Evaluation method and evaluation model of fractured shale permeability and construction method of evaluation model

Abstract

The invention provides a fractured shale permeability evaluation method, an evaluation model and a construction method thereof. The evaluation model evaluates the permeability of fractured shale by the evaluation method through the total permeability K of a shale reservoir, and the total permeability K of the shale reservoir is calculated through the shale permeability evaluation model; the construction method comprises the following steps: S1, deducing a permeability expression of a shale matrix based on a mixed fractal unit model and a Darcy law; S2, based on a fractal theory, establishing a fractal feature expression model of the opening and length of the natural fracture; S3, deriving a permeability expression of the natural fracture based on the model in the step S2 and the cubic law; S4, based on the permeability expression of the shale matrix and the permeability expression of the natural fracture, deducing the permeability expression of the whole shale reservoir. According to the method, the accuracy rate of predicting the permeability of the shale matrix and the natural fracture is up to 95% or above, and the evaluation cost is greatly saved.

Description

technical field [0001] The invention relates to the technical field of evaluation methods for shale permeability, in particular, to an evaluation method, an evaluation model and a construction method for fractured shale permeability. Background technique [0002] As we all know, shale is an unconventional gas-bearing reservoir, and its most special feature is the considerable development of natural fractures. Therefore, to evaluate the permeability of shale with fractures, we need to evaluate it from two aspects. On the one hand, the permeability of shale matrix needs to be evaluated, and on the other hand, the permeability of shale natural fractures needs to be evaluated. In the entire shale seepage system, due to the huge difference in permeability between natural fractures and matrix, the evaluation mechanisms are also quite different, so it is quite difficult to accurately evaluate the permeability of shale with natural fractures. [0003] For example, the patent appli...

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Problems solved by technology

The above-mentioned patent application documents all provide methods of how to use experiments to evaluate the effect of slick water on shale permeability, but they cannot be used to directly predict the permeability of shale matrix and natural fractures.

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