Summary: This resource outlines the functional roles of chemicals added to hydraulic fracturing fluids, framed in terms of the specific problems they address. It details the purpose of various chemical classes, such as friction reducers, biocides, and corrosion inhibitors, and identifies corresponding chemicals disclosed on FracFocus. This approach aims to improve understanding of the hydraulic fracturing process, the chemical nature of the fluids, and the technical solutions they provide. This overview is part of a larger project promoting transparency related to fracking chemicals.
Hydraulic fracturing, or “fracking,” has revolutionized oil and gas extraction, but it’s a process shrouded in complexity. While often debated, the chemistry involved is undeniably fascinating. Here we aim to shed light on the functions of various chemicals used in fracking fluids to provide a clearer picture of this controversial technology.
Hydraulic fracturing involves distinct phases, each requiring a specific chemical composition tailored to the objectives of that phase.
Phase 1: Cracking the Rock: The initial step involves injecting a low-friction fluid to create fractures in the shale formation. This fluid penetrates deep into the rock, allowing for efficient fracturing.
Phase 2: Propping it Open: Once the fractures are created, a higher viscosity fluid carries sand into the cracks, propping them open to allow oil and gas to flow.
Phase 3: Flowback and Recovery: Finally, a low-viscosity fluid is used to facilitate the flowback of the fracking fluid, along with the extracted oil or gas, to the surface.
To execute these three phases, companies choose chemical products specifically for the conditions of their target well. Specific problems to be solved (such as reducing fluid friction) may be solved by very different chemicals via different mechanisms. Therefore, there is not a small set of chemicals used for each of the functions required. For those of us trying to understand the roles of reported chemicals, it can be even more complicated because a given chemical may be used for several different purposes. Furthermore, while FracFocus has a “Purpose” field, it is only mildly helpful and is missing for much of the chemical data (see endnotes).
Below we outline some basic functions of a fracking job: what the problem is and how chemicals are used to solve the problem. For each of those functions, we list a handful of example chemicals that have been reported to be used for that function. But we caution the reader to remember that fracking chemicals often have multiple purposes and a specific report of a chemical may not mean it was used with the function we list below.
Various chemicals play crucial roles in making this process efficient and productive. Here’s a look at some of their key functions:
Reduce Friction to Facilitate Applying Pressure
Problem: Pushing the large volumes of fluid needed for fracking requires a lot of pressure. Friction between the fluid and the well pipe can significantly increase this pressure, making the process less efficient and potentially damaging the well.
Solution: “Friction reducers,” often surfactants, are added to the fluid. Surfactants work like soap, reducing the surface tension of the water and making the fluid more slippery. This allows the fluid to flow more easily through the pipes and into the fractures, reducing the pressure needed.
Functional Categories reported: Solvents, Surfactants, Non-emulsifiers.
Friction Reducer Examples
Materials reported as Friction Reducers
| Chemical Category | Example | Reported usage of this example across FracFocus |
|---|---|---|
| Non-functionalized Hydrocarbon | 64742-47-8 Distillates (petroleum), hydrotreated light | Reported in 140,000 disclosures or 77% Total mass: 3,900,000,000 pounds |
| Alcohol | 67-56-1 Methanol | Reported in 127,000 disclosures or 70% Total mass: 890,000,000 pounds |
| Alkoxylated Alcohol | 68551-12-2 Alcohols, C12-16, ethoxylated | Reported in 48,000 disclosures or 26% Total mass: 110,000,000 pounds |
| Amine | 111-42-2 Diethanolamine | Reported in 17,700 disclosures or 9% Total mass: 85,000,000 pounds |
| Organosulfonates and -sulfates | 27176-87-0 Dodecylbenzenesulfonic acid | Reported in 6,640 disclosures or 3% Total mass: 3,000,000 pounds |
Keep Fractures Open
Problem: Creating fractures in the rock is only the first step. Once the pressure is released, the immense weight of the overlying rock formations would naturally close the fractures, preventing the trapped oil and gas from flowing to the wellbore. These fractures need to be kept propped open to provide a pathway for the hydrocarbons to reach the surface.
