Discretizing two‐dimensional complex fractured fields for incompressible two‐phase flow

A method is introduced to discretize irregular and complex two‐dimensional fractured media. The geometry of the fractured media is first analysed by searching and treating the complex configurations. Based on that, the method generated a good mesh quality and allows for including finer grids. An incompressible two‐phase flow problem is solved to compare the developed method and a public method based on the approximation of a 1D fracture by the edges of a 2D finite element grid of the porous media. The comparison showed that the developed method (i) represents better the fractured domain by maintaining the geometric integrity of input surfaces and geologic data, (ii) provides, for sample and complex fractured domains, excellent and more accurate results, and (iii) is much less sensitive to the grid sizes. Furthermore, the method has to be more efficient than the other methods for transport problems and has to provide better predictable results; this is mainly based on point (ii) and because the method produces optimal triangular grids. Copyright © 2009 John Wiley & Sons, Ltd.     

A new Apparatus for Long-term Petrophysical Investigations on Geothermal Reservoir Rocks at Simulated In-situ Conditions

We present a new apparatus capable of maintaining in-situ conditions pertinent to deep geothermal reservoirs over periods of months while in the same time allowing a variety of continuous petrophysical investigations. Two identical devices have been set up at the GFZ-Potsdam. Lithostatic overburden- and hydrostatic pore pressures of up to 100 and 50 MPa, respectively can be simulated. In addition in-situ temperature requirements of up to 200°C can be met. The use of corrosion resistant parts throughout the pore pressure system allows investigations with highly saline formation fluids. Rock permeability, electrical conductivity as well as compressional- and shear-wave velocities can be measured simultaneously and the pore fluid can be sampled under pressure for further chemical analysis. Scientifically, the usage of the device focuses on risk potentials in exploration and exploitation of deep geothermal reservoirs. Particularly, the investigations address possible effects of fluid-rock interactions on the transport properties of a reservoir host rock.     

复合油藏球向渗流问题的解的相似结构

针对复合油藏,建立其球向不稳定渗流的试井分析模型;利用Laplace变换,解得在变流率生产情形下的储集层压力和井底压力的Laplace空间解;根据微分方程解的相似结构理论,得到在3种外边界条件下内外区的储集层压力的Laplace空间解的相似结构.解的相似结构的获得有利于进一步分析解的内在规律;便于在相应的实际问题中分析参数对于解的影响.     

Non‐equilibrium behaviour of equilibrium reservoirs in molecular simulations

We explore two widely used algorithms for fluid reservoirs in molecular simulations and demonstrate that they may induce non‐physical non‐equilibrium effects, even in systems that should be at equilibrium. For example, correlations of momentum and density fluctuations lead to a bias in the mean fluid velocity when measured as the mean over samples of instantaneous fluid velocity. The non‐physical behaviour is entirely computational in origin and is an instance of a more general issue in molecular simulations: a failure to correctly model stochastic properties may induce non‐equilibrium behaviour that does not exist in the corresponding physical system. Finally, we demonstrate that simple algorithm corrections eliminate this artifact. Copyright © 2005 John Wiley & Sons, Ltd.     

梯级水库群防洪系统多目标决策的灰色优选

将传统的优化技术与新发展起来的灰关联决策理论有机地结合起来,针对洪水调度的特点,提出了一个切实可行的梯级水库群洪水调度方案决策的灰色优选模型.最后,以乌江流域4个梯级电站的洪水调度方案优选进行了说明.     

CHARACTERISTIC DIFFERENCE METHODS FOR TWO-PHASE DISPLACEMENT IN NATURALLY FRACTURED RESERVOIRS

In this paper we shall give the characteristic difference methods for two phase displace meat problem in naturally fractured reservoirs.We shall prove the existence,uniqueness of the ap proximate solution and a priori discrete L2-error estimates.     

低渗油层压裂水平井两相流研究

依据压裂水平井不同流动区域的流动规律, 将压裂水平井的渗流分为裂缝中的高速非达西流 动区、裂缝控制影响的椭圆渗流区、远离裂缝的基质非达西渗流区, 考虑启动压力梯度的影 响, 对压裂水平井两相渗流进行了分析, 得到了低渗透油层压裂水平井的产量公式. 研究结 果表明, 裂缝的导流能力越大, 压裂水平井的产量越高. 但随着开采时间的增加, 其产量递减幅度越 大; 压裂裂缝长度越小, 压裂水平井的初始产量越高. 但随着生产时间的推移, 压裂裂缝的 长度越大, 产量的递减幅度越小; 中间裂缝长, 两翼裂缝短的情况下, 压裂水平井的产量最 高.     

裂隙岩体非稳态渗流数值模型及其应用

为解决裂隙岩体非稳态渗流问题, 发展了一种新的数值模型. 对于单裂隙渗 流求解, 其控制方程是基于一定假设的简化Navier-Stokes方程, 数值方法采用有限差分法 和流体体积法. 在裂隙网络中, 交界处渗流可以由专门的控制方程求解. 计算结果表明, 该 数值模型既可以大幅提高非稳态渗流的计算效率, 还可以避免孤立裂隙所带来的影响. 最后, 通过两个工程算例验证该数值模型的适用性.     

Naturally Ordered Abundant Semigroups in Which Each Idempotent Has a Greatest Inverse

The aim of this article is to study naturally ordered abundant semigroups in which every idempotent has a greatest inverse. After obtaining some characterizations, their structure is established.