页岩水平井环保型多硅基水基钻井液技术

Environmental friendly water-based drilling fluid using multiple silicon treatment agents for horizontal wells in shale reservoir

关键词:  页岩水平井  水基钻井液  硅基处理剂  环保性  抑制性  封堵性  润滑性

Key words:  horizontal well in shale reservoir  water-based drilling fluid  silicon treatment agent  environmental friendliness  inhibition  plugging  lubricity

摘要:

针对页岩水平井钻井过程中使用水基钻井液时面临的井壁易失稳、钻具摩阻扭矩大,井眼清洁困难等技术难题,通过引入硅酸钾钠、有机硅改性腐植酸钾盐、聚倍半硅氧烷等硅基处理剂,构建了环保型多硅基水基钻井液体系。该体系所用处理剂EC₅₀＞3×10⁴ mg/L,为无毒级别,抗温180 ℃,流变性能稳定,具有良好的抑制性、封堵性和润滑性,页岩滚动回收率98.53%,页岩线性膨胀率0.26%,HTHP失水量≤2.8 mL,极压润滑系数0.081,泥饼黏滞系数0.042,重金属含量满足二级排放标准,BOD值/COD值高达31.7%,易生物降解,表现出优异的环境友好性。环保型多硅基水基钻井液在东平1井页岩水平段进行了成功应用,钻进期间未发生任何井下复杂情况,动塑比保持在0.41 ～0.48,钻具摩阻6~8 t,平均井径扩大率仅为3.85%,平均机械钻速达10.28 m/h,在国内首次实现了水基钻井液在页岩水平段中的应用。 

Abstract:

In view of the technical problems of poor wellbore stability, high friction torque of drilling tools and bad borehole cleaning when using water-based drilling fluid in the horizontal wells in shale reservoir, an environmental friendly water-based drilling fluid used multiple silicon treatment agents was formed, which is consist of multiple silicon treatment agents such as potassium sodium silicate, organosilicon modified potassium humate, and polysilsesquioxane. The EC₅₀ of the agents used in this system is more than 3×10⁴ mg/L, reaching the non-toxic level. The temperature resistance of the system reaches 180 ℃, the rheological property is stable, and it has good inhibition, plugging and lubricity. The shale rolling recovery is more than 98.53%, the shale expansion rate is below 0.26%, the HTHP is less than 2.8 mL, the extreme pressure lubrication coefficient is 0.081 and the viscosity coefficient of mud cake is 0.042. The heavy metal content of the new water-based drilling fluid meets the requirement of secondary discharge national standard, and the BOD/COD is up to 31.7%, which is easy to be biodegraded, showing an excellent environmental friendliness. The drilling fluid has been successfully applied in the shale horizontal section of Dongping-1 well, effectively ensuring the stability of the shale horizontal section. The dynamic/plastic ratio maintains at 0.41-0.48, and the average wellbore diameter expansion rate of the horizontal section is only 3.85%. During drilling, the friction resistance of drilling tool is 6-8 t, and the average ROP is 10.28 m/h. It is the first application of water-based drilling fluid in shale horizontal section in China.