The effect of contact areas on seepage behavior in 3D rough fractures under normal stress

Abstract

The investigation of fluid flow in fractured rocks is a key issue in underground engineering. Reservoir sandstones as a case study, three specimens with different roughness using the Brazilian splitting were scanned to get the geometric morphology and aperture distribution, and the fractal dimension was introduced to characterize the fracture roughness. The flow experiments through the rough fractures subjected to different normal stresses were conducted to analyze the influence of the fractal dimension and the contact ratio on the nonlinear flow behavior, proving that the Forchheimer equation could better describe the flow nonlinearity. A modified Bandis model based on the experiments was proposed to calculate the max normal displacement of fracture under different normal stresses. Besides, a new model to forecast the nonlinear coefficient B was developed depending on the fractal dimension and the contact ratio, and a semi-empirical equation was employed to describe the critical Reynolds number. The influence of contact on the seepage path is simulated by COMSOL.

Seepage Characteristics of Shale Fracture and the Effect of Filling Sand under Normal Stress

“…The surface-developed interfacial area ratio Sdr and anisotropy degree Ka were used to analyze the influence of the relief degree and anisotropy on the seepage characteristics. The calculation formulas of each parameter were listed as follows [27][28][29]: The joint roughness coefficient JRC was introduced to study the influence of the fracture surface roughness on the seepage characteristics. The surface-developed interfacial area ratio S dr and anisotropy degree K a were used to analyze the influence of the relief degree and anisotropy on the seepage characteristics.…”

“…The surface-developed interfacial area ratio S dr and anisotropy degree K a were used to analyze the influence of the relief degree and anisotropy on the seepage characteristics. The calculation formulas of each parameter were listed as follows [27][28][29]:…”