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Abstract: The Use of 3-D Seismic in the Understanding and Monitoring of Waterflooding in a Naturally Fractured Gas Reservoir

G. J. Massonnat, F. Umbhauer, F. Odonne

The reservoir of the Meillon field (France) consists of vuggy limestone with natural fractures. Three different sets of fractures occur in the reservoir. A few years after the field was put on production, several wells located 700 m above the initial gas/water contact started producing water.

Flow simulation with a dual porosity model indicated that water bypasses most of the matrix gas by flowing in the fractures. Assuming that the production mechanism was understood, the organization of open fractures in the reservoir was poorly determined since a 3-D seismic interpretation provided a structural picture of the field.

To improve the characterization of the field's dynamic behavior, a multidisciplinary study was performed to integrate results from well-test interpretation, production logging, core analyses and drilling fluid losses with production history, and 3-D seismic interpretation. A study of fractures at different scales showed that major faults (determined from seismic) are the dominant control on water flooding.

An analog model (with paraffin) of these largest scale fractures was built to simulate displacement relative to shortening linked to the actual maximum horizontal stress direction. It shows that different compartments displace one to the other dependently, and that the different sets play different roles for flow relative to the angle with the direction of shortening.

The conclusion of the study is the recommendation to drill horizontal wells perpendicular to the actual stress, inside compartments delimited by the major faults seen on seismic. This design should increase productivity and avoid early water breakthrough.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994