非直井气体钻井岩屑起动的临界流速

注气量作为气体钻井的关键参数，直接关系到现场钻井的成败。目前用于气体钻井的注气量计算方法均是基于垂直井眼得到的，对于水平井、大斜度井的情况并不适用，从而给气体钻井在水平井、大斜度井的应用造成很大困难。在分析岩屑颗粒运动方式的基拙上，假设岩屑颗粒沉积在下井壁，注入气体后对岩屑颗粒进行受力分析，得到不同井斜角情况下岩屑颗粒起动所需的临界流速模型。以此速度作为气体的最小流速，从而得到最小注气量。分析认为，在井斜角为60700的情况下，岩屑颗粒起动所需气体速度最大;大粒径岩屑对注气量要求很高，实际钻井过程中应采用适当方法减少大粒径岩屑的数量

Starting velocity of cutting particles in gas drilling of horizontal or highly deviated well

Gas injection rate as the key parameters of gas drilling directly relates to the suecess of actual drilling. At present, the calculation methods of gas injection are based on vertical wells. These methods do nni apply for horizontal wells and highly deviated wells, which leads to the great diffieuhy fla application of gas drilling. Based on the analysis of movemenl mode of cutting particles, this paper first assumes that the cutting particles deposit in the low wall of bnrehule, then analyzes the stress of cutting particles after gas injection. The starling velocity model of cutting particles in different deviation angles is gotten, and this velocity is taken as the minimum velocity of gas, which can be used for ealeulating the minimum gas injection rate. Analysis suggests that the starling velocity of cutting particles reaches the maximum in the deviation angle 60-70°; Ihe large size cutting particles require a high starting velocity and the number of large size cutting particles should be reduce by using appropriate methods in actual drilling proicess.