State and origin of present-day stress fields in sedimentary basins

Abstract

The present-day stress field provides fundamental insight into the forces driving plate tectonics and intra-plate deformation. Furthermore, knowledge of the present-day stress field is essential in petroleum, geothermal and mining geomechanics applications such as the stability of boreholes and tunnels, and improving production through natural and induced fractures. The World Stress Map (WSM) Project has, for over 20 years, compiled a public global database of present-day tectonic stress information to determine and understand the state of stress in the Earth's lithosphere. The WSM database has revealed that plate-scale stress fields are controlled by forces exerted at plate boundaries (e.g. mid-ocean ridges, continental collision zones), commonly resulting in regional stress orientations sub-parallel to plate motion. However, the state and origin of present-day stress fields at smaller scales, such as within sedimentary basins, remains poorly understood in comparison. Detailed analysis of present-day stresses from within 70 sedimentary basins commonly reveals significant and complex variations in the present-day stress orientation, both across basins and within fields. For example, borehole breakouts in the North German Basin, Nile Delta and the Baram Delta province of northwest Borneo indicate broad regional rotations in the horizontal stress orientation. The present-day maximum horizontal stress orientations in the Gulf of Thailand are approximately north-south at the basin-scale (perpendicular to plate motion) and are perturbed locally to be sub-parallel to fault strike. The North Sea and Permian Basin of Texas display widely varying stress orientations between fields, with some neighbouring fields exhibiting perpendicular stress orientations. Basin- and field-scale stress fields result from the complex combination of numerous factors acting at different scales, including far-field forces (e.g. plate boundary forces), basin geometry (e.g. the shape of deltaic wedges), geological structures (e.g. diapirs, faults), mechanical contrasts (e.g. evaporites, overpressured shales, detachment zones), topography and deglaciation.