垂直井筒井液携砂流动规律研究及其在油井生产中的应用

借助自建的实验装置，研究了油井出砂砂粒在流体中的沉降规律，以此为基础提出了井液携砂能力计算模型，然后将这一研究结果与常规有杆泵抽油井生产参数设计方法相结合，提出了有杆泵抽油系统在携砂生产条件下的参数设计方法。     

用人工神经网络对岩性及含油层的预测

本文将反向传播(BP)人工神经网络用于油井岩性及含油层的预测，根据测井资料中的深侧向电阻、微侧向电阻、自然电位及声波时差四个参数对18口油井的地层的岩层特性进行预测，通过将实际岩心数据与预测结果进行比较，预测的正确性达90％以上。这表明。该技术用于岩层特性及含油层的多参数预测是成功的，从而为开发智能化油井岩层特性及油气资源储藏特点的预测系统提供了依据。对于创造我困预测油气储藏的智能化系统具有重大意义。     

油井套管结构的最小成本设计

油井套管的最小成本设计是工程中关心的问题,本文提出了Fibonacci搜索法与相对差商法相结合的套管截面尺寸参数和扶正器布局问题的混合整数-离散变量优化方法,解决了多工况、多约束下套管结构的优化问题,已应用于工程实际。     

RVSP勘探炸药震源爆炸的数值仿真

针对RVSP勘探存在的既要获得高的地震波能量,又要保证油井套管不被炸坏的矛盾,在理论分 析的基础上,使用AUTODYN数值仿真软件,研究了油井材料对炸药能量传递的影响,得到了距离震源10m 处的质点振动速度和压力变化曲线;分析了炸药震源半径与油井套管的变形的关系;讨论了炸药震源长度与 其能量传递以及油井套管变形的关系。开展了相应的实验研究,数值仿真与实验结果吻合较好。研究结果可 以为RVSP勘探的工程应用提供参考和依据。     

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基于射孔完井水平裂缝中支撑剂均匀充填，考虑充填层强度、油层和流体 物性以及裂缝的渗流条件，研究了地应力及渗流引起的附加应力联合作用的支撑剂充填层渗 流模型和力学模型，并进行现场应用. 研究表明，所建立的模型对压裂油井支撑剂回采出砂 状况分析具有较高的符合率，油井总体符合率、不出砂井符合率和出砂井符合率分 别为84.66\%, 84.18\%和88.10\%, 为大庆油田压裂油井防砂措施实施方案制定提 供了决策支持，有利于提高措施有效率.     

高含水原油对油管和抽油杆摩擦磨损性能的影响研究

在实验室考察了油井产出液含水量对抽油杆和油管摩擦磨损性能的影响,采用扫描电子显微镜观察了抽油杆和油管试样磨损表面形貌.结果表明:当油井产出液含水量处于70%～85%之间时,抽油杆和油管摩擦副的摩擦系数和磨损率随含水量增加呈增大趋势;当油井产出液含水量小于70%或大于85%时,摩擦系数和磨损率变化较小;油井产出液含水量对抽油杆和油管试样磨损表面形貌亦具有明显影响,当含水量较低(55%)时,抽油杆和油管磨损表面较光滑,存在少量犁沟;而当含水量较高(95%)时,磨损表面出现宽而深的犁沟,呈现严重粘着和擦伤迹象.     

俄罗斯切割索的现状

介绍了俄国切割索的现状，叙述了其种类、生产原理和实际用于水下切割废石油井架的切割实例。     

油藏数值模拟中井筒压力梯度的校正方法

有限元法用于油藏数值模拟具有独特的优越性. 由于井筒附近流动的特殊性,直接采用 数值模拟得到的压力梯度计算油井产量会导致较大的误差. 本文分析了数值模拟中井筒压力 梯度产生误差的原因,在此基础上提出了计算井筒压力梯度的校正公式. 计算结果表明,压 力梯度校正公式可显著提高油井产量的计算精度,并能有效地减少井筒附近的网格剖分数量, 从而提高了计算效率.     

