管输剪切模拟搅拌槽中流体平均剪切率的计算

计算搅拌槽内流体剪切率的Metzner-Otto方法只适用于计算某些叶轮搅拌槽系统内层流时叶轮区的平均剪切率,不能满足原油管输过程剪切作用模拟的需要。根据流体流动的能量耗散率与剪切率的关系,提出了通过搅拌的轴功率计算搅拌槽全槽流体平均剪切率的方法。针对牛顿流体和幂律流体,提出了全槽平均剪切率的计算式。以实验室用的一个小型搅拌系统为例,使用所提出的方法,建立了槽内流体平均剪切率与搅拌转速、流体体积、幂律流体稠度系数及流动特性指数关系的经验数学模型。该模型预测的结果与直接由实测扭矩计算的平均剪切率相当接近。本方法适用于各种类型的叶轮,不受流体流态的限制,其原理还适用于符合其他流变模型的非牛顿流体。     

剪切作用对聚丙烯酰胺驱油剂黏损率的影响规律

用控制应力流变仪,考察了30℃、不同剪切速率下,聚丙烯酰胺（HPAM）溶液表观黏度随剪切时间的变化,以反映管流剪切条件对HPAM溶液黏度的影响规律。根据现场条件,通过计算得到不同浓度HPAM驱油剂在输送管线流动对应的剪切速率和剪切时间。结果表明,在剪切速率为3.11⁷.76 s^-1、剪切时间为55²2min时,高浓度（5000mg/L）HPAM驱油剂黏度随剪切时间的延长略有上升,单位时间黏损率为-0.43%/h^-0.91%/h。在输送过程中的管流剪切对高浓度HPAM驱油剂黏度损失没有影响。在剪切速率为36.84⁹2.10 s^-1、剪切时间为2.26⁰.90h时,低浓度（1000、2000mg/L）HPAM驱油剂黏度随剪切时间的延长逐渐降低,单位时间黏损率分别为0.08%/h⁰.86%/h、0.07%/h⁰.30%/h。在低浓度范围内,随着HPAM驱油剂浓度的降低,剪切历史对HPAM驱油剂黏度及黏损率的影响增大。浓度的提高有利于降低驱油剂的黏损率。     

定性判别电潜泵剪切作用造成产液乳化的数值模拟方法

地层产液乳化是开采过程中常见的储层伤害类型之一。电潜泵剪切作用有可能造成或加剧产液乳化。产液乳化在流入井筒前产生还是在井筒内造成，判断难度较大。利用多相流连续性方程、动量方程、能量方程，建立考虑剪切作用的井筒多相流动态理论模型。将各相分量代入方程，建立油田产液的井筒多相流动态理论模型。再代入实际生产数据，建立适合油田的数学模型，计算了5口井产液量，与实际产液量相近，表明模型合适。预测该油田5口典型井的原油含水率分别为0、20%、40%、60%、80%时，井深与井内流体压力分布关系。结果表明，将产液提升单位高度消耗的能量，泵前小于泵后，电潜泵加剧了产出液的乳化程度。该研究为较准确地判断是否产液乳化造成储层伤害提供了依据。     

不同剪切率下含蜡原油触变性的描述式

评价含蜡原油管道停输再启动安全性的核心工作之一,是管道再启动压力的计算,而要获得准确的计算结果,则有赖于可靠的触变性数学表征.对4参数双曲模型进行改进,给出一个描述含蜡原油触变性的6参数关系式,该关系式计算较简便,能够描述含蜡原油在不同剪切率下的触变行为.对4种含蜡原油在24个温度下的触变性实验数据进行拟合表明,最低相关系数为0.847 2,最高相关系数为0.993 0,总平均相关系数为0.939 1.     

