Geophysics SIG Meeting – June (Online)

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Speaker: Gary Barnes – Bridgeporth Ltd.

Topic: Latest Advances in Airborne Gravity Gradiometry 

Abstract

2020 saw the launch of the latest in airborne Full Tensor Gradiometry (FTG) systems, the eFTG. “e” for enhanced. The launch of this system was the culmination of 5 years of development and testing by the manufacturer, Lockheed Martin, and the 1st and only system was exclusively released to Austin Bridgeporth, for commercial exploration projects. The first of these projects, in partnership with TGS, was the acquisition of over 120,000 sqkm of data over the Western Desert, onshore Egypt (Horus-1).

Operationally the Horus-1 project was a success. Operating in fierce turbulence generated by temperatures exceeding 45oC, the eFTG system routinely acquired in excess of 1,000 line km’s of accepted data per flight. This first survey allowed a real comparison with the older FTG systems. The noise improvement factor is approximately 3 for data acquired in reasonable conditions. This is in line with theoretical prediction based on the scaled-up size of the instrument. However, as turbulence increased the noise improvement factor increased dramatically where the eFTG outperforms the FTG (at a similar high turbulence) by a factor of 6.

As well as eFTG data, the campaign also acquired conventional scalar gravity data using the Gravity Module Assembly (AGMA), fully integrated with the eFTG instrument. In addition, magnetic data (for assisting with mapping shallow volcanics and imaging top basement), and engineering-grade LiDAR data (to provide a digital terrain model) were acquired. Following the Horus-1 survey, 2 additional proprietary surveys were acquired in the Gulf of Suez.

On the success of the Egypt campaign, in 2021 the eFTG system completed 3 high-resolution (line spacing of <500m) surveys onshore Gabon, where the system was incredibly effective in the mapping of both the post-salt and pre-salt geology. From West Africa, the system moved to Southeast Asia where over 23,000line km’s of data were acquired over frontier, thrust-belt geology.

The talk focuses on the high performance of the system, and the exploration challenges it significantly assisted with.

Gary Barnes – Bridgeporth Ltd.

Gary has been working in the potential fields exploration industry for the last 20 years focusing on gravity, gravity gradiometry and magnetic methods. He joined Bridgeporth in 2013 and works with the acquisition, processing and interpretation groups developing techniques that enhance the quality and use of potential field data to improve the understanding of sub-surface geology.

Prior to entering industry Gary completed an M.Phys from the University of Birmingham, followed by a PhD in Engineering Science from the University of Oxford.