动态近平衡连续油管钻井

动态近平衡连续油管钻井是指在钻进中利用欠平衡钻井液体系产生的静液柱压力与循环产生的当量循环密度（ECD）的静液柱压力共同作用，使井底压力高于孔隙压力；当泵速和实际当量循环密度发生改变、以及起下连续油管或更换底部钻具组合时，采用井口回压来维持近平衡条件。文中以阿拉斯加北部斜坡一超高压储层中几口连续油管过油管侧钻井为实例，陈述了连续油管超小井眼定向钻井系统与非常规方法相结合，维持井眼近平衡条件，进行近平衡连续油管钻井的经验。

DYNAMICALLY OVERBALANCED COILED-TUBING DRILLING

Dynamically overbalanced coiled-tubing drilling is to combine the hydrostatic pressure of an underbalanced mud system with the ECD's developed while circulating to maintain downhole pressures above pore pressure.Surface backpressure is to be used to maintain near-constant overbalanced conditions while the pump rate and resultant ECD varide or while tripping the CT and changing the BHA.In this paper,there are several through-tubing Coiled-Tubing sidetracking of wells in an overpressured reservoir on the North Slope of Alaska as examples to describe an ultraslimhole directional-drilling system combined with an unconventional approach to maintain overbalanced conditions when sidetracking these wells.