影响连续油管摩阻系数及压降因素分析

Analysis on Causes of Affecting Friction Factors and Pressure Loss in Coiled Tubing

连续油管作业技术在油田得到广泛的应用,但是钻井液在油管内的摩阻系数的研究比较复杂,尤其是在卷筒上的螺旋段。现有的经验公式有些和工程实际出入较大,有些只适用于某一情况。因此在分析前人的基础上得到了连续油管直管段,螺旋段摩阻系数和影响因素。在牛顿流体方面研究了曲率对摩阻系数的影响,另外发现在雷诺数较高情况下粗糙度对其影响不容忽略;在非牛顿流体方面研究了曲率和流性指数对摩阻系数的影响。根据摩阻计算模型研究了压降与下入深度的关系。分析结果表明,由于二次流的影响,螺旋段的摩阻系数比直管段的要大,所以,在相同的条件下,螺旋段的压降要比直管段的压降大,流性指数增大1倍,摩阻系数增大近1.5倍。

The coiled tubing technology has been widely used in oil fields all over the world, but the friction factors caused by behavior of fluid flow are relatively difficult to research, especially in the CT twisting in reel. The current equations concluded from the experience differ from our engineering practice, or some just make sense in some specific occasions. In this paper, on the basis of former study, some equations used in straight tubing and coiled tubing were summarized, their impact factors were studied. The influence of curvature on the friction factor of Newtonian fluid was analyzed, and it＇s found that the roughness of tubing is a vital factor in analysis of Newtonian fluid flow when Reynold number is high. In Non-newtonian fluid flow, effect of curvature and flow behavior index on the friction factor was investigated. According to calculation model, the relationship between pressure loss and depth was studied. Analysis results show that the friction factor in CT is higher than that in straight tubing because of the secondary flow. So under the same conditions, the pressure loss in CT is bigger than that in straight tubing. If the flow behavior index doubles, the friction factor in Non-newtonian fluid flow increases 1.5 times.