KELZAN® XC and KELZAN XCD

Sales Bulletin

Kelco Oil Field Group 10920 W. Sam Houston Pkwy North, Ste 800 Houston, TX 77064 (713) 895-7575

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KELZAN® XC and KELZAN XCD • Industry Standard Rheology Modifiers • Develop High Viscosity Fluids

at Low Concentrations • Provide Superior Suspension

and Hole Cleaning Properties • Compatible with Most Drilling

Fluid Additives • Reduce Total Well Costs through

Improved Hydraulic Efficiency Field Proven Viscosifiers. For more than thirty-five years Kelco has been the leader in biopolymer technology, offering a line of xanthan products that have become industry standards in rheology control. Two of these products are KELZAN XC and KELZAN XCD, well known for their proven field performance in a wide range of oilfield applications. First introduced as a non-dispersible xanthan, KELZAN XC became the product of choice until the dispersible grade, KELZAN XCD, was introduced in 1982. These products have established successful track records in challenging drilling conditions around the world. KELZAN XC and KELZAN XCD are versatile, cost effective additives in a wide variety of drilling fluid applications. When utilized with good drilling practices, KELZAN XC and KELZAN XCD formulated fluids help reduce total well costs. This is accomplished through improved hydraulics, which results in higher penetration rates and longer bit life. In addition, both products promote laminar flow in the annulus to minimize hole erosion and maintain well bore stability.

KELZAN XCD is the dispersible form of KELZAN XC, which improves polymer utility by reducing mixing time and virtually eliminating lumps and “fish eyes” often encountered when using non-dispersible polymers. Both polymers are especially effective in low colloid, minimum solids drilling fluids. They provide effective viscosity and suspension at low concentrations thereby eliminating the need for high concentrations of bentonite. For example, 1.0 lb of KELZAN XC or KELZAN XCD replaces up to 20 lb of bentonite. Due to enhanced suspension properties, a wide range of densities are possible by adding soluble salts or other conventional weighting agents.

Figure. 1. KELZAN® XC and KELZAN® XCD Viscosity vs. Shear Rate

in ASTM Seawater, 77ºF (25ºC)

1

10

100

1000

10000

100000

0.01 0.1 1 10 100 1000 10000

Shear Rate, sec-1

Visc

osity

, cP

SUSPENSION ANNULAR REGION

INSIDE DRILL STRING & BIT

REGION

1.5 lb/bbl

1.0 lb/bbl

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Table 1. KELZAN® XC and KELZAN® XCD Typical Rheological Properties in Various Waters, 75ºF (25ºC)

Plastic Yield K Viscosity, cP Viscosity, cP Point, lb/100 ft2 n dynes-secn/cm2 5.1 sec-1

Fresh Water 1.0 lb/bbl 3.5 8.5 0.25 12.9 380 1.5 lb/bbl 4.0 14.0 0.18 30.6 800 Seawater 1.0 lb/bbl 4.0 9.0 0.28 11.5 360 1.5 lb/bbl 5.0 15.0 0.20 29.0 790 Saturated NaCl 1.0 lb/bbl 6.5 11.0 0.30 12.9 420 1.5 lb/bbl 8.5 17.0 0.25 28.0 820 n and K calculated between 3 and 300 rpm

Universal Viscosifiers. The primary function of KELZAN® XC and KELZAN® XCD is to opti-mize rheological properties of water-based fluids under a wide range of shear conditions. Simply stated, they provide a drilling fluid that is “thin when it should be thin and thick when it should be thick”. This pseudoplastic behavior results in low viscosity under high shear condi-tions (while pumping, in the drill sting, in the bit region) and regains viscosity as shear is reduced (in the annular region where viscosity and suspension are desirable). These charac-teristics closely depict the ideal viscosity profile of a drilling fluid. Figure 1 illustrates the highly shear-thinning viscosity profile of KELZAN XC and KELZAN XCD hydrated in ASTM seawater when ex-posed to typical shear rates encountered in a circulating system. At high shear rates, such as inside the drill string or in the bit region, the fluid “thins out” and viscosity is minimized. As a result, horsepower utilization is optimized due to friction pressure reduction. Field experience has shown a 20-30% pressure reduction in small diameter tubing applications.

This thinning phenomenon under high shear provides a fluid with greater drilling efficiency, because more hydraulic horsepower is delivered to the bit for improved bottom hole cleaning and increased penetrations rates. As the flow rate (shear rate) decreases in the annular region, KELZAN XC and KELZAN XCD fluids “thicken up” and regain viscosity to provide required hole cleaning characteristics. Less pseudoplastic fluids would require addi-tional viscosifier or higher pumping rates to properly clean the hole of drilled cuttings. In-creased annular viscosity provided by these biopolymers promotes laminar flow, which helps reduce wellbore erosion. Controlling hole enlargement results in fewer hole cleaning problems, allows good formation evaluation, and ultimately lowers well completion costs. The ability of KELZAN XC and KELZAN XCD to viscosify diverse makeup waters is demon-strated in Table 1. Typically, both products can be used in monovalent brines up to saturation. Where high salinity brines are used, KELZAN XC is the preferred product since it will hydrate faster due to the lack of the chemical treatment that makes KELZAN XCD dispersible. Pilot testing is recommended in these applications to determine which product provides the best results.

