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More on chemical additives

From media coverage on fracking, the impression may be gained that hundreds of chemicals are used in fracking. In reality, the number for any one operation is much less than that. The composition will vary from operation to operation, depending on the local geology.

The chemicals are not toxic to humans in the concentrations used, and many if not all are biodegradable.

An example list of chemicals is provided below for a major fracking company in the US, Halliburton. Download an explanation of Halliburton's fracking processes here

Immediately below is a further practical example of the composition of fracking fluid, in this case for operations that may be carried out in New Zealand by Canadian joint venture Apache/TAG Oil, who would contract Baker Hughes to carry out the work.

 

Apache/TAG Oil

Water and quartz sand - 98-99% of the total fluid

Chemical additives - 1-2%, of which around half is a natural gel. A note explaining the use in fracking of each chemical additive is provided here

Bactericide – glutaraldehyde – also used in sterilising medical and dental equipment, in hand-wash soap, and as a disinfectant

Gel – guar gum – also used in ice cream, toothpaste, and in baked goods, sauces, salad dressings and other processed foods

Cross-linker – borate salts – also used in detergents, hand soaps, cosmetics

Clay stabiliser – choline chloride – also used as a poultry food additive

Gel breaker – hemicellulose enzyme – also used in washing powders, and in the food industry

Acidity adjuster – sodium, potassium, chlorine compounds – also used in laundry detergents

Surfactant – soap chemical - found in soaps and detergents

Note on fracking chemicals used by Baker Hughes

The additives form an engineered chemical system. Initially, they make the fracking fluid thick and slippery for ease of pumping, and to keep the sand in suspension. Once fissures are created in the reservoir rock, and sand grains are distributed through the fissures, a chemical change is introduced. Chemical reactions break down the thickening agent, to make it easier for the fracking fluid to return to the surface, while the sand remains to keep the cracks open.

A bactericide is used to prevent bacterial action underground causing corrosion of the well casing.

Gel is used to thicken the fracking fluid, and keep the sand in suspension, during injection of the fracking fluid into the reservoir rock.

The cross-linker is used to maintain the viscosity, or thickness, of the gel

The clay stabiliser is used to prevent clogging the well with any clay minerals present in rocks underground.

The gel breaker is injected to counteract the thickening action of the gel, to allow fracking fluid to return easily to the surface via the well, and allow the gas to flow.

The acidity adjuster compensates for deviations caused by the underground geology to the required acidity (or pH) for the fracking chemical system to work.

The surfactant increases the slipperiness of the fracking fluid for ease of pumping, and to help used fracking fluid return to the surface.

 

Halliburton

A note is provided below on each chemical used.

(The unit, ppm = parts per million. 10,000ppm = 1 percent.)

Water - 90 percent

Sand - 9 percent

Petroleum distillate (reduces friction) - 60ppm

Bellacide (bactericide) - 8ppm

Ammonium chloride (prevents clogging of the well) - 20ppm

Guar gum (natural gel) - 200ppm

Hemicellulase enzyme (natural gel breaker) - 2ppm

Sodium persulphate (gel breaker) - 20ppm

Hydrochloric acid (acid) - 135ppm

Propargyl alcohol (inhibits corrosion of equipment) - 1ppm

Methanol (inhibits corrosion of equipment) - 4ppm

 

Note on fracking chemicals used by Halliburton

Petroleum distillate makes the fluid slippery. Similar products are used in the manufacture of cosmetics such as hair, make-up, nail and skin products. 

Bellacide (tributyl tetradecyl phosphonium chloride) is used to prevent bacterial action interfering with the other additives, and the well casing.

Ammonium chloride (sal ammoniac) prevents clay minerals sticking to the side of the well during fracking. It occurs naturally as a mineral, and is used in cough mixture, processed foods, in hair shampoo and in diverse industrial processes. 

Guar gum is a natural gel, also used in processed foods such as ice cream, sauces and salad dressings, to thicken the fluid and keep the sand in suspension during injection of the fracking fluid into the reservoir rock.

Hemicellulase enzyme is a natural enzyme with wide application in, for example, laundry detergents, and drying coffee beans. In fracking, it is used to break down the natural gel when fracking is completed.   

Sodium persulphate is used to break down the natural gel. In the household, it is used in bleaches and detergents. 

Hydrochloric acid is introduced into the well at the beginning of each fracking stage in a 15% concentration. Once diluted with water in fracking, the acidity drops to around that of bread. Hydrochloric acid occurs naturally in the stomach.

Propargyl alcohol is used to prevent corrosion of equipment used in fracking.

Methanol (wood alcohol) occurs naturally in alcoholic beverages and spirits but in very low concentrations. In fracking fluids, it is used as a corrosion inhibitor, and occurs in a dosage of 0.1 per cent of the maximum safe level.

As a general comment, in the concentrations used, the chemicals are non-toxic to humans. But it is also clear that a slightly acidic fluid with various chemicals in it would be unpleasant to drink. Certainly, it would be unacceptable for used fracking fluid to enter the drinking water or aquifers, unless treated and/or adequately diluted.

For more information on disposal of used fracking fluids, click here