CHARACTERIZATION OF FRACTURED RESERVOIRS BY EFFECTIVE MEDIUM MODELLING AND JOINT INVERSION OF SEISMIC AND PRODUCTION DATA

摘要

This paper proposes a method for characterization of natural fractures in hydrocarbon reservoirs by quantitative integration of production data and (anisotropic) seismic attributes. The method is based on a unified model for the effective elastic and hydraulic properties of fractured porous media (which takes into account the effects of fracture geometry and fracture-fracture interaction in a consistent manner) and an Ensemble Kalman Filter (data assimilation) method (which provides uncertainties as well as mean values). In principle, our method can deal with fairly complex models of fractured reservoirs (e.g., involving multiple sets of vertical fractures that are embedded in a heterogeneous matrix). However, the initial inversion results presented here are based on a simplified model (involving a single set of horizontal fractures that are embedded in a homogeneous matrix). At the same time, the simplified model is both heterogeneous and anisotropic, since the fracture density was allowed to vary from grid block to grid block, in accordance with a (Gaussian) geostatistical model. An application to synthetic data suggests that one may obtain a significantly better estimate of the fracture density and permeability distributions within a fractured reservoir, by using time-lapse measurements of seismic attributes (the vertical P-wave acoustic impedance of each grid block) in addition to reservoir production data (bottomhole pressure, water cut, gas-oil ratio), in the dynamic reservoir characterization (history matching) process.