深水超深井钻井井筒温度剖面预测

Prediction of the borehole temperature profile in ultradeep drilling under ocean deepwater conditions

在深水海域进行超深井钻井时,钻井液温度变化幅度较大,温度剖面的准确预测对于深水超深井的安全钻进至关重要。为了准确预测深水超深井钻井温度剖面,为深水超深井钻井设计提供借鉴,通过能量守恒原理建立了钻井温度剖面的计算模型,考虑不同井段的传热方式不同,将井身结构分为海水段、套管段、裸眼段进行分析,并通过数值法求解。通过实例计算对影响温度剖面的因素进行了分析。结果表明,钻井液循环300 min后,钻井液温度剖面趋于稳定;钻井液在整个循环过程中,温度差可达150℃;排量对井壁温度的影响较小,对井底钻井液温度的影响较大,且排量越大,井底温度越高;由于目的层较深,入口温度对于井底温度的影响较小。研究结果可为我国深水超深井安全钻井提供参考。

The temperature of drilling fluid varies greatly when drilling an ultra deep well in deepwater sea area,so the accurate prediction of temperature profile is crucial to the safe drilling of deepwater ultra deep well.In order to accurately predict the borehole temperature profile of deepwater ultra deep well and provide the reference for the drilling design of deepwater ultra deep well,a model for calculating the borehole temperature profile was established according to the principle of energy conservation.In view that the heat transfer mode is different in different hole sections,the hole structure was divided into seawater section,casing section and open hole section for analysis and it was solved by means of numerical method.In addition,the factors influencing the temperature profile was calculated and analyzed by virtue of case calculation.It is shown that the temperature profile of drilling fluid tends to be stable after it is circulated for 300 min.In the whole circulation process of drilling fluid,the temperature difference is up to 150℃.The displacement has less influence on borehole temperature and greater influence on the drilling fluid temperature at the bottom hole.And besides,the greater the displacement is,the higher the bottom hole temperature is.The target layer is deeper,so the influence of the inlet temperature on the bottom hole pressure is less.The research results can provide the reference for the safe drilling of deepwater ultra deep wells in China.