Neftenol K (Complex Surfactant Neftepav K)

It is used as an additive to hydrochloric acid used for treating terrigenous and carbonate formations, to mud acid used for treating terrigenous reservoirs, to acid hydraulic fracturing compounds, to kill fluids, drilling muds and oil well flushing fluids.

Main brands:

1. NEFTENOL K brand NK-20 summer form

2. NEFTENOL K brand NK-40 winter form

Depending on the area of application, the amount of the main active substance and functional additives, Neftenol K is also available in the following grades:

Application areas:

1. Surfactant-acid treatments.
Add 4% Neftenol K to the working solution of hydrochloric or mud acid. Well treatment requires a surfactant-acid solution at a rate of 0.5-1.5 ^m³ per 1 m of perforated formation thickness. The reaction time is no more than 6 hours. The effectiveness of such treatments is, on average, twice as high as that of similar treatments without surfactant additives, while ensuring the absence of corrosion.

2. Gentle killing of oil and gas condensate wells.
Adding Neftenol K to salt-based killing fluids at a rate of 1-4% by weight reduces the time it takes to restore well conductivity after well workovers, reducing well recovery time by 2-7 times and reducing oil losses by 40-60% compared to wells killed without treatment.

3. Hydroacid hydraulic fracturing.
With the addition of Neftenol K to 24% hydrochloric acid. Statistics for the use of this hydraulic fracturing method in carbonate reservoirs show a 2.5-fold increase in oil flow rate and a 26% reduction in well water cut compared to traditional hydraulic fracturing.

Physicochemical quality indicators of surfactant Neftenol K

The reagent Neftenol K is protected by a patent of the Russian Federation and has a sanitary-epidemiological conclusion and a TEKSERT certificate of conformity.

The reagent is a multicomponent mixture of anionic and cationic surfactants of various chemical structures.

The cationic surfactant contained in Neftenol K does not release volatile chlorine-containing products during thermal degradation, therefore it does not adversely affect subsequent oil refining. The anionic surfactant does not form residues when in contact with mineralized formation water, as it forms water-soluble compounds when interacting with solutions of metal salts such as magnesium, calcium, iron, and others.

By adding Neftenol K to acids, it's possible to penetrate deeper into the formation, thereby increasing the effectiveness of treatments. Adding Neftenol K to wellkill fluids reduces well completion time and helps maintain the productivity of the near-wellbore formation zone, thanks to the hydrophobic properties of the reagent, which has a low interfacial tension between its solutions and the hydrocarbon phase.

The optimal concentration as an additive to acids is 4% ,
as a result we get:

1. Reduction of interfacial tension.

Below is a table showing the results of studies of inhibited 12% hydrochloric acid and mud acid (24% HCl + 3% HF), as well as these acids treated with surfactant Neftenol K of various concentrations.

Thus, with the addition of Neftenol K, the interfacial tension is sharply reduced, which characterizes the possibility of deeper penetration of the acid solution into the low-permeability reservoir.

2. Inhibition of corrosion rate.

The formula for Neftenol K is designed to be compatible with all corrosion inhibitors used in Russia as additives to hydrochloric acid. Therefore, there is no conflict between corrosion inhibitors added to hydrochloric acid at the factory and Neftenol K.

To evaluate the anti-corrosion properties of the reagent, several compositions of 12% hydrochloric acid with widely used surfactant additives were used; the results are presented in the table.

Adding Neftenol K to reduce interfacial tension not only doesn't "quench" the factory inhibitor, but also reduces the hydrochloric acid corrosion rate to 0.18 g/m² ^h . Manufacturers of inhibited hydrochloric acid guarantee low corrosion rates (approximately 0.2 g/m² ^h ) for a month, while adding 4% Neftenol K maintains the corrosion rate of inhibited hydrochloric acid for six months.

3. Preventing the formation of secondary sediments.

As a rule, acid compositions must retain iron ions during rock treatment, which prevents the formation of insoluble precipitates and facilitates the possibility of deep treatment of formations with hydrochloric acid.

