William C. Belfield¹

(1) Symplectic Reservoir Technology, Plano, TX

ABSTRACT: The Stochastic Continuum Cosimulation Approach to Predicting Spatial Distribution of Natural Fracturing in Porous Reservoirs

One goal in characterizing naturally fractured reservoirs is to predict the spatial distribution and properties of the fracture system in the interwell regions of the reservoir. A stochastic continuum approach avoids many of the intrinsic problems associated with discrete fracture models. In this approach matrix and fractures are treated as a single continuous system. Spatial distribution of fracturing in the reservoir is inferred with structural curvature as estimated from 3-D seismic. The impact of fracturing upon flow at the wellbore is measured by a 'fracture productivity index (FPI)', where FPI=kh(total)/kh(matrix). The FPI is a measure of effective permeability and reflects the amplification of matrix permeability by fracturing.

Collocated cokriging is used to relate FPI and curvature. Sequential Gaussian cosimulations in one test reservoir indicate that FPI is spatially heterogeneous. Infill drilling in areas with predicted high FPI values have wells with extensive lost circulation and/or high-rates of inflow. Wells in other areas do not exhibit these characteristics. Full-field transport modeling can be done either by assigning dual-porosity parameters or using discrete fracture models in those areas with high FPI values.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado