Applying FALCON® gravity gradiometry to hydrocarbon exploration in the Gippsland Basin, Victoria

Abstract

The Bass Strait FALCON airborne gravity gradiometer (AGG) survey was flown over an area of the Gippsland Basin in Bass Strait in July 2002. The survey, centred on the gas-producing Marlin and Snapper fields. coincided with a contemporary, detailed marine gravity survey. These marine gravity data, as well as pre-existing data from satellite gravity and sparse marine gravity surveys, were used in comparisons with the FALCON data.The vertical gravity gradient data outlined a major Eocene channel. Interpretation, including modelling of representative seismic lines, revealed the particular usefulness of these data for mapping shallow faults. Conventional vertical gravity from the FALCON survey was better at the longer wavelength features, typically the major tectonic elements such as basin bounding faults, and relative sediment thickness. Comparisons with the marine and satellite gravity data showed that the FALCON gravity reproduced all the information nailable in the other surveys at wavelengths up to the survey size. At shorter wavelengths, the FALCON data had higher sensitivity than all other datasets, including the detailed marine gravity. Incorporation of longer wavelengths from the satellite or other gravity into the FALCON gravity proved successful in improving the longer wavelength information and regional context. As a result of this study, the standard FALCON processing has been improved to allow such incorporation on all surveys where separately acquired sparse gravity data are available.

Conforming Falcon‡ gravity and the global gravity anomaly

“…The Falcon AGG survey in the Bass Strait has been reported by Rose et al (2006) whom I follow here. In July 2002, Fugro Airborne Surveys flew a Falcon survey over a 35 km by 40 km area of the Gippsland Basin in Bass Strait.…”

“… Marine gravity survey ship tracks within the study area (a) and (b) shaded pseudocolour image of the Northern Fields marine gravity (after Rose et al 2006) over the Gippsland Basin study area, Australia. …”

“…The survey details for the Northern Fields marine gravity data were described in Rose et al (2006) and I merely summarize key points here. The data were acquired and processed by Fugro Gravity and Magnetic Services, as part of a WesternGeco 3D seismic survey between October 2001 and July 2002, for Esso Australia Pty.…”

“…Such a merging of data sets is called ‘conforming’ and many Falcon gravity data sets have been conformed to available regional data sets. Examples have been published (Rose, Zeng and Dransfield 2006).…”

Structure Estimation of 2D Listric Faults Using Quadratic Bezier Curve for Depth Varying Density Distributions

“…There are numerous implementations, such as, structure estimation of sedimentary basins (Silva et al., 2006; Zhou, 2013; Pallero et al., 2015; A. Roy et al., 2021b), faults and folds (L. Roy et al., 2000; Chakravarthi & Sundararajan, 2004, 2007b; Roy & Kumar, 2021) due to crustal deformations, glaciology (Crossley & Clarke, 1970; Tinto & Bell, 2011) and hydro‐geology (Alatorre‐Zamora & Campos‐Enriquez, 1991; Güntner et al., 2007) etc. The exploration study includes mining (Jaffal et al., 2010; Veiga & Gunson, 2020), hydrocarbon exploration (Rose et al., 2006; W. Li et al., 2016), cavity detection (Mochales et al., 2008; Saibi et al., 2019) etc. The gravitational inversion is a useful tool to interpret the gravity data for subsurface imaging.…”