Ramsay 2D SS 2021 - Acquisition and Processing Reports

Abstract

Terrex Seismic (Terrex) was contracted by Peak Helium Pty Ltd (Peak Helium) to conduct the Ramsay 2D seismic survey consisting within the EP134 permit authority area. Recording was completed in 13 days with a total 121.6 linear km over eight 2D lines. Acquisition commenced on 24th January and finished on 9th February 2022.

The geophysical objectives of the Ramsay 2D seismic survey was to image structural targets in the Heavitree Formation, which conformably sits above the metamorphic basement. This is the reservoir target for the helium found at the Magee-1 well drilled in 1991. The survey was also designed to provide better imaging of the Bitter Springs formation, in particular the Gillen Member salt which provides the top seal for the Heavitree.

The acquired seismic data is of excellent quality considering the harsh ground conditions for acquisition. Shot gathers showing mostly clean first breaks despite heavy rain showers and windy conditions, which mostly affect the further offsets. The gathers are affected by the road noise and machinery used by the farmers. The whole line was active which increased the recorded offsets and reduced the signal to noise ratio where these offsets are usable.

Peak Helium engaged Howman Seismic Services to process the acquired 2D seismic data. The main objective of the processing was to produce a clear structural image of subsalt target interval (comprising the Heavitree Quartzite directly overlying Basement). A secondary objective was to retain true amplitudes throughout the sequence so as to allow further analysis of pre-stack amplitudes in the future.

Data quality in the area was good with clear reflections through the sedimentary successions down to 1500 ms. Residual statics, velocity picking and deconvolution were all impactful stages of the processing flow. Early noise attenuation was also critical due to the nodal nature of the acquisition (i.e. no field summation to quell environmental noise). The very long offsets were useful for imaging deeper events although time processing assumptions tend to break down leading to unreliable interpretation of these events.