Developing A Two-scale Fracture Model And Its Application For Drilling Strategy In A Fractured Carbonate Reservoir

Abstract

In this study, we present an integrated approach to develop a two-scale fracture model for the Ordovician carbonate fractured reservoir in the Yubei area. The objective of this study is to provide new insights into the impact of fractures on oil production and to recommend drilling strategy. Fractures are characterized by using log data, 3D seismic attribute, borehole image logs and reservoir production data. Image logs illustrate that the dominant reservoir fractures trending in the NE direction parallel to the present-day maximum horizontal compressive stress and are consistent with the major fault system. The electrofacies generated with conventional logs are calibrated into different fracture units by using borehole image logs and reservoir dynamic data. The dynamic behavior of the complex matrix and fracture system is characterized for fracture units at wells. For layer bound diffuse fractures, the fracture properties are modeled statistically set by set with borehole image logs, fracture seismic facies volume representing degree of the fracturation and seismic geometric attribute. Fracture lineaments at the corridor scale are extracted directly from edge-enhanced seismic attribute. Fracture lineaments are cleaned and meshed to define their topology relationships to construct a comprehensive DFN (Discrete Fracture Network) model. Fracture networks are characterized deterministically, which constitute a unique fracture model on the reservoir scale. DFN model provides a geological representation how these fractures are spatially organized in the subsurface and how they may enhance or inhibit fluid flow. The final fracture model honored the two scale fracture models. Grid-cell permeability properties are derived from the two-scale fracture model. Based on the dynamic behavior of fracture units, fracture properties are calibrated against the dynamic data. Our results show that NE orientated fractures are open and conductive. The high productivity zones are characterized by high permeability located in the vicinity of faults. Enhanced oil recovery operations could be optimized using production wells oriented at high angles to NE orientated fractures.