In oilfield industry, well is the basis of crude oil exploitation, and drilling quality is one of the key factors of crude oil production. Most of the circulating fluid used in rotary drilling is liquid, also known as "drilling fluid". The main functions of drilling fluid in drilling engineering are as follows: 1. Cleaning the bottom hole and carrying cuttings; 2. Cooling and lubricating the bit and drill string; 3. Forming mud cake and protecting wellbore; 4. Controlling and balancing formation pressure; 5. Suspending cuttings and weighting agent; 6. Providing relevant information of the drilled formation.

Before 1920s, Natural mud drilling fluid formed by clear water and cuttings is used. Later, it was found that drilling fluid with good colloidal stability could ensure the safety of drilling, so chemical treatment agent for drilling fluid was developed. Now, polyacrylamide polymer has played an important role in filtration reduction, flocculation, shale inhibition, dilution and plugging in drilling.

Polyacrylamide flocculants used in drilling fluid include non hydrolytic polyacrylamide and hydrolytic polyacrylamide. The former belongs to total flocculant and the latter belongs to selective flocculant. There are great differences in the electrification and hydration degree between the drilling cuttings and the high-quality soil. The high-quality soil has a large negative charge and a large cation exchange capacity, strong hydration dispersion and thick hydration shell. However, the negative charge of the cuttings is less and the hydration shell is thin. There are only polar amide groups in NPAM. There is no negative charge, and the hydration shell is thin, and the repulsive force between it and high quality soil and poor quality soil is small. When the two kinds of particles meet, adsorption and bridging can occur. Therefore, NPAM flocculant not only flocculates drilling cuttings in drilling fluid, but also flocculates high-quality soil in drilling fluid. When HPAM reaches a certain degree of hydrolysis, it has higher negative charge density and thicker hydration shell. When it is close to the high-quality soil particles, there will be a large electrostatic repulsion force and hydration membrane repulsion force between them, so it is difficult to adsorb the high-quality soil particles; when it is close to the drilling cuttings, it is easy to produce adsorption, form flocculation agglomerates, remove them from the drilling fluid, and play the role of selective flocculation. Generally, the molecular weight of HPAM is more than 2 million, and the degree of hydrolysis is about 30%. The drilling speed is 19% higher than that of conventional drilling fluid and 45% higher than that of mechanical drilling fluid. In addition, the drilling fluid conditioner made of polyacrylamide can greatly reduce the sticking accidents, reduce the wear of equipment, and prevent the occurrence of lost circulation and collapse.