PAC‑R and PAC‑L are brand names for polyanionic cellulose (PAC) — one of the most widely used filtration-control polymers in water-based drilling fluid. The generic product class is manufactured by multiple qualified factories and is specified by test performance, not by brand. Ironstone supplies drilling-grade PAC in high-viscosity and low-viscosity grades, with a certificate of analysis for every batch.
Polyanionic cellulose is a purified cellulose polymer — chemically, a sodium carboxymethyl cellulose manufactured to a higher degree of substitution and higher purity than regular technical-grade CMC. The higher substitution makes the polymer more soluble and more tolerant of salts and hardness, which is why PAC keeps working in seawater and field brines where cheaper CMC grades lose performance. In the mud, PAC does two jobs: it reduces API fluid loss by helping form a thin, low-permeability filter cake, and it adds viscosity to the water phase.
The two grades are the same polymer chemistry at different viscosity levels. The naming varies by supplier — L and LV mean low viscosity; R and HV mean regular or high viscosity — but the split is always the same:
| Grade | Main job in the mud | Choose it when |
|---|---|---|
| PAC HV / R class | Filtration control plus meaningful viscosity | You want one product to do both jobs — common in simple WBM programs and top-hole sections. |
| PAC LV / L class | Filtration control with minimal viscosity increase | The mud is already at target rheology and you only want the filtrate down — common in dense, solids-loaded, or brine systems. |
If you currently buy PAC‑R, the matching generic grade is a PAC‑HV; if you buy PAC‑L, the match is a PAC‑LV.
A brand name is not a specification. These are the parameters we compare between the candidate product’s COA and the data of the product you use today — at the same dosage, in the same test fluid:
| Parameter | Why it decides the match |
|---|---|
| Apparent viscosity at stated dosage | Confirms the grade (HV vs LV) and that dosing tables carry over without re-engineering the program. |
| API filtrate at stated dosage | The core job. Test in the fluid that matches your operation — fresh water, seawater, or saturated salt. |
| Performance in salt systems | Salt tolerance is what separates true PAC from lower-substitution CMC sold under a PAC label. |
| Purity / active polymer content | Diluted or blended products show up here — and in a price that looks too good per kilogram. |
| Moisture | Affects true active content per sack and storage life in humid ports. |
| Particle size and dispersion behavior | Decides how the product mixes through your hopper without forming fish-eyes (undissolved lumps). |
Test methods for polyanionic cellulose are covered by API Specification 13A. We report COA results against the 13A test procedures and state the edition on the document.
Do not switch a whole program on a lab sheet alone. Run the candidate PAC side by side with your current product: same dosage, same base fluid, same test sequence — viscosity, filtrate, and a mixing check through your actual hopper. If the bench results hold, run one well or one section on the candidate while your current product stays on the shelf as backup. Only then move the program. We support this sequence with a batch-specific COA, and a sample where the product qualifies.