Research on Scale Inhibition and Plugging Technology of Drilling Fluid in High-Salinity Scaling-Prone Reservoirs

In Zaoyuan-Wangguantun oilfield, when the drilling fluid intrudes into high-salinity scaling-prone reservoirs, inorganic scales are formed, blocking the oil-flow channels. Based on the Davis-Stiff saturation index method, the scaling trend was predicted, and static scaling experiments were carried out for verification. Meanwhile, an evaluation process for dynamic scaling damage of cores was established, and a preliminary understanding of the degree of inorganic scale damage to the reservoir during the drilling process was obtained. On this basis, the scale-inhibition and plugging agent PS-Ca was developed. After adding it to the drilling fluid, the scale-inhibition rate of the filtrate is over 90%, and the core permeability damage rate is controlled within 5%. This technology was field—tested in two wells in the Zaoyuan/Wangguantun oilfield. The core permeability recovery of the reservoir drilling fluid was 88.2%, and the initial daily oil production was 19.3 t, exceeding the expected production by 12.3 t. The research results show that the scale—inhibition and plugging technology can not only improve plugging to reduce the invasion of drilling fluid, but also reduce the inorganic scale damage to the reservoir caused by the invading filtrate, meeting the requirements for reservoir protection during the drilling process of high-salinity scaling-prone reservoirs in the Zaoyuan/Wangguantun oilfield.