Drilling fluid is essential in oil drilling operation, which can carry and suspend cuttings, stabilize borehole wall and balance formation pressure, cool and lubricate drill bits and drilling tools, and transmit hydrodynamic force. The performance of drilling fluid directly affects the wellbore quality and drilling speed. At the same time, with the development of petroleum exploration, the drilling depth is increasing, and the number of cluster wells, highly deviated directional wells and horizontal wells is also increasing rapidly. Avoiding differential pressure sticking, reducing drilling tool torque and reducing drill string wear have become urgent problems to be solved in drilling operations.

Adding lubricant to drilling fluid is one of the most effective measures to reduce differential pressure sticking, reduce drilling tool torque and reduce drill string wear. At present, lubricants used at home and abroad can be divided into two categories: one is liquid lubricants, such as petroleum and its products, modified products of animal and vegetable oils, etc. Second, solid lubricants, such as graphite powder, key disulfide powder, plastic pellets, glass pellets and metal pellets.

Among them, the use effect of plastic pepper balls is better than other lubricants. It is a copolymer produced by cross-linking styrene and divinylbenzene, and plastic pepper balls are added in drilling operation to make it participate in the formation of mud cake, so as to prevent the adhesion of drilling tools and mud cake and achieve the purpose of lubrication and anti-sticking. Plastic pepper balls are non-toxic, odorless, non-fluorescent, acid-resistant, alkali-resistant, recyclable, and so on. Their density is usually 1. 03~I. 05g/cm3, and their temperature resistance is above 190°C, and their compressive strength is above 100N. They are inert in drilling fluids, insoluble in water and oil, and suitable for most types of drilling fluids. At the same time, their surface viscosity, dynamic shear force and compressive strength are also affected. However, the plastic small pepper ball solid lubricant for drilling fluid produced by current technology has limited temperature resistance and extrusion resistance, uneven and low particle size, and uneven density distribution, which can not fully meet the needs of drilling engineering; At the same time, due to the high density of existing plastic pepper balls, they are easy to sink in drilling fluid and are unevenly distributed, which limits the application of plastic pepper balls as solid lubricants in drilling fluid.