高原铁路冻土区低温环保钻井液体系设计与循环过程温度场分析

Design of low‑temperature green drilling fluid systems for frozen soil areas along plateau railway and analysis of the circulation temperature fields

川藏铁路位于高原高寒高山峡谷地带,沿线冻土覆盖率高达80%,环境生态脆弱。在地质勘察钻探施工中,钻井液不仅要有良好的耐低温性和流变性,还要满足环保性要求。本文以钠膨润土为钻井液造浆材料,NaCl为防冻剂,CMC和生化黄腐酸钾为降滤失剂,黄原胶为增粘剂;根据正交试验优选出0、-5和-10℃地层温度条件下的钻井液配方;利用ANSYS模拟软件对不同温度下钻井液在钻进循环过程中的温度场分布进行模拟;还设计了一种环保钻井液材料包。试验结果表明,优选的钻井液配方在低温条件下的流动性、动切力和粘度等方面性能良好,同时经济性和环保性也满足现场施工要求;模拟结果表明优选的4种低温钻井液在各自“适用温度”条件下防冻效果良好,安全系数高,能保证钻进过程的正常进行。

The Sichuan-Tibet Railway is located in the high‑cold and alpine valley area of the plateau.The permafrost coverage rate along the railway is as high as 80%,and the environment and ecology are fragile.In geological exploration drilling,drilling fluid should not only have good low temperature resistance and rheology,but also meet the requirements for environmental ptotection.Bentonite was used as drilling mud material,with NaCl as the antifreezer,CMC and biochemical potassium fulvic acid as the fluid loss reducers,and xanthan gum as the viscosity enhancer.The orthogonal test was used to optimize the drilling fluid formulations under the formation temperature conditions of 0℃,-5℃and-10℃.The ANSYS simulation software was used to simulate the temperature field distribution of the drilling fluid during the drilling period at different temperatures.An environment‑friendly drilling fluid material package was also designed.The test results show that the optimal drilling fluid formulation has good performance in terms of fluidity,dynamic shear force and viscosity under low temperature conditions;meanwhile,it also meets the field requirements for economics and environmental protection.The simulation results show that the four optimized low‑temperature drilling fluids provide good antifreezing effect and high safety under their respective“applicable temperature”conditions,which can ensure the normal progress of the drilling process.