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Investigation of shale gas microflow with the Lattice Boltzmann method

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Petroleum Science 2015年第1期12卷 96-103页

作者： xiao-ling Zhang li-zhi xiao Long Guo Qing-Ming Xie State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum Key Laboratory of Shale Gas Exploration Ministry of Land and Resources Chongqing Institute of Geology and Mineral Resources

In contrast to conventional gas-bearing rocks, gas shale has extremely low permeability due to its nano- scale pore networks. Organic matter which is dispersed in the shale matrix makes gas flow characteristics more complex. The traditional Darcy＇s law is unable to estimate matrix permeability due to the particular flow mechanisms of shale gas. Transport mechanisms and influence factors are studied to describe gas transport in extremely tight shale. Then Lattice Boltzmann simulation is used to establish a way to estimate the matrix permeability numerically. The results show that net desorption, diffu- sion, and slip flow are very sensitive to the pore scale. Pore pressure also plays an important role in mass fluxes of gas. Temperature variations only cause small changes in mass fluxes. The Lattice Boltzmann method can be used to study the flow field in the micropore spaces and then provides numerical solutions even in complex pore structure models. Understanding the transport characteristics and establishing a way to estimate potential gas flow is very important to guide shale gas t＇eserve estimation and recovery schemes.

关键词： Shale gas Permeability Adsorption Desorption Diffusion Slip effect

Influences of spin on the properties of a weak-coupled magnetopolaron in quantum dot

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Optoelectronics Letters 2008年第4期4卷 307-310页

作者： li zhi-xin xiao Jing-lin Department of Mathematics and Physics Hebei Normal University of Science ＆ Technology Qinhuangdao 066004 China

Considering the influences of the spin on the ground state energy,the properties of a weak-coupled magnetopolaron in quantum dots are studied by using a linear combination operator and unitary transformation *** numer... 详细信息

关键词：晶体量子点弱耦合磁极化子旋转基态能量

An Improved Car-Following Model for Multiphase Vehicular Traffic Flow and Numerical Tests

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Communications in Theoretical Physics 2006年第2X期46卷 367-373页

作者： li zhi-Peng GONG xiao-Bo liU Yun-Cai Institute of Image Processing and Pattern Recognition Shanghai Jiaotong University Shanghai 200240 China

This paper attempts to introduce an improved difference model that modifies a car-following model, which takes the next-nearest-neighbor interaction into account. The hnprovement of this model over the previous one lies in that it performs more realistically in the dynamical motion for small delay time. The traffic behavior of the improved model is investigated with analytic and numerical methods with the finding that the new consideration could further stabilize traffic flow. And some simulation tests verify that the proposed model can demonstrate some complex physical features observed recently in real traffic such as the existence of three phases： free flow, coexisting flow, and jam flow; spontaneous formation of density waves; sudden flow drop in flow-density plane; traffic hysteresis in transition between the free and the coexisting flow. Furthermore, th.e improved model also predicts that the stable state to relative density in the coexisting flow is insusceptible to noise.

关键词： car-following models density waves traffic flow

Identification of low-resistivity-low-contrast pay zones in the feature space with a multi-layer perceptron based on conventional well log data

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Petroleum Science 2022年第2期19卷 570-580页

作者： Lun Gao Ran-Hong Xie li-zhi xiao Shuai Wang Chen-Yu Xu State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum(Beijing)Beijing102249China

In the early exploration of many oilfields,low-resistivity-low-contrast(LRLC)pay zones are easily overlooked due to the resistivity similarity to the water *** identification methods are model-driven and cannot yield satisfactory results when the causes of LRLC pay zones are *** this study,after analyzing a large number of core samples,main causes of LRLC pay zones in the study area are discerned,which include complex distribution of formation water salinity,high irreducible water saturation due to micropores,and high shale ***,different oil testing layers may have different causes of LRLC pay *** a result,in addition to the well log data of oil testing layers,well log data of adjacent shale layers are also added to the original dataset as reference *** densitybased spatial clustering algorithm with noise(DBSCAN)is used to cluster the original dataset into 49 clusters.A new dataset is ultimately projected into a feature space with 49 *** new dataset and oil testing results are respectively treated as input and output to train the multi-layer perceptron(MLP).A total of 3192 samples are used for stratified 8-fold cross-validation,and the accuracy of the MLP is found to be 85.53%.

