Why Chemicals Are Used
Chemical additives are present in most fracture fluids. These additives serve primarily to increase viscosity, which helps the fluid to carry proppant more effectively, and reduce friction, which allows the fluid to flow more easily to and into the target formation. Additives tend to make up less than 1% of fracture fluids and can serve several purposes, from corrosion inhibitors, which prevent the metal in a wellbore from deteriorating, to anti-bacterial agents. The table depicts generic hydraulic fracturing chemical additives by type, purpose, downhole result, common use (outside of oil and gas) and typical usage in unconventional reservoirs.
| Used in Unconventional Reservoirs | Type | Purpose | Downhole Result | Common use |
|---|---|---|---|---|
| Yes | Acid | Helps dissolve minerals and initiate cracks in the rock | Reacts with minerals present in the formation to create salts, water, and carbon dioxide (neutralized) | Swimming pool chemical and cleaner |
| Yes | Corrosion Inhibitor | Prevents the corrosion of the pipe | Bonds to metal surfaces (pipe) downhole. Any remaining product not bonded is broken down by micro-organisms and consumed or returned in produced water. | Used in pharmaceuticals, acrylic fibres and plastics |
| Rare | Iron Control | Prevents precipitation of metal oxides (in pipe) | Reacts with minerals in the formation to create simple salts, carbon dioxide and water all of which are returned in produced water | Food additive; flavouring in food and beverages; lemon juice |
| Yes | Anti-Bacterial Agent | Eliminates bacteria in the water that produces corrosive by-products | Reacts with micro-organisms that may be present in the treatment fluid and formation. These micro-organisms break down the product with a small amount of the product returning in produced water. | Disinfectant; sterilizer for medical and dental equipment |
| Rare | Scale Inhibitor | Prevents scale deposits downhole and in surface equipment | Product attaches to the formation downhole. The majority of product returns with produced water while remaining reacts with microorganisms that break down and consume the product. | Used in household cleansers, de-icer, paints, automotive antifreeze |
| Rare | Clay Stabilizer | Prevents formation clays from swelling | Reacts with clays in the formation through a sodium - potassium ion exchange. Reaction results in sodium chloride (table salt) which is returned in produced water. | Used in low-sodium table salt substitute, medicines, and IV fluids |
| Yes | Friction Reducer | “Slicks” the water to minimize friction in the pipe | Remains in the formation where temperature and exposure to the "breaker" allows it to be broken down and consumed by naturally occurring micro-organisms. A small amount returns with produced water. | Used in cosmetics including hair, make-up, nail and skin products |
| Common, but often over used | Surfactant | Used to increase the viscosity of the fracture fluid | Generally returned with produced water, but in some formations may enter the gas stream and return in the produced natural gas | Used in glass cleaner, multi-surface cleansers, antiperspirant, deodorants and hair-color |
| Only in hybrid hydraulic fracturing programs | Gelling Agent | Thickens the water in order to suspend the sand | Combines with the "breaker" in the formation thus making it much easier for the fluid to flow to the borehole and return in produced water | Cosmetics, baked goods, ice cream, toothpaste, sauces, and salad dressings |
| Only with gel | Breaker | Allows a delayed break down the gel polymer chains | Reacts with the "crosslinker" and "gel" once in the formation making it easier for the fluid to flow to the borehole. Reaction produces ammonia and sulphate salts which are returned in produced water. | Used in hair coloring, as a disinfectant, and in the manufacture of common household plastics |
| In some hybrid hydraulic fracturing programs | Crosslinker | Maintains fluid viscosity as temperature increases | Combines with the "breaker" in the formation to create salts that are returned in produced water | Used in laundry detergents, hand soaps and cosmetics |
| Only with gel | pH Adjusting Agent | Maintains the effectiveness of other components, such as crosslinkers | Reacts with acidic agents in the treatment fluid to maintain a neutral (non-acidic, non-alkaline) pH. Reaction results in mineral salts, water and carbon dioxide; a portion of each is returned in produced water. | Used in laundry detergents, soap, water softener and dish washer detergents,washing soda |
| Yes | Oxygen scavengers | Removes oxygen from the water to protect the pipe from corrosion | Cosmetics, food and beverage processing, water treatment |