Fuzzy Structure Element Method for Solving Fuzzy Trilinear Seepage Model of Shale Gas Reservoir

The seepage of shale gas reservoir is more complicated than that of the conventional energy because of its unique reservoir forming characteristics and physical properties. Accordingly, to achieve the large-scale exploitation of shale gas reservoir, the internal seepage characteristics of the reservoir should be clarified. Shale reservoirs are often accompanied by extreme heterogeneity and responsible variability. This phenomenon reveals that it is not reasonable to idealize the reservoir permeability as a fixed value. However, the conventional percolation model often idealizes the reservoir permeability to a specific amount. This will obviously lead to a reduction in the accuracy of the model. In the present study, the concept of fuzzy permeability was proposed. In other words, a fuzzy number was used to describe the reservoir permeability. Subsequently, the trilinear fuzzy seepage model was built and solved using the fuzzy structure element. To solve the practical application problem, a single numerical solution corresponding to the fuzzy solution set was found using the technique of defuzzification by the obtained fuzzy solution set. Finally, the fuzzy seepage model and the conventional seepage model were compared and analyzed by the numerical simulation.