深水控制泥浆帽钻井水力参数设计与计算

Design and Calculation of Hydraulic Parameters for Controlling Mud Cap in Deepwater Drilling

深水控制泥浆帽钻井技术可以应对严重漏失地层和高压、高含硫地层的钻井问题,但钻井水力参数的设计与计算较为困难。为此,结合深水钻井工艺流程,建立了深水控制泥浆帽钻井井底压力计算模型,给出了深水钻井不同工况下的钻井液密度确定准则和钻井液当量循环密度计算方法,并基于井筒内循环压耗分析得到了水面泵和水下泵的泵压计算方法;针对严重漏失地层和高压、高含硫地层的井筒压力分布特点,给出了该工况下的泥浆帽高度计算方法;结合井眼清洁准则和漏失量与漏失压差的关系,给出了牺牲流体排量计算方法,并以此为基础提出了深水控制泥浆帽钻井水力参数设计流程。以一口深水井为例,对控制泥浆帽钻井水力参数进行了算例分析,结果表明:泥浆帽高度主要由井底压力的大小决定,钻井液密度与排量的大小可对其产生一定影响,所以通过调节泥浆帽高度可以控制井筒压力。

Deepwater control mud cap drilling is an advanced technology to deal with thief zone, high- pressure and high sulfur-bearing formation,but its drilling hydraulic parameters design and calculation are more complex. According to the drilling process in deepwater,the calculation model of BHP for deepwater control mud cap drilling was established. The guidelines for determining drilling fluid density under differ- ent conditions and calculation method of ECD were proposed, based on the analysis of circulating pressure loss,the calculating methods for pump pressure were put forward at subsea and surface respectively. The calculation method of mud cap height was proposed according to the characteristics of wellbore pressure distribution in thief zone,high pressure and high sulfur-bearing formation. Based on the wellbore cleaning rule and the relationship between lost amount and lost pressure differential, the calculation method of sacri- ficed flow rate was proposed, and hydraulic parameter design process for deep water controlled mud cap drilling was put forward. Based on the basic data of a deepwater well, hydraulic parameters for deepwater mud cap drilling were calculated and analyzed. The results show that the mud cap height is mainly decided by bottom-hole pressure,the density and flow rate have some impact, thus wellbore pressure can be con- trolled by adjusting the mud cap height.