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Fluid Stability

Fluids formulated with KELZAN® XC and KELZAN® XCD exhibit exceptional rheo- logical stability in a wide variety of oilfield environments. Optimum fluid performance is achieved where the concentration of KELZAN XC or KELZAN XCD is equal to or preferably exceeds a critical polymer concentration. Typically, this will be above 1.0 lb/bbl, and is dependent on other additives in the system. At these use levels, molecular entanglements or networks are formed which improve the suspension and carrying capacity of KELZAN XC and KELZAN XCD formulated fluids. Shear Stability – KELZAN XC and KELZAN XCD fluids are highly resistant to degradation that can occur in high shear rate regions of the circulating system. While some polymers require frequent additions to maintain viscosity, maintenance treatments required for KELZAN XC and KELZAN XCD formulated fluids are usually significantly lower. pH – While the normal pH tolerance range is between pH 2 and 12, the presence of soluble calcium or magnesium may cause a loss of viscosity when the pH exceeds 11. Pretreat-ment with sodium bicarbonate and/or SAPP prior to encountering a calcium/high pH con-tamination (usually cement cuttings) can protect against viscosity loss. Salt Tolerance – KELZAN XC and KELZAN XCD are exceptionally cost effective in inhibi-tive systems containing dissolved electrolytes, including potassium chloride, field brines, seawater, as well as heavy brines containing sodium chloride, sodium bromide, calcium chloride, and formate salts. Compatibility – KELZAN XC and KELZAN XCD are compatible with most additives commonly used in water-based drilling fluids. As a precaution, however, pilot testing with specific cationic additives (corrosion inhibitors, shale inhibitors, and some biocides) and multivalent salts is recommended to verify compatibility.

Temperature Stability – KELZAN XC and KELZAN XCD are stable up to 250°F (127°C). The use of oxygen scavengers, low molecular weight alcohols, and salts can extend the temperature stability of fluids containing KELZAN XC and KELZAN XCD. Specially formulated systems have been used to successfully drill wells with bottom hole temperatures in excess of 300°F (149°C). Figure 3 illustrates the temperature stability of KELZAN XC and KELZAN XCD biopoly-mer in ASTM seawater and saturated sodium chloride.

Figure 2. Effects of Salt on Thermal Stability of KELZAN® XC and KELZAN XCD

1.5 lb/bbl

0

20

40

60

80

100

120

75 85 96 124 153 182 210 236 255 267 274 279 279 279 264 236 212 187 167 144 125 108 92 76

Temperature, oF

Visc

osity

, cP

@ 1

00 s

ec-1

1 hr @ 280oF

10 lb/gal NaCl Brine

ASTM Seawater

Logistics – In comparison with other commonly used drilling fluid viscosifiers, relatively small amounts of KELZAN XC and KELZAN XCD are required to prepare functional drilling fluids. Normally, 1.0 lb/bbl KELZAN XC or KELZAN XCD will provide the same effective carrying capacity and suspension as approximately 20 lb/bbl premium grade bentonite. This favorable replacement ratio has provided significant freight and handling savings to operators in remote land and offshore locations around the world.

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KELZAN® and XANVIS® are registered trademarks of cp Kelco ApS and/or CP Kelco U.S., Inc. and may be registered or applied for in other countries. © 2003 CP Kelco ApS

The information contained herein is, to our best knowledge, true and accurate, but all recommendations or suggestions are made without guarantee, since we can neither anticipate nor control the different conditions under which this information and our products are used. It is our policy, to assist our customers and to

help in the solution of particular problems, which may arise in connection with application of our products. Rev. 09/05

Miscellaneous Applications

More than just a drilling fluid. Enhanced rheological properties provided by KELZAN® XC and KELZAN® XCD improve the perfor-mance of a wide range of drilling, workover and completion fluids. Under-Reaming – The flat velocity profile provided by KELZAN XC and KELZAN XCD fluids enhances hole cleaning and suspension under the low annular velocities encountered during under-reaming operations. Weighted Kill Fluids – Because of their ability to develop low shear rate viscosity required to suspend insoluble weight materials, KELZAN XC and KELZAN XCD are highly functional in the formulation of high density kill fluids. Spotting Fluids – In some situations where highly permeable formations are exposed, seepage losses occur where there is an absence of filter cake building materials. Such losses can be controlled with viscosity provided by KELZAN XC and KELZAN XCD at a concentration of 2.0 to 3.0 lb/bbl. These concentrations have also been beneficial in stabilizing some unconsolidated sand sections because of the visco-elastic nature of these fluids. Spacer Fluids – The unique rheology of KELZAN XC and KELZAN XCD along with their compatibility with most fluid additives make them essential ingredients in the formulation of weighted or unweighted spacer fluids.

Pipeline Pigging Fluids – At concentrations above 1.5 lb/bbl, KELZAN XC and KELZAN XCD develop exponential increases in low shear rate viscosity while maintaining a low apparent viscosity as measured at 1022 sec-1. This feature allows the formulation of high viscosity pipeline pigging fluids with a high degree of solids transport for improved pipeline cleanout. Milling Fluids – Another application where KELZAN XC and KELZAN XCD have pro-vided significant reductions in operating costs is in the formulation of milling fluids. Typically, these fluids are made up with 3.0 to 4.0 lb/bbl of either polymer and have proven to be highly successful in transporting metal cuttings to the surface. Even at these high polymer concen-trations, these fluids shear thin, allowing cut-tings to be readily removed from the system by solids control equipment. For additional workover and completion applications including coring, perforating, gravel packing and coiled tubing fluids, XANVIS®, the payzone polymer is highly recommended.