长输管线气体泄漏率的计算方法研究

应用计算流体力学理论,给出了长输管线气体泄漏率新的计算方法.当管线破坏的孔径较小(属于小孔泄漏)时,采用孔模型计算气体泄漏率;当管线发生全截面断裂时,利用管线模型计算;孔径介于两者之间时则利用新推荐的方法.由计算实例可知,管内起始压力大于1.5MPa时,临界流阶段泄漏的气体质量占总泄漏质量的90%以上,可用临界流阶段的平均泄漏率代替总平均泄漏率;也可用起始泄漏率的30%近似代替总平均泄漏率.随管内起始压力的增加,这种近似效果更好.利用文中的数学模型可以较好地估算不同孔径的气体泄漏率,可为定量评价长输管线失效后对环境的影响提供依据.     

基于COMSOL的剪切速率对超声波流量测量影响分析

为了分析影响超声波流量测量结果的因素,提高超声波流量测量的准确性,需要研究聚合物溶液剪切速率对于流体流态和超声波流量计接收声压的影响,利用多物理场有限元软件COMSOL建立超声波流量计三维模型进行仿真,通过流体域的背景流速曲线和超声波接收器波形图来分析剪切速率的影响。结果表明,在其他条件不变的情况下,随着剪切速率的增大流体流态趋向于湍流,超声波流量计接收器声压最大值与最小值相差1%,其对超声波流量计测量结果影响较小可忽略。     

大庆原油的粘弹性实验研究

用RSH150控制应力流变仪对大庆原油进行了振荡剪切实验。结果表明,储能模量和耗能模量随测量温度的降低呈指数规律增加;存在使流变性恶化的“最差加热温度”;降温速率越高,测量温度下蜡晶结构强度和胶凝温度越低。在同样的剪切温度下,粘弹性参数和胶凝温度随粘性流动能量耗散增加而急剧降低直至达到稳定状态;在同样的粘性流动能量耗散下,剪切温度越接近测量温度,储能模量和耗能模量越低,胶凝温度越低;当剪切温度接近或超过反常点时,测量温度下的粘弹性参数基本不随剪切温度变化;原油结构在经历剪切后具有不可逆的恢复特性。     

搅拌测量法测定油水混合液流动特性

对于非均匀混合(乳化)、不稳定的油水两相体系,传统的黏度计无法测量其黏度。通过搅拌可以维持油水两相的均匀混合状态,并且搅拌轴的扭矩反映了流体的当量黏度。基于这一原理,建立了搅拌测量油水混合液流动性的方法,包括搅拌桨叶类型的选择、根据搅拌轴扭矩确定一定搅拌转速下的黏度、根据搅拌转速及流体黏度确定搅拌槽的平均剪切率。针对单相原油和油水混合液,将该方法的测量结果分别与同轴圆筒黏度计和试验环道的测试结果进行了对比,验证了其可靠性。应用该方法,对高含水油水混合液在不同温度和含水率条件下的流动性进行了测量,结果具有良好的规律性。     

密闭取心饱和度校正动态模型及影响因素分析

针对密闭取心过程中孔隙、流体体积和溶解气随压力下降而改变导致测试饱和度出现较大误差的问题,应用油藏工程和渗流力学等理论与方法,基于溶解气驱理论和多相流分流量原理,建立了综合考虑孔隙、流体体积和溶解气随压力变化的岩心饱和度校正动态模型,编制了相应的计算流程,并评价了各影响因素的敏感性。结果表明:按岩心综合油水饱和度改变率大小排序,影响密闭取心饱和度的因素依次为溶解气体黏度、溶解气油比、原油体积系数、原油黏度、油水相对渗透率、原油压缩系数和岩石压缩系数。密闭取心饱和度校正动态模型能够反映压降过程中岩心的饱和度变化,吻合取心过程中的变化趋势,且校正结果和标定饱和度的相对误差平均为0. 8%,可为分析实际油藏油水饱和度分布提供可靠的依据。     

剪切作用与加剂原油粘度关系的数学模型

分析了剪切作用对加剂大庆原油粘度的影响规律,建立了剪切后加剂原油粘度与剪切过程中粘性流动熵产关系的数学模型.根据剪切效应的一般规律及机理,提出了近似确定模型中参数的简易方法.按照此方法,只须测定一定温度下空白原油的粘度或表观粘度、未剪切时加剂原油的粘度或表观粘度,及在某一个剪切温度下及某一个粘性流动熵产条件下原油的粘度或表观粘度,即可近似确定该数学模型中的参数,从而预测在不同温度时剪切后的原油在该温度下的粘度或表观粘度.结合含蜡原油粘度与温度关系机理模型,还可以预测同一加剂原油经受剪切后在其他温度下的粘度.对中原原油和加剂轮南丘陵混合原油加剂试验数据的验证结果表明,该模型有较好的预测准确性.     

