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Non-Darcy flow in oil accumulation (oil displacing water) and relative permeability and oil saturation characteristics of low-permeability sandstones

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Petroleum Science 2010年第1期7卷 20-30页

作者： Zeng Jianhui Cheng Shiwei Kong Xu Guo Kai Wang Hongyu State Key laboratory of Petroleum Resources and Prospecting China University of Petroleum Beijing 102249 China School of Natural Resources and Information Technology China University of Petroleum Beijing 102249 China CNPC Greatwall Drilling Company Beijing 100101 China

Hydrocarbon resources in low-permeability sandstones are very abundant and are extensively distributed. Low-permeability reservoirs show several unique characteristics, including lack of a definite trap boundary or caprock, limited buoyancy effect, complex oil-gas-water distribution, without obvious oil-gas-water interfaces, and relatively low oil （gas） saturation. Based on the simulation experiments of oil accumulation in low-permeability sandstone （oil displacing water）, we study the migration and accumulation characteristics of non-Darcy oil flow, and discuss the values and influencing factors of relative permeability which is a key parameter characterizing oil migration and accumulation in low-permeability sandstone. The results indicate that： 1） Oil migration （oil displacing water） in low- permeability sandstone shows non-Darcy percolation characteristics, and there is a threshold pressure gradient during oil migration and accumulation, which has a good negative correlation with permeability and apparent fluidity; 2） With decrease of permeability and apparent fluidity and increase of fluid viscosity, the percolation curve is closer to the pressure gradient axis and the threshold pressure gradient increases. When the apparent fluidity is more than 1.0, the percolation curve shows modified Darcy flow characteristics, while when the apparent fluidity up＂ non-Darcy percolation curve; 3） Oil-water is less than 1.0, the percolation curve is a ＂concave- two-phase relative permeability is affected by core permeability, fluid viscosity, apparent fluidity, and injection drive force; 4） The oil saturation of low- permeability sandstone reservoirs is mostly within 35%-60%, and the oil saturation also has a good positive correlation with the permeability and apparent fluidity.

关键词： Non-Darcy flow relative permeability oil saturation low-permeability sandstone

Micro-mechanisms of residual oil mobilization by viscoelastic fluids

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Petroleum Science 2008年第1期5卷 56-61页

作者： Zhang Lijuan Yue Xiang＇an Guo Fenqiao Key laboratory of Petroleum Engineering Ministry of Education China University of Petroleum Beijing 102249 China Development Department Sinopec Exploration and Production Research Institute Beijing 100083 China

Four typical types of residual oil, residual oil trapped in dead ends, oil ganglia in pore throats, oil at pore corners and oil film adhered to pore walls, were studied. According to main pore structure characteristics and the fundamental morphological features of residual oil, four displacement models for residual oil were proposed, in which pore-scale flow behavior of viscoelastic fluid was analyzed by a numerical method and micro-mechanisms for mobilization of residual oil were discussed. Calculated results indicate that the viscoelastic effect enhances micro displacement efficiency and increases swept volume. For residual oil trapped in dead ends, the flow field of viscoelastic fluid is developed in dead ends more deeply, resulting in more contact with oil by the displacing fluid, and consequently increasing swept volume. In addition, intense viscoelastic vortex has great stress, under which residual oil becomes small oil ganglia, and finally be carried into main channels. For residual oil at pore throats, its displacement mechanisms are similar to the oil trapped in dead ends. Vortices are developed in the depths of the throats and oil ganglia become smaller. Besides, viscoelastic fluid causes higher pressure drop on oil ganglia, as a driving force, which can overcome capillary force, consequently, flow direction can be changed and the displacing fluid enter smaller throats. For oil at pore corners, viscoelastic fluid can enhance displacement efficiency as a result of greater velocity and stress near the corners. For residual oil adhered to pore wall, viscoelastic fluid can provide a greater displacing force on the interface between viscoelastic fluid and oil, thus, making it easier to exceed the minimum interfacial tension for mobilizing the oil film.

关键词： Viscoelastic chemical flooding displacement mechanism residual oil swept volume

Formation mechanism of carbonate cemented zones adjacent to the top overpressured surface in the central Junggar Basin,NW china

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Science china Earth Sciences 2010年第4期53卷 529-540页

作者： YANG Zhi1,2,ZOU CaiNeng1,3,HE Sheng2,LI QiYan1,HE ZhiLiang3,WU HengZhi5,CAO Feng1,MENG XianLong4,WANG FuRong2 & XIAO Qilin21 State Key laboratory of EOR,Research Institute of Petroleum Exploration & Development,Petrochina,beijing 100083,china 2 Key laboratory of Tectonics and Petroleum Resources of Ministry of Education,china university of Geosciences,Wuhan 430074,china 3 State Key laboratory of EOR,Research Institute of Petroleum Exploration & Development,Petrochina,beijing 100083,china 4 Research Institute of Petroleum Exploration and Production,SINOPEC,beijing 100083,china 5 Southwest Branch Company,SINOPEC,Chengdu 610051,china State Key laboratory of EOR Research Institute of Petroleum Exploration & Development PetroChina Beijing China Key laboratory of Tectonics and Petroleum Resources of Ministry of Education China University of Geosciences Wuhan China State Key laboratory of EOR Research Institute of Petroleum Exploration & Development Petrochina Beijing China Southwest Branch Company SINOPEC Chengdu China Research Institute of Petroleum Exploration and Production SINOPEC Beijing China

