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The co-development of shale matrix laminations and nanopores leads to obvious anisotropy and pressure sensitivity of gas permeability, which has a large impact on gas reservoir simulation. The change curves of gas permeability and pressure in different directions of the test cube rock samples are carried out by using the pulse attenuation method permeability meter to study the gas flow ability of shale under overburden pressure conditions, evaluate the differences of shale laminations and matrix permeability, establish the pressure-sensitive equations of gas permeability in ultra-low-permeability rocks, and explore the differences and controlling factors of the shale gas seepage ability under the stratigraphic conditions.

(1) Permeability of granular samples

Samples with two levels of flow channels, matrix and fracture, can be tested by crushing them into granular samples, which can effectively eliminate the influence of fracture and obtain the permeability characteristics of matrix part. Our company can automatically and continuously carry out multi-pressure point granular permeability testing to obtain the characteristics of apparent permeability change with pressure, and the accuracy of the self-developed optimization solution method is higher than the algorithm recommended by GRI specification.

(2) Overburden pressure pulse permeability

Nanopore throats dominate in tight reservoir rocks, and nonlinear mechanisms such as slip effects make the apparent permeability vary with pore fluid pressure. In addition, for fracture development samples, the permeability has obvious anisotropy and changes with the effective stress. Comprehensively evaluating the apparent permeability changes with pore fluid pressure and effective stress in different directions of tight rocks can effectively improve the consistency between gas reservoir simulation and the actual reservoir.