页岩气水平井钻井沉砂卡钻监测方法研究及应用

Research and application of monitoring methods for solids settling and sticking in shale gas horizontal well drilling

页岩气有利目标箱体地层多发育天然微裂缝,呈现硬脆性力学特征,地层稳定性差,水平井钻进过程中井壁容易剥落产生掉块,如果不能及时将掉块从井筒环空循环排除,可能导致钻井沉砂卡钻事故。鉴于目前还无法直接测量井壁剥落掉块严重程度,进行了利用随钻环空压力监测环空掉块数量及其在环空中分布情况的研究。通过定义最小关泵压力、最大关泵压力、平均关泵压力、停泵和开泵状态及停泵时间实现了环空压力监测窗口自动捕捉;根据提取不同窗口的特征建立随钻环空压力数据与停泵期间井壁剥落掉块严重程度表征关系,通过定义沉砂卡钻风险等级实现了对页岩气钻井沉砂卡钻风险评价。现场测试实例表明,该方法可以实现对沉砂卡钻风险的识别,有助于对沉砂卡钻事故的预判和预防,提高页岩气水平井施工安全性,具有现场应用推广价值。

Natural micro-fractures mainly develop in favorable target box formation of shale gas,presenting mechanical characteristics of hard and brittle and the formation stability is poor.During the drilling of horizontal wells,wellbore wall easily peels off and produces blocks.If the block cannot be removed in time from the annulus circulation of wellbore,drilling solids settling and sticking accidents may occur.Given the fact that the severity of wellbore peeling is not yet possible to be directly measured,a study of monitoring the number of annulus blocks and their distribution in annuls using the annulus pressure while drilling was conducted.By defining the minimum pump shutoff pressure,maximum pump shutoff pressure,average pump shutoff pressure,pump shutoff and on status and pump shutoff time,automatic capture of annulus pressure monitoring window was realized.Phenetic relationship between annulus pressure data and the severity of wellbore wall peeling while drilling was established based on the characteristics of different windows.By defining solids settling and sticking risk rank,the risk assessment of solids settling and sticking in shale gas drilling was realized.Field test examples showed that this method can realize the identification of solids settling and sticking risk.It is conductive to the pre-judgement and precaution of solids settling and sticking,improving the safety of shale gas horizontal well construction,and is worth on-site promotion and application.