New scaling of fractures in a giant carbonate platform from outcrops and subsurface

Abstract

We scale properties of fractures in the Late Kimmeridgian carbonate platform of the Arabian Shelf from outcrop and subsurface strata. The platform is flat-lying undeformed except from low-relief anticlines and domes, at which the strata hosts the world's most prolific petroleum reserves. The strata exhibit stylolites and veins, besides the dominant fractures. The fractures are opening-mode, steep, and forming major sets of NW–SE and NE–SW orientations. Faults are uncommon. Fracture abundance varies significantly across the platform, but it is constrained spatially by inherent variation in mechanical stratigraphy and temporally by anticlinal growth and isotope geochemistry. In early burial stages, the platform strata were slightly deformed by bed-parallel stylolites and mutually crosscutting veins. The strata fracturing increased by the anticlinal growth in the Late Cretaceous. Fracture spacing is an average of 2 m in the horizontal-bedded outcrops in Central Arabia and 0.30 m in the equivalent subsurface in a dome in Eastern Arabia. The dome is an end member in the deformation spectrum of the platform interior, with up to c. 5° structural dip and 2% dilational strain expressed in the doming and a few major faults. This finding indicates that carbonate platforms can reach fracture oversaturation under such a subtle tectonic extension.