Hydraulic Fracture Growth Geometries in Unconventional Reservoirs: Closing Gaps among Perceptions, Predictions, and Reality

English Abstract:

One of the challenges to informing the current discussion on the economic and environmental sustainability of the process of extracting hydrocarbons from unconventional reservoirs is the preponderance of gaps among our perceptions, model predictions, and the real geometries of hydraulic fractures. The basic problem starts with the fact that real geometries are never fully observed at reservoir scale. However, a synthesis of mapping data from mine-through experiments, monitored field experiments, natural and laboratory analogues, and coupled models that account for the role of the pre-existing fracture network on hydraulic fracture growth do provide an emerging picture, albeit still far from complete, of the basic drivers that lead to complex, network-like hydraulic fracture geometries in some cases but not in others. A similar synthesis is able to give at least a rudimentary understanding of conditions in which hydraulic fractures are expected to be well-contained within the targeted reservoir layer. Furthermore, there is a growing, yet far from complete, understanding of the dynamics that determine whether the idealized uniform division of injected fluid among multiple possible entry points can be achieved. But in spite of what is understood, or at least thought to be understood, about the drivers of various hydraulic fracture geometries, idealized and/or artistically-rendered sketches dominate the images of hydraulic fracture geometry that underpin not only the current public and technical discussions, but in many cases also the fracture geometries that are used as inputs to reservoir simulators upon which well design and production decisions hinge. This talk will synthesize data with modeling results with the aim of bringing closer alignment between the perceived and actual growth geometries achieved in hydraulic fracturing stimulations of unconventional reservoirs.