RU2386666C1 - Acidic composition for processing low-permeability terrigenous reservoirs - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to oil extracting industry, particularly to compositions for bottom-hole acidising a terrigenous reservoir. The acidic composition contains the following, in wt %: inhibited hydrochloric acid 9.0-15.0, fluorine-containing reagent - hydrofluoric acid or ammonium bifluoride or ammonium fluoride 4.0-7.4, organic solvent - polyethylene glycol - 4 or Glycol-Reagent 5.0-30.0, surfactant - Neonol AF_9-12 0.1-0.2, water - the rest.

EFFECT: preparation of a composition for processing a terrigenous reservoir which has low rate of reaction with the rock at reservoir temperature in order to increase the processed area and reducing the danger of sedimentation, as well as a much lower surface tension value at the boundary with hydrocarbons and low rate of corrosion, compatibility with corrosion inhibitors added into commercial-grade acid; the composition does not form emulsions upon contact with oil or hydrocarbons.

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Description

The invention relates to the oil industry, in particular to compositions for acidizing the bottom-hole zone of a terrigenous formation.

It is known that acid compositions containing organic solvents have the ability to even out the reaction rate in the formation: to slow down the reaction rate in water-saturated interlayers and accelerate them in oil-saturated interlayers due to the oil washing properties of these solvents.

A known composition for processing the bottom-hole zone of wells, which includes, wt.%: An aqueous solution of hydrochloric acid 10-18, an aqueous solution of hydrofluoric acid 1.5-5.0, an organic solvent, the rest, and as an organic solvent, the composition contains a mixture saturated alkane hydrocarbons and aromatic hydrocarbons [1].

The disadvantages of the known composition are the low efficiency of exposure to low permeability reservoirs, since the solvents used in the acid composition slightly improve the conditions for filtering into the reservoir for the acid composition, insignificantly slow down the reaction rate of acids with the rock at temperatures from 70 ° C and above and do not allow it to be removed from the treated zone reaction products of acid with the rock.

It is also known to use butyl cellosolve as a solvent in a clay acid composition [2].

The disadvantages of the known composition are the use of expensive and scarce reagents widely used in chemical synthesis as components of the acid composition, as well as the insufficient slowdown of the reaction rate of the acid composition with the rock.

The closest technical solution to the proposed composition is an acid composition for processing terrigenous reservoirs of the following component composition, wt.%: Inhibited hydrochloric acid 8.0-15.0, fluorine-containing reagent - hydrofluoric acid or ammonium bifluoride, or ammonium fluoride 1.5-10 , 0, boric acid 1.0-3.0, Alkylphosphate-Himeko or Efiroks-7, or Fosfol-10 0.5-2.0, isopropyl alcohol 5.0-10.0, fresh water the rest [3].

A disadvantage of the known composition is that this composition forms emulsions in contact with oil and hydrocarbons.

The objective of this technical solution is to create a composition for treating a terrigenous formation with a slow reaction rate with the rock at the formation temperature to increase the coverage of the formation by processing and reduce the risk of precipitation, as well as lower surface tension at the border with hydrocarbons and a low corrosion rate, compatible with corrosion inhibitors introduced into commodity acid, as well as non-emulsifying contact with oil and hydrocarbons, which will increase improve the efficiency of acid treatment with its use, as well as expand the range of acid compositions for treating the bottomhole zone of low-permeability terrigenous strata and utilize large-scale production waste.

The problem is solved in that the acid composition for the treatment of low permeable terrigenous reservoirs, including inhibited hydrochloric acid, a fluorine-containing reagent - hydrofluoric acid or ammonium bifluoride, or ammonium fluoride, an organic solvent, a surfactant - surfactant and water, characterized in that contains as an organic solvent polyethylene glycol-4 or "Reagent-Glycoil", as a surfactant - Neonol AF _9-12 in the following ratio of components, wt.%:

Inhibited hydrochloric acid 9.0-15.0 The specified fluorine-containing reagent 4.0-7.4 Polyethylene glycol-4 or "Reagent-Glycoil" 5.0-30.0, Neonol AF _9-12 0.1-0.2 Water - the rest.

