In the oilfield industry, CMC (Carboxymethyl Cellulose) and PAC (Polyanionic Cellulose) are commonly used additives in drilling fluids, completion fluids, and other oilfield applications.

CMC (Carboxymethyl Cellulose)

Function: 

CMC is primarily used as a viscosifier, fluid-loss control agent, and rheology modifier in water-based drilling fluids.

Properties: 

Helps in controlling filtration loss by forming a thin, low-permeability filter cake on the wellbore.

Improves the viscosity of drilling fluids, providing better hole-cleaning efficiency.

Enhances the stability of drilling fluids, especially in water-sensitive formations.

Types: 

CMC-LV (Low Viscosity): Primarily used for fluid-loss control.

CMC-HV (High Viscosity): Used for both viscosity enhancement and fluid-loss control.

PAC (Polyanionic Cellulose)

Function: 

 PAC is a higher-performance derivative of CMC, commonly used as a fluid-loss control agent and        viscosifier in drilling and completion fluids.

Properties: 

Superior fluid-loss control compared to standard CMC.

Provides better thermal stability, making it more effective in high-temperature applications.

Improves mud rheology and prevents shale hydration and swelling.

Types: 

PAC-LV (Low Viscosity): Used mainly for fluid-loss control with minimal impact on viscosity.

PAC-HV (High Viscosity): Used for both viscosity enhancement and fluid-loss control.