Effects of Thermal and Shear History on the Viscoelasticity of Daqing Crude Oil

The relationship between the viscoelasticity and thermal and shear history of waxy crude is important for the safety analysis of waxy crude pipeline operation. A series of oscillatory shear experiments were performed to test the viscoelastic parameters of Daqing crude oil with a controlled-stress rheometer RSH150. The results indicate that the storage modulus and loss modulus increase in an exponential fashion with decreasing testing temperature. There exists a worst heating temperature for the rheological behavior. The strength of waxy structure and gelation temperature increase as the cooling rate is reduced. The shear action is characterized by energy dissipation due to viscous flow. At the same shear temperature, the strength of waxy structure decreases rapidly and finally attains a stable state as the energy dissipation due to viscous flow is increased. Keeping the same energy dissipation due to viscous flow, the closer the shear temperature is to the test temperature, the lower storage modulus, loss modulus, and gelation temperature would emerge. When being close to or higher than the abnormal point, the shear temperature has few influences on the viscoelasticity. The recovery of waxy structure after shear action exhibits an irreversible property.     

Effects of Thermal and Shear History on the Viscoelasticity of Daqing Crude Oil

Abstract

The relationship between the viscoelasticity and thermal and shear history of waxy crude is important for the safety analysis of waxy crude pipeline operation. A series of oscillatory shear experiments were performed to test the viscoelastic parameters of Daqing crude oil with a controlled-stress rheometer RSH150. The results indicate that the storage modulus and loss modulus increase in an exponential fashion with decreasing testing temperature. There exists a worst heating temperature for the rheological behavior. The strength of waxy structure and gelation temperature increase as the cooling rate is reduced. The shear action is characterized by energy dissipation due to viscous flow. At the same shear temperature, the strength of waxy structure decreases rapidly and finally attains a stable state as the energy dissipation due to viscous flow is increased. Keeping the same energy dissipation due to viscous flow, the closer the shear temperature is to the test temperature, the lower storage modulus, loss modulus, and gelation temperature would emerge. When being close to or higher than the abnormal point, the shear temperature has few influences on the viscoelasticity. The recovery of waxy structure after shear action exhibits an irreversible property.     

井下油管的流动诱导腐蚀数值模拟研究

根据现代流体力学的基本理论建立了流体运动的连续性方程、动量、湍流动能、湍流耗散率的守恒方程以及化学组分的传质守恒方程。根据流动诱导腐蚀的特点,建立了流动诱导腐蚀的数学模型。采用SIMPLE算法求解流动数学模型,用壁函数法计算了管壁附近湍流边界层的流体力学参数,并用VisualBasic6.0编制了计算机程序,对油管腐蚀过程进行了数值模拟。模拟结果表明,在正常生产过程中,油气井油管的中上部腐蚀严重,建议油管防腐工作的重点放在降低中上部油管的腐蚀方面。应用文中方法及求解程序,设计合理的油管直径及组合,可防止或减轻由于腐蚀、冲蚀等对油管造成的严重后果,减少油气井的维护费用,从而取得良好的经济效益。     

Friction pressure correlations for turbulent flow of drag reducing polymer solutions in straight and coiled tubing

