Understanding Present-Day Stress in the Oil Patch and Its Implications for Subsurface Fluid Flow
Mark Tingay, Oliver Heidbach, Birgit Müller, and John Reinecker
World Stress Map Project, Karlsruhe, Germany
The present-day tectonic stress is a major control on subsurface fluid flow and is critical for optimizing production in waterflood operations. Fluid flow during injection is primarily focused in the present-day maximum horizontal stress (SHmax) direction and changes in pumping rates are most strongly observed in producer-injector pairs that are oriented in line with SHmax. Furthermore, there is a correlation between the strike of non-sealing faults and the SHmax orientation in several regions (e.g. North Sea and Brunei), indicating that these faults may have been breached, and columns lost, due to recent reactivation.
The World Stress Map Project has compiled a free public database of present-day stress information, consisting of over 14000 quality-ranked stress measurements. This global database provides fundamental insights into the state and origin of present-day stress in the crust. Present-day stresses at large scales (>1000 km) are controlled by plate boundaries forces, primarily from oceanic ridges and collision zones. However, many basin- and field-scale variations in stress orientation are observed within sedimentary basins, the origins of which are still poorly understood. Basin- and field-scale stress variations can result from far-field forces, basin geometry (e.g. the shape of deltaic wedges), geological structures (e.g. diapirs, faults) and mechanical contrasts (e.g. evaporites, overpressured shales). We discuss the occurrence and controls on present-day stresses in the oil patch and demonstrate the importance of stress information for production issues such as flood design and fracture stimulation, and exploration concerns such as fault seal breach and borehole instability.