深层页岩气水平井井筒瞬态温度场研究与应用

Research and Application of Wellbore Transient Temperature in Deep Shale Gas Horizontal Wells

深层页岩气水平井钻井过程井筒瞬态循环温度对旋转导向工具的选择具有重要作用。基于井筒与地层间的对流换热机理及能量守恒原理,建立了井筒瞬态温度场模型;分析了循环时间、排量、水平段长度和入口温度对井筒瞬态温度的影响;优选了页岩气水平井轨迹控制方法,提出了降低井底循环温度的工程措施。结果表明,上部井段环空钻井液循环温度随循环时间和排量的增加而增加,而下部井段环空钻井液循环温度反而降低;随着水平段长度增加,环空钻井液循环温度增加,水平段越长,循环降温效果越低;随着钻井液入口温度增加,钻井液出口温度增加,下部井段环空钻井液循环温度随入口温度的变化较小。当垂深超过4000 m后,水平段较短时,可采用旋转导向钻井工具;水平段较长,井底循环温度高于135℃后,推荐采用螺杆配LWD测量工具。采用增加循环时间、排量及边循环边下钻的方式可降低井底循环温度,以确保旋转导向工具和LWD工具处于安全工作温度内。

Wellbore transient circulation temperature is of great importance in the selection of rotary steering tool during the deep shale gas horizontal well drilling process.A wellbore transient temperature model was established with consideration of heat exchange mechanism between the wellbore and the formation and the principle of energy conservation.The effects of circulation time,flow rate,horizontal length and drilling fluid inlet temperature on the annulus transient temperature were analyzed.The shale gas horizontal well trajectory control method was optimized,and then the measures for reducing the bottom hole circulation temperature were proposed.The results show that the annulus drilling fluid temperature in the upper part increases with the increase of circulation time and flow rate,while the drilling fluid temperature in the lower part decreases.As the horizontal length increases,the annulus drilling fluid circulation temperature increases,and the longer the horizontal length,the lower the cycle cooling effect.With the increase of the drilling fluid inlet temperature,the drilling fluid outlet temperature increase,but the drilling fluid temperature in the lower part changes little.When the vertical length is more than 4000 m,the rotary steering drilling tool can be used with the short horizontal length,and the downhole motor with LWD measuring tool is recommended for long horizontal length and bottom hole circulation temperature is higher than 135℃.The bottom hole circulation temperature can be reduced by increasing the circulation time and flow rate and using the circulating while tripping-in,so as to ensure that and the rotary steering tool and LWD tool are within the safe working temperature.