After setting up the instrumentation on the research aircraft (Diamond Aircraft HK36TTC-ECO Dimona VH-OBS) at ARA’s facilities at Parafield Airport, South Australia, a local test flights was carried out and the aircraft and crew relocated to Karratha/WA, a 4 day ferry flight over nearly 3000km. The campaign had been planned to take place in 2020, but was substantially delayed by the Covid-19 related border restrictions in Australia.

 

The aircraft and instrumentation was identical to the one used in the main Surat-study in 2018, except that a stronger pump was used for the Los Gatos gas analyzer (see also Neininger BG, Kelly BFJ, Hacker JM, Lu X, Schwietzke S, 2021: Coal seam gas industry methane. https://doi.org/10.1098/rsta.2020.0458. emissions in the Surat Basin, Australia: comparing airborne measurements with inventories. Phil. Trans. R. Soc. A379: 20200458).

 

The measurement flights near Karratha took place on 18th, 19th, 20th, 22nd and 23rd September 2021. Karratha Airport was selected as base for these flights, an international airport with a Control Zone. All flying required specific flight clearances, but the cooperation with Karratha Tower was excellent. Substantial coordination was also required with the intense helicopter traffic between the airport and the offshore oil- and gas-platforms.

 

All systems worked perfectly during all flights and the weather conditions were suitable for research flights, but – as expected – not necessarily for determining actual emission rates in all cases.

 

The main flight strategy used were stacks of traverses through the well-defined plumes from the Pluto and the KGP-facilities. This type of flight pattern is called a “curtain”. Such curtains were flown at various distances downwind from the facilities and across the prevailing wind.

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At the beginning and end of each flight, a vertical sounding was flown to the top of the convective boundary layer as is standard for such flight patterns. However, it turned out later during the processing that such soundings were not really required for these specific cases of emission plumes. This will be explained in more detail in the Final Report for the study.

 

Further analysis in progress seems to indicate that there is also a third source of methane emissions. This may either be the YARA Ammonia Plant located about 2km to the SE of Pluto or the Pilbara Port area located to the South and SW of Pluto. 

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