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当鑽孔中发生卡鑽和陷埋事故,采用一般处理方法无效时,則需要反囘井内鑽具,这不仅需要很長时間,同时容易产生鑽桿脫落事故。为此,我們利用了中和点反囘鑽具的方法反囘井內鑽桿。这一方法經初步試用,效果很好。当鑽具在孔內不吊悬时,每个連接絲扣均受压力,其压力分佈情况是上部小,下部大,故上部絲扣在扭卸时的摩擦力也小于下部絲扣扭卸摩擦力。所以当反囘鑽桿时,多是一次从上部反囘几根或一、二根,因而花費时間較長。假如我們針对上述情况將鑽具絲扣的摩擦力,加以調整,即上部絲扣摩擦力大于下部絲扣摩擦力,使在鑽桿柱下部造成一个中和点(鑽桿柱中不受張力,也不受压力的地点称中和点),
When a stuck drill and a buried accident occur in the borehole, if the general treatment method is invalid, the drill tool in the well needs to be reversed, which not only takes a long time but also easily causes the drill pipe to fall off accidentally. To this end, we use the method of neutralizing the drill bit to reverse the drill pipe in the well. This method after a preliminary trial, the effect is very good. When the drill does not hang in the hole, each connecting thread buckle under pressure, the pressure distribution is the upper small, the lower part of the upper thread buckle in the twisting of the friction is less than the lower thread twist twist friction . So when the drill pipe back, mostly from the top back a few or one, two, and thus take longer. If we adjust the friction of the drill threading against the above situation, that is, the upper threading friction is greater than the lower threading friction, resulting in a neutralization point in the lower part of the drill string (the drill string free from tension , And the place without pressure is called neutralization point)