Are open-source aerial images useful for fracture network characterisation? Insights from a multi-scale approach in the Zagros Mts.

Abstract

Multi-scale fracture characterisation in reservoir analogues is crucial for determining orientation clustering, length scaling laws, abundance, and topology of the fracture network, all of which are essential for modelling flow of geofluids. In this study, we examine the application of Bing Maps imagery for fracture network analysis in the Kuh-e-Asmari anticline (Zagros Mountains, Iran), a scarcely vegetated area which is a good outcropping analogue for fractured reservoirs. Image-derived fracture characterisation is conducted at three distinct scales (1:50,000, 1:5,000 and 1:500) using the NetworkGT plugin in QGIS and was compared with structural data collected in the field (i.e. scan lines). The results reveal a scale dependency, with the advantages and disadvantages of each scale summarised as follows. The 1:50,000 is the only spatially continuous dataset. The 1:5,000 dataset, potentially spatially continuous, enables the analysis of fracture and connectivity distribution in great detail, emphasising strongly fractured/connected elongated zones, which may represent damage zones of known, previously mapped fault strands. The 1:500 scale does not ensure the spatial continuity of the dataset; however, similar to scan lines, it can perform detailed analyses of the fracture network in potentially interesting areas. We conclude that structural field surveys can be combined with multi-scale mapping on aerial images to better define the length and abundance distribution of fractures.