Visual Simulation of Soil-Structure Destruction with Seepage Flows

This paper introduces a method for simulating soil-structure coupling with water, which involves a series of visual effects, including wet granular materials, seepage flows, capillary action between grains, and dam breaking simulation. We develop a seepage flow based SPH-DEM framework to handle soil and water particles interactions through a momentum exchange term. In this framework, water is seen as a seepage flow through porous media by Darcy's law; the seepage rate and the soil permeability are manipulated according to drag coefficient and soil porosity. A water saturation-based capillary model is used to capture various soil behaviors such as sandy soil and clay soil. Furthermore, the capillary model can dynamically adjust liquid bridge forces induced by surface tension between soil particles. The adhesion model describes the attraction ability between soil surfaces and water particles to achieve various visual effects for soil and water. Lastly, this framework can capture the complicated dam-breaking scenarios caused by overtopping flow or internal seepage erosion that are challenging to simulate.

Quantitative assessment of hydraulic tortuosity of oil and gas reservoirs in Western Siberia based on capillarimetric studies

It is known that a capillary model with a given size pore channels distribution does not allow estimating the absolute reservoir permeability with sufficient accuracy. In this case, it is necessary to introduce a certain correction factor into the formula, which is called either the lithological factor or hydraulic tortuosity. The paper shows that the need for a correction factor appears mainly due to the capillary model inconsistency to the real geometry of the reservoir void space. In this regard, we propose to use the dumbbell model when calculating the absolute permeability, in which the filtering channels are represented by alternating pores and interporous narrowings. This paper presents a methodology for calculating the hydraulic tortuosity for reservoirs of Western Siberia based on the results of capillary studies, as well as based on the data from the capacitive properties study. Hydraulic tortuosity is explained by the process of expansion of current lines in the pores and their contraction in the interporous tubules of the rock. It is noted that the residual water leads to a narrowing of the pores’ open area and, accordingly, to a certain decrease in the hydraulic tortuosity.

A Fractal Model for Predicting the Relative Permeability of Rough-Walled Fractures

The relative permeability and saturation relationships through fractures are fundamental for modeling multiphase flow in underground geological fractured formations. In contrast to the traditional straight capillary model from porous media, the realistic flow paths in rough-walled fractures are tortuous. In this study, a fractal relationship between relative permeability and saturation of rough-walled fractures is proposed associated with the fractal characteristics of tortuous parallel capillary plates, which can be generalized to several existing models. Based on the consideration that the aperture distribution of rough-walled fracture can be represented by Gaussian and lognormal distributions, aperture-based expressions between relative permeability and saturation are explicitly derived. The developed relationships are validated by the experimental observations on Gaussian distributed fractures and numerical results on lognormal distributed fractures, respectively.