水平井分段采油优化模型

考虑水平井的分段采油,研究了封闭油藏、定压油藏、底水油藏三类油藏的渗流模型,建立了以水平段每段长度和中心点位置为研究对象的新优化模型,并对水平井分段数、每一段的长度及距离跟端位置等待优化的问题利用遗传算法最终给出了一套具有实际应用价值的最优分段方案。     

考虑二次梯度项及动边界的双重介质低渗透油藏流动分析

在传统试井模型的非线性偏微分方程中根据弱可压缩流体的假设,忽略了二次梯度项,对于低渗透油藏这种方法是有疑问的.低渗透问题一个显著的特点就是流体的流动边界随着时间不断向外扩展.为了更好地研究双重介质低渗透油藏中流体的流动问题,考虑了二次梯度项及活动边界的影响,同时考虑了低渗透油藏的非达西渗流特征,建立了双重介质低渗透油藏流动模型.采用Douglas-Jones预估-校正差分方法获得了无限大地层定产量生产时模型的数值解,分别讨论了不同参数变化时压力的变化规律及活动边界随时间的传播规律,还分析了考虑和忽略二次梯度项影响时模型数值解之间的差异随时间的变化规律,做出了典型压力曲线图版,这些结果可用于实际试井分析.     

水平井开采石油遇到的几个流体力学问题

本文从渗流力学和流体动力学方面讨论了利用水平井技术开采石油时在油藏工程和采油工程中遇到的几个力学问题,如水平井产量的计算,水平井非稳态试井及流场分析,水平井井筒内压力降及其对产量的影响、水平井近井油藏和井筒内流体流动耦合等,半提出水平井开采机理仍存在很多基础理论需要研究解决。     

低渗透油藏爆炸压裂产能分析及压裂改造区域优化设计

基于爆炸压裂裂缝分布规律,提出爆炸压裂缝网双重介质复合流动产能模型,应用Laplace变换Stehfest数值反演,得到了定压条件下封闭外边界低渗透油藏爆炸压裂生产井产能表达式。在模型正确性验证的基础上结合某低渗透油藏储层特征参数研究了爆炸压裂改造区域参数对封闭边界油藏产量的影响,同时对爆炸压裂改造改造体积优化设计进行了研究。研究结果表明,爆炸压裂改造区域半径主要影响生产中期产能,改造区域渗透率对生产早期和中期影响比较大,且对于实例油藏爆炸压裂改造比为0.1时效果最好。     

裂缝性低渗透油藏流-固耦合理论与数值模拟

根据裂缝性低渗油藏的储层特征,建立适合裂缝性砂岩油藏渗流的等效连续介质模型。将渗流力学与弹塑性力学相结合,建立裂缝性低渗透油藏的流-固耦合渗流数学模型,并给出其数值解.通过数值模拟对一实际井网开发过程中孔隙度、渗透率的变化以及开发指标进行计算,并和刚性模型以及双重介质模型的计算结果进行了分析比较.     

基于离散裂缝的多段压裂水平井数值试井模型及应用

水平井压裂技术已经成为开发低渗透油气藏、页岩气藏和致密气场等非常规油气藏的关键技术。基于离散裂缝模型,对裂缝进行简化,建立了二维多段压裂水平井有限导流数值试井模型,利用有限元方法求解模型,获得多段压裂水平井试井理论曲线和压力场特征。分析表明:多段压裂水平井的试井理论曲线一共分为七个阶段:井筒储存段、裂缝线性流段、裂缝-地层双线性流段、裂缝干扰段、地层线性流段、系统径向流段和边界作用段,其中裂缝-地层双线性流段和裂缝干扰是其典型特征。分析了裂缝数量、裂缝间距、裂缝不对称、裂缝不等长和裂缝部分缺失等因素对试井理论曲线的影响,结果表明:裂缝数量和裂缝间距对试井理论曲线的影响最大。较多的裂缝、较大裂缝间距、对称的裂缝和等长的裂缝有利于降低压裂水平井井底的流动阻力,提高产能。将建立的数值试井模型应用于四川盆地一口多段压裂水平井的压力恢复测试的数值试井解释,结果表明:本文建立的模型可以较好的拟合压力恢复测试数据,可以获得裂缝的导流能力和裂缝长度,为压裂效果评价和压裂设计提供指导。      

