What surfactants are used in oil extraction?
1. Surfactant for heavy oil exploitation
Due to the high viscosity and poor fluidity of heavy oil, it brings many difficulties to exploitation. In order to exploit these heavy oils, sometimes an aqueous solution of surfactants needs to be injected downhole to convert the high-viscosity heavy oil into a low-viscosity oil-in-water emulsion, which is pumped to the surface. The surfactants used in this heavy oil emulsification and viscosity reduction method are sodium alkyl sulfonate, polyoxyethylene alkyl alcohol ether, polyoxyethylene alkyl phenol ether, polyoxyethylene polyoxypropylene polyene polyamine, polyoxyethylene Ethylene alkyl alcohol ether sulfate sodium salt, etc. The produced oil-in-water emulsion needs to be separated from water, and some industrial surfactants are also used as demulsifiers for dehydration. These demulsifiers are water-in-oil emulsifiers. Commonly used are cationic surfactants or naphthenic acid, asphaltic acid and their polyvalent metal salts.
2. Surfactant for the exploitation of waxy crude oil
The extraction of waxy crude oil requires frequent dewaxing and dewaxing. Surfactants act as wax inhibitors and wax removers. There are oil-soluble surfactants and water-soluble surfactants for wax prevention. The former plays a role in preventing wax by changing the properties of the wax crystal surface. Commonly used oil-soluble surfactants are petroleum sulfonates and amine surfactants. Water-soluble surfactants play a role in preventing wax by changing the properties of wax-deposited surfaces (such as oil pipes, sucker rods and equipment surfaces). The available surfactants are sodium alkyl sulfonate, quaternary ammonium salt, alkane polyoxyethylene ether, aromatic hydrocarbon polyoxyethylene ether and their sulfonic acid sodium salts. The surfactants used for wax removal are also divided into two aspects, oil-soluble for oil-based wax remover, water-soluble sulfonate type, quaternary ammonium salt type, polyether type, Tween type, OP type surfactant, Sulfated or sulfoalkylated peregal and OP surfactants are used in water-based wax removers. In recent years, domestic and foreign have organically combined wax removal and prevention, and also organically combined oil-based wax remover and water-based wax remover to produce hybrid wax remover. This wax remover uses aromatic hydrocarbons and mixed aromatic hydrocarbons as the oil phase, and uses the emulsifier with wax removal function as the water phase. When the selected emulsifier is a non-ionic surfactant with a suitable cloud point, it can make it reach or exceed its cloud point at the temperature below the wax deposition section of the oil well, so that the mixed wax remover can be Before entering the wax deposition section, the demulsification is broken, and two kinds of wax removers are separated, which play the role of wax removal at the same time.
3. Surfactant for stabilizing clay
Stabilizing clay is divided into two aspects: preventing clay mineral expansion and preventing clay mineral particle migration. To prevent clay swelling, cationic surfactants such as amine salt type, quaternary ammonium salt type, pyridinium salt type, and imidazoline salt can be used. Fluorine-containing nonionic-cationic surfactants are available to prevent the migration of clay mineral particles.
4. Surfactant for acidification measures
In order to improve the acidification effect, a variety of additives are generally required to be added to the acid solution. All surfactants that are compatible with acid solution and are easily adsorbed by the formation can be used as acidification retarders. Such as fatty amine hydrochlorides, quaternary ammonium salts, pyridinium salts in cationic surfactants and sulfonated, carboxymethylated, phosphated or sulfated polyoxyethylene alkanes in amphoteric surfactants phenol ethers, etc. Some surfactants, such as dodecyl sulfonic acid and its alkylamine salts, can emulsify acid in oil to produce acid-in-oil emulsion, which is used as acidification industrial liquid and also plays a retarding role.
5. Surfactant for fracturing measures
Fracturing measures are often used in low-permeability oil fields, which is to use pressure to open up the formation to form fractures, and use proppant to prop up the fractures to reduce fluid flow resistance and increase production and attention. Some fracturing fluids are formulated with surfactants as one of the ingredients.
6. Surfactant for profile control and water plugging measures
In order to improve the development effect of water injection and restrain the rising rate of water cut in crude oil, it is necessary to adjust the water absorption profile on the water injection well and take measures to increase production by plugging the water on the production well. Some of these methods of profile control and water shutoff often use some surfactants.
7. Surfactant for sand control measures
Before sand control operation, it is necessary to inject a certain amount of active water prepared by surfactant as a pre-fluid to pre-clean the formation to improve the sand control effect. At present, the commonly used active agents are mostly anionic surfactants.
8. Surfactant for crude oil dehydration
In the primary and secondary oil recovery stages, the produced crude oil is mostly water-in-oil type demulsifier. Three generations of products have been developed, the first being carboxylates, sulfates and sulfonates. The second generation is low molecular weight nonionic surfactants such as OP, peregal and sulfonated castor oil. The third generation is a polymer nonionic surfactant.
9. Surfactant for water treatment
After the oil well produced fluid is removed from the crude oil, the produced water needs to be treated to meet the reinjection requirements. The purpose of water treatment has six aspects, namely corrosion inhibition, scale prevention, sterilization, deoxidation, degreasing and removal of suspended solids. Therefore, corrosion inhibitors, scale inhibitors, bactericides, oxygen scavengers, oil degreasers and flocculants should be used.
10. Surfactant for chemical flooding
The primary and secondary oil recovery can recover 25%-50% of the underground crude oil, and there are still many crude oil left in the ground that cannot be recovered. Carrying out tertiary oil recovery can enhance oil recovery. The tertiary oil recovery method is mostly chemical flooding, that is, adding some chemical agents to the injected water to improve the water flooding efficiency. Among the chemicals used, some are industrial surfactants.