This composition is a homogeneous system that is well filtered in a porous medium, which not only cleans the bottom-hole zone of the formation from deposits of salts and residual drilling fluids, but also creates new filtration channels and maintains high oil-displacing properties in the reservoir conditions after neutralization. Unlike the known one, the proposed composition contains lower polymers of ethylene oxide and propylene with ethylene glycol (PEG-4) or waste containing them - a mixture of bottoms from the production of ethylene glycol and glycol monoesters with block copolymers of ethylene and propylene oxides ("Reagent-Glycoil"). A new combination of the essential features of the claimed technical solution allows to obtain a new, higher technical result, expressed in improving the technological properties of the composition due to its homogeneity, effective slowdown of the reaction rate with the rock even at high temperatures, increased oil permeability after processing, and, as a result , increasing the penetrating ability of the acid composition, as well as the removal of alcohol-soluble asphaltenes, resins, bound water, the removal of reaction products s breed.

All reagents used in the claimed composition are produced by domestic industry.

1. Inhibited hydrochloric acid, containing 24.0 wt.% HCl, is produced according to TU 2122-131-05807960-97.

2. Hydrofluoric acid containing 50.0 wt.% HF is available in accordance with TU 48-5-184-78.

3. Ammonium bifluoride - a white powder containing 97.0 wt.% Of the basic substance, is produced according to TU 113-08-544-83.

4. Ammonium fluoride - a white powder containing 97.0 wt.% Of the basic substance, is produced according to GOST 4518-75.

5. The lower polymer - polyethylene glycol-4 (PEG-4) is a polymer of ethylene oxide with ethylene glycol. The average molecular weight is 200, produced according to TU 6-13-115-97.

6. Reagent-Glycoil - a mixture of bottoms from the production of ethylene glycol and monoesters of glycols with block copolymers of ethylene and propylene oxides (PEG wastes), are produced according to TU 2422-130-05766801-2003, the properties of which are shown in table 1.

7. Nonionic surfactants-Neonol AF _9-12 - monoalkylphenols based on propylene trimers, ethoxylated, are produced according to TU 38-507-63-171-91.

Ammonium bifluoride or ammonium fluoride can be used in the proposed compositions with 23.0-30.0 wt.% The concentration of the solvent to obtain an acid solution without dilution with fresh water.

Polyethylene glycol-4 is used as a heat-resistant solvent for washing dies in the production of polyester fibers.

Reagent-Glycoil is intended for use as a defoamer of water systems used in the oil and gas industry, additives to drilling fluids and in microbiological processes for the production of yeast.

The introduction of nonionic surfactants - Neonol AF _9-12 in the proposed solvent in the acidic composition contributes to a significant decrease in the interfacial tension of the interface between the acidic composition and the formation medium and, as a result, to increase the productivity of the formation, as well as faster recovery of spent acidic solutions and reaction products.

For a comparative evaluation of the effectiveness of the action, the compositions according to the invention were prepared.

The content of components in the acid compositions are presented in table 2.

Examples of the preparation of acid formulations.

Example 1. In a 250 ml Teflon beaker in 22.4 ml of fresh water, 62.5 g of a 24% HCl solution, 10.0 g of a 50% HF solution, 5.0 g of solvent "Reagent-Glycoil" and 0.1 g of nonionic surfactants Neonol AF _9-12 . After stirring for 5-10 minutes, a composition was obtained with the following content of ingredients, wt.%: HCl - 15.0; HF - 5.0; Nonionic surfactants Neonol AF _9-12 - 0.1; "Reagent-Glycoil" - 5.0; water - the rest (composition No. 1).

Example 2. In a 250 ml Teflon beaker, weighed 69.5 g of a 24% HCl solution, 7.4 g of NH ₄ F, 23.0 g of Reagent-Glycoil solvent and 0.1 g of nonionic surfactant Neonol AF _{9 -12} . After stirring for 5-10 minutes, a composition was obtained with the following content of ingredients, wt.%: HCl - 9.0; HF - 4.0; Nonionic surfactants Neonol AF _9-12 - 0.1; "Reagent-Glycoil" - 23.0; water - the rest (composition No. 3). As a result of the interaction of NH ₄ F with HCl, the concentration of HCl decreases and HF is formed, water is not introduced into the composition.

