By subtracting the solar, regional, and aircraft effects, the resulting aeromagnetic map shows the spatial distribution and relative abundance of magnetic minerals (primarily the iron oxide mineral magnetite and pyrrhotite) in the upper levels of the Earth’s crust.

Different rock types have varying content of magnetic minerals, so the magnetic map allows visualisation of the geological structure of the upper crust, especially where bedrock is obscured by surface sediments, soil, or water. Faults and fractures also tend to contain accumulations of magnetite from migrating fluids and hence magnetic surveying can assist in mapping of faults and fractures.

The DC-3 aircraft was first developed and produced by the Douglas Aircraft Company in the 1930s. The design has been extensively modified and improved over the decades, resulting in an extremely safe and robust aircraft that has had many uses, including aerial surveying. It is still widely regarded as one of the most significant transport aircraft in aviation history and played a crucial role in revolutionising modern air travel.

The DC-3 aircraft is responsible for popularising air travel, particularly in the United States. Early eastbound transcontinental flights could cross the U.S. in about 15 hours with three refuelling stops, while westbound trips against the wind took 17+ hours. A few years earlier, such a trip entailed short hops in slower and shorter-range aircraft during the day, coupled with rail travel overnight.

The DC-3’s legacy and iconic status continue to be celebrated, and a considerable number of them are still in service around the world. Its timeless design and historical significance have made it an enduring symbol of aviation history.

One of the last talks on the second day was on ‘The Evolution of Core Studies in the Revolution of Exploration and Development Models’ presented by Melissa Johanssen of Geode-Energy who explained the various sedimentary features visible in some spectacular lagoonal, estuarine and deep-water cores from various North Sea wells. Particularly worthy of mention because of the great work undertaken by North Sea Core CIC in rescuing and preserving 1,000s of feet of precious core which would otherwise have ended up in landfill. Now a secured resource for education and industry.

Earthline’s Jon Watson was invited to present at the Critical Minerals Exploration Challenge, which focussed on research and innovation partnership.

A question was asked during the morning session by Josh Bamford, Head of Tech & Innovation at the British High Commission New Delhi, “How do you prioritise exploration in an area 3x size of the UK?”.

Jon’s talk addressed this point specifically by explaining how airborne geophysics offers the ideal solution for large, data-sparse areas. The ability to acquire multiple geophysical measurements, including gravity gradiometry, scalar gravity, magnetics, gamma-ray spectrometry, LiDAR from a single aircraft, not only offers rapid data acquisition (often over 1,000-line km’s per day), but also at low-cost, with minimal environmental footprint.

Regional surveying over larger areas can produce a daily fast-track subsurface image of the area flown, allowing the prioritising of denser acquisition over identified areas of interest, and in turn limiting acquisition over areas that seem less prospective. Once processed and interpreted, targets can be identified for further land-based exploration and drilling.

Lockheed Martin are the only manufacturer to have successfully built and commercialised full and partial tensor gravity gradiometers. The technology was developed during the 1970s cold war. The first FTG-like devices were originally designed to operate in the ocean and, after declassification, were modified to acquire data in the more dynamic airborne environment. Except for some minor upgrades and construction of a partial tensor system (rather than a truly full tensor system), little has changed over a quarter of a century.
 
However, in August 2020, after five years of development and testing, the eFTG instrument was exclusively released to Earthline Consulting. It was then mobilised to acquire data over an underexplored region of the Egyptian Western Desert (Figure 1). This new instrument, with a reported fourfold improvement in signal-to-noise ratio on its closest competitor (i.e. the Lockheed Martin built FTG; note no ‘e’), was tasked with acquiring gravity gradiometry data for a TGS-led multiclient programme, specifically designed to unlock the treasures that exist beneath 120,000 km2 of the Egyptian Western Desert. 
On the face of it, a routine survey until you factor in the significant challenges. Firstly, the acquisition would take place in summer when the temperatures exceed 45°C, generating fierce turbulence; secondly, the survey area is three-quarters the size of Florida; and thirdly, the acquisition was to take no more than ten weeks. Quite the challenge for the first sortie into hydrocarbon exploration for the instrument, a challenge the eFTG overcame, surpassing all expectations. 
 
The Ganope Petroleum Company manages and supervises all upstream and downstream oil and gas activities in Egypt between latitudes 28° and 22°N. The Western Desert is a vast kaleidoscope of rolling terrain and sand dunes punctuated by rugged ridges and a large north–south trending valley (Figure 1). Exploration in this remote landscape dates back over 15 years, but little has been undertaken of late, primarily because three wells were drilled into a shallow basement, condemning the area to the ‘not prospective’ bin. This analysis was reinforced by several incorrect publications showing a shallow basement to extend over much of Ganope’s Western Desert area. A particular blow was the West Kom Ombo (WKO) well, sited to detect the western extent of the Kom Ombo Basin, a proven hydrocarbon basin with production to the east. The eFTG multiclient survey was to be the first high resolution dataset to be flown over this frontier area.

Earthline uses the calibrated, processed and ground-classified point cloud data from the LiDAR sensor to generate a high-resolution Digital Terrain Model (DTM) to remove topography signals from the gravity gradient and scalar gravity datasets.

This alone validates the use of a LiDAR system. LiDAR sensors have the ability to image points that are beneath vegetation; this means trees and other plants will not cause false elevation readings. This is something alternative methods are unable to provide. Therefore, the ground surface derived from the

LiDAR point cloud is more accurate than any other publicly available datasets (such as NASA’s Shuttle Radar Topography Mission (SRTM) data or Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) topography).

Airborne geophysical surveying offers numerous environmental and other benefits, including rapid data acquisition, high accuracy, as well as significantly reduced environmental and HSE impact. 

These surveys minimise environmental disturbance and reduce the need for extensive land access, clearances and permissions in areas without roads and other means of access. They also allow prioritisation of areas for more detailed exploration, reducing the need for extensive drilling, which can be environmentally disruptive.