The results of studies with inhibited 12% hydrochloric acid and inhibited 12% hydrochloric acid treated with 4% surfactant Neftenol K are shown in the table.

A hydrochloric acid solution with the addition of Neftenol K is much more effective at retaining iron ions. A liter of 12% inhibited hydrochloric acid retains only 0.001 g of iron, while the acid treated with Neftenol K retains 5.1 g of iron, which is 50,000 times more.

4. Slowing down the reaction rate of acid with rock.

The figure below shows the results of studies of changes in the rate of dissolution of carbonate rock by acid solutions.

Inhibited hydrochloric acid is characterized by a violent reaction with carbonate rock, whereas the addition of 4% Neftenol K is characterized by a lower (more than 4 times) rate of dissolution of carbonate rock.

Over time, during treatment, the dissolution rate of hydrochloric acid with the addition of Neftenol K becomes higher than that of pure inhibited hydrochloric acid. Thus, in addition to the deeper penetration of acid treated with Neftenol K, we can speak of the prolonged action of this acid composition.

5. Preventing the formation of emulsion when interacting with oil.

During acid treatments, stable emulsions often form when acids interact with oil, and precipitation occurs in formation waters. There is also a high risk of wax and paraffin deposition from the oil. Using a methodology adopted by international companies, the compatibility of hydrochloric acid with the addition of Neftenol K was assessed with oil and formation water. Other surfactant additives to hydrochloric acid were also used for comparison. Research has shown that only the addition of Neftenol K to hydrochloric acid prevents these complications, specifically, preventing the formation of emulsions, precipitation, and wax and paraffin deposition. The results are presented in the table.

6. Resistance to mineral aggression and temperature.

Neftenol K is unconditionally resistant to mineral attack and temperature when used in concentrations from 0.02 to 1.0%. Salting out of the reagent occurs only in highly mineralized waters when the temperature rises above 50°C.

The areas of reliable application of Neftenol K are:

– in concentrations up to 4.0% in low-mineralized waters up to a temperature of 90°C;
– in concentrations up to 4.0% in highly mineralized soils up to a temperature of 50°C;
– in concentrations up to 1.0% in highly mineralized waters up to a temperature of 90°C.

7. Maintaining reservoir productivity.

Filtration tests were conducted to assess the permeability recovery of porous media during well-kill simulations. Core samples characterized by hydrophilic and hydrophobic properties were used for the experiments, and their air permeabilities were determined. The samples were then saturated with water and displaced with kerosene, oil, surfactant, and then oil again. Permeability values and the oil permeability recovery coefficient were determined throughout the entire test period.

For hydrophilic reservoirs, the permeability recovery factor for Neftenol K is 0.715. This is due to the hydrophobic properties of this surfactant, and hydrophobization of the surface of large and medium pore channels significantly reduces the amount of water trapped within them during drainage, thereby promoting more complete recovery of the oil-permeability ratio. For hydrophobic reservoirs, the permeability recovery factor for Neftenol K is 0.875.

8. Reducing the corrosive aggressiveness of salt solutions for well killing.

The effect of adding Neftenol K to a well-killing salt solution on its corrosiveness was studied. A heavy "Liman" solution with a mineral content of 1.18 g/ ^cm3 was used as the well-killing solution. The results of the additive's effect on the corrosiveness of the well-killing solution are presented below.

Research has shown that surfactants do not increase the corrosiveness of well-killing solutions. Furthermore, Neftenol K has a protective effect, reducing the corrosiveness of the "Liman" solution by more than half.

Thus, the surfactant for hydrochloric acid treatments Neftenol K has the following useful properties:

– reduces surface tension at the kerosene-water interface;
– reduces the corrosive activity of acid as an effective inhibitor;
– does not react with standard corrosion inhibitors traditionally used in the production of hydrochloric acid (unlike most surfactants used for these purposes);
– has the property of reducing the reaction rate with carbonates, which, together with low surface tension, allows the acid to penetrate much deeper into the formation and carry out treatment not in the immediate vicinity of the bottomhole zone, which makes the treatment more effective;
– has a summer and winter commercial form.