Aiming at the technical problems such as fluid loss reduction, rheology and inhibition coordination, and well wall stability of ultra-high density drilling fluid system under high temperature and high pressure conditions, the ultra-high density composite brine drilling fluid system with a density of 2.6g/cm3 was developed by carrying out research work such as optimization of high-temperature resistant drilling fluid treatment agent, optimization of drilling fluid particle size distribution, and optimization of drilling fluid system composition.

The ultra-high temperature brine system provides:

- Strong salt resistance

- Good compatibility

- A wide range of applicable densities improves the problem of barite settling

- Good thermal stability under high temperature and pressure conditions

- Strong anti-pollution ability, good anti-pollution ability to inferior soil, bivalent ions and formation gases

- Drilling fluid rheology can be controlled

High temperature and high pressure filtration loss is small, mud cake is thin