Wholesale Fracturing of Carbonate Rocks during Subsidence

Abstract

We constrain fracture networks in flat-lying shallow water carbonates producing fracture models at scale from cm-to tens of meters over a large area of several tens of km2.Imaging is integrated with structural observation on the ground and isotope studies on the vein infill. Structures observed are sub-vertical mode I and hybrid veins displaying a conjugate pattern, sub-vertical stylolites and sub-horizontal stylolites. The structures formed during subsidence through a stress field characterized by the presence of a significant sub-horizontal tectonic stress. Little deformation occurred in the uppermost 400-500m. Wholesale fracturing affected the carbonates at depths between 500 and 800m resulting in a pervasive network of open fractures and stylolites. Increasing development of sub-horizontal stylolites generated the calcite which eventually sealed the fractures. Using the acquired fracture network, we test the impact of different aperture models on flow simulations