1、 Surfactant for heavy oil recovery
Due to the high viscosity and poor fluidity of heavy oil, it has brought many difficulties to exploitation. In order to exploit these heavy oils, it is sometimes necessary to inject the aqueous solution of surfactant into the well to convert the high viscosity heavy oils into low viscosity oil in water emulsions and extract them to the surface. The surfactants used in this heavy oil emulsion viscosity reduction method include sodium alkyl sulfonate, polyoxyethylene alkyl alcohol ether, polyoxyethylene alkyl phenyl phenol ether, polyoxyethylene polyoxypropylene polyene polyamine, polyoxyethylene alkyl alcohol ether sulfate sodium salt, etc. The oil in water emulsion produced needs to separate water and use some industrial surfactants as demulsifiers for dehydration. These demulsifiers are water in oil emulsifiers. Cationic surfactants or naphthenic acids, asphaltene acids and their polyvalent metal salts are commonly used.
Special heavy oil can not be produced by conventional pumping unit, but needs steam injection for thermal recovery. Surfactant is needed to improve the thermal recovery effect. Injecting foam into steam injection well, that is, injecting high temperature resistant foaming agent and non condensable gas, is one of the common modulation methods.
The commonly used foaming agents are alkyl benzene sulfonates α— Sulfonated polyoxyethylene alkyl alcohol ethers, and sulfonated polyoxyethylene alkyl phenol ethers. As fluorine-containing surfactants have high surface activity and are stable to acid, alkali, oxygen, heat and oil, they are ideal high-temperature foaming agents. In order to make the dispersed oil easily pass through the pore throat structure of the formation, or make the oil on the surface of the formation easy to be driven out, it is necessary to use a surfactant called film diffusion agent, and the commonly used surfactant is an oxyalkylated phenolic resin polymer surfactant.
2、 Surfactant for exploitation of waxy crude oil
In order to exploit waxy crude oil, it is necessary to frequently prevent and remove wax. Surfactant is used as wax inhibitor and wax remover. Oil soluble surfactant and water-soluble surfactant are used for wax control. The former can prevent wax by changing the surface properties of wax crystals. The commonly used oil-soluble surfactants are petroleum sulfonates and amine surfactants. Water soluble surfactants can prevent wax by changing the properties of waxy surfaces (such as tubing, sucker rod and equipment surfaces). Available surfactants include sodium alkyl sulfonate, quaternary ammonium salt, alkane polyoxyethylene ether, aromatic polyoxyethylene ether and their sodium sulfonate salts. The surfactants used for wax removal are also divided into two aspects. Oil soluble surfactants are used for oil-based wax removal agents, water-soluble surfactants such as sulfonate type, quaternary ammonium salt type, polyether type, Tween type, Op type surfactants, sulfate ester hydrochloride or sulfoalkylated additive type and op type surfactants are used for water-based wax removal agents. In recent years, domestic and foreign companies have organically combined wax removal and prevention, and also organically combined oil-based wax remover and water-based wax remover to produce mixed wax remover. This wax remover uses aromatic hydrocarbon and mixed aromatic hydrocarbon as oil phase and emulsifier with wax removal function as water phase. When the selected emulsifier is a non-ionic surfactant with appropriate cloud point, it can make the temperature below the wax deposition section of the oil well reach or exceed its cloud point, so that the mixed wax remover can demulsify before entering the wax deposition section, separate two kinds of wax removers, and play the role of wax removal at the same time.
3、 Surfactant for stabilizing clay
Stabilizing clay components can prevent expansion of clay minerals and migration of clay minerals particles. Cationic surfactants such as amine salt, quaternary ammonium salt, pyridine salt and imidazoline salt can be used to prevent clay swelling. Non ionic cationic surfactants containing fluorine can be used to prevent the migration of clay mineral particles.
4、 Surfactant for acidizing measures
In order to improve the acidification effect, a variety of additives are generally added to the acid solution. Any surfactant that can be compatible with acid solution and easily adsorbed by formation can be used as acid retarder. Such as aliphatic amine hydrochloride, quaternary ammonium salt, pyridine salt in cationic surfactants and polyoxyethylene alkyl phenol ether in amphoteric surfactants which are sulfonated, carboxymethylated, phosphate ester hydrochloride or sulfate ester hydrochloride. Some surfactants, such as dodecyl sulfonic acid and its alkyl amine salt, can emulsify acid liquid in oil to produce acid in oil emulsion, which also plays a slowing role as an acidification industrial liquid.
