长北气田水平井钻井液润滑剂的优选与应用

为降低长北气田152.4 mm水平段钻进中的扭矩和阻力，尽可能地增加水平段长度，提出在原有钻井液体系的基础上，通过更换无荧光植物油润滑剂，提升钻井液体系的润滑性，以满足现场钻井要求。润滑剂ETL与体系具有良好的配伍性能， 浓度为1%时，摩擦系数降低率可达到60%。静、动态润滑性评价实验结果均表明：ETL的加入，钻井液可以在钻具表面形成良好的润滑膜，从而降低体系摩擦系数，静态可降低50%，动态可降低30%。静态岩心伤害实验平均伤害率为5%，动态岩心伤害实验平均伤害率为11%。根据上述室内研究成果，选用润滑剂ETL作为钻井液体系，在CB2-3井水平段钻井中应用，钻进中扭矩控制在18 kN·m以内，顺利钻完两个分支井，其中第一分支井水平段长为1 316 m，第二分支井水平段长为Φ1 929 m，后者刷新了中国陆上Φ152.4 mm小井眼水平段长度的纪录。

Selection and application of drilling fluid lubricant for horizontal wells in the Changbei gas field

It is a challenge for the engineers to increase the horizontal section as long as possible and reduce the torque and resistance during drilling in the horizontal section of 152.4 mm in the Changbei gas field. Thus, based upon the previous drilling fluid system, the non fluorescence rape oil was used for lubricant so as to meet the requirement of drilling operation on fields by improving the lubricity of the drilling fluid system. The experiment on the selection of lubricants shows that the lubricant, ETL, is more compatible with drilling fluid than the others and the reducing rate of friction coefficient is up to 60% at 1% of the concentration of ETL. It is seen from the static or dynamic experiments on assessing the lubricity after the addition of ETL, there is such good lubricity film formed on the surface of drilling strings that the coefficient of friction can reduce significantly, the reducing rate of coefficient is 50% under the static test or 30% under the dynamic test. The average rate of static damage on cores is about 5% and the one of dynamic damage on cores is 11% and SEM photos verify further that ETL can not give rise to further damage on cores or reservoir. According to the indoors study results, the lubricant ETL was added into the drilling fluid to be applied successfully in the well CB2 3: the torque was maintained less than 18 kN·m; the two horizontal branch wells were drilled smoothly, with the first branch is 1316 meters long and second one 1929 meter long, the length of which set up a new record for 152.4mm horizontal hole on Chinese continent.