Carbonate cemented zones are normally adjacent to the top overpressured surface in the central Junggar Basin,NW *** carbon and oxygen isotopic compositions and petrological investigations of carbonate cements in the carbonate cemented zones indicate that:(1) carbonate cements are composed dominantly of ferrocalcite,ferroan dolomite,and ankerite;(2) carbonate cements are formed under a high temperature circumstance in the subsurface,and organic fluid migration has an important effect on the formation of them;and(3) carbon and oxygen ions in the carbonate cements migrate from the underlying overpressured *** suggests that the occurrence of carbonate cemented zones in this region results from multiple phases of organic fluid expulsion out of the overpressure compartment through geological *** study provides a plausible mechanism of the formation of carbonate cemented zones adjacent to the top overpressured surface in the clastic sedimentary basins,and has an important implication for understanding the internal correlation between the formation of carbonate cemented zones adjacent to top overpressured surface and geofluids expulsion out of overpressured system.

关键词： carbonate cemented zones formation mechanism stable carbon and oxygen isotopic top overpressured surface central Junggar Basin coal-bearing strata

On the use of simplex methods in constructing quadratic models

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Science china Mathematics 2007年第7期50卷 913-924页

作者： Qing-hua ZHOU 1 College of Mathematics and Computer,Hebei university,Baoding 071002,china 2 State Key laboratory of Scientific and Engineering Computing,Institute of computational Mathematics and Scientific/Engineering Computing,Academy of Mathematics and Systems Science,Chinese Academy of Sciences,beijing 100080,china College of Mathematics and Computer Hebei University Baoding China State Key laboratory of Scientific and Engineering Computing Institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing China

In this paper, we investigate the quadratic approximation methods. After studying the basic idea of simplex methods, we construct several new search directions by combining the local information progressively obtained during the iterates of the algorithm to form new subspaces. And the quadratic model is solved in the new subspaces. The motivation is to use the information disclosed by the former steps to construct more promising directions. For most tested problems, the number of functions evaluations have been reduced obviously through our algorithms.

关键词： unconstrained optimization trust region method quadratic model Lagrange function simplex methods direct methods 90C56

Numerical simulation of non-Archie electrophysical property of saturated rock with lattice Boltzmann method

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Petroleum Science 2009年第1期6卷 24-28页

作者： Yue Wenzheng Tao Guo Liu Dongming Yang Wendu State Key laboratory of Petroleum Resource and Prospecting China University of Petroleum Beijing 102249 China Key laboratory of Earth Prospecting and Information Technology China University of Petroleum Beijing 102249 China Research Centre of Well Logging CNPC Key Laboratory of Well Logging China University of Petroleum Beijing 102249 China CNPC Logging Changqing Business Division Xi＇an Shaanxi 710201 China Sichuan Petroleum Administration Logging Company Ltd. CNPC Chongqing 401147 China

The electrophysical property of saturated rocks is very important for reservoir identification and evaluation. In this paper, the lattice Boltzmann method （LBM） was used to study the electrophysical property of rock saturated with fluid because of its advantages over conventional numerical approaches in handling complex pore geometry and boundary conditions. The digital core model was constructed through the accumulation of matrix grains based on their radius distribution obtained by the measurements of core samples. The flow of electrical current through the core model saturated with oil and water was simulated on the mesoscopic scale to reveal the non-Archie relationship between resistivity index and water saturation （I-Sw）. The results from LBM simulation and laboratory measurements demonstrated that the I-Sw relation in the range of low water saturation was generally not a straight line in the log-log coordinates as described by the Archie equation. We thus developed a new equation based on numerical simulation and physical experiments. This new equation was used to fit the data from laboratory core measurements and previously published data. Determination of fluid saturation and reservoir evaluation could be significantly improved by using the new equation.

关键词： Non-Archie relation digital core model lattice Boltzmann method numerical simulation rock physical experiment

Constructions of Some Exact VortexSuperposition Solutions

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Communications in Nonlinear Science and Numerical Simulation 1999年第4期4卷 3-5页

作者： Xin HU Yonghan HUANG(Department of Mechanics and Engineering Science, State Key laboratory for TurbulenceResearch, Peking university, beijing 100871, china) Department of Mechanics and Engineering Science State Key Laboratory for Turbulence Research Peking University Beijing 100871 China

IntroductionOneofthemostusefulmethodstosolvetheN-Sequationistodecomposethevelocity（l）(z)where.（'）--acNow,***3=w3（t）,wewillthengetco3=coear(jb（t）dt).Ifwetakeg=--M（axl+fixs）+ac,T=--M（Axf+Bx;）+cohere,goandcos... 详细信息