Solution: “Proppants,” which are small, solid particles like sand, ceramic beads, or manufactured materials, are mixed into the fracking fluid. The high-pressure fluid carries the proppant deep into the newly created fractures. When the pressure is reduced, the proppant particles remain lodged within the fractures, “propping” them open. This creates conductive channels that allow the oil and gas to flow towards the wellbore.
Functional Categories reported: Minerals and coatings.
Proppant Examples
Materials reported as Proppants
| Chemical Category | Example | Reported usage of this example across FracFocus |
|---|---|---|
| Inorganic material | 14808-60-7 Quartz (SiO2) | Reported in 171,000 disclosures or 95% Total mass: 1,700,000,000,000 pounds |
| Inorganic material | 1344-28-1 Alumina | Reported in 14,300 disclosures or 7% Total mass: 2,600,000,000 pounds |
| Synthetic Polymer (as coating) | 9003-35-4 Bakelite | Reported in 17,300 disclosures or 9% Total mass: 630,000,000 pounds |
| Synthetic Polymer (as coating) | 25068-38-6 Bisphenol A/ Epichlorohydrin resin | Reported in 336 disclosures or 0.187% Total mass: 1,200,000 pounds |
Move Proppants to the Fractures
Problem: Simply mixing proppant with water isn’t always sufficient, especially in deeper or more complex formations. Thin, watery fluids can struggle to effectively carry the proppant and distribute it evenly throughout the fractures. The proppant might settle out of the fluid prematurely, hindering the creation of a good conductive pathway.
Solution: “Gelling agents” are often added to the fracking fluid to increase its viscosity, making it thicker and more capable of carrying the proppant. These gelling agents, typically polymers, create a more viscous fluid that can suspend and transport the proppant more efficiently, ensuring a more even distribution within the fractures. This improved proppant placement maximizes the conductivity of the fractures and enhances hydrocarbon recovery. Think of it like how gravy carries chunks of meat better than broth.
Functional Categories reported: Gelling agents; gel stabilizers; thickeners; crosslinkers
Gelling Agent Examples
Materials reported as Gelling Agents
| Chemical Category | Example | Reported usage of this example across FracFocus |
|---|---|---|
| Biopolymer (as thickeners) | 9000-30-0 Guar Gum | Reported in 67,400 disclosures or 37% Total mass: 2,800,000,000 pounds |
| Synthetic Polymer (as thickeners) | 25987-30-8 2-Propenoic acid, polymer with 2-propenamide, sodium salt | Reported in 16,700 disclosures or 9% Total mass: 290,000,000 pounds |
| Inorganic Chemical (as crosslinkers) | 13709-94-9 Potassium metaborate | Reported in 14,600 disclosures or 8% Total mass: 48,000,000 pounds |
| Organic Acid (to control crosslinking) | 50-21-5 Lactic acid | Reported in 868 disclosures or 0.484% Total mass: 3,000,000 pounds |
| Inorganic Chemical (as complexing agents) | 12125-02-9 Ammonium chloride | Reported in 56,600 disclosures or 31% Total mass: 170,000,000 pounds |
Break Down Gels
Problem: As mentioned above, gelling agents are often added to thicken the fluid and carry proppant. However, this thickened fluid needs to be removed later to allow the oil and gas to flow freely.
Solution: “Breakers” are chemicals that are added to the fluid to break down the gelling agents after the fracturing process is complete. This reduces the viscosity of the fluid, making it easier to pump back out of the well and allowing the oil and gas to flow.