边界元理论在复杂外边界油藏水平井渗流中的应用

受构造作用的影响,实际油藏的外边界往往是复杂多样的.本文从渗流理论出发建立了复杂外边界油藏水平井渗流数学模型,并采用Lord Kelvin点源解、贝塞尔函数积分和泊松叠加公式等方法求解了复杂外边界油藏水平井的边界元基本解,利用边界元的理论建立了复杂外边界油藏水平井井底压力响应数学模型.通过计算得到了无因次压力和压力导数双对数理论图版,并在其基础上分析了复杂外边界油藏水平井渗流特征及其影响因素.     

变形三重介质低渗透油藏垂直裂缝井的非线性流动分析

不仅考虑低渗透油藏具有启动压力梯度的渗流特征,还考虑应力敏感地层中介质的变形;发展了Cinco-Ley H.提出的有限导流垂直裂缝井双线性流理论,将流体在垂直裂缝与地层中形成的流动划分为两个区域—垂直裂缝中的线性流区域和变形三重介质低渗透油藏中的非线性流区域;由此建立了变形三重介质低渗透油藏有限导流垂直裂缝井的非线性流...     

钢-复合材料组合结构材料选型优化设计映射解法

建立了基于拓扑分布的钢-复合材料组合结构材料选型优化的数学模型,通过变量连续化,用映射函数对材料选型优化模型进行函数变换,使其能适应更多的优化算法进行求解.分别采用线性函数、指数函数、对数函数、阶跃函数、反三角函数和分段函数等对原始模型进行了变换,得到相应材料选型优化模型并求解.以组合浮筏材料选择动力学优化为例,对比研...     

二级多点近似方法在整星结构优化设计中的应用

以整星结构为研究对象,针对含有离散变量的混合变量优化问题,应用二级多点近似方法给出从卫星拓扑布局设计到尺寸的一体化优化求解过程。首先,对整星结构进行仿真和振动试验,设计满足总体指标要求且已得到在轨验证。其次,建立以极小化卫星质量为目标的多工况优化模型后利用分段多点逼近函数建立了显式近似问题。最后,采用遗传算法和变尺度法分别对离散/连续两类变量寻优,并以拓扑构型一致性和目标函数的下降程度作为收敛的判定依据。结果显示,在满足频率和静力的约束下,卫星质量降低了7.9%,且结构分析迭代次数仅为50~60次,从而验证了该方法在求解整星结构多变量多工况下的一体化设计问题时具有很高的计算效率和准确性。     

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.     

考虑多重运移机制耦合页岩气藏压裂水平井数值模拟

页岩作为典型的微纳尺度多孔介质,游离气与吸附气共存,传统的达西定律已无法准确描述气体在页岩微纳尺度的运移规律.基于双重介质模型和离散裂缝模型构建页岩气藏分段压裂水平井模型,其中基岩中考虑气体的黏性流、Knudsen 扩散以及气体在基岩孔隙表面的吸附解吸,吸附采用Langmuir等温吸附方程;裂缝中考虑黏性流和Knudsen扩散,在此基础上建立基岩-裂缝双重介质压裂水平井数学模型并采用有限元方法对模型进行求解.结果表明,基岩固有渗透率越小,表面扩散和Knudsen扩散的影响越大,反之则越小;人工裂缝的性质包括条数、开度、半长以及间距,主要影响压裂水平井生产早期,随着人工裂缝参数值的增加,压裂水平井产能增加,累产气量也越大.其次,页岩气藏压裂诱导缝和天然裂缝的发育程度对页岩气藏的产能有很大的影响,水平井周围只有人工裂缝,周围天然裂缝不开启或不发育时,页岩气藏的水平井的产能较低.      

