RE: AGES Proceedings Volume3 Apr 2020 18:01
McArthur Basin
The Beetaloo Sub-basin is a significant depocentre of
Mesoproterozoic Roper Group sedimentary succession,
which underlies the Mesozoic Carpentaria Basin in the
vicinity of Dunmarra and Daly Waters. It is the Territory’s
most advanced shale gas play. The most prospective
shale units in the Roper Group occur within the Velkerri
and Kyalla formations. Drilling of the middle Velkerri
Formation has demonstrated the consistent presence of
gas-saturated, quartz-rich shale source rocks that are
mature for gas over extensive areas and appear to meet all
of the physical and chemical parameters for a successful
shale gas play. Following the successful hydraulic
fracturing and production testing from the Amungee
NW-1H exploration well by Origin Energy Limited
(Origin) in 2016, Origin announced a 2C Contingent Gas
Resource Estimate for the Velkerri B-shale pool of 6.6 Tcf
(trillion cubic feet) over 1968 km2
, with Original Gas In
Place of 61.0 Tcf . Wells drilled to date by Santos Limited
(Santos), Origin and Pangaea Resources Pty Ltd indicate
a P50 Gas-In-Place Resource for the Velkerri B-shale
alone of at least 500 Tcf, with the additional potential for
liquids across the basin. Following the implementation
of required recommendations of the Inquiry, exploration
activity in the sub-basin recommenced in 2019.
Exploration in the central part of the Beetaloo Subbasin is operated by Origin in joint venture with Falcon Oil
and Gas Ltd. In October 2019, Origin spudded the Kyalla
117 N2-1 well, which was designed to test the liquids-rich
shale gas play in the Kyalla Formation. The well reached a
vertical total depth of 1895 m and intersected a thickness of
nearly 900 m of Kyalla Formation, including three sourcerock reservoirs with thicknesses of between 75 and 125 m.
Each source-rock interval exhibited elevated gas shows
with relatively high C3, C4 and C5; diagnostic fracture
injection tests (DFIT) were performed on each interval.
The joint venture commenced the horizontal section of
the well in December at ~1800 m total depth within the
lower Kyalla Formation with a planned horizontal section
of 1000–2000 m. In January, the joint venture announced
that the horizontal well encountered operational challenges
at 700 m horizontal length, and that the initial horizontal
well would be plugged and followed-up by sidetracking
and drilling of a new horizontal production hole section.
In November 2019, Santos re-entered the previously
drilled Tanumbirini-1 vertical well and commenced a
four-stage stimulation program. Initial production test
results confirmed a gas discovery in the middle Velkerri
shale gas play, with gas flow rates of over 1.2 mmscf/d
(million standard cubic feet per day) recorded, which
exceeded initial expectations for the vertical well.
(Cont)
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