油气井钻井过程中井喷预测机理研究

A study of blowout prediction mechanism during drilling in oil and gas wells

在油气井钻井作业过程中,井喷前会有各种预兆如:①钻井液返出量增加;②钻井液池中钻井液体积增加;③停泵后钻井液外溢;④循环系统压力上升或下降;⑤钻井时悬重增加或减少;⑥返出的钻井液中有油花气泡等。上述预兆对预防井喷起着至关重要的作用。为此,在分析井喷原因及井喷预测机理的基础上,利用钻压、大钩负荷、转盘转速、返出流量、泵压、钻井液密度、硫化氢浓度等,建立了井喷预测数学模型,提出了井喷事故发生的危险指数,通过对该指数的计算和分析,便可预测井喷事故发生的可能性。实例验证结果表明,该井喷预测模型能为防止井喷的发生提供科学依据。

During the drilling process,these phenomena usually appear just before blowout breaks out,such as the amount of backflow increased,the volume of drilling fluid in the pit increased,drilling fluid overflown after pump off,the circulating pressure increased or dropped,suspension weight increased or decreased,oil and/or gas to be observed in the backflow drilling fluid.These phenomena play a vital role in preventing blowout.Herein analysis is made on the causes and prediction mechanism of well blowout,based on which a mathematical model for blowout forecast is established,parameters like WOB,hook load,rotary RPM,backflow volume,pump pressure,drilling fluid density and H2S content are included within.The risk indexes of blowout are then proposed.The possibility of a blowout can be predicted by calculating and analyzing the risk indexes.And finally the newly established model is proved to be able to provide scientific evidence for blowout prevention through many case studies.