“零电位”水基钻井液体系

Study and Application of "Zero Potential" Water Base Drilling Fluid

针对塔里木油田深井、超深井上部地层泥页岩水化膨胀阻卡,下部地层温度高,常规水基钻井液性能调控、维护困难等问题,通过优选阳离子抑制剂CPI、阳离子包被剂CPH-1和CPH-2、阳离子降滤失剂CPF-1和CPF、阳离子封堵剂CPA等,形成了一套＂零电位＂水基钻井液体系。该体系阳离子浓度可达8 000 mg/L,其黏土颗粒的Zeta电位可达-10 m V左右,稍高于原地层条件下岩屑颗粒的Zeta电位,从而阻止电荷迁移,稳定井壁;在1.0~2.3g/cm3密度范围内,在80~180℃下,在很少处理剂加量下,体系均表现出良好的流变性和降失水能力;能抗20%盐、2%钙和5%黏土污染。该钻井液在塔里木油田已应用20余井,由钻井液引起的事故与复杂损失时间相比于传统水基钻井液减少10.2%,机械钻速提高14.9%,钻井周期缩短9.8%,为深井安全、快速、高效钻井提供了新的钻井液体系。

The ＂zero potential＂ theory was used to optimize the formulation of drilling fluid used in deep well and ultra-deep well drilling in Tarim Basin to overcome shale swelling and pipe sticking in top formations and difficulties in mud property maintenance in lower deep formations.Using optimized cationic polymers,a ＂zero potential＂ water base drilling fluid was formulated.This drilling fluid had high concentration of cations,and clay particles of high zeta potential,almost equal to or slightly higher than the zeta potential of the ＂in-situ＂ drilled cuttings,meaning that the potential difference between the formation and the drilling fluid is ＂zero＂,hence greatly mitigating the possibility of borehole wall instability caused by frequent migration of electric charges between formation and drilling fluid.This drilling fluid also had good rheology and filtration property,and was resistant to contaminations from the introduction of salt,calcium and clays,especially at high temperatures in deep and ultra-deep wells.The ＂zero potential＂ drilling fluid had been used in 20 wells in Tarim Basin.Compared with conventional water base drilling fluids,total time spent in dealing with drilling fluid-related downhole troubles was reduced by 10.2%,ROP increased by 14.9%,and drilling time reduced by 9.8%.The successful application of the ＂zero potential＂ drilling fluid in Tarim Basin provides a means of fast,safe and efficient drilling deep wells,and enriches and further develops the idea of ＂zero potential＂ drilling fluid.