Fracture Modelling Using Seismic Based Fracture Intensity Volume, a Case Study in Middle East

Abstract

Abstract In this paper, a case study in a fractured carbonate reservoir is presented to demonstrate the approach of fracture modeling using fracture intensity volume. Fracture information described from well data and fracture prediction data generated from pre-stack seismic data are both used to establish discrete fracture model. FMI logs, mud losses, log interpretation results and production data are used to describe fracture characteristics on each well. Fractures are divided into 4 sets based on fracture scales, fracture dip and strike interpreted from FMI log. Fracture density logs for each set is generated separately, and each set of logs is used separately for fracture modeling. Seismic attribute of pre-stack azimuthal anisotropy is generated. This attribute volume is compared with FMI interpreted fracture density along wellbores for over 120 wells. The consistency of seismic attribute with well data is good for 90 per cent of wells. Hence the seismic attribute of pre-stack azimuthal anisotropy is used as fracture intensity volume for fracture prediction. A DFN model is established for each set of fractures using FMI interpreted fracture density as hard data and the seismic based fracture intensity volume as constraining data. Fracture properties are calculated based on discrete fracture network and calibrated by well test analysis. Introduction The characterization of fracture reservoirs is one of the biggest challenges for geoscientists. It is attractive to us not only because of the contribution that fractured reservoirs have made to oil and gas production, but also because of the complexity of fracture system. Many attempts have been made in the past to find ways predicting fractures. Geomechanical researchers try to construct a fracture mechanical model from tectonic history (Mace et al., 2004). Geologists try to characterize fractures from facies type, porosity, and reservoir zonation. Geophyisists try to forecast fracture system by seismic properties, acoustic impedance, and spectral imaging attributes (Creties Jenkins et al., 2009). In this paper, an integrated approach is used for fracture prediction and fracture modelling. Fracture features including fracture inclination, azimuth and density are summerized in each zone from image logs. Some normal seismic attributes such as curvatures, ant-tracking volume, coherence volume, are calculated. What is more, a fracture intensity volume based on pre-stack anisotropy attributes calculated by FRS software is used. By using fracture density logs calculated from image logs, an integrated fracture intensity volume is interpolated with the combined seismic volume as a trend. This fracture intensity volume is used for creating Discrete Fracture Network.