Geometrical characterization of fracture systems using point clouds and SEFL-Software: example of the Añisclo anticline carbonate platform, Central Pyrenees

Abstract

Natural fracture systems contribute significantly to rock mass anisotropies. Characterizing these systems is essential for understanding processes of fluid flow, energy exploration and storage, slope stability or tectonic processes that can affect the permeability or compaction of the material, as well as reflect its temporal evolution. This work presents a set of automatic and supervised algorithms integrated into the open-access software solution SEFL, designed to characterize fracture systems using remote sensing data sets. The software implements various strategies to quantify geometrical parameters with deterministic or stochastic descriptions, facilitating a detailed characterization of the fracture system for numerical simulations. Geological outcrops provide direct access to the rock masses and discontinuities, offering analogies with materials that are otherwise inaccessible for its direct study. The digital acquisition of the terrain using high-resolution techniques, such as Terrestrial Laser Scanner (TLS) or photogrammetry to obtain point clouds, enabled post-field studies, particularly for fracture systems that are complex, inaccessible, or large in scale. Additionally, SEFL offers a tool based on the concept of fracture stratigraphy to identify mechanical units, which are essential frameworks for measuring and calculating fracture properties. This new methodology has been applied to study the fractured Eocene limestone outcrop at the hinge of the Añisclo anticline (South-Central Pyrenees, NE Iberia) which has been digitally acquired and characterized. SEFL output data interpretations revealed an outcrop characterized by over two thousand modelled fractures, five fracture sets, fourteen fracture stratigraphic units, and 1-2 fractures/m.