致密油储层毛细管力自发渗吸模型分析

部分致密油井压后关井一段时间,压裂液返排率普遍低于30%,但是致密油气井产量反而越高,这与压裂液毛细管力渗吸排驱原油有关。然而,致密油储层致密,物性差,渗流机理复杂,尚没有形成统一的自发渗吸模型。本文基于油水两相非活塞式渗流理论,建立了压后闷井期间压裂液在毛细管力作用下自发渗吸进入致密油储层的数学模型,采用数值差分方法进行求解,并分析了相关影响因素。结果显示渗吸体积、渗吸前缘移动距离与渗吸时间的平方根呈线性正相关关系,与经典Handy渗吸理论模型预测结果一致,说明毛细管力自发渗吸模型可靠性较高。数值计算结果表明毛细管水相扩散系数是致密储层自发渗吸速率的主控参数,毛细管水相扩散系数越高,自发渗吸速率越大。毛细管水相扩散系数随着含水饱和度先增加后减小;随着束缚水饱和度、油相和水相端点相对渗透率增加而增加;随着相渗特征指数、油水黏度比和残余油饱和度增加而减小。该研究有助于深入认识致密油储层压裂液渗吸机理,对优化返排制度、提高致密油井产量具有重要意义。     

田菁胶减阻用于油井压裂工艺取得良好效果

油井压裂工艺是大幅度增产原油的重要开采措施。用一定性能的植物胶加水配成粘稠的胶冻(水基压裂液),携带大量沙粒,填入油层中用强压压开岩层,使之出现宽裂缝,形成人工渗透层,可以提高油井的原油产量,很多国家已有报道。在燃化部规划院的组织下,经石油化工院、上海土产公司、大庆油田、胜利油田、      

A semi-analytic solution of a wellbore in a non-isothermal low-permeability porous medium under non-hydrostatic stresses

The transient stress, displacement, pore pressure and temperature fields around a wellbore in a thermo-poro-elastic (THM) medium subject to non-hydrostatic remote stresses are analyzed under non-isothermal plane-strain conditions. The linear THM model proposed by Coussy (1989) is adopted in the analysis with a focus on thermal effects in low-permeability saturated rocks, characterized by a latent heat associated with local changes of fluid mass content. Non-dimensionalized parameters are identified by reformulating the fully-coupled governing equations and boundary conditions. The wellbore problem is simplified by decomposing it into axisymmetric and deviatoric loading cases. The corresponding analytical solutions are obtained in Laplace space. The inverse Laplace transforms are performed numerically to find the time-dependent distributions of field variables in the rock mass around the wellbore. These numerical results show that although the pore pressure diffusion has little influence on temperature and stress, temperature changes can strongly affect the pore pressure and stress around the wellbore. The temperature change can lead to changes in near-well stresses and the resulting significant change in wellbore breakdown pressure illustrates the importance of considering the THM coupling.     

井筒气液两相流对致密气压裂水平井试井的影响

多段压裂水平井技术是目前开采致密气最常用的方法之一,在致密气压裂水平井试井测试中常常伴随着一定的产水量,井筒气液两相流会增加井筒流体的流动阻力,加大井筒流体流动对试井解释的影响.为了明确井筒气液两相流对致密气藏压裂水平井试井的影响,提高产水致密气压裂水平井的试井解释精度,建立了一种井筒气液两相流与地层渗流耦合的试井模型,采用数值方法对模型进行求解,获得了考虑井筒气液两相流的压裂水平井试井理论曲线、压力场分布及裂缝产量分布.研究结果表明:井筒气液两相流会增加试井理论曲线中压力和压力导数值,造成靠近入窗点的压力扩散要快于远离入窗点的压力扩散,引起靠近入窗点的裂缝产量要高于远离入窗点的裂缝产量.现场实例分析进一步说明,不考虑井筒两相流可能会对产水压裂水平井的试井解释结果产生很大误差,主要表现为水平井筒假设为无限大导流能力会使得拟合得到的表皮系数偏大,将测试点视为入窗点会使得拟合得到的原始地层压力偏小.所建立的考虑井筒两相流的压裂水平井试井模型为产水致密气井试井资料的正确解释提供了重要技术保障.      

