2D Discrete Element Numerical Modelling of Carbonate Mechanical Stratigraphy to Generate Discrete Fracture Networks

Abstract

Natural fractures control primary fluid flow in low matrix permeability carbonate hydrocarbon reservoirs. Fracture stratigraphy partitions a rock succession based on quantifiable fracture parameters. Mechanical stratigraphy is defined by physical rock properties. However, mechanical stratigraphy can vary spatially and temporally due to lateral facies changes and post depositional diagenetic modification. Carbonate rocks are particularly susceptible to repeated episodes of diagenetic alteration. The consequence of this is that extant mechanical stratigraphy in outcrop and core/boreholes need not always correlate with fracture stratigraphy. Fracture stratigraphy is the product of tectonic history and the mechanical stratigraphy that existed when fracturing occurred). In this study mechanical variables are defined as the starting input parameters to construct geologically appropriate carbonate mechanical stratigraphies that are then forward modelled using a numerical 2D discrete element method to generate discrete fracture networks (DFN). DFN define fluid pathways, and may be classified into fracture stratigraphic units. This approach allows mechanical stratigraphy and fracture stratigraphy to be characterised separately.