Publications

Gravity data has been an important tool for petroleum exploration for many decades. With recent advances made through the introduction of gradiometry, a derivative of the gravity method, the technology has become more important than ever. Differing from the conventional gravity method which measures the potential gravity of a given location in the earth, gradiometry measures the rate of change of potential gravity within three axes of the Cartesian coordinate space. Since it measures the rate of change, the wavelength of the measurement is shorter meaning the data resolution is higher. In petroleum exploration, this higher resolution data makes it possible to not only identify the regional basin configurations but also the prospect and lead scale gravity anomalies. The gradiometry discussed in this paper is a full tensor gradiometer consisting of the nine tensor components which are particularly advantageous in revealing subsurface geology. The vertical component measurement, Tzz, measures the rate of change of gravity in vertical direction and is commonly used to identify both deep and shallow basement structures. The horizontal components, Txx or Tyy, measure the rate of change of gravity in the horizontal direction and are better suited to identify lateral discontinuities, lineament information and faulting. The combination of these tensor components yields a unique set of data which are not part of the conventional gravity acquisition. In central Kalimantan, a recently acquired airborne gradiometry survey shows how this type of survey can be valuable for frontier petroleum exploration. In an area where no existing seismic data are available, gradiometry data provides increased resolution of the subsurface which could not been achieved by conventional gravity. With conventional gravity, the resolution of the subsurface is coarse and subsurface trends are unclear. Using the gradiometry method, the resolution is improved to the point where highs and lows can clearly be identified and these structures are consistent with folding trends mapped at the surface. Moreover, this method clearly identifies fault and lineament trends which are consistent with similar mapped events on the surface. The strong agreement between gradiometry data and surface geological mapping increases the confidence to use this type of data in frontier basins for structure identification as well as advancing the exploration program in areas of limited data.