Targeting oil and gas in the Perth Basin using an airborne gravity gradiometer

In recent years there has been renewed interest in the hydrocarbon potential of the Perth Basin in Western Australia. It is close to the regional capital city and the gas pipeline that runs between Dampier in the north and Bunbury in the south. Recent discoveries of gas by AWE have shown that there is a working hydrocarbon system within at least the northern and central parts of the basin. In most parts of the basin, modern seismic data is relatively scarce. In the current low oil price environment, explorers are looking for cost-effective ways of exploring and targeting seismic acquisition. Airborne gravity gradiometry is such a technique. It has been widely used in frontier basins to understand the basin architecture (Bain et al., 2013, Roberts et al., 2015), sedimentary structure (Feijth et al., 2015 and Kovac et al. 2013) and planning of seismic acquisition (Moore et al., 2012). The Black Swan geophysical survey was conducted by CGG to assist oil and gas producer, Empire Oil and Gas, in identifying target areas for hydrocarbon exploration. The main tools employed were the Falcon Airborne Gravity Gradiometer (AGG), magnetic and digital terrain data. The survey was flown east-west with a nominal flying height of 100 m with 1 000-m line spacing, using a flight line to tie line ratio of 10:1. Structural interpretation has been carried out in two phases. Regional interpretation provided an overview of major regional structures and aimed to analyse the linkage between segments within the exploration blocks. It was derived from regional, publicly available gravity and magnetic data. Detailed structural interpretation was derived from the AGG (Airborne Gravity Gradiometer) data in order to improve current understanding of the tectonic pattern within Empire Oil’s exploration blocks. Depth to magnetic basement was calculated using publicly available government data. The survey identified areas containing large structural leads and trends for targeting future gas exploration activities, including infill 2D seismic acquisition.