Some surfactants can be used as acid solution demulsifiers, and branched surfactants such as polyoxyethylene polyoxypropylene propylene glycol ether, polyoxyethylene polyoxypropylene pentaethylene hexamine can be used as acid solution demulsifiers.
Some surfactants can be used as waste acid scavenging AIDS. The surfactants that can be used as scavenging aids include amine salt, quaternary ammonium salt, pyridine salt, non-ionic, amphoteric and fluorine-containing surfactants.
Some surfactants can be used as acidizing anti sludge agents, such as oil-soluble surfactants, such as alkyl phenols, fatty acids, alkyl benzene sulfonic acids, quaternary ammonium salts, etc. Because of their poor acid solubility, they can be dispersed in acid solution with non-ionic surfactants.
In order to improve the acidizing effect, it is necessary to add a wetting inversion agent into the acid solution to reverse the wettability of the near well zone from lipophilic to hydrophilic. The mixture of polyoxyethylene polyoxypropylene alkyl alcohol ether and phosphate salt polyoxyethylene polyoxypropylene alkyl alcohol ether is adsorbed to the formation as the second adsorption layer, and plays a wetting inversion role.
In addition, some surfactants, such as aliphatic amine hydrochloride, quaternary ammonium salt or non-ionic anionic surfactant, are used as foaming agents to make foam acid working fluid to achieve the purpose of retarding corrosion and deep acidification, or foam is made as acidizing pre fluid, which is injected into the formation and then injected with acid fluid. The Jamin effect produced by the bubbles in the foam can turn the acid solution, forcing the acid solution to mainly dissolve the low permeability layer and improve the acidification effect.
5、 Surfactant for fracturing measures
Fracturing measures are often applied in low permeability oil fields, that is, to open the formation with pressure to form fractures, and to support the fractures with proppant to reduce fluid flow resistance and achieve the purpose of increasing production and injection. Some fracturing fluids are prepared with surfactant as one of the components.
Oil in water fracturing fluid is prepared by water, oil and emulsifier. Emulsifiers used include ionic, nonionic and amphoteric surfactants. If the thickened water is used as the external phase and the oil is used as the internal phase, the thickened oil in water hydraulic fracturing fluid (polymer emulsion) can be prepared. This fracturing fluid can be used at a temperature below 160 ℃ and can automatically demulsify and drain.
Foam fracturing fluid is a fracturing fluid with water as the dispersion medium and gas as the dispersion phase. Its main components are water, gas and foaming agent. Alkyl sulfonates, alkyl benzene sulfonates, alkyl sulfate salts, quaternary ammonium salts and op type surfactants can be used as foaming agents. The concentration of foaming agent in water is generally 0.5-2%, and the ratio of gas phase volume to foam volume is in the range of 0.5-0.9.
Oil based fracturing fluid is a fracturing fluid prepared with oil as solvent or dispersion medium. The most widely used oil in the field is crude oil or its heavy fraction. In order to improve its viscosity temperature performance, it is necessary to add oil-soluble petroleum sulfonate (molecular weight 300-750). Oil based fracturing fluid also includes hydraulic fracturing fluid in oil and oil foam fracturing fluid. The emulsifiers used in the former are oil-soluble anionic surfactants, cationic surfactants and non-ionic surfactants, and the foam stabilizer used in the latter is a fluoropolymer surfactant.
The fracturing fluid for water sensitive formation is an emulsion or foam prepared by using the mixture of alcohol (such as ethylene glycol) and oil (such as kerosene) as the dispersion medium, liquid carbon dioxide as the dispersion phase, and polyoxyethylene alkyl alcohol ether salted by sulfate ester as emulsifier or foaming agent to fracture the water sensitive formation.
Fracturing fluid for fracturing and acidizing is both fracturing fluid and acidizing fluid. It is used in carbonate formation, and the two measures are carried out at the same time. Related to surfactants are acid foam and acid emulsion. The former uses alkyl sulfonate or alkyl benzene sulfonate as foaming agent and the latter uses sulfonate surfactant as emulsifier.
