无隔水管钻井浅部地层井筒循环压耗分析

Analysis of Circulating Pressure Drop in Surface Formation Wellbore in Riserless Drilling

无隔水管钻井液回收钻井技术能够较好地解决深水浅部地层的钻井难题。基于圆管流量方程及其在环空中的推广应用,分别建立钻柱内和环空中钻井液全流态的井筒循环压耗计算方法。算例分析结果表明,层流状态下钻柱内和环空中循环压耗随排量增大均缓慢增加,而过渡流和紊流下循环压耗随排量增加的速度较快;RMR无隔水管钻井系统在钻井过程中存在一个临界排量,只有泵排量不小于临界排量才能够保证井筒循环的连续性;钻遇浅部地层时井筒压力中还是钻井液液柱压力起主导作用,循环压力的影响相对较小。研究内容可为我国开展深水无隔水管钻井提供一定的技术支持。

Riserless mud recovery drilling technology can properly address the drilling difficulties in deepwater drilling in shallow formations?Based pipe flow equation and its application in the annulus, a wellbore circulating pressure loss calculation method for whole flow regime in drill pipe and annulus has been established?Study results show that, under laminar flow condition, pressure drop in the drill string and annulus increase slowly with the in?crease of flow rate?While under transition and turbulent flow condition, the circulating pressure drop grows faster with the increase of flow rate?RMR riserless drilling system has a critical flow rate?The pump displacement must be no less than the critical flow rate to ensure the continuity of wellbore circulation?During drilling shallow formation, the hydrostatic pressure rather than the circulating pressure drop, plays a leading role in bottom hole pressure?The study could provide technical supports for domestic deepwater riserless drilling.