关键词： exact solution Stokes-Helmholtz decomposition vorticity equation

Origin of tectonic stresses in the Chinese continent and adjacent areas

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Science china Earth Sciences 2007年第1期50卷 67-74页

作者： ZHU ShouBiao1,2& SHI YaoLin3 1 Institute of Crustal dynamics, china Earthquake Administration, beijing 100085, china 2 Department of Geophysics, Peking university, beijing 100871, china 3 laboratory of computational Geodynamics, Graduate university of Chinese Academy of Sciences, beijing 100049, china Institute of Crustal dynamics China Earthquake Administration Beijing 100085 China Department of Geophysics Peking University Beijing 100871 China laboratory of computational Geodynamics Graduate University of Chinese Academy of Sciences Beijing 100049 China

Based on data of principal stress orientation from focal mechanism and of geological features in china, we made pseudo-3D genetic algorithm finite element (GA-FEM) inversion to investigate the main forces acting on the Chinese continent and adjacent areas which form the Chinese tectonic stress field. The results confirm that plate boundary forces play the dominant role in forming the stress field in china, as noticed by many previous researchers. However, we also find that topographic spreading forces, as well as basal drag forces of the lower crust to the upper crust, make significant contribution to stresses in regional scale. Forces acting on the Chinese continent can be outlined as follows: the collision of the India plate to the NNE is the most important action, whereby forces oriented to the NW by the Philippine plate and forces oriented to the SWW by the Pacific plate are also important. Topographic spreading forces are not negligible at high topographic gradient zones, these forces are perpendicular to edges of the Tibetan Plateau and a topographic gradient belt running in the NNE direction across Eastern china. Basal drag forces applied by the ductile flow of the lower crust to the base of upper crust affect the regional stress field in the Tibetan Plateau remarkably, producing the clockwise rotation around the eastern Himalaya syntax.

关键词： genetic algorithm finite element method topographic spreading forces ductile lower crust Chinese continent.

Limitation of fault-sealing and its control on hydrocarbon accumulation——An example from the Laoyemiao Oilfi eld of the Nanpu Sag

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Petroleum Science 2008年第4期5卷 295-301页

作者： Jiang Zhenxue Dong Yuexia Li Hongyi Liu Luofu Liu Guangdi Li Xiaoying Basin and Reservoir Research Center China University of Petroleum Beijing 102249 China State Key laboratory of Petroleum Resources and Prospecting China University of Petroleum Beijing 102249 China Research Institute of Exploration and Development Jidong Oilfield PetroChina Tangshan Hebei 063004 China School of Resources and Information Technology China University of Petroleum Beijing 102249 China

Based on previous studies on the internal structures of fault belts, the fault belts in the Laoyemiao Oilfield of the Nanpu Sag can be divided into three units, a crushed zone, an upper induced fracture zone and a lower induced fracture zone according to the log response characteristics. The upper induced fracture zone is characterized by the development of pervasive fractures and has a poor sealing or non-sealing capability. It therefore can act as pathways for hydrocarbon migration. The lower induced fracture zone consists of fewer fractures and has limited sealing capability. The crushed zone has a good sealing capability comparable to mudstone and can thus prevent lateral migration of fluid. Through physical modeling and comparing laboratory data with calculated data of oil column heights of traps sealed by faults, it is concluded that the fault-sealing capability for oil and gas is limited. When the oil column height reaches a threshold, oil will spill over from the top of reservoir along the lower induced fracture zone under the action of buoyancy, and the size of reservoir will remain unchanged. Analysis of the formation mechanisms of the fault-sealed reservoirs in the Nanpu Sag indicated that the charging sequence of oil and gas in the reservoir was from lower formation to upper formation, with the fault playing an important role in oil and gas accumulation. The hydrocarbon potential in reverse fault-sealed traps is much better than that in the consequent fault-sealed traps. The reverse fault-sealed traps are favorable and preferred exploration targets.

关键词： Limitation of fault-sealing fault belt oil column height hydrocarbon accumulation Nanpu Sag

A computational model for feature binding

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Science china(Life Sciences) 2008年第5期51卷 470-478页

作者： SHI ZhiWei1,2, SHI ZhongZhi1, LIU Xi1,2 & SHI ZhiPing1 1 Key laboratory of Intelligent Information Processing, Institute of Computing Technology, Chinese Academy of Sciences, beijing 100190, china 2 Graduate university of Chinese Academy of Sciences, beijing 100049, china Key laboratory of Intelligent Information Processing Institute of Computing Technology Chinese Academy of Sciences Beijing China Graduate university of Chinese Academy of Sciences Beijing China

The "Binding Problem" is an important problem across many disciplines, including psychology, neuroscience, computational modeling, and even philosophy. In this work, we proposed a novel computational model, Bayesian Linking Field Model, for feature binding in visual perception, by combining the idea of noisy neuron model, Bayesian method, Linking Field Network and competitive mechanism. Simulation Experiments demonstrated that our model perfectly fulfilled the task of feature binding in visual perception and provided us some enlightening idea for future research.

关键词： Binding Problem computational model Bayesian Linking Field Model