Target delineation using Full Tensor Gravity Gradiometry data

Abstract

FTG Gravity data acquired on airborne and marine platforms measure 5 independent Tensor components that collectively describe a total gravity field. The components capture unique signature patterns related to specific attributes of target geology that when collectively interpreted enable detailed imagery of the target itself in terms of geometry, composition and depth of burial. The horizontal tensor components Txx, Tyy, Txy, Txz & Tyz are commonly used to identify and map lineaments associated with structural and / or stratigraphic changes or target geometry in a survey area. The vertical tensor component, Tzz, is used to estimate depth and predict compositional information related to target geology. However, these components have traditionally been interpreted separately from one another and often run the risk of missing out on key information. This paper describes application of a semi-automated approach that combines the individual components into singular representations to best extract the signature pattern common to all components as revealed by the underlying geology. The examples presented are taken from an Air-FTG® survey onshore Brazil to image the structural framework and identify target geology ahead of a seismic programme, and a Marine-FTG® survey offshore Norway to resolve salt body geometries imaging areas of overhang development. The resultant interpretation enables the end-user to fast-track the exploration initiative by quickly evaluating target geology for detailed follow-up.