In drilling operations, the efficiency of mud systems plays a critical role in ensuring operational success, cost control, and formation stability. Among the essential additives used in water-based drilling fluids, Polyanionic Cellulose (PAC) stands out for its versatility and performance. PAC is generally classified into two primary types: PAC-LV (Low Viscosity) and PAC-HV (High Viscosity) ,also called PAC R. Each serves distinct functions depending on the specific drilling environment and project goals.

What Is PAC?

PAC is a cellulose-based polymer used to improve the rheological and filtration properties of drilling mud. It is compatible with both fresh and saline water systems and is favored for its biodegradability and minimal environmental impact.

PAC-LV vs. PAC-HV: Key Differences

PAC-LV is designed to provide low viscosity while delivering effective filtration control. It is particularly suitable for low-solids mud systems, often used in horizontal drilling and high-rate circulation operations. This grade contributes minimally to the fluid’s yield point, making it ideal when maintaining thin, manageable mud is crucial. Typical dosage rates for PAC-LV range from 0.3 to 1.0 lb/bbl.

On the other hand, PAC-HV significantly increases the viscosity of the drilling fluid while also offering strong filtration control. This makes it an excellent choice for vertical and deviated wells, especially where enhanced hole cleaning is necessary. PAC-HV also contributes to gel strength and overall mud stability. The recommended dosage generally falls between 0.5 and 2.0 lb/bbl.

Advantages of PAC-LV

• Excellent for low-solids mud systems
• Controls fluid loss without significantly altering mud viscosity
• Reduces differential sticking
• Performs well in high-salinity environments

Advantages of PAC-HV

• Enhances mud viscosity and gel strength
• Better hole cleaning in vertical and inclined wells
• Offers superior fluid-loss control
• Suitable for both fresh and brine-based fluids

Choosing the Right PAC Grade

The choice between PAC-LV and PAC-HV depends on operational needs. PAC-LV is the preferred option when the objective is to control filtration without increasing viscosity—especially valuable in high-circulation environments or when using sensitive downhole tools. In contrast, PAC-HV should be selected when increased viscosity is needed to carry cuttings more effectively, particularly in large-diameter or deep wells.

Industry Insight

With increasing demand for environmental compliance and cost-effective solutions, PAC polymers—especially when sourced from reliable suppliers—offer sustainable and performance-driven benefits in drilling fluid formulations.