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PESA Vic/Tas August Technical Meeting
Wednesday, 21 August, 2019 @ 12:00 pm - 2:00 pm
The Pluto 4D Project is Australia’s first 4D acquired over a gas field and has been an outstanding success despite the prior high technical risk of not being able to detect 4D signals above the background noise. At the time the first 4D Monitor Survey was acquired the Pluto field had been online for 3 years 9 months and produced approximately 1 Tcf of gas.
4D feasibility studies carried out previously showed that saturation changes (related to water ingress) were expected to show strong 4D responses near the gas water contact (GWC) and would be interpretable if the monitor survey was run after approximately 3 years of production. If the monitor survey was delayed, the pressure response could become too large and eventually convolved with the water saturation signal making interpretation difficult if not impossible.
Strong “hardening” responses on the 4D difference volumes are interpreted as water ingress into the field. These are seen in all reservoir sequences in the Triassic from the TR27 to the TR32 units and range from strong (obvious) to weak (possible). Several examples are shown – the strongest response is seen in the large Triassic (TR27.3) valley within an essentially shale prone unit, which shows water ingress into the valley and moving upwards from the GWC towards the producing well.
The results/insights from the 4D data have provided excellent control points for the history matching for the Pluto Field so far