Monitoring Reservoir Deformation on Land - Evidence for Fault Re-Activation from Microseismic, InSAR, and GPS Data

Three different types of areal reservoir monitoring data have been acquired over a compacting reservoir in Oman: (i) microseismic, (ii) GPS, and (iii) InSAR. The aim of this project is to demonstrate the value of these data for reservoir management.<br><br>More than 7,500 microseismic events were located during two years of continuous monitoring from five observation wells, 1 - 2 km apart. Microseismic events predominately occur on a specific subset of pre-existing faults. More than 2 years of near-continuous GPS monitoring are now available from a network of 50 sites. The pattern of horizontal displacements reveals a clear asymmetric pattern diagnostic of slip occurring on some buried portion of the main fault system. This is due to differential compaction on either side of the fault within the gas reservoir. Interferometric Synthetic Aperture Radar satellite images over the field show a sequence of increasing strain localisation above a specific fault segment that suddenly becomes a new centre for microseismic activity.<br><br>Together these data lead to the view that large-scale fault reactivation is occurring above, within, and below the depleting gas reservoir. To date, no well failures have been attributed to reservoir deformation. Microseismic and geodetic monitoring of the field is continuing.<br>