Example 3. In a 250 ml Teflon beaker, weighed 64.2 g of a 24% solution of HCl, 5.7 g of NH ₄ F · HF, 30.0 g of solvent — Reagent-Glycoil, and 0.1 g of nonionic surfactant Neonol AF _9-12 . After stirring for 5-10 minutes, a composition was obtained with the following content of ingredients, wt.%: HCl - 12.8; HF - 4.0; Nonionic surfactants - 0.1 Neonol AF _9-12 ; "Reagent-Glycoil" - 30; water - the rest (composition No. 4). As a result of the interaction of NH ₄ F · HF with HCl, the concentration of HCl decreases and HF is formed, water is not introduced into the composition.

Example 4. In a 250 ml Teflon beaker in 22.3 ml of fresh water, 62.5 g of a 24% HCl solution, 10.0 g of a 50% HF solution, 5.0 g of PEG solvent were successively dissolved with a plastic stick while stirring with a plastic stick. -4 and 0.2 g of nonionic surfactants Neonol AF _9-12 . After stirring for 5-10 minutes, a composition was obtained with the following content of ingredients, wt.%: HCl - 15.0; HF - 5.0; PEG-4 - 5.0; Nonionic surfactants Neonol AF _9-12 - 0.2; water - the rest (composition No. 5).

Similarly were prepared compounds No. 2, 6-8 of table 2.

In laboratory conditions, the following properties of the proposed composition were determined: the ability of the proposed composition to prevent the formation of emulsions, surface tension at the border of the proposed composition is a hydrocarbon; the rate of dissolution of terrigenous rocks at a temperature of 15-20 ° C for deposits of the Ural-Volga region and 80 ° C, typical of most deposits of Western Siberia.

The ability of the proposed compositions to prevent the formation of emulsions with hydrocarbons was determined by the volume of the aqueous and hydrocarbon phase after shaking equal volumes of hydrocarbon and acid composition in a graduated bottle, followed by exposure at a temperature equal to the temperature of the formation for 24 hours. In the experiments we used oil from the Arlansky field of Bashneft OJSC, well 7886. For comparison, a similar experiment was conducted with a clay acid of 5% HF + 15% HCl. The results are shown in table 3.

Interfacial tension at the border with a hydrocarbon (kerosene) was determined in the obtained compositions using a stalagmometer according to the method described in RD 39-1-199-79, 1979, Ufa, p.15-17. The proposed composition has significantly lower values of interfacial tension at the border with kerosene (3-0.3 m / Nm).

The corrosion rate of steel was determined by the generally accepted method of weight loss of plates made of steel grade 08 KP after keeping them for 24 hours in the tested acid composition at 20 ° C. The corrosion rate of steel in the proposed composition was 0.27 g / m ² hour. The proposed composition has a low corrosion activity.

The dissolving ability of the proposed acid composition and the composition of the prototype in relation to terrigenous rock was investigated by the example of the dissolution of clay and mudstone. Of the rocks composing sandstones, a relatively high reaction rate of hydrofluoric acid with clay and low with quartz. The clay was dissolved at a temperature of 20 ° C. In experiments at 80 ° С, mudstone of the Priobskoe deposit was used. Preparation of the rock for the experiments consisted of isolating a certain fraction (less than 0.1 mm), determining the moisture content and carbonates.

To conduct dissolution tests, 3.0 g of rock samples were taken, brought to constant weight at a temperature of 105 ° C and weighed to the fourth decimal place. The amount of test solution was 50 ml. The test solution was poured into a 100 ml Teflon glass and kept in a thermostat at the test temperature for 15 minutes, after which the prepared rock sample was placed in it for a specified time. After a predetermined time, the remaining rock was filtered off, washed with distilled water until there were no chlorides in the washings, dried to constant weight, and weighed. The filtrate was determined by titration of the concentration of hydrofluoric and hydrochloric acids.

The solubility of the rock (%) was calculated by the formula:

P = (m ₁ -m ₂ ) * 100% / m ₁ ,

where m ₁ is the mass of the rock before the experiment, g;

m ₂ - rock mass after the experiment, g

The obtained experimental data on the dissolution of clay in clay compositions with different concentrations of hydrofluoric acid made it possible to determine that at a 1.9% concentration of HF the reaction with clay practically does not occur, therefore, the calculated maximum inhibition of the HF reaction is 31% for the initial concentration equal to 4.0%, and 45% for an initial HF concentration of 5.0%.

The following parameters were adopted to analyze the experimental data and evaluate the effectiveness of the reagents introduced into the acid composition.