Accurate determination of friction pressure losses of dilute drag reducing polymer solutions remains to be a challenge in many practical applications. These include a wide variety of hydraulic operations performed on a daily basis in the oil and gas industry. Most drilling, completions, and stimulation jobs require pumping fluids at high flow rates, which in turn generates high frictional pressure losses, enhanced by the use of small diameter tubing or coiled tubing. Curvature in this latter is believed to generate secondary flows and thus extra flow resistance. Therefore, good drag reduction characteristics of fluids are desirable.In this study, energy dissipation by eddies in turbulent flow of viscoelastic fluids is assumed to be the mechanism causing drag reduction. Various concentrations of Nalco ASP-700 and Nalco ASP-820 dilute polymer solutions are tested at ambient temperature in laboratory-scale and full-scale flow loops installed with straight and coiled tubing sections exhibiting different values of diameter, curvature ratio and pipe roughness. In addition, flow tests are conducted at 100 °F and 130 °F using the laboratory-scale flow loop.Effects of concentration, temperature, curvature ratio, and pipe roughness on drag reduction are discussed in light of Fanning friction factor versus solvent Reynolds number plots. Results show that drag reduction in coiled tubing is lower than in straight tubing. As curvature ratio increases, drag reduction decreases. The effect of increasing temperature is to decrease drag reduction in straight tubing and increase it in coiled tubing. In turn, the effect of increasing pipe roughness is to slightly decrease drag reduction in straight tubing up to a certain Reynolds number value and then it starts to increase. For coiled tubing, the effect of increasing pipe roughness is to decrease drag reduction.In this study, generalized correlations for the prediction of drag reduction in dilute polymer solutions flowing in straight and coiled tubing are developed on the basis of the energy dissipation of eddies in turbulent flow field and a shear rate dependent relaxation time. In addition, correlations are validated using experimental data for a low concentration guar fluid flowing through full-scale flow loop.     

基于CFX的水平管等径三通失效分析数值模拟

应用计算流体动力学（CFD）方法及CFX软件,建立水平管等径三通中的流体湍流和冲蚀数学模型。考虑等径三通近壁面处湍流的衰减,设定流动介质的气相为连续相,液相为离散相,边界条件设定为质量入口和压力出口组合,其中进口为气液两相质量流量和体积分数,出口为截面平均静压。采用稳态模拟和有限体积法对充分发展的气液两相流管内流动进行数值模拟,经过计算得到流动介质的速度流线、速度矢量及气液分布。其中,气相速度最大为21．2m／s,液相速度最大为13．4m／s;流速增大时,气液两相流的壁面切应力相应增大,气相最大切应力为36．87Pa,液相最大切应力为68．24Pa。剪切力破坏管壁腐蚀产物膜,加剧腐蚀产物膜的脱落。综合各因素解释等径三通冲蚀磨损的原因,同时结合失效样品壁厚检测结果,论证气液两相流对水平管等径三通冲蚀磨损的失效规律。     

油水分离器中水洗流场液滴破裂特性初探

对水洗流场中液滴的界面膜剪切破裂机理进行了分析和初步探讨,认为水洗流场中控制着液滴产生变形和剪切破裂的无因次群有3个,其中韦伯数群控制着液滴的破裂;在紊流状态的水洗流场中,导致液滴破碎的水力学因素可归结为由于时均的速度梯度而产生的粘性剪切力和由于紊流而产生的瞬时剪切力和局部压力波动等;当流场动压力所提供的流场能量较小时,主要以粘性剪切力为主控制着液滴的变形;当连续相提供的能量达到使液滴破裂的能量时,瞬时剪切力和局部压力波动将控制着液滴的破碎。当液滴振动的动能Ek≥液滴的表面自由能Es,液滴发生破裂。     

内管旋转的垂直同心环形管内单相流动特性的试验研究

分别以空气、油、水为工作介质对内管旋转的垂直同心环形管内的单相流动特性进行了系统的试验研究。首先在100 Re 70000的范围内对内管不转的环形管内的摩擦阻力进行了试验测定,并与几种摩阻关系式进行了比较,得出同心环形管内紊流摩擦系数比圆管摩擦系数约高6%~10%,Sadatomi的关系式可用于4000 Re 70000的范围内的紊流计算。采用测量轴向摩擦压降的方法,对内管旋转的环形管内的流动离心不稳定性以及摩阻进行了试验研究,得出了直径比小于0.8时,层流向层流+Taylor涡旋的转换边界及紊流+Taylor涡旋向紊流的过渡边界,并针对不同流型给出了适用于较大环形间隙环形管的摩阻关系式。