Heat transfer measurements and correlations for air–water flow of different flow patterns in a horizontal pipe

Heat transfer coefficients were measured and new correlations were developed for two-phase, two-component (air and water) heat transfer in a horizontal pipe for different flow patterns. Flow patterns were observed in a transparent circular pipe using an air–water mixture. Visual identification of the flow patterns was supplemented with photographic data, and the results were plotted on the flow regime map proposed by Taitel and Dukler and agreed quite well with each other. A two-phase heat transfer experimental setup was built for this study and a total of 150 two-phase heat transfer data with different flow patterns were obtained under a uniform wall heat flux boundary condition. For these data, the superficial Reynolds number ranged from 640 to 35,500 for the liquid and from 540 to 21,200 for the gas. Our previously developed robust two-phase heat transfer correlation for a vertical pipe with modified constants predicted the horizontal pipe air–water heat transfer experimental data with very good accuracy. Overall the proposed correlations predicted the data with a mean deviation of 1.0% and an rms deviation of 12%.     

A new computation model of fractured horizontal well coupling with reservoir

Based on Green's functions and Newman's product principle, pressure drop formula was derived for considering simultaneous production of fractures and horizontal wellbore in unsteady state. A reservoir/fractured horizontal well coupling model is developed for finite conductivity condition that can be solved by the combination of quasi‐Newton method and PSO (Particle Swarm Optimization) algorithm. The solution of a practical example shows that lots of factors can affect the productivity of the fractured horizontal well. The number of the fractures has an optimizing range. Different fractures have different flow rates and the production in the central fracture is the lowest. The distribution of production rate in the wellbore has a wave‐like shape due to the influence of fractures. The closer fractures are the lower flow rate in well segments. Considering the horizontal wellbore production, the production rates in the fractures are asymmetric and the corresponding pressure drop curve is smoother. Copyright © 2010 John Wiley & Sons, Ltd.     

履带车辆路面激励响应的简化计算

为了快速计算履带车辆在路面不平度激励下的动力学响应,基于合理假设采用理论力学方法建立了某履带车辆的简化动力学模型,用ADAMS 软件建立了同种工况下的履带车辆动力学模型,并把两种模型的求解结果进行了对比,验证了简化模型的合理性. 研究结果为基于简化模型的动力学方程对车辆悬挂系统进行优化和逆动力学分析奠定了基础.     

Two-phase flow for a horizontal well penetrating a naturally fractured reservoir with edge water injection

This paper examines the two-phase flow for a horizontal well penetrating a naturally fractured reservoir with edge water injection by means of a fixed streamline model. The mathematical model of the vertical two-dimensional flow or oil-water for a horizontal well in a medium with double-porosity is established, and whose accurate solutions are obtained by using the characteristic method. The saturation distributions in the fractured system and the matrix system as well as the formula of the time of water free production are presented. All these results provide a theoretical basis and a computing method for oil displacement by edge water from naturally fractured reservoirs.     

A New Analytical Approximation for the Flow into a Well in a Finite Reservoir

A new approach is presented for the pressure calculation around a horizontal well or a partially penetrating vertical well in a finite height reservoir. The new method matches the asymptotic solutions close to- and far from the well. To this end, the reservoir is divided into two distinct volumes with ellipsoidal and elliptically cylindrical symmetry, respectively. Comparison with other techniques shows that the new expressions yield excellent results. The method is also applicable to reservoirs containing one elliptical, vertical or horizontal fracture, and can be used with account of a zone of altered permeability around the well or fracture due to formation damage or stimulation.     

Horizontal boundary-layer natural convection in a porous medium saturated with a gas

Boundary-layer analysis is performed for free convection flow over a hot horizontal surface embedded in a porous medium saturated with a gas of variable properties. The variable gas properties are accounted for via the assumption that thermal conductivity and dynamic viscosity are proportional to temperature. A similarity solution is shown to exist for the case of constant surface temperature. Numerical results for the stream function, horizontal velocity, and temperature profiles within the boundary layer as well as for the mass of entrained gas, surface slip velocity, and heat transfer rate at different values of the wall-temperature parameter are presented. Asymptotic solutions for large heating are also available to support the numerical work.