--> Abstract: Evaluation of Vertical Permeability Anisotropy in Fractured Reservoirs, by G. J. Massonnat and E. Manisse; #90982 (1994).

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Abstract: Evaluation of Vertical Permeability Anisotropy in Fractured Reservoirs

G. J. Massonnat, E. Manisse

In fractured reservoir flow simulations, the vertical permeability anisotropy ratio (Kv/Kh) is one of the most poorly defined input parameters. In the best cases, this ratio is obtained from well-test interpretation with partial penetration models. More generally, it is considered as a parameter that can be varied to allow matching of actual data in flow simulations. However it is obtained, extrapolation of the anisotropy ratio away from the well is difficult due to the lack of geological basis in its estimation. A more rigorous association with the fracture descriptions and structural controls is clearly required.

This study presents a new approach based on stochastic fracture generation (Boolean technique) combined with upscaling techniques to calculate permeability tensors at different scales.

Several geological cases are tested ("homogeneous" or layered reservoir) as well as the influence of many parameters: fracture form index, fracture width, and matrix permeability. For each case, the influence of fracture density is evaluated; typical curves, anisotropy ratios vs. density of fractures, are obtained, whose general form is the same, thereby allowing comparisons to be made.

In general, the fracture form index (length/height ratio) is the

most significant parameter; it is also the least well documented in the literature. Initial results from outcrop studies proves that the hypothesis retained for the stochastic generation of fractures were in the range of variation. This result supports the typical curves obtained, and two field-case studies provide a validation of the method by closely matching the experimental data.

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