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油井排砂用射流泵流体流动特性探讨

作者:完美论文网  来源:www.wmlunwen.com  发布时间:2020/11/18 15:01:51  

摘要:在油田开采过程中,受流体冲砂作用的影响,砂砾会逐渐从地层脱落并随流体进入油井中形成井底沉砂,由此造成油层的堵塞,导致油井产油率的下降,甚至停产。此外,当细砂进入采油设备,会对设备造成磨损,从而增加采油成本。因此,对油井进行清砂和排砂至关重要。射流泵本身不存在运动部件,其具有密封性好、性能稳定等优点,不易出现卡泵、堵泵等现象,因此其在油井排砂中的应用效果十分显著。然而,用射流泵进行油井排砂时,由于固相颗粒的存在,油井排砂射流泵的效率较低。因此,需要对油井排砂射流泵进行深入研究,分析油井排砂射流泵几何参数结构对射流泵性能的影响,优化射流泵,以及油井排砂射流泵内部流体流动特性研究。

本文对射流泵的基本理论和油井排砂射流泵进行了较为系统的阐述,采用数值计算的方法对油井排砂射流泵几何参数结构进行研究,同时对油井排砂射流泵流体流动特性进行了研究,分析了不同流量比、不同粘度、不同固相比和不同出口压力条件下,射流泵内湍动能、压力场和速度特性的变化,以及油井排砂射流泵特性曲线的影响因素。数值计算结果表明:

(1)油井排砂射流泵几何参数结构对泵效的影响主次顺序依次为面积比、喉嘴距、扩散管长度、喉管收缩角和喉管长度,其中影响油井排砂射流泵性能的主要因素是面积比;当油井排砂射流泵在面积比为5,喉嘴距为3.1mm,喉管长度为70mm,喉管收缩角为50°,扩散管长度为60mm时,油井排砂射流泵的效率最高。

(2)油井排砂射流泵的湍动能主要集中在喷嘴出口处和扩散管入口处,湍动能最大峰值出现在喷嘴出口处,随着流量比的增加,液固射流泵的湍流强度逐渐变小;随着固相比的增大,射流泵的吸入室的压力逐渐增加;射流泵在吸入室和喉管中存在逆流现象,在喷嘴出口处的压力较小时,容易造成逆流现象的出现。

(3)粘度在1mPa·s至5mPa·s变化时,粘度对油井排砂射流泵性能曲线的影响较小,当粘度在5mPa·s至10mPa·s变化时,粘度对油井排砂射流泵性能曲线的影响较强;油井排砂射流泵的性能曲线和效率曲线都随着流体粘度的增加而降低;随着流体粘度的增加,油井排砂射流泵的最佳工况点偏向小流量比方向。

(4)射流泵随着固相初始体积分数的不同,液固射流泵最佳流量比也不相同,最高效率也不相同;在固相初始体积分数变化范围为10%到30%之间时,最佳流量比的范围在0.9到1.1之间。

(5)在固相初始体积分数为10%时,流量比在1.0时效率最大,且最大值为17.3%;在固相初始体积分数为15%时,流量比在1.0时效率最大,且最大值为16.5%;在固相初始体积分数为20%时,流量比为1.1时效率最大,且最大值为15.8%;在固相初始体积分数为25%时,流量比在1.1时效率最大,且最大值为15.2%;在固相初始体积分数为30%时,流量比为0.9时效率最大,且最大值为14.8%;随着固相初始体积分数的增加,液固射流泵的最大效率减小。

关键词:射流泵;喉嘴距;效率;液固两相流;数值计算

Abstract: In the process of oilfield exploitation, affected by the sandblasting effect of the fluid, the sand and gravel will gradually fall off from the formation and form bottom sediment with the fluid into the oil well, thereby causing blockage of the oil layer, resulting in a decline in the oil production rate of the oil well, or even stop production. In addition, when fine sand enters oil production equipment, it will cause wear on the equipment, thereby increasing oil production costs. Therefore, it is essential to clean and drain sand in the oil wells. The jet pump itself has no moving parts; it has the advantages of excellent sealing performance,stable performance and so on, and is not prone to stuck pumps and blocked pumps. Therefore, its application effect in oil well sand drainage is very significant. However, when the jet pump is used to drain sand in oil wells, the efficiency of the jet pump for sand discharge in oil wells is low due to the presence of solid particles. Therefore, it is necessary to conduct in-depth research on the sand discharge jet pump of the oil well, analyze the influence of the geometric parameter structure of the sand discharge jet pump on the performance of the jet pump, optimize the jet pump, and study the internal fluid flow characteristics of the sand discharge jet pump of the oil well.

In this paper, the basic theory of the jet pump and the sand discharge jet pump of the oil well is systematically described. The numerical parameters are used to study the geometric parameter structure of the sand discharge jet pump of the oil well, and the fluid flow characteristics of the sand discharge jet pump of the oil well are also studied. The changes of turbulent kinetic energy, pressure field, and velocity characteristics in the jet pump under different flow ratios, different viscosities, different solid ratios, and different outlet pressures are analyzed, as well as the influencing factors of the characteristic curve of the sand discharge jet pump of the oil well. The numerical calculation results show that:

(1) The effect of the geometric parameter structure of the sand discharge jet pump of the oil well on the pump efficiency is in order of area ratio, throat distance, diffusion tube length, throat contraction angle and throat length, among which the performance of the sand discharge jet pump of the oil well has mainly affected The factor is the area ratio; when the sand discharge jet pump of the oil well has an area ratio of 5, the throat distance is 3.1 mm, the throat length is 70 mm, the throat shrinkage angle is 50°. The diffuser length is 60 mm, the sand discharge jet pump of the oil well is the most efficient.

(2) The turbulent kinetic energy of the sand discharge jet pump of the oil well is mainly concentrated at the nozzle outlet and the entrance of the diffusion tube. The maximum peak value of the turbulent kinetic energy appears at the nozzle outlet. With the increase of the flow ratio, the turbulent intensity of the liquid-solid jet pump gradually becomes smaller; With the increase of solid phase, the pressure of the suction chamber of the jet pump gradually increases; the jet pump has a reverse flow phenomenon in the suction chamber and the throat when the pressure at the nozzle outlet is small, which is easy to cause the reverse flow phenomenon.

(3) When the viscosity changes from 1mPa·s to 5mPa·s, the viscosity has little effect on the performance curve of the sand discharge jet pump of the oil well. When the viscosity changes from 5mPa·s to 10mPa·s, the viscosity has an influence on the performance of the sand discharge jet pump of the oil well. The impact of the curve is strong; the performance curve and efficiency curve of the sand discharge jet pump of the oil well decrease with the increase of the fluid viscosity; with the rise of the fluid viscosity, the best working point of the sand discharge jet pump of the oil well is biased towards the direction of small flow ratio.

Key words: Jet pump; throat distance; efficiency; liquid-solid two-phase flow; numerical calculation

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