China University Of Geosciences（Wuhan）
本文将超声处理与沉降法相结合，在5%高浓度淀粉溶液条件下制备纳米淀粉颗粒。通过超声处理可以降低5%高浓度淀粉溶液的粘度，再利用沉降法制备小粒径的纳米淀粉颗粒。该方法所制备的纳米淀粉颗粒平均尺度小至30nm，粒度主要集中于20-50nm、分布相对均匀，且在150℃能抗盐至20g/L NaCl。在基浆中加入1.0%的纳米淀粉颗粒后，表观黏度、塑性黏度、动切力和滤失量分别为22.0 mPa?s、14.5 mPa?s、11.5 Pa和9.3 mL。在150℃下老化16 h后，表观黏度、塑性黏度、动切力和滤失量分别为21.1 mPa?s、14.0 mPa?s、10.8 Pa和10.0 mL。纳米淀粉颗粒改善钻井液性能的机制在于，其与膨润土能形成网络结构，能提升钻井液的综合性能，且抗高温能力强。超声处理与沉降法相结合的方法操作简易，成本低廉，易于推广应用，所形成的技术能为开发一种新型的纳米钻井液体系提供重要的技术支撑。
In order to meet the requirements of environmental protection and efficient drilling of unconventional shale reservoirs, it is necessary to develop a new type of drilling fluid system with excellent performance and environmental friendliness. In this paper, ultrasonic treatment and precipitation method are combined to solve the problem. First, ultrasonic treatment is used to reduce the viscosity of starch solution with a high concentration of 5%. Thus, the precipitation method is used to prepare nano-starch particles under the condition of high concentration starch solution. After preparation by the method, the average size of the nano starch particles is as small as 30nm, and the particle size is mainly concentrated in 20-50nm with a relatively uniform distribution. The salt resistance of the nano starch particles is 20g/L NaCl at 150°C. After adding 1.0% nano starch particles to the base slurry, the apparent viscosity, plastic viscosity, dynamic shear force and fluid loss are 22.0 mPa.s, 14.5 mPa.s, 11.5 Pa and 9.3 mL, respectively. After aged at 150℃, the apparent viscosity, plastic viscosity, dynamic shear force and fluid loss after 16 hours are 21.1 mPa.s, 14.0 mPa.s, 10.8 Pa and 10.0 mL, respectively. More importantly, nano-starch particles and bentonite can form a network structure, which can increase the apparent viscosity, plastic viscosity, and shearing force of the drilling fluid, and decrease fluid loss, and it can still maintain excellent performance after aging under high temperature. The combination of ultrasonic treatment and sedimentation method is easy to be operated, low cost, easy to be promoted and applied. The formed technology can provide an important technical support for the development of a new type of nano-drilling fluid system.