PAC HV (polyanionic cellulose, high viscosity) is a water-soluble anionic polymer used in water-based drilling fluids to build viscosity and carry cuttings out of the hole. It is produced by carboxymethylation of cellulose, and the high-viscosity grade delivers substantially more rheology per pound than PAC LV — which is why it is the standard choice for hole cleaning in large-diameter and deviated sections.
RAHA Gilsonite Co. supplies drilling-grade PAC HV from Turkish production, shipped from Mersin, Ambarlı and Izmir, alongside the rest of the water-based mud package: PAC LV, CMC, KCl, bentonite and gilsonite.
What PAC HV Is
Polyanionic cellulose is cellulose that has been chemically modified so the polymer chain carries negatively charged carboxymethyl groups. Those charges keep the chain extended in water, and an extended chain in solution means viscosity.
The difference between the HV and LV grades is molecular weight. A longer chain builds more viscosity at lower loading; a shorter chain packs into a tighter filter cake. PAC HV is the viscosity grade — it is what you reach for when the problem is cuttings sitting in the annulus, not fluid invading the formation.
Chemical and Physical Properties
| Property | Specification |
|---|---|
| Chemical name | Polyanionic cellulose, high viscosity |
| Appearance | White to off-white free-flowing powder |
| Degree of substitution (DS) | ≥ 0.85 |
| Viscosity (1% solution, Brookfield) | ≥ 600 mPa·s |
| Moisture content, max. | ≤ 10% |
| pH (1% solution) | 6.5 – 8.5 |
| Purity (PAC content, min.) | ≥ 85% |
| Particle size | 95% passing 60 mesh |
| NaCl content, max. | ≤ 10% |
| Packaging | 25 kg kraft paper bags or jumbo bags |
Degree of substitution is the number that matters. DS measures how many carboxymethyl groups sit on each cellulose unit. Below roughly 0.85 the polymer loses salt tolerance and stops performing in brine systems — which is where most drilling actually happens. A low-DS product may test acceptably in fresh water and fail on the rig.
Functions in Drilling Fluids
Viscosity enhancement
PAC HV raises fluid viscosity at low concentration, improving the fluid’s capacity to lift cuttings from bottom hole to surface.
Rheology control
It gives pseudoplastic, shear-thinning behaviour — high viscosity at low shear for suspension while the pumps are off, low viscosity at high shear for pumping efficiency while circulating.
Filtration control
PAC HV forms a thin, flexible filter cake on the wellbore wall, reducing filtrate loss and limiting formation damage. PAC LV does this better, but HV contributes.
Shale inhibition
The anionic polymer adsorbs onto clay surfaces, encapsulating cuttings and reducing hydration and dispersion in reactive formations.
Thermal stability
PAC HV holds its performance through shallow and medium-depth wells. Like all cellulose polymers it degrades at sustained high temperature — see the gilsonite section below for what that means in practice.
PAC HV vs PAC LV vs CMC
| Parameter | PAC HV | PAC LV | CMC |
|---|---|---|---|
| Primary function | Viscosity builder | Fluid loss control | Both, lower performance |
| Typical concentration | 0.5 – 2.0 lb/bbl | 1.0 – 4.0 lb/bbl | 1.0 – 5.0 lb/bbl |
| Filter cake quality | Good | Excellent | Moderate |
| Hole cleaning capacity | Excellent | Moderate | Moderate |
| Salt tolerance | High (DS ≥ 0.85) | High | Lower |
| Relative cost | Higher | Higher | Lower |
In practice PAC HV and PAC LV run together. One builds the rheology, the other builds the cake. Using a single grade to do both means over-treating on one axis to get adequate performance on the other. CMC is the economical substitute where conditions are undemanding.
PAC HV and Gilsonite — Where the Polymer Stops
PAC HV controls filtration through a filter cake, which works as long as the pore throats it bridges are small enough for the polymer to span. It is also an organic polymer, which means two limits: it degrades thermally, and it cannot plug a fracture.
