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Onshore shale oil is difficult to develop due to its special pore structure and low permeability characteristics. Artificial fracturing causes a large amount of fracturing fluid to intrude into the reservoir, resulting in a complex reservoir seepage pattern. Therefore, this paper aims to explore the changes in the reservoir at the macro and micro levels due to the interaction between fracturing fluids and shale oil reservoirs. For this, four rock samples from shale oil reservoirs and two fracturing fluids commonly used in the mine were used. Then, core repulsion, scanning electron microscopy, X-ray diffraction and CT scanning experiments were carried out successively. The following results were derived from our analyses. (1) Permeability of the rock samples was reduced by an average of 24.47% after replacement by fracturing fluid, while the experimental groups with larger fluid-grain sizes and well-developed fracture networks suffered more significant solid-phase damage and fluid-phase trapping. (2) Fracturing fluids have different effects on fractures at different scales; large fractures (>7.71 μm) were widened, while small fractures (<3.47 μm) were shrunk or even plugged. (3) Based on the water-sensitive effect, fracturing fluids can disperse and transport clay minerals, resulting in fluid-phase damage and an average decrease of 14.33% in clay content in the reservoir. (4) Analysis of the digital core model shows that fracturing fluid intrusion and retention can cause solid-phase damage to the reservoir matrix, with 38.14% and 60% damage to the pore and throat channels, respectively. This paper uses a combination of physical experiments and numerical analysis to investigate the interaction mechanism between fracturing fluids and shale oil reservoirs from both microscopic and macroscopic perspectives. Overall, the results of this study provide experimental support for future studies on the seepage characteristics of this type of reservoir and the design of fracturing construction schemes. [ABSTRACT FROM AUTHOR]

In previous studies, it is found that the frame and pore in porous media both possess the fractal geometric character. So the permeability and porosity models of bi-fractal porous media are derived based on the assumption that a porous media consists of fractal solid clusters and capillary bundles. The expressions of presented models are constituted by the fractal parameters of solid cluster and those of capillary bundle. Good agreement between model predictions and experimental data is obtained. This verifies the validity of the permeability and porosity models for bi-fractal porous media. The sensitive parameters that influence the permeability and porosity are specified, and their effects on the relationship between permeability and porosity are discussed. [ABSTRACT FROM AUTHOR]

Interest in tight gas reservoirs (TGR) has quickly spread worldwide. Most researches on the permeability stress-sensitivity of tight gas reservoirs mainly concentrated on experimental approach, physical modeling or pressure behavior analysis, while transient production rate performance does not attract much attention. This study developed a dual-porosity model of a horizontal well in fractured tight gas reservoirs considering the stress-sensitivity effect. The solution methods include variable substitution, perturbation technique, Laplace transformation, Sturm-Liouville eigenvalue theory, orthogonal transformation and numerical inversion. The results showed that the production rate decreases with the increasing of permeability modulus and the derivative curve will be warped up during the whole system late radial flow stage. The influences of other parameters are also analyzed. The work undertaken here has both theoretical and practical significance in predicting production performance and evaluating underground fluid transport in such formations. [ABSTRACT FROM AUTHOR]

Flow in porous media under stress is very important in various scientific and engineering fields. It has been shown that stress plays an important role in effect of permeability and porosity of porous media. In this work, novel predictive models for permeability and porosity of porous media considering stress sensitivity are developed based on the fractal theory and mechanics of materials. Every parameter in the proposed models has clear physical meaning. The proposed models are evaluated using previously published data for permeability and porosity measured in various natural materials. The predictions of permeability and porosity show good agreement with those obtained by the available experimental data and illustrate that the proposed models can be used to characterize the flow in porous media under stress accurately. [ABSTRACT FROM AUTHOR]

Transport phenomenon in porous media is essential in various scientific and engineering fields. The permeability and porosity of porous media serve important functions in transport phenomena. In this study, a complex model that considers the characters of pore microstructure and fluid in porous media is developed for the permeability and porosity of porous media. The flow rate expressions of this model are compared with those of previous models. As the proposed models relate the properties of fluids to the structural parameters of porous media, the various expressions of the developed model can reveal the phenomena of all types of fluid flow in a variety of porous media. The predicted permeabilities and porosities show good agreement with the available experimental data and illustrate that the proposed model can be used to characterize flow in porous media. [ABSTRACT FROM AUTHOR]