Author: Unionchem Publish Time: 2026-02-24 Origin: Qingdao Unionchem Co.,Ltd.
In the formulation of drilling fluids or construction mortars, Polyanionic Cellulose (PAC) is often the "make or break" ingredient. It is the backbone of filtration control. However, simply ordering "PAC" is not enough.
Are you drilling in a high-salinity offshore environment? Do you need to suspend heavy cuttings, or just control water loss without thickening the mud?
Choosing the wrong grade—specifically confusing PAC-LV (Low Viscosity) with PAC-R (Regular/High Viscosity)—can lead to pump pressure issues, poor hole cleaning, or excessive costs. Here is a structured guide to selecting the precise PAC grade for your operational needs.
Before looking at your specific application, you must understand the two primary categories of PAC defined by API 13A standards.
What it does: It reduces fluid loss (filtration rate) without significantly increasing the viscosity of the system.
When to use it: Use this when your fluid is already thick enough (high solids content) or when you need to keep pump pressures low. It’s a pure filtration control agent.
What it does: It performs a dual function: it reduces fluid loss and increases viscosity.
When to use it: Use this when you need to build viscosity to carry cuttings out of the hole (hole cleaning) or when using a low-solids fluid that needs body.
(Compare the specifications of our LV and R grades on the Polyanionic Cellulose (PAC) Product List.)
To choose the "best" PAC, you must evaluate three critical variables in your project.
Fresh Water: Standard PAC works well here, but you might even get away with high-grade CMC if temperatures are low.
Saltwater / Saturated Brine: This is PAC territory. You need a High-Purity PAC (min 95% or 98%). The high Degree of Substitution (DS) in premium PAC allows it to repel salt ions and maintain its shape. Standard CMC will fail here.
High Density Muds (Weighted): If you are adding a lot of Barite or Hematite, the mud is already thick. Adding a high-viscosity polymer will make it unpumpable. Choose PAC-LV.
Low Density / Spud Muds: If you are just starting a well with water and bentonite, you need viscosity to lift the rock chips. Choose PAC-R.
The Trap: Buying the cheapest bag of PAC often leads to higher costs.
The Reality: A cheap "PAC" might actually be a blended CMC/Starch product. You might need 3x the dosage to achieve the same fluid loss control as 1 bag of Unionchem Premium PAC. Always calculate the "Cost per Barrel" of mud, not the "Cost per Ton" of powder.
Let’s look at three real-world scenarios to see which PAC wins.
The Challenge: Drilling through salt domes. The water is saturated brine.
The Best Choice: Polyanionic Cellulose - Low Viscosity (PAC-LV).
Why: You need maximum filtration control to prevent the formation from collapsing, but you cannot afford high viscosity in deep, cold water lines. PAC-LV controls the fluid loss without spiking the rheology.
The Challenge: Shallow well, loose sand, need to remove cuttings quickly.
The Best Choice: Polyanionic Cellulose - Regular (PAC-R).
Why: The PAC-R encapsulates the sand (preventing collapse) and provides the "carrying capacity" to lift the sand to the surface.
The Challenge: Need water retention so the cement cures properly.
The Best Choice: High Viscosity PAC.
Why: In construction, "Regular" or High Viscosity is almost always preferred to provide the necessary "slip" and water holding capacity.
Selecting the best Polyanionic Cellulose is not about finding the "strongest" product; it is about finding the right rheological fit.
Need filtration control only? Go Low (PAC-LV).
Need filtration + lifting power? Go High (PAC-R).
Drilling in salt? Ensure High DS/Purity.
At Unionchem, we produce PAC grades that strictly adhere to API 13A specifications, ensuring that whether you choose LV or R, the performance is guaranteed.
Ready to optimize your mud system?Review our PAC Technical Data Sheets or contact our engineers for a dosage recommendation.
Q1: Can I mix PAC-LV and PAC-R in the same tank?
A: Yes, this is common. You might use PAC-R to build the initial viscosity and then switch to PAC-LV to maintain filtration control as the drill solids increase, preventing the mud from becoming too thick.
Q2: How do I know if my PAC is high quality?
A: Check the API Fluid Loss test result. A high-quality PAC should provide less than 10ml fluid loss at a low dosage (e.g., 1.0 g/350ml) in a standard test. Also, check for "Fish Eyes"—good PAC should dissolve without leaving gummy lumps.
Q3: Is PAC better than Xanthan Gum?
A: They serve different purposes. Xanthan Gum is for viscosity and suspension (LSRV), but it does not control fluid loss well. PAC is primarily for fluid loss control, though PAC-R adds viscosity. They are often used together.
Q4: What is the shelf life of PAC?
A: When stored in a cool, dry place, PAC is very stable and typically has a shelf life of 2 years. It is resistant to bacterial degradation compared to starch.
