Carboxymethyl cellulose (CMC) is mainly used as a viscosity enhancer and filtrate reducer in drilling operations. By improving the performance of drilling fluids, it ensures wellbore stability, enhances chip carrying efficiency, and reduces formation damage. It is a key treatment agent in water-based drilling fluid systems.

1、 Core function: dual effect of increasing viscosity and reducing filtration loss
CMC plays two core functions in drilling fluids and has been validated by multiple studies and engineering practices:
Thickening effect
CMC dissolves in water to form a high viscosity colloidal solution, which can significantly increase the apparent viscosity and plastic viscosity of drilling fluids.
Enhance the suspension ability of rock debris to prevent rock debris from settling and causing buried or stuck drilling when the pump is stopped;
Improve rheological properties to enable drilling fluid to more effectively carry cuttings to the surface during circulation.
Filtration reduction effect
Under the action of pressure difference, CMC can quickly form a thin and dense filter cake in the wellbore:
The carboxyl sodium groups in its molecular chain ionize to form a strong hydration layer, preventing free water from infiltrating the formation;
At the same time, through adsorption bridging, clay particles aggregate into a network structure, reducing the permeability of the filter cake, and the API filtration loss can be controlled within 10mL.
2、 Auxiliary functions: wall protection, salt resistance, and thermal stability
In addition to its main functions, CMC also has multiple engineering advantages:
Stable wellbore: By suppressing shale hydration expansion, the risk of wellbore collapse is reduced, especially suitable for water sensitive formations.
Good salt resistance: It can be stably used in freshwater to saturated saltwater and is suitable for a variety of complex ion environments.
Strong temperature resistance: Conventional CMC can withstand high temperatures of 130-150 ℃. If antioxidants (such as sodium sulfite) are added, the temperature resistance can be increased to over 160 ℃.
Good compatibility: It has good compatibility with various drilling fluid treatment agents (such as humic acid and polyols) and is suitable for low solid and solid free drilling fluid systems.
3、 Application scenarios and engineering value
Widely used in conventional onshore wells, shallow water drilling, and high-temperature deep well pre exploration sections;
Widely used in high salinity areas such as Xinjiang, effectively solving the problem of water loss control in saltwater drilling fluids;
As an environmentally friendly treatment agent, it is biodegradable and in line with the development trend of green drilling.