摘要
气体钻井过程中,喷嘴处容易产生声速流,且在声速流条件下,伴随着压力间断和喷嘴低温,会导致钻头'冰包',环空压力急剧上升而立管却无法检测的现象,容易造成地面及井下事故。以超临界CO2气体钻井为例对钻头渐缩喷嘴压力、温度、流速变化对声速流的影响进行研究。结果表明:气体从喷嘴喷出后,压力急剧降低,体积快速膨胀,产生焦耳-汤姆逊效应,使得喷嘴出口温度急剧降低,降低幅度取决于气体性质以及上下游压力比;在进行气体钻井设计时,尤其是需要高压力、大排量喷射钻井时,首先要估算井底压力范围,再计算喷嘴上游临界压力,确定钻头上游安全压力带作为水力参数设计的参考标准,控制好井底与钻头上游之间的压力关系,避免声速流的发生。
The sonic flow occurred easily at the bit nozzles during gas drilling, meanwhile, the pressure discontinuity and low-temperature at the nozzle result in ice-bailing of bit which will further cause the pressure gauge failure on the standpipe with the annular pressure increasing rapidly, and the accidents will happen easily on the ground and downhole. The effects of pressure, temperature and velocity variation of the bit nozzles on sonic flow were investigated taking supercriticai CO2 gas drilling as an example. The results show that when the supercritical CO2 jets out from the bit nozzles, the pressure drops rap- idly and the volume expands suddenly. At the same time, Joule-Thomson effect occurs which results in the temperature of nozzle outlet drops suddenly and the decrease range of temperature depends on the gas properties and the pressure ratio between upstream and downstream. In the gas drilling design with high jetting pressure and large flow rate, first, estimate the downhole pressure, and then calculate the nozzle critical pressure of upstream and provide the secure pressure zone for the bit of upstream which can be regarded as reference standard for hydraulic parameters design. Controlling the pressure relation between the upstream of bit and the bottom hole can avoid sonic flow in the nozzles.
出处
《中国石油大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2010年第4期67-69,74,共4页
Journal of China University of Petroleum(Edition of Natural Science)
基金
国家'973'重点基础研究发展规划项目(2010CB226704)
关键词
钻井
声速流
喷嘴
温度
压力
二氧化碳
oil well drills
sonic flow
nozzle
temperature
pressure
CO2
