick organic rich shale sections with over 7 other sections with the potential to be harvested using unconventional hydrocarbon production techniques. The Kyalla Shale resides between 800-1000 Mya at a depth of 1500 m below with a thickness of 800 m. The Velkerie Shale resides resides between 1100-1300 Mya at a depth of 2600 m with a thickness of 800 m.

History

The section seems to have begun when the section existed during the Neoproterozoic Age, about 750 Mya. Such that, this area of interest was a rift, meaning that this was an area that began to separate due to tectonic plates separating, and this rift structure formed during the Mesoproterozoic age. This rift basin has sedimentary rock which has been compacted on top of the original formations which have disposed farther into the formation adding pressure and compaction.

The most recent vertical cross section show that there is a current rift basin which has many areas of interest. You can see an updip spike towards the north side causing normal faults to form in the lower regions of the area of interest, creating a bowl shape for the entire section.

The hydrocarbon basin has been an area of interest for many years, but the first proof of hydrocarbons was in the 1980's. When 12 exploration wells were drilled for 27,000 feet of core samples. These sections are very promising for not just the amounts of oil present in the multiple layers within the formation, but for the gas located at the bottom of the section. This gas formation is very large when considering the idea that all of this gas is highly compressed, and I find it odd that the gas formation lies on the bottom of an oil formation. This tells me that there are multiple source rocks, and this basin and sections are dynamic. Meaning this location suggests that there are multiple caps and multiple separations. When looking at cross sections most shale sections are separated by a sandstone formation.

New Information for Public

At the conference in 2010, the data and proportion of exploration and production was presented and the layers in question are hydrocarbon rich shale sections. These shale sections contain siltstone and fine sandstone according to the vertical rheologic sections presented. The Hydrocarbon sections are quite complex; but the cores seem to be type 1 and 2 kerogen liquid hydrocarbon.

Looking at the stratigraphy from the top down, we can see 14 major rock formations to the bottom of the basin. Starting from the top to the bottom starting with a Post-Cambrian top-soil formation at the surface. Next, the Tindall Limestone is the first formation encountered spanning from 50-250 m, and followed by the Antrim Volumetric formation which consists of a combination of many formation structures. The Tindall Limestone sections dates back 250 Million years ago, late Cambrian, while the Antrim Vol. dates back approximately 275-500 Mya. The Bukalara Sandstone formation lies at 310-400 m below the surface and does not consists of any potential hydrocarbons at this point. This sandstone section dates back up to 500 Mya, and underneath the Bukalara Sandtone formation lies a major section with the potential to house hydrocarbons. The Hayfield Mudstone section lies from 400-520 m below the surface, and is considered a hydrocarbon rich environment dating back approximately 500-800 Mya. A sandstone formation known as Hayfield Sandstone exists within the Hayfield Mudstone, and this sandstone formation is only 600-650 meters and dates back to approximately 750 Mya. The Jamison Sandstone formation exists from 850 to 920 m below the surface, and this sandstone acts as a cap rock for the the first layer of shale which is of interest. However it does not exists consistently throughout the entire formation with concern to other log readings. The entire Kyalla Shale formation exists from 950 to 1650 m, and exists as two structures separated by a thin sandstone formation that is about 40 meters in height. The top layer of the Kyalla Shale is known as the Upper Kyalla Shale, and this section is about 400 m thick existing from 1000 m to approximately 1400 m. The entire Kyalla section dates back from 800 to about 1000 Mya. The Lower Kyalla Shale region exists from 1400-1650 m, and this shale section is unique to the upper half of the Kyalla Shale. In which, the lower shale has that small sandstone section which also contains pockets of oil according to the log readings. Next, the Moroak Sandstone is similar to the Jamison Sandstone; however, looking at the log data, there doesn't appear to be any hydrocarbon like the Jamison Sandstone. In reality, it acts as a cap rock for the next shale section. The largest shale section which exists in the Beetaloo basin is the Valkerri Shale section which exists from approximately 1900 to 2900 ft and there are scattered sandstone sections throughout the mid and upper regions of the shale section dating back approximately 1100 to 1300 million years ago. There is also a metamorphic intrusion located in the lower section of the shale. Below this section lies the Bessie Creek Sandstone starting at approximately 2900 ft and dates back approximately 1300-1400 Mya, and this section exists as one of the last areas of potential hydrocarbon producing areas. The intrusions which exists in certain sections throughout the basin is actually Dolerite which seeped up due the the fact that this basin sits within a rift basin. ,

Below the Bessie Creek Sandstone formation lies 5 more sections which do not appear to contain any hydrocarbon material. These formations are, in order from youngest to oldest: Corcoran Formation, Abner Sandstone formation, Crawford Formation, Mainoru Formation, and Limmen Sandstone. The Corcoran Formation appears to be mostly mudstone and is part of the Roper Group, and this formation is mostly made up of Mudstone dating back 1400 million years ago. Next, there is the Abner Sandstone formation which dates back approximately 1450 to 1600 million years age during the Proterozoic Era. There is a Dolerite intrusion, or rather a sill, located towards the lower half of the Abner Sandstone which dates back 1100 to 1280 million years ago. Next, the Crawford Formation appears to be similar to sandstone and dike intrusions exists within this formation as well. Below the Crawford formation lies the Mainoru formation which consists mostly of mudstone, and this formation is followed by the Limmen Sandstone. There are two other basins which exists essentially with the Beetaloo Basin and these basins are part of the McArthur and Nathan basin, which extends out into the the gap between the Indian and South Pacific ocean, south of Papua New Guinea.