Numerical Estimation of the Degree of Reservoir Permeability Heterogeneity Using Pressure Drawdown Tests

This study aims to correlate the response of pressure transient test to permeability distribution type. For this purpose, correlated permeability distributions in x–y direction are generated using fractional Brownian motion (fBm) as it has been shown in literature that permeability in carbonate reservoirs exhibits an fBm type distribution horizontally. 2-D fBm permeability distributions created using mid point displacement method are employed as data to a black oil simulator. The intermittence exponent, H or fractal dimension of the distribution, D, as defined by D=2 – H, characterizes the distribution type. All permeability distributions are normalized to represent the same arithmetic mean (20, 100, and 500 mD) and uniform variance so that only their fractal dimension that underlies the smoothness of the distribution distinguishes them. Many different realizations of permeability distributions are generated based on the random number seeds used and pressure transient (drawdown) tests are simulated using a black oil simulator package (ECLIPSE 100). Pressure transient analysis is performed using PanSystem package. As a base case and for the comparison purpose, the same procedure is repeated for the totally homogeneous case (the same permeability for all grids) and a random (normally distributed) permeability distribution with the same mean and uniform variance. The effects of permeability distribution type on the pressure response are clarified. A strong impact of heterogeneity is observed as an increase in skin effect with increasing fractal dimension of permeability distribution. This additional (or pseudo) skin effect due to heterogeneity is correlated to the fractal dimension of the permeability distribution. As a further step, the procedure is repeated for different flow rates applied during the drawdown test. The correlation between the fractal dimension of permeability distribution and additional skin is improved by incorporating the rate into it. The methodology followed can be used in the assessment of reservoir heterogeneity quantitatively using pressure transient response.     

单层短程线网壳结构模型试验研究

模型试验是全面掌握工程结构基本特性的有效手段之一。根据模型相似理论设计并制作了单层短程线网壳结构模型,同时设计了可动砝码加载方案,加工制作了砝码及支托。对结构杆件进行了材料拉伸试验,对结构模型进行了静载试验和模态试验研究,成功获得了结构模型的静内力分布规律及模态参数。试验结果与有限元计算结果对比分析表明,静载试验结果与有限元计算结果吻合较好,模态试验结果与有限元计算结果吻合稍差。所采用的加载方案、试验手段及分析方法对类似的模型试验研究都具有一定的参考价值,所得到的试验数据为大型空间网格结构实际工程的在线损伤识别及健康监测研究提供了第一手资料。     

Dynamic characteristics of a beam specimen featuring electrorheological fluids

The experimental investigations are focused on evaluating the elastodynamic response characteristics of beams fabricated in electrorheological (ER) fluids when the beams are subjected to forced vibration. The beams used in this experiment are composed of three kinds of materials: structural material, damping material and sealant material. Beams with different ER fluids and different structural material are made and tested. The results demonstrate clearly the ability to significantly change the vibrational characteristics of beams fabricated in smart composites by changing the electric field intensity imposed on the fluid domains. With the ASTM standard E756-83 equations, the Young's modulus of the beams and the shear modulus of ER fluids are evaluated.     

Investigation of stresses in he orthogonal cutting of fiber-reinforced plastics

A photoelastic study was conducted to examine the stress fields in the cutting process of fiber-reinforced plastics (FRPs). Force measurements were made and used in the analysis of the stress fields. Machined surfaces of workpieces with fibers oriented away from the cutting direction showed that the fibers were machined by shearing and tensile fracture; and when fibers were inclined towards the cutting tool, the fibers failed by shearing and bending. In addition, fiber-matrix debonding was observed to be maximum for fibers oriented at 45 deg towards the tool's path. Fiber orientation was shown to have an influence on the machining forces and stresses.Paper was presented at the 1994 SEM Spring Conference held in Baltimore, MD on June 6–9.     

撞击载荷作用下单层球面网壳动力响应模型实验研究

通过单层KIEWITT8型网壳模型在落锤撞击作用下的实验,研究单层网壳在撞击作用下的动力稳定性。利用动态应变仪和力传感器,获取了落锤撞击网壳时撞击力时程曲线、杆件轴力时程曲线和稳定临界力。利用高速摄影机拍摄了撞击历程、撞击失稳模态及破坏形态。结果表明:撞击作用为三角脉冲荷载形式,其最大幅值和脉宽与撞击冲量和网壳所处变形阶段的刚度性能相关;撞击荷载持续作用的时间为3.00~22.36 ms;撞击接触时间的突然增大对应着网壳的失稳;杆件开始响应的时刻比撞击力开始作用的时刻滞后0.2~0.4 ms;对失稳前的撞击,落锤回弹速度较大;对失稳时的撞击,落锤回弹速度很小;模型具有较大的后屈曲抗撞击能力,在顶点垂直撞击下没有发生连续断裂。     

