Influence of gas-containing on flow field characteristics and separation performance in oil-water separation string

doi:10.11949/0438-1157.20241327

Abstract

Abstract:

Single-well injection-production technology is an effective way to realize the economic exploitation of high water cut oilfield. However, the adverse effect of gas on the oil-water separation has become one of the main problems restricting the scale application of single-well injection-production technology. The research took downhole oil-water separation string with double pump suction production system as the research object, combining numerical simulation, PIV flow field test and High-speed camera experiment to study the influence law of different gas content on the flow field characteristics and separation performance. The results show that with the increase of inlet gas content, axial velocity in hydrocyclone overflow tube is reduced. The maximum tangential velocity in the swirl cavity decreases from 2.98 m/s to 2.88 m/s. In addition, due to the gas expands the low-pressure zone in the hydrocyclone, the pressure in the cyclone also decreases. Moreover, due to the gas will aggravate the turbulence phenomenon in the flow field, the maximum turbulent kinetic energy in the producing section string increases from 0.21 J/kg to 0.32 J/kg. With the increase of gas content, the oil phase separation efficiency show an accelerated decline trend, and it decreased the oil-water separation efficiency by 14.43% at most in research scope. It is validated by the agreement between the numerical and experiment results.

Key words: hydrocyclone, oil-water separation, single-well injection-production technology, separation performance, flow field analysis

摘要：

同井注采技术是实现高含水油田经济开采的有效途径，但含气条件对井下油水分离的不利影响成为限制同井注采技术规模化应用的主要问题之一。以双泵抽吸式油水分离管柱为研究对象，采用数值模拟、PIV流场测试及高速摄像实验研究方法，开展不同含气量下油水分离管柱的流场特性及分离性能研究。结果表明，含气量的增加会导致旋流器溢流管内轴向速度降低，旋流腔内切向速度最大值由2.98 m/s降低为2.88 m/s；此外，气相会扩大旋流器内低压区范围，致使旋流器内压力水平下降；并且，气相会加剧流场湍流现象，采出段内湍流动能最大值由0.21 J/kg增加到0.32 J/kg；随着含气量的增大，油相分离效率降幅加快，在研究范围内最大下降了14.43%。数值模拟结果与实验结果呈现较好的一致性。

关键词: 水力旋流器, 油水分离, 同井注采, 分离性能, 流场分析

CLC Number:

TQ 051.8

Minghu JIANG, Fan WANG, Lei XING, Lixin ZHAO, Xinya LI, Dingwei CHEN. Influence of gas-containing on flow field characteristics and separation performance in oil-water separation string[J]. CIESC Journal, 2025, 76(7): 3361-3372.

蒋明虎, 汪帆, 邢雷, 赵立新, 李新亚, 陈丁玮. 井下含气对油水分离管柱流场特性及性能影响[J]. 化工学报, 2025, 76(7): 3361-3372.

Figures/Tables 11

Fig.1 Structure and working principle of oil-water separation string

Table 1 Key structural parameters of oil-water separation string

主要结构参数	尺寸/mm
分离管柱总长L₁	1816
采出段L₂	530
旋流器总长L₃	482
倒锥长度L₄	210
回注段长度L₅	500
采出段直径D₁	75
旋流腔直径D₂	50
回注段直径D₃	75

Fig.2 Grid division and independence test

Fig.3 Experimental process flow chart

Fig.4 Experimental treatment and verification analysis

Fig.5 Axial velocity and flow diagrams at different positions

Fig.6 Tangential velocity and swirl intensity

Fig.7 Axial pressure and cross section pressure distribution under different gas content

Fig.8 Vortex core and minimum pressure of reinjection section

Fig.9 Turbulent kinetic energy and Reynolds number under different gas content

Fig.10 Gas，oil distribution and separation efficiency

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