Applications

• Increases viscosity for cuttings transport and suspension
• Performs effectively in all water-based fluids, including highly weighted and low-solids systems, freshwater, seawater, salt, and heavy-brine systems

How it improves wells

DUO-VIS NS nondispersible, nonclarified xanthan gum viscosifier provides an optimized rheological profile with elevated low-shear-rate viscosity and highly shear-thinning characteristics with low n values. These characteristics frequently result in fluids with inverted flow properties, i.e., with the yield point greater than the plastic viscosity. Shear-thinning fluids have low effective viscosities at the high shear rates encountered inside the drillstring and at the bit. This low effective viscosity for minimal pressure losses and standpipe pressures enables optimized hydraulics and maximized ROPs. Conversely, at the low shear rates experienced in the annulus, DUO-VIS NS viscosifier enables the fluid to have a high effective viscosity for adequately cleaning the well and suspending cuttings.

Apply slowly

Add DUO-VIS NS viscosifier slowly through the hopper to prevent lumping and minimize waste. Add at the rate of approximately one 25-lbm [11.3-kg] sack every 7 to 10 min. The time required for the product to yield its ultimate viscosity depends on salinity, temperature, and shear.

The addition of thermal stabilizers and associated additives will improve temperature stability in DUO-VIS NS viscosifier from 250 to 300 degF [121 to 148 degC].

Advantages

• Minimum frictional pressure losses for additional hydraulic horsepower at the bit and low, high-shear-rate viscosity for maximum penetration rates
• Viscous laminar flow in the annulus for improved wellbore stability with maximum hole-cleaning and suspension capacity

Limitations

• Trivalent ions such as chromium and iron may cause biopolymer precipitation and loss of viscosity or crosslinking
• Not tolerant of high-pH or high-calcium-ion conditions
• Should be pretreated with either sodium bicarbonate or sodium acid pyro-phosphate and possibly citric acid prior to drilling cement
• Subject to bacterial degradation; a biocide should be used to prevent fermentation
• Slightly anionic nature of DUO-VIS NS viscosifier requires special mixing procedures when mixed with cationic materials

Toxicity and handling

Bioassay information is available upon request. Handle as an industrial chemical, wearing protective equipment and observing the precautions described in the safety data sheet.

Packaging and storage

DUO-VIS NS viscosifier is packaged in 25-lbm [11.3-kg] or 55.1-lbm [25-kg], plastic-lined, multiwall paper sacks. Store in a dry location away from sources of heat or ignition and minimize dust.