Pore structure characteristics are important to oil and gas exploration in complex low-permeability reservoirs. Using multifractal theory and nuclear magnetic resonance （NMR）, we studied the pore structure of low-pe...Pore structure characteristics are important to oil and gas exploration in complex low-permeability reservoirs. Using multifractal theory and nuclear magnetic resonance （NMR）, we studied the pore structure of low-permeability sandstone rocks from the 4th Member （Es4） of the Shahejie Formation in the south slope of the Dongying Sag. We used the existing pore structure data from petrophysics, core slices, and mercury injection tests to classify the pore structure into three categories and five subcategories. Then, the T2 spectra of samples with different pore structures were interpolated, and the one- and three-dimensional fractal dimensions and the multifractal spectrum were obtained. Parameters a （intensity of singularity） andf（a） （density of distribution） were extracted from the multifractal spectra. The differences in the three fractal dimensions suggest that the pore structure types correlate with a andf（a）. The results calculated based on the multifractal spectrum is consistent with that of the core slices and mercury injection. Finally, the proposed method was applied to an actual logging profile to evaluate the pore structure of low-permeability sandstone reservoirs.展开更多
Cerebral artery stenosis is an important cause and risk factor to ischemic cerebrovascular disease. This paper describes a simple and effective method for the detection of cerebral artery stenosis in magnetic resonanc...Cerebral artery stenosis is an important cause and risk factor to ischemic cerebrovascular disease. This paper describes a simple and effective method for the detection of cerebral artery stenosis in magnetic resonance angiography(MRA).Because of the complex structure of the brain blood vessels, the fast and accurate segmentation method is needed. Here, we used the information of the maximum intensity projection(MIP) image to get 3 D vascular structure. As skeleton was one of useful measures for charactering region-based shape features, we extracted 3 D-skeleton of blood vessels by using fast marching method(FMM). Finally, the accurate cross-sectional areas based on cerebrovascular skeleton were computed to determine the location and extent of vascular stenosis. The results showed that our method could effectively detect the cerebral artery stenosis.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41202110)Open Fund of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)(Grant No.PLN201612)+1 种基金the Applied Basic Research Projects in Sichuan Province(Grant No.2015JY0200)Open Fund Project from Sichuan Key Laboratory of Natural Gas Geology(Grant No.2015trqdz07)
文摘Pore structure characteristics are important to oil and gas exploration in complex low-permeability reservoirs. Using multifractal theory and nuclear magnetic resonance （NMR）, we studied the pore structure of low-permeability sandstone rocks from the 4th Member （Es4） of the Shahejie Formation in the south slope of the Dongying Sag. We used the existing pore structure data from petrophysics, core slices, and mercury injection tests to classify the pore structure into three categories and five subcategories. Then, the T2 spectra of samples with different pore structures were interpolated, and the one- and three-dimensional fractal dimensions and the multifractal spectrum were obtained. Parameters a （intensity of singularity） andf（a） （density of distribution） were extracted from the multifractal spectra. The differences in the three fractal dimensions suggest that the pore structure types correlate with a andf（a）. The results calculated based on the multifractal spectrum is consistent with that of the core slices and mercury injection. Finally, the proposed method was applied to an actual logging profile to evaluate the pore structure of low-permeability sandstone reservoirs.
文摘Cerebral artery stenosis is an important cause and risk factor to ischemic cerebrovascular disease. This paper describes a simple and effective method for the detection of cerebral artery stenosis in magnetic resonance angiography(MRA).Because of the complex structure of the brain blood vessels, the fast and accurate segmentation method is needed. Here, we used the information of the maximum intensity projection(MIP) image to get 3 D vascular structure. As skeleton was one of useful measures for charactering region-based shape features, we extracted 3 D-skeleton of blood vessels by using fast marching method(FMM). Finally, the accurate cross-sectional areas based on cerebrovascular skeleton were computed to determine the location and extent of vascular stenosis. The results showed that our method could effectively detect the cerebral artery stenosis.
