Fault-Guided Propagation of Production and Injection-Induced Stresses in North Texas

Summary The problem of fault reactivation in geologic basins with multiple faults and multiple wells producing and injecting different fluids must be addressed for a sustainable energy future. We have not been able to solve that problem by extrapolating our understanding of induced seismicity in simple systems with only one or two planar faults and with only one type of flow: injection or production. At the scale of a thousand square kilometers and decades of production and injection activities spread over hundreds of wells, many assumptions that are often used to simplify the problem cease to hold. This is the case in the Dallas-Fort Worth-Irving region of north Texas, USA, which experienced a sequence of earthquakes during 2008–2015. Production of gas and water from the Barnett shale formation and injection of waste water in the Ellenburger dolomite formation contributed to the 2008–2015 Dallas Fort Worth Airport (DFW) sequence, with epicenters relatively close to the wells. However, the 2015 Irving sequence is more difficult to comprehend because the epicenters are relatively far, 15–40 km, from the closest Ellenburger injector. Here, we unravel the modulation of fault stability and stress transfer mechanisms due to simultaneous production and injection activities in a region with complex faulting and stratigraphy. By linking a model of the Bend Arch-Fort Worth basin with a model of the Dallas-Fort Worth-Irving region, we find novel mechanisms of stress interaction and propagation across different stratigraphic and structural units. We present evidence to support the hypothesis of basin-scale injection’s contribution to the observed seismicity and, therefore, far-field triggering. In a novel application of the potency-magnitude scaling method to induced seismicity, we show the method’s superiority compared with the traditional moment tensor method in capturing the induced event time distribution and the event magnitude-frequency relationship.