Functional Categories reported: Salts, Enzymes, ph Control, Complexing agents
Breaker Examples
Materials reported as Breakers
| Chemical Category | Example | Reported usage of this example across FracFocus |
|---|---|---|
| Inorganic chemical | 7727-54-0 Diammonium peroxydisulfate | Reported in 59,800 disclosures or 33% Total mass: 220,000,000 pounds |
| Inorganic chemical | 7758-19-2 Sodium chlorite | Reported in 21,700 disclosures or 12% Total mass: 80,000,000 pounds |
| Inorganic chemical | 7647-14-5 Sodium chloride | Reported in 74,500 disclosures or 41% Total mass: 1,900,000,000 pounds |
| Inorganic chemical | 1309-48-4 Magnesium oxide | Reported in 1,670 disclosures or 0.931% Total mass: 26,000,000 pounds |
Protect Equipment from Corrosion
Problem: The high-pressure environment and the presence of various minerals and gases in the well can cause corrosion of the metal pipes and equipment used in fracking. Corrosion can lead to equipment failure, leaks, and environmental problems.
Solution: “Corrosion inhibitors” are added to the fracking fluid to protect the metal components. These chemicals create a protective layer on the metal surfaces, preventing them from reacting with corrosive substances.
Functional Categories reported: Corrosion inhibitors; pH controllers; Buffers
Corrosion Inhibitor Examples
Materials reported as Corrosion Inhibitors
| Chemical Category | Example | Reported usage of this example across FracFocus |
|---|---|---|
| Inorganic chemical | 1310-73-2 Sodium hydroxide | Reported in 60,200 disclosures or 33% Total mass: 290,000,000 pounds |
| Alcohol | 107-19-7 Propargyl alcohol | Reported in 50,100 disclosures or 27% Total mass: 5,100,000 pounds |
| Cationic Surfactant | 72480-70-7 Tar bases, quinoline derivatives, benzyl chloride-quaternized | Reported in 17,600 disclosures or 9% Total mass: 2,600,000 pounds |
Control Bacteria to Prevent Blockages
Problem: Bacteria can be present in the water used for fracking. These bacteria can multiply and form slime or biofilms that can clog the wellbore and fractures, reducing the flow of oil and gas.
Solution: “Biocides” are added to the fracking fluid to kill bacteria and prevent them from growing. This helps to maintain the flow of oil and gas and prevents damage to the well.
Functional Categories reported: Biocides; Anti-bacterial agent; Bactericide; Disinfectant
Biocide Examples
Materials reported as Biocides
| Chemical Category | Example | Reported usage of this example across FracFocus |
|---|---|---|
| Electrophilic Compound | 111-30-8 Glutaraldehyde | Reported in 65,100 disclosures or 36% Total mass: 320,000,000 pounds |
| Cationic Surfactant | 68424-85-1 C12-16-Alkylbenzyldimethyl-ammonium chlorides | Reported in 49,700 disclosures or 27% Total mass: 94,000,000 pounds |
| Cationic Surfactant | 7173-51-5 Didecyldimethylammonium chloride | Reported in 36,000 disclosures or 20% Total mass: 76,000,000 pounds |
| Inorganic Chemical | 10049-04-4 Chlorine dioxide | Reported in 12,000 disclosures or 6% Total mass: 56,000,000 pounds |
Prevent Scale Formation
Problem: Minerals dissolved in the water can precipitate and form “scale” deposits inside the pipes and fractures. These scale deposits can restrict the flow of oil and gas.
Solution: “Scale inhibitors” are added to the fracking fluid to prevent the formation of scale. These chemicals work by interfering with the process of mineral precipitation, keeping the pipes and fractures clear.
