塔式立管气液两相流的压力波动特性试验研究

为了研究深水油气田塔式立管系统气液两相流压力波动特性,通过室内试验分析了不同流型下的压力变化特征、压力波动幅值等。室内试验得到了6种流型,每种流型对应特定的压力波动形式,且最大波动幅度出现在严重段塞流向稳定流转变过程中的过渡流型Ⅱ上。通过分析立管底部的最大、最小压力,得出如下规律:压力波动幅值随折算气速的增加呈现先增大后减小的趋势,且流型的转变对气速的敏感性高于液速。通过概率密度函数(Probability Density Function,PDF)和累计分布函数(Cumulative Distribution Function,CDF)的统计学分析,得出系统压力的PDF和CDF曲线在各种流型下的分布形态:下倾管底部压力PDF曲线在严重段塞流下高压区单峰特征显著;过渡流型下左右两峰相当,呈两端高、中间低的形态;稳定流型下峰值数量增加、压力范围集中;CDF曲线在高压区的拐点与PDF曲线的峰值对应。跨接管底部压力PDF曲线峰值均处于低压区,且中间高、两端低。在严重段塞流下,曲线呈现双峰和三峰分布,稳定流表现为单峰对称分布。结合压力PDF和CDF曲线可辅助分析和判别流型,并直观获得塔式立管系统压力概率分布特征,以此作为其疲劳损坏和安全评估的参考依据。

Experimental investigation on pressure fluctuation characteristics of gas-liquid two-phase flow in hybrid tower riser

In order to investigate the pressure fluctuation characteristics of gas-liquid two-phase flow in the hybrid tower riser system in deep-water oil and gas fields, an indoor test was carried out in this paper to analyze the varying characteristics,amplitude fluctuation and other characteristics of pressure in different flow patterns. In the test, six flow patterns were identified.Each flow pattern is corresponding to the specific pressure fluctuating pattern, and the maximum fluctuating amplitude occurs in the transitional flow pattern Ⅱ during the transform from the severe slugging flow to stable flow. It is shown that the pressure fluctuation amplitude increases firstly and then decreases with the increase of the superficial gas velocity by analyzing the maximum and minimum pressures at the bottom of the riser, and the change of flow pattern is more sensitive to gas velocity than liquid velocity. The pressure distribution characteristics under different flow patterns were obtained based on the statistical analysis of Probability Density Function(PDF) and Cumulative Distribution Function(CDF). In the working condition of severe slugging,the PDF curve for the pressure at the bottom of the downward inclined pipeline presents the remarkable characteristic of single peak in the high pressure zone, that in the transitional flow pattern has two equal peaks at the right and the left sides in the form of high in both ends and low in the middle, and that in the stable flow pattern has more peaks with a narrow range of pressure. The turning point of CDF in the high pressure zone corresponds to the peak of the PDF curve. The peaks of the PDF curves for the pressure at the bottom of the jumper pipe are in the range of low pressure zone and they are high in the middle and low in both ends. The PDF curves present two or three peaks in the working condition of severe slugging and a single symmetrical peak in the pattern of stable flow. In conclusion, combined with PDF and CDF curves of pipeline pressure, flow patterns can be discriminated and analyzed, and the system pressure probability distribution characteristics can be attained intuitively, so as to provide the important basis for the fatigue damage and safety assessment of pipelines.