关键词： Low-resistivity-low-contrast(LRLC)pay zones Conventional well logging Machine learning DBSCAN algorithm Multi-layer perceptron

A machine learning framework for low-field NMR data processing

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Petroleum Science 2022年第2期19卷 581-593页

作者： Si-Hui Luo li-zhi xiao Yan Jin Guang-zhi liao Bin-Sen Xu Jun Zhou Can liang College of Artificial Intelligence and College of Petroleum Engineering China University of PetroleumBeijing102249China China National Logging Corporation Xi©anShaanxi 710076China Changzhou Institute of Technology ChangzhouJiangsu213000China

Low-field(nuclear magnetic resonance)NMR has been widely used in petroleum industry,such as well logging and laboratory rock core ***,the signal-to-noise ratio is low due to the low magnetic field strength of NMR tools and the complex petrophysical properties of detected *** the noise and highlighting the available NMR signals is very important for subsequent data *** denoising methods are normally based on fixed mathematical transformation or handdesign feature selectors to suppress noise characteristics,which may not perform well because of their non-adaptive performance to different noisy *** this paper,we proposed a“data processing framework”to improve the quality of low field NMR echo data based on dictionary *** learning is a machine learning method based on redundancy and sparse representation *** information in noisy NMR echo data can be adaptively extracted and reconstructed by dictionary *** advantages and application effectiveness of the proposed method were verified with a number of numerical simulations,NMR core data analyses,and NMR logging data *** results show that dictionary learning can significantly improve the quality of NMR echo data with high noise level and effectively improve the accuracy and reliability of inversion results.

关键词： Dictionary learning Low-field NMR Denoising Data processing T_(2)distribution

A new method for fluid identification and saturation calculation of low contrast tight sandstone reservoir

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Petroleum Science 2024年第5期21卷 3189-3201页

作者： Shuai Wang Ran-Hong Xie Guo-Wen Jin Jiang-Feng Guo li-zhi xiao State Key Laboratory of Petroleum Resources and Engineering China University of Petroleum(Beijing)Beijing102249China

The resistivity difference between oil and gas layers and the water layers in low contrast tight sandstone reservoirs is subtle. Fluid identification and saturation calculation based on conventional logging methods are facing challenges in such reservoirs. In this paper, a new method is proposed for fluid identification and saturation calculation in low contrast tight sandstone reservoirs. First, a model for calculating apparent formation water resistivity is constructed, which takes into account the influence of shale on the resistivity calculation and avoids apparent formation water resistivity abnormal *** on the distribution of the apparent formation water resistivity obtained by the new model, the water spectrum is determined for fluid identification in low contrast tight sandstone *** this, according to the average, standard deviation, and endpoints of the water spectrum, a new four-parameter model for calculating reservoir oil and gas saturation is built. The methods proposed in this paper are applied to the low contrast tight sandstone reservoirs in the Q4 formation of the X53 block and X70 block in the south of Songliao Basin, China. The results show that the water spectrum method can effectively distinguish oil-water layers and water layers in the study area. The standard deviation of the water spectrum in the oil-water layer is generally greater than that in the water layer. The new four-parameter model yields more accurate oil and gas saturation. These findings verify the effectiveness of the proposed methods.

关键词： Low contrast reservoirs Fluid identification Saturation calculation Water spectrum method Conventional logging

Low-field NMR inversion based on low-rank and sparsity restraint of relaxation spectra

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Petroleum Science 2022年第6期19卷 2741-2756页

作者： Si-Hui Luo li-zhi xiao Yan Jin Jiang-Feng Guo xiao-Bo Qu Zhang-Ren Tu Gang Luo Can liang College of Artificial Intelligence and College of Petroleum Engineering China University of PetroleumBeijing102249China State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing102249China School of Electronic Science and Engineering(National Model Microelectronics College) Xiamen UniversityFujian361005China School of Electronic Science and Engineering National Model Microelectronics College Xiamen University Changzhou Institute of Technology ChangzhouJiangsu213000China