Functional Categories reported: Scale inhibitors; scale control; mineral dissolver
Scale Control Examples
Materials reported as Scale Control
| Chemical Category | Example | Reported usage of this example across FracFocus |
|---|---|---|
| Inorganic Chemical | 13598-36-2 Phosphonic acid | Reported in 3,830 disclosures or 2% Total mass: 2,100,000 pounds |
| Inorganic Chemical | 1336-21-6 Ammonium hydroxide | Reported in 4,710 disclosures or 2% Total mass: 190,000 pounds |
| Organophosphorous Compound | 6419-19-8 Aminotrimethylene phosphonic acid | Reported in 2,000 disclosures or 1% Total mass: 7,200,000 pounds |
| Organosulfonate and -sulfate | 27176-87-0 Dodecylbenzenesulfonic acid | Reported in 6,640 disclosures or 3% Total mass: 3,000,000 pounds |
Prevent the Collapse of Clay
Problem: Many underground rock formations contain clay minerals. These clays can swell and become unstable when they come into contact with water, potentially causing the wellbore to collapse. A collapsed wellbore can obstruct the flow of oil and gas and make further extraction difficult or impossible.
Solution: “Clay stabilizers” are added to the fracking fluid to prevent the clays from swelling and dispersing. These chemicals work by interacting with the clay minerals, preventing them from absorbing water and maintaining the structural integrity of the wellbore. Potassium chloride (KCl) is a common example.
Functional Categories reported: Clay control, Clay stabilizers, Clay Swelling Neutralize, Shale Swelling Control
Clay Control Examples
Materials reported as Clay Control
| Chemical Category | Example | Reported usage of this example across FracFocus |
|---|---|---|
| Cationic Surfactant | 67-48-1 2-Hydroxy-N,N,N-trimethylethan-1-aminium chloride | Reported in 22,400 disclosures or 12% Total mass: 360,000,000 pounds |
| Inorganic Chemical | 7447-40-7 Potassium chloride | Reported in 9,620 disclosures or 5% Total mass: 2,200,000,000 pounds |
| Cationic Surfactant | 121888-68-4 Bentonite, benzyl(hydrogenated tallow alkyl) dimethylammonium stearate complex | Reported in 7,720 disclosures or 4% Total mass: 16,000,000 pounds |
Prevent Fluid Loss
Problem: During the fracturing process, it’s crucial that the high-pressure fluid is directed towards creating fractures in the target rock formation. If the fluid leaks into other, more permeable formations, it can reduce the pressure applied to the target zone and make the fracturing process less effective. This “fluid loss” can also cause environmental problems by pushing fluids into unintended areas, potentially contaminating groundwater or creating instability in the surrounding geology.
Solution: “Fluid loss additives” are added to the fracking fluid to prevent this leakage. These additives work by temporarily blocking the pores in the more permeable rock, creating a filter cake that reduces the flow of fluid into unwanted formations. Examples include starches, polymers, or even finely ground materials. These additives are designed to be broken down later to allow for the flow of hydrocarbons from the target formation.
Functional Categories reported: Fluid loss control, water loss additive, diverting agent
Fluid Loss Control Examples
Materials reported as Fluid Loss Control
| Chemical Category | Example | Reported usage of this example across FracFocus |
|---|---|---|
| Organic Acid | 65-85-0 Benzoic acid | Reported in 294 disclosures or 0.164% Total mass: 2,100,000 pounds |
| Carboxylic Acid Ester | 117-81-7 Di(2-ethylhexyl) phthalate | Reported in 45 disclosures or 0.0251% Total mass: 1,300 pounds |
| Non-functionalized Hydrocarbon | 8002-74-2 Hydrocarbon waxes | Reported in 69 disclosures or 0.0384% Total mass: 91,000 pounds |
Endnotes
- This summary is not a complete cataloging of FracFocus chemicals. Like Elsner and Hoelzer (2016), we focus on the most common chemicals reported in the different groups.
- Note about functions: Although FracFocus can provide hints on the functions of the chemical through the “Purpose” column, it is not reliable for a few reasons. First, “Purpose” generally refers to the product, not the individual ingredients of the product. Further, in roughly half of disclosures in FracFocus, the Systems Approach is used in which the Purpose (and TradeName and Supplier) are dissociated from individual chemical records. Because of this loose connection between a chemical and (an often non-specific) Purpose value, it is hard to pinpoint the function of many chemical records.