水平井中钻柱旋转对岩屑运移影响规律研究

由于水平井井身结构的特殊性,岩屑较易在斜井段及水平段中沉积形成岩屑床,进而导致卡钻等一系列问题。分析了水平井岩屑运移机理,并建立了水平井中岩屑运移临界流速数学模型。研究钻柱偏心度、转速、井斜角、岩屑粒径及流体粘度对于临界流速的影响。研究表明,钻柱转速增大,直井段岩屑运移临界流速增大,水平段岩屑运移流速减小;井斜角较小时,岩屑运移所需的临界流速随偏心度增大;井斜角较大时,在偏心度较小条件下,岩屑运移所需的临界流速略有增大;而在偏心度较大条件下,岩屑受钻柱转动影响进入悬浮运移状态,运移所需的临界流速急剧减小。岩屑粒径越大其运移所需的临界流速越高,钻井液黏度的增大有利于降低岩屑运移临界流速。

Study on the Influence of the Rotation of Drill String on Cuttings Transportation in Horizontal Well

Because of the peculiarities of the casing program of horizontal well, it"s easier for cuttings to deposit in the horizontal and inclined sections of the wellbore and cause a series problems such as pipe sticking etc. in the operation. This paper analyzes the mechanisms of cuttings transport in horizontal wells and establishes the mathematical model of critical velocity for cuttings transport to study how eccentricity, rotate speed, inclination, cuttings size and viscosity affect the critical velocity. We draw the conclusion that with the rotate speed of the drilling string increases, the critical velocity increases in vertical section and in contrast decreases in horizontal section. When the inclination is relatively small, critical velocity increases with the increase of the eccentricity; when the inclination is larger, critical velocity increases slightly with small eccentricity and decreases sharply in large eccentricity because of the suspension state of the cuttings affected by the rotation of the string. The critical velocity is higher if the cuttings size is greater. Increasing the viscosity of the drilling fluid is good for reducing the cuttings transport critical velocity.