Gilsonite addresses both. It is a solid natural asphaltite, not a rheology modifier — it works by physical bridging. Particles enter microfractures and pore throats, soften at bottom-hole temperature, and deform into a seal the polymer cake never reaches.
| Aspect | PAC HV | Gilsonite |
|---|---|---|
| Mechanism | Polymer rheology and filter cake | Physical bridging and sealing |
| Thermal limit | Degrades at sustained high temperature | Stable well beyond polymer range |
| Fractured formations | Cannot bridge a fracture | Seals microfractures directly |
| Also provides | Cuttings transport, encapsulation | Lubricity, shale stabilization |
| Typical loading | 0.5 – 2.0 lb/bbl | 2 – 8 lb/bbl |
Further reading: gilsonite in water-based muds, fluid loss control with gilsonite, and gilsonite in shale stabilization.
Recommended Treating Concentrations
| Application | PAC HV Concentration |
|---|---|
| Viscosity building, freshwater | 0.5 – 1.0 lb/bbl |
| Standard WBM system | 1.0 – 2.0 lb/bbl |
| High hole-cleaning requirement | 2.0 – 3.0 lb/bbl |
| Saltwater and KCl systems | 1.0 – 2.5 lb/bbl |
Exact concentrations should be set by laboratory testing and adjusted for formation characteristics, mud weight and temperature.
Applications
- Top-hole sections in unconsolidated formations requiring high viscosity
- Large-diameter boreholes where annular velocity is low and hole cleaning capacity is the constraint
- Shallow to medium-depth wells within the polymer’s thermal stability range
- KCl/polymer systems alongside PAC LV, PHPA and xanthan gum
- Horizontal and directional wells where cuttings transport in deviated sections is critical
- Workover and completion fluids where formation damage prevention governs
Sourcing PAC HV from Turkey
Turkey has become a significant producer of drilling-grade PAC for regional and export markets. For buyers in the Middle East, Central Asia and Eastern Europe, the practical advantages are:
- Lead time. Proximity shortens transit against Western European and North American sources.
- Freight cost. Established routes through Mersin, Ambarlı and Izmir to Gulf, Caspian and Black Sea destinations.
- Price. Competitive against Western production at comparable specification.
- Quality control. Manufactured under API and ISO protocols, with certificate of analysis per shipment.
Quality standards
| Standard | Scope |
|---|---|
| API 13A | Specification for drilling fluid materials |
| ISO 13500 | Petroleum and natural gas industries, drilling fluid materials |
| OCMA | Oil Companies Materials Association specification for PAC |
Each shipment carries a Certificate of Analysis covering all key physical and chemical parameters.
Packaging and Shipping
| Specification | Detail |
|---|---|
| Standard packaging | 25 kg multi-layer kraft paper bags |
| Bulk option | 1,000 kg jumbo bags |
| Pallet configuration | 40 bags per pallet (1,000 kg) |
| Container load | 20 MT per 20′ FCL |
| Origin | Turkey |
| Lead time | 2 – 4 weeks, subject to stock |
| Loading ports | Mersin, Ambarlı (Istanbul), Izmir |
Frequently Asked Questions
Molecular weight. PAC HV has longer polymer chains that build more viscosity at lower loading, making it the hole-cleaning grade. PAC LV has shorter chains that pack into a tighter filter cake, making it the filtration grade. Most systems run both together rather than over-treating with one.
DS measures how many carboxymethyl groups sit on each cellulose unit, and it governs salt tolerance. Below roughly 0.85, the polymer loses performance in brine systems. A low-DS product can test acceptably in fresh water and still fail on a rig running saltwater or KCl mud.
Yes, and they address different limits. PAC HV builds rheology and a polymer filter cake; gilsonite bridges and seals microfractures that the cake cannot span, and remains stable at temperatures where cellulose polymers degrade. In fractured or hotter formations the combination covers what the polymer alone does not.
Half to one pound per barrel for freshwater viscosity building, one to two for a standard water-based system, two to three where hole cleaning is the controlling requirement, and one to two and a half in saltwater or KCl systems. Final figures come from laboratory testing against the actual formation and mud weight.
Two to four weeks subject to stock availability, loading from Mersin, Ambarlı (Istanbul) or Izmir. A 20-foot container carries 20 metric tonnes in 25 kg bags.
PAC HV Supply from Turkey
Drilling-grade PAC HV, PAC LV, CMC, KCl, bentonite and gilsonite supplied from Dubai and Ankara offices. Certificate of Analysis per shipment. Specification sheets, samples and quotations available on request.
Related products: PAC LV · CMC · KCl · Bentonite · Drilling Fluids · Water Based Muds · Gilsonite
