Almost every hydraulic fracturing operation requires chemicals to improve efficiency and lower the costs of the operation.
Usually, chemicals make up less than 1% of fracturing fluid and proppant another 5-10% but for the entire operation the volume of chemicals required can add up pretty fast.
The goal is to pump as few chemicals as possible without sacrificing efficiency because over-pumping can significantly increase the cost of the operation.
The in-house lab department is often involved in hydraulic fracturing operations to perform testing and ensure that the right chemicals are used for the job.
What Chemicals are Used in Hydraulic Fracturing?
1. Friction Reducers (FR)
Friction reducers are used to lower the pumping pressure which helps to decrease the fuel consumption by the pumps and allows them to last longer.
Depending on the operation some friction reducers can also increase the viscosity of the fluid which might be beneficial when it comes to carrying proppant downhole.
Friction reducers work by decreasing the turbulence of the fluid flow and making it more laminar.
Laminar flow means that the fluid particles are more organized and move in layers while in turbulent flow there is no clear pattern and particles move in every direction.
There are different types of chemicals that can be used as friction reducers but polyacrylamide is the most common one.
Related: Top 5 Chemicals Used for Coiled Tubing Operations
2. Gelling Agents
A gel is often used to increase the viscosity of the fracturing fluid to improve its sand carrying capacity.
Depending on the frac type gel can also be crosslinked to increase its viscosity even further and reduce fluid loss in the formation.
Crosslinking involves bonding several chains of polymers together.
There are many ways to create crosslinked gels but in hydraulic fracturing often metal ions like borate and zirconium are used.
Common gel chemicals used in frac are guar, guar derivatives, and cellulose.
3. Breakers
Often whenever gels are used for frac, breakers are added as well to break the gel down in the formation and prevent any unwanted decrease in the permeability around the wellbore.
Most breakers are either oxidizers or enzymes.
Downhole temperatures and pH often dictate what type of breaker is used.
For example, in higher temperature cases enzymes might be used to ensure that the gel is not broken down until it gets all the way down into the well.
Common breakers are ammonium persulphate and magnesium peroxide.
Related: Basic Hydraulic Fracturing Calculations
4. Biocides
Biocides are used in almost every frac operation to kill the bacteria in the fluid that can potentially create unwanted by-products like H2S and damage the formation and equipment.
The frac fluid is usually pretreated before the operation or biocide is pumped on the fly during the frac.
Some examples of the biocides used are glutaraldehyde and bronopol.
5. Buffers
The main goal of buffers is to adjust the pH of the fluid used for the frac.
This is required because some chemicals need a certain pH for optimal performance.
6. Clay Control
In clay formations, special chemicals are used to prevent clays from swelling and moving when they come into contact with water.
Potassium chloride and choline chloride are often used for clay control.
7. Acids
Acids are often pumped before the frac to prepare the perforations and formation for the frac.
Usually, hydrochloric acid is used.
However, there is also a trend toward using synthetic acids that are not as corrosive and more environmentally friendly.
Often corrosion inhibitors and non-emulsifiers are added to the acid blend to decrease corrosion of the pipe and prevent emulsions in the well.
Related: What is Perforating in Oil and Gas?
8. Surfactants/Non-emulsifiers
As the name suggests non-emulsifiers help to prevent emulsion between frac and formation fluids.
Surfactants also help to reduce the interfacial tension in the formation and help fluids to flow more easily.
One example of surfactants is sodium lauryl sulfate which is sometimes used in soaps and detergents.
9. Corrosion Inhibitors
Used to decrease the rate of corrosion in the metal when pumping acid.
Corrosion inhibitors are often pumped when performing annular frac operations with coiled tubing to protect the coil and casing.
10. Proppant (Sand)
The most common type of proppant is sand.
There are different types of sand used depending on the downhole conditions.
Different types of sand have different grain geometry, size, purity, and weight.
Deeper wells usually require high-strength sand that can sustain high formation pressures without crushing.
The main goal of the proppant is to keep fractures open after the fracturing operation is completed.
The small spaces between the sand particles allow hydrocarbons to flow into the wellbore.
There are also synthetic types of proppant like ceramic beads and resin-covered sand that are used for more specialized operations.
Usually, man-made proppant is more expensive than natural sand.
Sand is mainly composed of silicon dioxide.
Related: Advantages and Disadvantages of Hydraulic Fracturing
Other Chemicals Used for Hydraulic Fracturing Operations
There are also other more specialized chemicals that are sometimes pumped during the fracturing operations.
Some examples are iron control, scale control, sand activators, gel stabilizers, and solvents.
How to Find the Exact Chemicals Used for Fracturing Operations?
Different companies use different frac chemicals.
The purpose of this post is to give an overview of common chemical types used and not specific chemical names.
If you are interested in learning more about the exact chemical names, you can usually find them online in different disclosure registries.
For example, if you want to know what is used for frac in Canada you can see it here.
There you can see the breakdown of chemicals used for any specific well.
Read next: What is Hydraulic Fracturing?
References:
http://www.fracfocus.ca/en/chemical-use/what-chemicals-are-used