基本结构有限元算法及大地电磁测深一维连续介质正演

提出了一种新的数值方法——基本结构有限元法. 从经典的伽辽金法（Galerkin method）出发,首先定义了基本结构插值基函数,在此基础上建立了基本结构方程,然后用有限元法进行进一步的具体实现. 该算法被成功应用到大地电磁测深一维连续介质正演计算中. 采用了6种不同的单元插值基函数进行计算,并对计算结果进行了比较和分析.     

节理岩体断裂的分形机理研究

本文在考察了节理化岩体的断裂力学特征的基础上，结合现代分形几何原理，建立起追踪裂纹裂分形模型，对不连续岩体的断裂韧性的分形效应进行了深入研究，并通过压剪试验得到难。     

基于经验模态分解的分数维地震随机噪声衰减方法

经验模态分解算法（EMD）是一种基于有效波和噪声尺度差异进行波场分离的随机噪声压制方法,但由于实际地震数据波场复杂,导致模态混叠较严重,仅凭该方法进行去噪很难达到理想效果.本文基于EMD算法对信号多尺度的分解特性,结合Hausdorff维数约束条件,提出一种用于地震随机噪声衰减的新方法.首先对地震数据进行EMD自适应分解,得到一系列具有不同尺度的、分形自相似性的固有模态分量（IMF）;在此基础上,基于有效信号和随机噪声的Hausdorff维数差异,识别混有随机噪声的IMF分量,对该分量进行相关的阈值滤波处理,从而实现有效信号和随机噪声的有效分离.文中从仿真信号试验出发,到模型地震数据和实际地震数据的测试处理,同时与传统的EMD处理结果相对比.结果表明,本文方法对地震随机噪声的衰减有更佳的压制效果.

     

某地洼区F_1等断裂带构造地球化学特征及其铀成矿规律的探讨

本文运用地洼成矿理论和构造地球化学的方法,研究了区内 F_1成矿断裂等的构造特征和元素的变化规律以及铀等成矿元素的不断累增富集的成矿作用过程.区内钠矿床的形成大体上经历了铀的预富成岩(形成铀源地质体)→断裂动力改造热液(热水)成矿→表生淋积等三个主要发展阶段,形成了一个具有层控特征的多因复成铀矿床,从而为本区指明了找矿方向.     

临汾区块地应力三维数值模拟研究

在地质构造分析和岩石力学性质测试的基础上,进行了临汾区块的地应力有限元三维数值模拟研究,探讨了地应力在区域和层域上的分布规律及其对区内煤层气成藏的影响。研究表明,应力强度总体上随深度递增,断层对应力强度分布具有明显的影响;断层附近应力强度的最大值分布在断层与断层的交叉点、断层与底部硬质岩层界面附近,应力性质在断层夹块内和支断层一侧发生转变出现拉应力区,断层与地表的交点附近也呈现局部拉应力区;煤层软弱带呈现应力降低。研究区的地应力分布特征有利于煤层气从深部向浅部运移,并在背斜轴部相对富集。     

分形理论在空间网络分布特征研究中的应用

探讨了以图论为基础的空间网络的测度方法,以及以分形理论为基础的表达空间网络分布特征的几种分维数,并阐述了各种分维数的地理意义,最后对于分维数的测算进行了评述.     

基于CCGIS的三维城市模璎数据生产

立足于生产实际阐述了一种基于CCGIS的三维城市生产工艺,重点说明了三维城市模型数据生产流程和控制,并结合恩施三维信息查询系统为例对该生产工艺进行验证。     

起伏海面的雷电电磁场传播特征及其对闪电定位精度的影响

为了研究起伏海面对雷电电磁传播的影响,本文利用Barrick表面阻抗理论和Wait近似算法,采用改进二维分形海面模型模拟起伏海面,利用数值模式,分析起伏海面的雷电电磁传播特征,并进一步讨论了起伏海面对时差法闪电定位系统定位精度的影响。结果表明:起伏海面对垂直电场和磁场的峰值的影响不显著,但会引起波形的上升期时间的延长,浪高越大,影响越明显;随着观测距离的增加,雷电垂直电场波形的上升时间逐渐变长;风速的变化与雷电垂直电场波形的上升时间成正比;由于海面起伏引起雷电电磁场波形在传播中的变化会影响基于时差法闪电定位系统的定位精度,定位误差可达几至十几公里。     

Theoretical aspects of cap-rock and fault seals for single- and two-phase hydrocarbon columns

