长庆气田小井眼钻井液技术研究与应用

Study and Application of Drilling Fluid Technology for Slim Hole Drilling in Changqing Gas Field

为解决长庆气田小井眼施工中存在的井漏、地层自呼吸、井壁失稳、携岩困难、电测成功率低等问题,从水力参数、岩屑清除和钻井液体系入手,在兼顾降低循环压耗和提高环空净化能力的同时,设定合理的泵排量,以此预防井漏、避免地层自呼吸现象;从新的实验评价方法入手,结合小井眼钻井液施工特点,优选出复合抑制剂CQFY作为主抑制剂、天然高分子降滤失剂NAT20作为降滤失剂、无荧光白沥青NFA-25作为封堵剂,确定钻井液体系配方。2018年至今施工的φ165.1 mm井眼和φ152.4 mm井眼均使用了该技术。现场应用表明,该技术可有效保证井壁稳定,井径规则,并可预防井漏,避免地层自呼吸现象,提高了钻速,电测成功率高。完成φ165.1 mm井眼235口井,电测成功率为84.7%,φ152.4 mm井眼7口,电测成功率为100%,取得了较好的应用效果。

Mud loses,formation ballooning,borehole wall destabilization,difficulty in cuttings carrying and low success rate of wireline logging are problems encountered in slim hole drilling in the Changqing gas field.Technical measures have been taken to solve these problems.For example,reasonable flow rates can be used to prevent mud losses and formation ballooning,taking into account the reduction of circulation pressure and the improvement of hole cleaning.Also,in selecting the drilling fluid that was suitable for drilling the slim hole,new mud additive evaluation methods were used,taking into account the operational characteristics of slim hole drilling fluids,to select CQFY as the main inhibitor,a natural polymer NAT20 as the filter loss reducer and a non-fluorescence white asphalt NFA-25 as the sealant.Using these additives,a drilling fluid was formulated through optimization.The drilling fluid technology aforementioned has been used to drill theφ165.1 mm hole section andφ152.4 mm hole section since year 2018.Field operation showed that the drilling fluid technology effectively mitigated the drilling problems previously encountered;totally 235 wells ofφ165.1 mm in diameter and 7 wells ofφ152.4 mm in diameter were drilled successfully,borehole wall collapse,mud losses,formation ballooning were avoided and ROP increased.Success rates of wireline logging for theφ165.1 mm andφ152.4 mm wells were 84.7%and 100%,respectively.