Fracture Network Characterization: From Active Mine Sites to Subsurface Geological Models

Accurate characterization of fracture networks is an important component in developing 3D geological models that predict the pathways for the interaction of surface waters and groundwater resources at mining sites. Natural resources managers dealing with source water protection, watershed management, and environmental compliance monitoring can benefit from the integration of new technologies to map discontinuities (fractures, joints, etc.) in geological reservoirs.

To better understand the character of natural fracture networks at an active quarry research site located in a structurally complex setting the authors collected a dataset comprised of fracture plane orientations, fracture intensity variations, geologic framework, and lithofacies. The application of unmanned aerial vehicles (UAVs), LIDAR (Light Detection and Ranging) and photogrammetry allowed for collection of a high fidelity, high confidence geotechnical dataset. The purpose of this research was to use an outcrop derived dataset to propagate fracture networks into the subsurface and analyze potential zones of high permeability contributing to water discharges. Multiple fracture sets were identified. Listric faults associated with negative flower structures show increased fracture intensity near the fault zones. Fracture sets remain consistent throughout the interbedded chalks, marls, and limestones. However, there is an apparent variability of fracture spacing associated with changes in lithology. In order to better analyze fracture patterns and fracture drivers a 3D geological model consisting of structural framework, lithofacies model, and discrete fracture network (DFN) was developed. The incorporation of high resolution data into subsurface reservoir models improved the mapping capability for fluid migration pathways. The resulting reservoir model contributed to a better understanding of surface water and groundwater interactions allowing for improved water resource management, source water protection, and mine planning.