Cap-rock seals can be divided genetically into those that fail by capillary leakage (membrane seals) and those whose capillary entry pressures are so high that seal failure preferentially occurs by fracturing and/or wedging open of faults (hydraulic seals). A given membrane seal can trap a larger oil column than gas column at shallow depths, but below a critical depth (interval), gas is more easily sealed than oil. This critical depth increases with lower API gravity, lower oil GOR and overpressured conditions (for the gas phase). These observations arise from a series of modelling studies of membrane sealing and can be conveniently represented using pressure/ depth (P/D) profiles through sealed hydrocarbon columns. P/D diagrams have been applied to the more complex situation of the membrane sealing of a gas cap underlain by an oil rim; at seal capacity, such a two-phase column will be always greater than if only oil or gas occurs below the seal.These conclusions contrast with those for hydraulic seals where the seal capacity to oil always exceeds that for gas. Moreover, a trapped two-phase column, at hydraulic seal capacity will be less than the maximum-allowed oil-only column, but more than the maximum gas-only column. Unlike membrane seals, hydraulic seal capacity should be directly related to cap-rock thickness, in addition to the magnitude of the minimum effective stress in the sealing layer and the degree of overpressure development in the sequence as a whole.Fault-related seals are effectively analogous to membrane cap-rocks which have been tilted to the angle of the fault plane. Consequently, all of the above conclusions derived for membrane cap-rocks apply to both sealing faults sensu stricto (fault plane itself seals) and juxtaposition faults (hydrocarbon trapped laterally against a juxtaposed sealing unit). The maximum-allowed two-phase column trapped by a sealing fault is greater than for equivalent oil-only and gas-only columns, but less than that predicted for a horizontal membrane cap-rock under similar conditions. Where a two-phase column is present on both sides of a sealing fault (which is at two-phase seal capacity), a deeper oil/water contact (OWC) in one fault block is associated with a deeper gas/oil contact (GOC) compared with the adjacent fault block. If the fault seal is discontinuous in the gas leg, however, the deeper OWC is accompanied by a shallower GOC, whereas a break in the fault seal in the oil leg results in a common OWC in both fault blocks, even though separate GOC's exist. Schematic P/D profiles are provided for each of the above situations from which a series of fundamental equations governing single- and two-phase cap-rock and fault seal capacities can be derived. These relationships may have significant implications for exploration prospect appraisal exercises where more meaningful estimates of differential seal capacities can be made.The membrane sealing theory developed herein assumes that all reservoirs and seals are water-wet and no hydrodynamic flow exists. The conclusions on membrane seal capacity place constraints on the migration efficiency of gas along low-permeabiligy paths at depth where fracturing, wedging open of faults and/or diffusion process may be more important. Contrary to previous assertions, it is speculated that leakage of hydrocarbons through membrane seals occurs in distinct pulses such that the seal is at or near the theoretically calculated seal capacity, once this has been initially attained.Finally, the developed seal theory and P/D profile concepts are applied to a series of development geological problems including the effects of differential depletion, and degree of aquifer support, on sealing fault leakage, and the evaluation of barriers to vertical cross-flow using RFT profiles through depleted reservoirs. It is shown that imbibition processes and dynamic effects related to active cross-flow across such barriers often preclude quantitative analysis and solution of these problems for which simulation studies are usually required.     

Geomechanical modelling to assess fault integrity at the CO2CRC Otway Project,Australia

This paper presents the first published 3D geomechanical modelling study of the CO2CRC Otway Project, located in the state of Victoria, Australia. The results of this work contribute to one of the main objectives of the CO2CRC, which is to demonstrate the feasibility of CO₂ storage in a depleted gas reservoir. With this aim in mind, a one-way coupled flow and geomechanics model is presented, with the capability of predicting changes to the in situ stress field caused by changes in reservoir pressure owing to CO₂ production and injection. A parametric study investigating the pore pressures required to reactivate key, reservoir-bounding faults has been conducted, and the results from the numerical simulation and analytical analysis are compared. The numerical simulation indicates that the critical pore fluid pressure to cause fault reactivation is 1.15 times the original pressure as opposed to 1.5 times for the comparable analytical model. Possible reasons for the differences between the numerical and analytical models can be ascribed to the higher degree of complexity incorporated in the numerical model. Heterogeneity in terms of lateral variations of hydrological and mechanical parameters, effect of topography, presence of faults and interaction between cells are considered to be the main sources for the different estimation of critical pore pressure. The numerical model, which incorporates this greater complexity, is able then to better describe the state of stress that acts in the subsurface compared with a simple 1D analytical model. Moreover, the reactivation pressures depend mainly on the state of stress described; therefore we suggest that numerical models be performed when possible.