钻井全过程井筒-地层瞬态传热模型

A transient heat transfer model of wellbore and formation during the whole drilling process

井筒-地层温度是影响井筒压力控制、井壁稳定性预测、井下动力钻具与测量设备优选的关键因素之一。基于钻井液循环和停止循环期间井筒-地层各单元控制组件能量交换机理,建立了实际钻具组合与井身结构条件下循环和停止循环期间井筒-地层传热耦合数值模型。结合1口深井基础数据,分析了循环与停止循环期间井下温度分布规律。研究表明:套管下深长度对井筒温度影响较大,在套管段随着循环和停止循环时间增加,环空温度几乎不变,而在裸眼段随着循环时间增加环空温度降低,随着停止循环时间增加环空温度逐渐升高;循环期间钻井液对地层温度的扰动距离为2.8m,而停止循环期间扰动距离为4.6m。

Wellbore-formation temperature is one of the key factors that affects the wellbore pressure control,the sidewall stability prediction,and the optimization of mud motor and measuring equipments.Based on the energy exchange mechanism of individual control-unit components of wellbore and formation during circulation and circulation-stop periods of drilling fluid,we established a coupling numerical model for wellbore-formation transient heat transfer during circulation and circulation-stop periods under conditions of the actual downhole string assembly and casing program.Combined with basic data of a deep well,we analyzed wellbore and formation temperature distributions during circulation and circulation-stop periods and the results showed that the wellbore temperature distribution is remarkably influenced by casing length and the annular temperature in the casing section hardly changes with increasing the circulation and circulation-stop time.However,the annular temperature in the open-hole section decreases with the increase of the circulation time,while it gradually increases with the increase of the circulation-stop time.The disturbance distance of drilling fluid to the formation temperature is commonly about 2.8m during the circulation process,while it is about 4.6m during the circulation-stop period.