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Frequently Asked Questions

With a dedicated team of experts, industry-leading research and development efforts, and a state-of-the-art technical service laboratory, no other company can provide our level of expertise in formate brine technology.

What is cesium formate brine?

Cesium formate brine is simply cesium formate dissolved in water. The result is heavy brine with densities that increase with the level of cesium formate in solution. It's part of the formate brine family, together with sodium and potassium formate brines, and is manufactured in highly pure 80% w/w aqueous solution with density of 2.20 g/cm3/18.36 lb/gal. 

In pure form, it's highly compatible with reservoirs as it only contains monovalent ions and is incapable of forming scales. Anti-oxidant and water-structuring properties help protect polymers against thermal degradation at high temperatures, which facilitates its use as a HPHT drilling fluid. With a natural pH of 10 – 10.5, it’s highly compatible with metals and elastomers and has full compatibility with water-soluble polymers, such as xanthan. Additionally, it’s safe to handle and non-hazardous to the environment.

Other common questions

Are formate-based drilling and completion fluids compatible with hydrogen sulphide?

Carbonate/bicarbonate pH buffer added to formate brine gives useful protection against H2S. The alkaline pH helps to push the chemical equilibrium towards formation of bisulphide, which is less harmful than H2S. If H2S influx is expected, an H2S scavenger is recommended. A few H2S scavengers have been identified that are compatible with formate brines. More information on this topic may be found in the Formate Technical Manual, section B5.

Are there specific stuck pipe release pills and procedures?

Formulations and procedures for solids-free stuck pipe release pills are available for mud weights up to 2.15 g/cm3/18.0 lb/gal. New stuck pipe release products based on formates that work in all types of mud are also available. Contact us for more information.

How stable is cesium formate pH over long periods in the field?

A carbonate/bicarbonate buffer stabilizes pH in formate brines. See section A6 of the Formate Technical Manual for further information.

What is used as a slug for tripping?

A high-density slug is easily made using high-density spike fluid or through adding powdered cesium formate.

What action can be taken to deal with subsurface losses?

Most conventional measures and additives used to combat lost circulation are equally valid for formate-based muds. Since most uses of formate fluids are in reservoir drilling, non-damaging and/or acid soluble materials such as calcium carbonate are recommended. More information on this topic can be found in section C1 of the Formate Technical Manual.

What are the recommended procedures for displacements and well clean-ups?

Procedures for well clean-ups and displacements vary from operation to operation. Sacrificial water-based mud and/or potassium formate has proved useful in minimizing losses during well clean-ups and displacements from oil-based mud. More information on this topic can be found in section C1 of the Formate Technical Manual.

What percentage of losses is expected during an operation?

Naturally the amount of losses experienced depends on the nature of the operation and the quality of pre-planned fluid management procedures and their implementation. Losses during a series of nine completions and workovers averaged 10.5% of the fluid handled. When fluid intentionally left in the hole is deducted, average losses reduce to 7.9% of the volume handled. These figures cover all losses for the well, including transit and reclamation losses. More information on this topic can be found in section B5 of the Formate Technical Manual.

Which polymers can be used in formate-based drilling fluids?

All conventional polymers used in water-based muds can be used in formate-based fluids. These include xanthan gums, PACs, starches and so on. One useful property of formate fluids is that they extend the temperature stability of these polymers. More information on this topic can be found in section B5 of the Formate Technical Manual.

What pipe dopes do you recommend with formates?

In the field, formates have been used with many different pipe dopes without any reported problems. Pipe dopes containing copper-, graphite- and lithium-based grease have proven compatible, as have pipe dopes containing zinc. Testing of other products is underway. More information on this topic can be found in section B9 of the Formate Technical Manual.

Is barite soluble in cesium formate?

At alkali pH, or normal pH in other words, barite is almost totally insoluble in cesium formate. Analysis of brine returns from the field containing large amounts of solid barite and subjected to prolonged exposure to high temperatures (204°C/400°F) had maximum soluble barium content of only 22 ppm.

Can perforating guns be used in formates?

Perforating guns are used successfully in formate brines.

Can formate brines be used for pressure testing?

Formate brines have a high-bulk modulus, which means they are not very compressible and are ideal for pressure testing. Field results using a 2.19 g/cm3 /18.29 lb/gal fluid indicated a bulk modulus of between 450,000 and 550,000 compared with around 315,000 for water. In applications where a high-density hydraulic fluid is required, such as sub-sea umbilicals, formate brines are an ideal fluid. As a solids-free fluid system, formate brines are also well suited to subsurface safety valve (SSSV) pressure testing.

Can a dye be used for spacer identification?

Fluorescein dye, for example, can be used to identify spacers.

What is the recommended filtration method for formate brines and how well do they filter?

Formate brines do not differ from conventional brines in terms of filtration equipment. However, cesium formate brines do filter more easily than zinc bromide brines due to their lower viscosity. For mildly dirty brine a cartridge filter is recommended. Preferably this should be a twin-pod unit loaded first with nominal- and then absolute-rated cartridges. For more severe contamination a DE unit is recommended. Normal DE or perlite can be used as the filtration media and charcoal can be added to remove any discoloration. Both the cartridge and DE units should be blown down with rig air before changing the cartridges or opening the DE press.

Where do you mine pollucite?

We have owned the Tantalum Mining Corporation (TANCO) since 1993. TANCO mines and processes pollucite. Mining is carried out using the room and pillar method. Ore is harvested with underground machinery and hoisted to the surface for processing using various techniques, such as gravity concentration, flotation and grinding. Pollucite is mined, ground to 200 mesh, and processed into cesium formate and fine cesium chemicals. Cesium formate is concentrated through an evaporation process, buffered and packed in IBCs.