The fracturing fluid also uses surfactant as demulsifier, drainage aid and wetting inversion agent like the acidizing fluid, so it will not be described here.
6、 Surfactant for profile control and water plugging measures
In order to improve the effect of water injection development and restrain the rising rate of water content in crude oil, it is necessary to adjust the water injection profile in the water injection well and take water plugging stimulation measures in the production well. Some of the profile control and water shutoff methods often use some surfactants.
HPC / SDS gel profile control agent is composed of hydroxypropyl cellulose (HPC) and sodium dodecyl sulfate (SDS) in fresh water.
Sodium alkyl sulfonate and alkyl trimethyl ammonium chloride are respectively dissolved in water, mixed into two working fluids, and injected into the formation successively. The two working fluids are in circuitous phase in the formation, resulting in alkyl sulfite precipitation of alkyl trimethylamine, blocking the high permeability layer.
Polyoxyethylene alkyl benzene phenol ether, alkyl aryl sulfonate, etc. can be used as foaming agent, dissolved in water to prepare a working fluid, and then injected into the formation alternately with liquid carbon dioxide working fluid, forming foam in the formation (mainly high permeability layer), blocking and profile control.
Quaternary ammonium salt surfactant is used as foaming agent, dissolved in silicic acid sol prepared by ammonium sulfate and water glass and injected into the formation, and then non condensing gas (natural gas or chlorine gas) is injected. Foam with liquid as dispersion medium can be generated in the formation first, and then silicic acid sol is gelled to produce foam with solid as dispersion medium, which plays a role in plugging high permeability layer and profile control.
Sulfonate surfactant is used as foaming agent, polymer compound is used as thickening and foam stabilizing agent, and gas or gas generating substances are injected to generate water-based foam on the ground or formation. This kind of foam is in the oil layer, and a large amount of surfactant moves to the oil-water interface, causing foam damage. Therefore, it is a selective and oil well water shutoff agent without plugging the oil layer.
The oil-based cement water plugging agent is a suspension of cement in oil. The cement surface is hydrophilic. When it enters the water outlet layer, water displaces the oil well on the cement surface and acts with the cement to solidify and block the water outlet layer. In order to improve the fluidity of this plugging agent, carboxylate type and sulfonate type surfactants are usually added.
The water-based micellar solution plugging agent is a micellar solution mainly composed of petroleum ammonium sulfonate, hydrocarbons and alcohols. It has high saline content in the formation, variable viscosity and water plugging effect.
The water-based or oil-based cationic surfactant solution water shutoff agent is mainly composed of alkyl carboxylate and alkyl ammonium chloride active agents, which is only applicable to sandstone formation.
Active heavy oil plugging agent is a kind of heavy oil with water in oil emulsifier dissolved in it, which produces high viscosity water in oil emulsion after the formation detours to achieve the purpose of water plugging.
Oil in water plugging agent is prepared by emulsifying heavy oil in water with cationic surfactant as oil in water emulsifier.
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 the pre liquid to pre clean the formation to improve the sand control effect. At present, most of the commonly used active agents are anionic surfactants.
8、 Surfactant for crude oil dehydration
In the primary and secondary oil recovery stages, water in oil demulsifiers are mostly used for the crude oil produced. Three generations of products have been developed. The first generation is carboxylate, sulfate and sulfonate. The second generation is low molecular non-ionic surfactants such as OP, pingpingjia and sulfonated castor oil. The third generation is polymer nonionic surfactant.
In the later stage of secondary oil recovery and tertiary oil recovery, most of the crude oil produced exists in the form of oil in water emulsion. There are four types of demulsifiers used, such as tetradecyl trimethoxy ammonium chloride and Didecyl dimethyl ammonium chloride. They can react with anionic emulsifiers to change their hydrophilic oil balance value, or adsorb on the surface of water-wet clay particles to change their wettability and destroy the oil in water emulsion. In addition, some anionic surfactants and oil-soluble nonionic surfactants that can be used as water in oil emulsifiers can also be used as oil in water emulsion demulsifiers.
