Most of the world's massive fields produce from naturally fractured vuggy carbonate reservoirs. However, modeling such reservoirs is a challenging task due to the co-existence of porous and free-flow domains over a wide range of scales. Realistic characterization of fractured vuggy reservoirs requires preservation of the geological structure and reproduction of patterns. In this study, we model a discrete fracture-vug network using microtomography and multiple-point geostatistics (MPG) modeling technique. For this purpose, one micro-CT scan image of a real core is used to generate a micro-scale geological model (the reference model and the first training image) having three structures; matrix, fractures, and vugs.

The structures in the reference model are also separated into matrix-fracture and matrix-vug to construct two other training images. The three training images are then used in MPG to generate multiple equiprobable models that mimic the original networks of the fractures and vugs. The models created using matrix-fracture and matrix-vug training images are combined into fracture-vug-matrix models by superimposing the fracture networks from the matrix-fracture models on their corresponding matrix-vug models. The spatial continuity, patterns reproduction, and flow performance of the generated models are compared with those of the reference model. The results show that, although the fracture patterns are not well reproduced, all the generated realizations preserved the structures and reproduced the spatial continuity of the reference model. In addition, the study revealed that the flow curves of the models generated with the introduced combined MPG method bracket better with the curve of the reference model than those of the direct MPG method. These results lay the foundation for future application of the presented method to field-scale modeling of naturally fractured vuggy reservoirs.

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