深层页岩油水平井复合盐弱凝胶钻井液技术

Technology of compound salt weak gel drilling fluid for long horizontal wells in deep shale oil reservoirs

王广财 刘万成 陈向明 郑江波 马平平 熊开俊 孔繁玲

WANG Guangcai LIU Wancheng CHEN Xiangming ZHENG Jiangbo MA Pingping XIONG Kaijun KONG Fanling

中国石油吐哈油田分公司采油工艺研究院 长江大学石油工程学院

Research Institute of Oil Production Technology, PetroChina Tuha Oilfield Company, Hami 839000, Xinjiang, China College of Petroleum Engineering, Yangtze University, Wuhan 430100, Hubei, China

吐哈油田准东吉新2区块深层长段水平井钻井过程中存在泥岩井壁易失稳、井眼净化难度大、减摩降阻困难等问题，对钻井液抑制性、封堵防塌性、携岩性和润滑性提出了较高要求，为此，进行了钻井液技术研究。采用NaCl、KCl、甲酸钠和ZNP-1复配，使钻井液体系具有强抑制性，解决了井壁失稳难题；采用“沥青粉+丙烯基树脂封堵剂+固壁剂”实现了微米~亚微米~纳米孔喉微裂缝全封堵；采用低荧光润滑剂和囊包减阻剂复配，提高了钻井液润滑能力；采用弱凝胶提切剂提高了钻井液携岩能力。最后形成了复合盐弱凝胶钻井液体系配方：清水+4%膨润土+0.2%烧碱+15%NaCl+5%KCl+15%NaCOOH+1%ZNP-1+1%DRGJ-1+0.5%LV-CMC+4%沥青粉+2%树脂封堵剂+2%固壁剂+0.3%弱凝胶+2%低荧光润滑剂+3%囊包减阻剂+重晶石，并对其性能进行了评价，结果表明：16 h泥页岩线性膨胀率为7.21%，动切力不小于11 Pa，滤饼黏滞系数不大于0.061 2，钻井液活度不大于0.76，高温高压滤失量低于10 mL，可抗10%钻屑和5%CaSO₄污染。在吉新2区块应用5井次，与邻井吉新2、吉新2-2井相比，钻井周期降低了33.05%，二开平均井径扩大率降低了68.49%，平均复杂率降低了68.19%。该技术为油田同类型深层长段水平井安全优快钻井提供了技术支撑。

When drilling long horizontal wells in the deep reservoir of Block Jixin 2 in Tuha Oilfield, several challenges were identified, including the instability of shale wellbore, difficulty in hole cleaning as well as challenges in reducing friction and resistance. This prompted the need for advanced drilling fluid technology with high performance in inhibiting properties, sealing and collapse prevention, cutting carrying capacity and lubrication. Therefore, a study on drilling fluid technology was conducted. By compounding NaCl, KCl, sodium formate and ZNP-1, the drilling fluid system exhibits strong inhibition, effectively addressing the wellbore instability issue. The system employed "asphalt powder + acrylic resin plugging agent + wall cementing agent" to achieve full plugging of pores and fissures of micron, sub-micron and nano size. Additionally, a combination of low-fluorescence lubricant and encapsulated friction reducer was used to enhance the lubrication capability of the drilling fluid. A weak gel shear thinning agent was incorporated to improve the carrying capacity of the drilling fluid. The formulation of the compound salt weak gel drilling fluid system is finalized as follows: water+4% bentonite+0.2% caustic soda+15%NaCl+5%KCl+15%NaCOOH+1%ZNP-1+1%DRGJ-1+0.5%LV-CMC+4% asphalt powder+2% resin plugging agent+2% solid wall agent+0.3% weak gel+2% low-fluorescence lubricant+3% encapsulated friction reducer+barite. The performance of this system was evaluated, and the results showed a linear expansion rate of 7.21% of mud shale after 16 hours, a dynamic shear force of not less than 11 Pa, a filtrate viscosity coefficient not exceeding 0.0612, a drilling fluid activity of not more than 0.76, a high-temperature and high-pressure filtrate loss less than 10 mL, and resistance against 10% drill cuttings and 5% CaSO contamination. The technology was applied in 5 wells in Block Jixin 2, and when compared to neighboring wells such as Jixin 2 and Jixin 2-2, the drilling cycle was reduced by 33.05%, the average wellbore diameter enlargement rate decreased by 68.49%, and the average complexity rate decreased by 68.19%. This technology provides a technical support for safe and efficient drilling of similar deep long horizontal wells in oilfields.

10.13639/j.odpt.202307067