9、 Surfactant for water treatment
After crude oil is removed from the produced fluid of the oil well, 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, oxygen removal, oil removal and solid suspension removal. Therefore, the use of corrosion inhibitors, scale inhibitors, bactericides, deoxidizers, degreasers and flocculants involves the following aspects of industrial surfactants:
Industrial surfactants used as corrosion inhibitors include salts of alkyl sulfonic acid, alkyl benzene sulfonic acid, perfluoroalkyl sulfonic acid, linear alkyl amine salts, quaternary ammonium salts, alkyl pyridine salts, imidazoline and its derivatives, polyoxyethylene alkyl alcohol ethers, polyoxyethylene dialkylpropynyl alcohol, polyoxyethylene rosin amine, polyoxyethylene octadecylamine, polyoxyethylene alkyl alcohol ether alkyl sulfonates, and various quaternary amine internal salts, Di (polyoxyvinyl) alkyl groups and their derivatives.
Surfactants used as scale inhibitors include phosphate ester salts, sulfate ester salts, acetate salts, carboxylic acid salts and their polyoxyvinyl compounds. The thermal stability of sulfonate ester salt and carboxylate salt is obviously better than that of phosphate ester salt and sulfate ester salt.
The industrial surfactants used as fungicides include linear alkyl amine salts, quaternary amine salts, alkyl pyridine salts, imidazoline and its derivatives salts, a variety of quaternary ammonium internal salts, and di (polyoxyvinyl) alkyl and its derivatives internal salts.
Industrial surfactants used as degreasers are mainly surfactants with branched structure and containing sodium Dithiocarboxylate groups.
10、 Surfactant for chemical oil displacement
1、 Secondary oil recovery can recover 25% - 50% of underground crude oil, and many crude oil can not be recovered underground. Tertiary oil recovery can improve oil recovery. Chemical flooding is often used in tertiary oil recovery, that is, adding some chemicals into the injected water to improve the water displacement efficiency. Some of the chemicals used belong to industrial surfactants, and their brief introduction is as follows:
The chemical oil displacement method with surfactant as the main agent is called surfactant flooding. Surfactant plays an important role in enhancing oil recovery by reducing oil-water interfacial tension and increasing capillary number. Since the surface of sandstone formation is negatively charged, the surfactants used are mainly anionic surfactants, and most of them are sulfonate surfactants. It is made by sulfonating petroleum fractions with high aromatic hydrocarbon content with sulfonating agents (such as sulfur trioxide) and then neutralizing them with alkali. Specifications: 50% - 80% of active substance, 5% - 30% of mineral oil, 2% - 20% of water, and 1% - 6% of sodium sulfate. Petroleum sulfonates are resistant to temperature but not salt and high valent metal ions. Synthetic sulfonates are prepared from corresponding hydrocarbons by corresponding synthetic methods. Among them α— Olefin sulfonates, especially salt and high valence metal ions. In addition, some anionic nonionic surfactants and carboxylate surfactants can also be used for oil displacement. Surfactant oil displacement requires two kinds of auxiliaries: one is cosurfactant, such as isobutanol, diethylene glycol butyl ether, urea, sulfolane, alkylene benzene sulfonate, etc., and the other is dielectric, including acid-base salts, mainly salts, which can reduce the hydrophilicity of surfactants, relatively increase the lipophilicity, and also change the hydrophilic lipophilic balance value of surfactants. In order to reduce the loss of surfactant and improve the economic effect, surfactant flooding also requires the use of chemical substances called sacrificial agents. Materials that can be used as sacrificial agents include basic substances, polycarboxylic acids and their salts, oligomers and polymers can also be used as sacrificial agents, and lignosulfonate and its modifiers are a kind of sacrificial agents.
The oil displacement method using two or more chemical oil displacement main agents is called composite flooding. This oil displacement method related to surfactants includes: surfactant + polymer thickening surfactant flooding; Alkali enhanced surfactant flooding of alkali + surfactant or surfactant enhanced alkali flooding; Alkali + surfactant + polymer composite flooding. Composite flooding usually has higher recovery than single drive. According to the analysis of the current development trend at home and abroad, ASP flooding has higher advantages than ASP flooding. The surfactant used for ASP flooding is mainly petroleum sulfonate, which is usually combined with sulfuric acid and phosphorus of polyoxyethylene alkyl alcohol ether
