Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Stress Rotations Around Salt Diapirs: Examples from the Gulf of Mexico Delta Systems, USA
(1) for Tectonics, Resources and Exploration (TRaX), University of Adelaide, Adelaide, SA, Australia.
(2) Deep Exploration Technologies Cooperative Research Centre, Adelaide, SA, Australia.
(3) JRS Petroleum Research, Adelaide, SA, Australia.
Delta—deepwater fold-thrust belts (DDWFTBs) are linked systems of extension and compression. Gravitational potential, imparted by large accumulations of sediment on the delta top, generate margin-parallel extensional stresses that drive down-dip margin-normal compressional stresses in the deepwater fold-thrust belt (or delta toe). This margin-parallel, margin-normal stress pattern has been observed in a number of DDWFTBs worldwide, namely, the Baram, Godavari and Nile DDWFTBs. However, several stress orientations on the Gulf of Mexico delta top, determined from petroleum well data, show up to 45° rotations from the expected margin-parallel orientations.
Three-dimensional seismic data from three areas across the Gulf of Mexico delta top demonstrate the presence of salt diapirs piercing the overlying deltaic sediments. Many of these salt diapirs are adjacent to wells that demonstrate stress orientations that are rotated from the expected margin-parallel orientations. The contrast between geomechanical rock properties of the deltaic sediments and adjacent salt diapirs result in the rotation of the in-situ stress field. The maximum horizontal stresses are rotated to become parallel to the interface between the ‘soft’ salt diapirs and the ‘stiff’ deltaic sediments.
Understanding the stress orientations is vital to petroleum exploration and development (e.g. fault reactivation, fracture stimulation, water-flood design and wellbore stability). Therefore, we use 3D seismic data and 3D numerical modelling to better predict stress orientations across the Gulf of Mexico.