In this paper,we proposed a novel method for low-field nuclear magnetic resonance(NMR)inversion based on low-rank and sparsity restraint(LRSR)of relaxation spectra,with which high quality construction is made possible for one-and two-dimensional low-field and low signal to noise ratio NMR *** this method,the low-rank and sparsity restraints are introduced into the objective function instead of the smoothing *** low-rank features in relaxation spectra are extracted to ensure the local characteristics and morphology of *** sparsity and residual term are contributed to the resolution and precision of spectra,with the elimination of the redundant relaxation *** process of the objective function is designed with alternating direction method of multiples,in which the objective function is decomposed into three subproblems to be independently *** optimum solution can be obtained by alternating iteration and updating *** first,numerical simulations are conducted on synthetic echo data with different signal-to-noise ratios,to optimize the desirable regularization parameters and verify the feasibility and effectiveness of proposed ***,NMR experiments on solutions and artificial sandstone samples are conducted and analyzed,which validates the robustness and reliability of the proposed *** results from simulations and experiments have demonstrated that the suggested method has unique advantages for improving the resolution of relaxation spectra and enhancing the ability of fluid quantitative identification.

关键词： Low-field NMR Inversion method Low-rank and sparsity restraint Relaxation spectra Data processing

Positron emission tomography imaging for the assessment of mild traumatic brain injury and chronic traumatic encephalopathy:recent advances in radiotracers

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Neural Regeneration Research 2022年第1期17卷 74-81页

作者： Chu-Xin Huang Yan-Hui li Wei Lu Si-Hong Huang Meng-Jun li li-zhi xiao Jun liu Department of Radiology the Second Xiangya Hospital of Central South UniversityChangshaHunan ProvinceChina Department of Neurology the Second Xiangya Hospital of Central South UniversityChangshaHunan ProvinceChina PET-CT Center the Second Xiangya Hospital of Central South UniversityChangshaHunan ProvinceChina

A chronic phase following repetitive mild traumatic brain injury can present as chronic traumatic encephalopathy in some cases,which requires a neuropathological examination to make a definitive *** emission tomography(PET)is a molecular imaging modality that has high sensitivity for detecting even very small molecular changes,and can be used to quantitatively measure a range of molecular biological processes in the brain using different radioactive *** changes have also been reported in patients with different forms of traumatic brain injury,especially mild traumatic brain injury and subsequent chronic traumatic ***,PET provides a novel approach for the further evaluation of mild traumatic brain injury at molecular *** this review,we discuss the recent advances in PET imaging with different radiotracers,including radioligands for PET imaging of glucose metabolism,tau,amyloid-beta,γ-aminobutyric acid type A receptors,and neuroinflammation,in the identification of altered neurological *** novel radiolabeled ligands are likely to have widespread clinical application,and may be helpful for the treatment of mild traumatic brain ***,PET functional imaging with different ligands can be used in the future to perform largescale and sequential studies exploring the time-dependent changes that occur in mild traumatic brain injury.

关键词： amyloid-β chronic traumatic encephalopathy flumazenil fluorodeoxyglucose mild traumatic brain injury positron emission tomography tau protein traumatic brain injury

Research advances in the study of Pistacia chinensis Bunge, a superior tree species for biomass energy

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Forestry Studies in China 2007年第2期9卷 164-168页

作者： li Hong-lin Zhang zhi-xiang lin Shan-zhi li xiao-xu College of Biological Sciences and Biotechnology Beijing Forestry University Beijing 100083 P. R. China

As a renewable energy, biomass energy has aroused wide attention and studies of this issue have become a hot topic throughout the world. Pistacia chinensis Bunge （Anacardiaceae） is a superior species for biomass energy with high oil content in seeds and wide geographic distribution. It is a dioeciously, deciduous arbor, flowering from March to April and bearing fruits from September to November. The classification, regional distribution and biological characteristics ofP chinensis are stated in this paper, then, research advances in the growth, breeding and physiology of this species are summarized. The problems in present studies are broached. Finally, a future direction for research is proposed.

关键词： Pistacia chinensis Bunge biomass energy of forest