多孔氧化铝薄膜横观各向同性弹性性质的研究

电化学阳极氧化生成的氧化铝薄膜含有高度有序的纳米孔阵列,本文首先假设氧化铝薄膜基体(无孔部分)为各向同性,结合其周期性孔结构特点和均匀化理论,可以得到氧化铝基体和薄膜弹性性质之间的关系。然后利用单轴拉伸结合电子散斑干涉(ESPI)的方法得到薄膜面内的杨氏模量为63.4GPa,并根据均匀化方法得到的基体与薄膜弹性性质的关系进一步推出薄膜横观各向同性的其它弹性参数,如基体杨氏模量等。为证明结果的可靠性,利用推出的弹性参数建立三维有限元模型,模拟纳米压痕实验,得到的加卸载曲线与实验曲线相吻合。     

Using laser ultrasonics for nondestructive residual stress evaluation

A non-contact measuring technique of ultrasonic waves velocity is proposed, in which Rayleigh waves are detected by a laser Doppler velocimeter and the velocity is measured precisely by means of a sing-around unit and a digital oscilloscope. With the proposed technique, the acoustoelastic coefficient of Rayleigh waves in mild steel SS41 is obtained, which is in good agreement with that obtained by the contact method. Furthermore the non-contact technique is applied to evaluate the residual stress in a butt-welded steel plate, the result is reasonable.     

一种滑动轴承试验台的研制与牙轮钻头镶嵌滑动轴承摩擦磨损性能的台架试验

在石油钻井中，滑动轴承牙轮钻头的应用日益增多，但轴承的工作环境却相当恶劣。为了提高钻头滑动轴承的工作寿命，并为这类轴承的设计提供科学依据，针对其实际应用工况，特殊设计制造了一种ＩＰＧ－２型滑动轴承试验台，并且利用其在３０ｋＮ、４０ｋＮ和５０ｋＮ的３种载荷条件下，对牙轮钻头镶嵌铜合金的滑动轴承进行了台架试验研究，着重考察了铜合金镶嵌区尺寸之大小对轴承摩擦磨损性能的影响。结果表明，在相邻两个镶嵌区之间的基体区表面宽度与铜合金的镶嵌区宽度之比值分别为１、２、３和４的几种镶嵌滑动轴承中，它们的摩擦学性能依次变差，即以第一种镶嵌轴承的摩擦磨损性能最好，这是由于镶嵌材料铜合金的抗剪切强度比钢基体的低，在摩擦力的作用下容易向非镶嵌区基体表面及与之对摩部件表面发生材料转移并形成转移膜的缘故。这种研究结果可以直接应用于钻头滑动轴承的设计。     

Free-edge stress concentration in angle-ply laminates

Summary For a symmetric [±]s-angle-ply laminate coupon within the framework of linear elasticity the free-edge effect is treated in a closed-form analytical way. To that end, for uniaxial tension the near-edge deformation is traced back to a complex-analytical potential. For the given boundary conditions the respective potential is determined and thus the resultant displacement field and the accompanying stresses. Thereby, in particular, a logarithmic singularity is obtained for the free-edge stress concentration.     

Mathematical Modeling,Control, Computer Simulation and Laboratory Experiments of a Spatial Servopneumatic Parallel Robot

In this paper (Part I), the special construction of a controlled parallel structure, called spatial servopneumatic multi-axles test facility (MAP), will be theoretically and numerically investigated and controlled. The investigations include the following steps: (i) design of mathematical models of different complexity of both, the test facility mechanics in terms of DAEs and ODEs (a multi-body system which contains 13 rigid bodies under spatial motion, connected by joints), and the servopneumatic actuators; (ii) construction of different linear and nonlinear (model based) control algorithms; (iii) development of a computer simulation program of the MAP; and (iv) evaluation of various computer simulation runs, obtained by applying different control algorithms and spatial command-input signals. The results show that the efficiency of the control algorithms is closely related to their complexity and cost. In order to check the closeness to reality of the computer simulation results and their benefit for industrial applications, laboratory experiments must be formed with the same MAP, the same control algorithms, and applying the same command-input signals which have been used in the computer simulations. These experimental investigations will be presented in Part II of the paper.