Abstract: Evaluating Reservoir Fracture Distribution for Planned Miscible Gas Injection: Rhourde El Baguel Field, Algeria

BELFIELD, W. and M. CLONTS

An enhanced oil recovery project using miscible gas injection is planned for the Rhourde el Baguel field. The reservoir is a 300 meter thick Cambrian sandstone located at 3000 meters depth. Average matrix permeability is low (less than 1 to 10 md). However, some initial wells produced at rates of more than 10 MBOPD reflecting fracture enhancement. Understanding the nature and spatial distribution of the fracture system is important to evaluating the potential success of an EOR project.

Core examination indicates that fracturing is related to the presence of faults. Analysis of fault spatial distribution was based on engineering data rather than the few available 2-d seismic lines.

Fracture index (FI) relates formation permeability from pressure build-up tests to matrix permeability estimated from core data. A large FI indicates a permeable and well-connected fracture network. Low fracture index reflects either a low-permeability and/or poorly connected network. Fracture indices from 20 wells were established. Kriging was applied to values from these wells to estimate FI areal distribution. The results indicate that a substantial portion of the field has low fracture indices and natural fractures will probably not have an adverse impact in these areas. These results were supported by inferences from a pilot waterflood and interference test.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria