In the research of fractal cities, the fractal dimension is very important. It is used to describe the fractal character of the city. The authors have designed two approaches to calculate the fractal dimension by the ...In the research of fractal cities, the fractal dimension is very important. It is used to describe the fractal character of the city. The authors have designed two approaches to calculate the fractal dimension by the box-counting method through an example of Beijing, which are called the vector method and the grid method, respectively. The former calculates the fractal dimension through an intersecting analysis in ArcView; and the latter is carried out by programming in Matlab. They are compared from three aspects： the calculating process, the limits in use, and the results. As a result, the conclusion is made that there are merits and faults on both methods, and they should be chosen to use properly in practical situation.展开更多
In-situ thermal upgrading is used to tune the pore system in low-maturity oil shales. We introduce fractal dimension(D), form factor(ff) and stochastic entropy(H) to quantify the heating-induced evolution of pore morp...In-situ thermal upgrading is used to tune the pore system in low-maturity oil shales. We introduce fractal dimension(D), form factor(ff) and stochastic entropy(H) to quantify the heating-induced evolution of pore morphological complexity and azimuthal disorder and develop a model to estimate the impact on seepage capacity via permeability. Experiments are conducted under recreated in-situ temperatures and consider anisotropic properties—both parallel and perpendicular to bedding. Results indicate that azimuthal distribution of pores in the bedding-parallel direction are dispersed, while those in the bedding-perpendicular direction are concentrated. D values indicate that higher temperatures reduce the uniformity of the pore size distribution(PSD) in the bedding-parallel direction but narrow the PSD in the bedding-perpendicular direction. The greater ff(> 0.7) values in the bedding-parallel direction account for a large proportion, while the dominated in the bedding-perpendicular direction locates within 0.2-0.7, for all temperatures. The H value of the bedding-parallel sample remains stable at ~0.925 during heating, but gradually increases from 0.808 at 25℃ to 0.879 at 500℃ for the beddingperpendicular sample. Congruent with a mechanistic model, the permeability at 500℃ is elevated~1.83 times(bedding-parallel) and ~6.08 times(bedding-perpendicular) relative to that at 25℃—confirming the effectiveness of thermal treatment in potentially enhancing production from low-maturity oil shales.展开更多
文摘In the research of fractal cities, the fractal dimension is very important. It is used to describe the fractal character of the city. The authors have designed two approaches to calculate the fractal dimension by the box-counting method through an example of Beijing, which are called the vector method and the grid method, respectively. The former calculates the fractal dimension through an intersecting analysis in ArcView; and the latter is carried out by programming in Matlab. They are compared from three aspects： the calculating process, the limits in use, and the results. As a result, the conclusion is made that there are merits and faults on both methods, and they should be chosen to use properly in practical situation.
基金financially supported by the National Key Research and Development Program of China (Grant No. 2022YFE0129800)the National Natural Science Foundation of China (Grant No. 42202204)support from the G. Albert Shoemaker endowment。
文摘In-situ thermal upgrading is used to tune the pore system in low-maturity oil shales. We introduce fractal dimension(D), form factor(ff) and stochastic entropy(H) to quantify the heating-induced evolution of pore morphological complexity and azimuthal disorder and develop a model to estimate the impact on seepage capacity via permeability. Experiments are conducted under recreated in-situ temperatures and consider anisotropic properties—both parallel and perpendicular to bedding. Results indicate that azimuthal distribution of pores in the bedding-parallel direction are dispersed, while those in the bedding-perpendicular direction are concentrated. D values indicate that higher temperatures reduce the uniformity of the pore size distribution(PSD) in the bedding-parallel direction but narrow the PSD in the bedding-perpendicular direction. The greater ff(> 0.7) values in the bedding-parallel direction account for a large proportion, while the dominated in the bedding-perpendicular direction locates within 0.2-0.7, for all temperatures. The H value of the bedding-parallel sample remains stable at ~0.925 during heating, but gradually increases from 0.808 at 25℃ to 0.879 at 500℃ for the beddingperpendicular sample. Congruent with a mechanistic model, the permeability at 500℃ is elevated~1.83 times(bedding-parallel) and ~6.08 times(bedding-perpendicular) relative to that at 25℃—confirming the effectiveness of thermal treatment in potentially enhancing production from low-maturity oil shales.