Fluid-solid coupling model for studying wellbore instability in drilling of gas hydrate bearing sediments

As the oil or gas exploration and development activities in deep and ultra- deep waters become more and more, encountering gas hydrate bearing sediments （HBS） is almost inevitable. The variation in temperature and pressure can destabilize gas hydrate in nearby formation around the borehole, which may reduce the strength of the formation and result in wellbore instability. A non-isothermal, transient, two-phase, and fluid-solid coupling mathematical model is proposed to simulate the complex stability performance of a wellbore drilled in HBS. In the model, the phase transition of hydrate dissociation, the heat exchange between drilling fluid and formation, the change of mechanical and petrophysical properties, the gas-water two-phase seepage, and its interaction with rock deformation are considered. A finite element simulator is developed, and the impact of drilling mud on wellbore instability in HBS is simulated. Results indicate that the re- duction in pressure and the increase in temperature of the drilling fluid can accelerate hydrate decomposition and lead to mechanical properties getting worse tremendously. The cohesion decreases by 25% when the hydrate totally dissociates in HBS. This easily causes the wellbore instability accordingly. In the first two hours after the formation is drilled, the regions of hydrate dissociation and wellbore instability extend quickly. Then, with the soaking time of drilling fluid increasing, the regions enlarge little. Choosing the low temperature drilling fluid and increasing the drilling mud pressure appropriately can benefit the wellbore stability of HBS. The established model turns out to be an efficient tool in numerical studies of the hydrate dissociation behavior and wellbore stability of HBS.     

Flow Performance of Perforated Completions

A powerful approximate method for modeling the flow performance of perforated completions under steady-state conditions has been developed. The method is based on the representation of the perforation tunnels surrounding a wellbore by the equivalent elongated ellipsoids. This makes possible an analytical treatment of a 3D problem of steady-state flow in a porous medium with complex multiple production surfaces. The solution is obtained for a vertical wellbore fully penetrating through a horizontal formation in the presence of permeability anisotropy. The perforations are oriented horizontally, arranged in almost arbitrary patterns, repeating along the wellbore, and may have different lengths and shapes. The hydraulic resistances of perforations flowing inside them as well as the crushed zones around them with impaired permeability are neglected. The approximate solution found was verified by comparing the previous analytical/numerical solutions for a small number of perforations. This approach allows one to determine the local skin or the effective wellbore radius for any perforated interval, which can then be integrated into the conventional calculations of well productivity and used for the perforating gun selection during perforation job design.     

中国力学学会员2000年、2001年国际、国内学术活动计划(续)

本期新设立的这一“科学家谈力学”小栏目,是响应曾先后担任过中国力学学会理事长的钱令希、郑哲敏、王仁、庄逢甘、白以龙等５位院士“关于撰写科普文章,宣传力学贡献的倡议信”,为两院院士和资深教授用深入浅出的方式宣传力学对科学、技术、国防和经济建设所做的贡献,提供一个发表的园地．下面刊登的“倡议信"和王仁院士的文章,就作为本栏目的开篇．     

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.     

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。     

井壁失稳区域确定方法及影响因素分析简

井壁失稳区域及其面积能够反映井壁失稳破坏特性及其严重程度,以井壁安全系数作为识别准则,建立了井壁失稳区域识别方法,并基于Monte-Carlo 方法,给出了井壁失稳面积的计算方法. 以井壁坍塌为例,分析了钻井液密度、井斜角及方位角对井壁失稳区域特性的影响,以本文建立的失稳区面积计算方法,分析了不同地应力场中井眼轨迹对井壁失稳区大小的影响,评价结果符合工程实际,表明能够利用本文方法评价井壁失稳特性及其严重程度.     

Finite element formulation for transport equations in a mixed co-ordinate system: An application to determine temperature effects on the single-well chemical tracer test

Heterogeneous equation systems in a pair of coupled co-ordinate systems are solved by a finite element method. The specific physical application studied is the effect of temperature on single-well chemical tracer (SWCT) tests to measure residual oil saturation (volume fraction of immobile oil phase) remaining after waterflooding of an oil reservoir. Since temperature effects are caused by injecting cooler surface fluid down a well into a warm reservoir, the vertical temperature profile in the wellbore as well as the temperature distribution in the porous oil-bearing layer must be considered. The entire system is modelled to account for the different transport mechanisms. However, it is expedient to divide the connected geometrical region into two model domains. The equations for each submodel are expressed in an appropriate set of co-ordinates. The variational formulation of each model is then discussed. A significant temperature effect on the estimation of residual oil saturation occurs when the radial temperature and concentration wave propagation speeds in the porous formation are about the same. In this case the temperature gradient is located across the chemical tracer bank, causing the chemical reaction rate to vary radially. The temperature effects are demonstrated for two actual field tests in complex reservoirs.     

Sensitivity coefficients of single-phase flow in low-permeability heterogeneous reservoirs

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