ΔV ₀ - inhibition of the reaction rate of hydrofluoric acid in the initial reaction period when the reagent is introduced into the acid composition,%. Slowing down the reaction rate is a decrease in the reaction rate of hydrofluoric acid when a moderator is introduced into the composition relative to the reaction rate of hydrofluoric acid without it, expressed in%.

ΔV is the inhibition of the reaction rate of hydrofluoric acid in the final reaction period when the reagent is introduced into the acid composition,% (reaction time at a temperature of 20 ° C - 6 hours, at a temperature of 80 ° C - 3 hours).

ΔР is the change in the solubility of the rock when a moderator is introduced into the acid composition relative to the solubility of the rock in the acid composition without it, expressed in%, moreover with a sign (+) - increase and with a sign (-) - decrease solubility. The range of changes in solubility corresponds to the change at the initial moment of the reaction and in its final period.

The test results of the claimed and known composition, taken as a prototype, are presented in table 4. From the presented data it follows that the proposed composition has a lower rate of interaction with terrigenous rock, the rate of interaction at a temperature of 20 ° C with clay is reduced by 72.9-100% from the maximum possible, while in the known composition the deceleration of the HF reaction occurs only by 12.2% of the maximum possible.

The test results show that at a temperature of 20 ° C, the optimal concentration of the solvent in the acid composition is 30 wt.%, Where inhibition is 72.9-100% of the maximum possible. Concentration above 30 wt.% Is economically disadvantageous.

The test results at a temperature of 80 ° C show the advantages of the proposed composition compared with the known. The slowdown in the rate of hydrofluoric acid in the proposed compositions is observed at all solvent concentrations (5-23 wt.%). The maximum deceleration is achieved at 23 wt.% Concentration and is 89% of the maximum possible.

The results of studies of acid compositions clearly indicate a significant improvement in their technological characteristics.

Information sources

1. RF patent №2199661, ЕВВ 43/27, published on 02/27/2003 - analogue.

2. RF patent №2213216, ЕВВ 43/27, published September 7, 2003 - analogue.

3. RF patent №2244816, ЕВВ 43/27, published on January 20, 2005 - prototype.

Table 1. No. p / p Name of indicator Norm Test method one Appearance Dark fluid According to 4.2 TU 2 Mass fraction of water,%, no more 0.5 According to GOST 14870, section 2 3 Density at 20 ° С, g / cm ³ , no more 1.15 GOST 18995.1, section 1 four Dynamic viscosity at a temperature of 25 ° C, cSt (mm ² / s), within 30.0-65.0 GOST 33 5 Pour point, ° C, not higher Minus 30 GOST 20287 p. 2 Table 2. The content of the components in the compositions. Composition number Composition, wt.% Hcl Hf NH ₄ F NH ₄ F
Hf organic solvent Nonionic surfactants
AF _9-12 water PEG-4 glycoil one 15.0 5,0 - - - 5 0.1 rest 2 15.0 4.0 - - - 10 0.1 rest 3 9.0 - 7.4 - - 23 0.1 rest four 12.8 - - 5.7 - thirty 0.1 rest 5 15.0 5,0 - - 5 - 0.2 rest 6 15.0 4.0 - - 10 - 0.2 rest 7 9.0 - 7.4 - 23 - 0.2 rest 8 12.8 - - 5.7 thirty - 0.2 rest

Table 3. The stability of oil emulsions. Composition number The amount of acid composition separated from the emulsion,% 1-8 100.0 prototype 63,4 clay acid 52.0

Table 4. The effectiveness of acid formulations. Composition number The content of organic solvent, wt.% 20 ° C 80 ° C ΔV ₀ ,% ΔV,% ΔP,% % of max ΔV ₀ ,% ΔV,% ΔP,% % of max one 5 0 0 0 14.0 6.0 + (22-5) 31,0 2 10 0 8.5 -8.5 10.0 6.0 + (22-5) 22.0 3 23 3.8 0 +10.2 12,2 40,0 5.7 +10.0 89.0 four thirty 22.6 25,4 72.9 5 5 0 0 0 7.7 5.7 + (24-10) 17.0 6 10 0 8.5 -8.5 11.5 9,4 + (28-10) 25.6 7 23 0 0 +4.6 30.8 24.5 + (22-5) 68,4 8 thirty 32,7 35.5 +3.4 one hundred 9 10 0 10,2 -5.3 10.5 - - - - (prototype)

Claims (1)

An acidic composition for treating low-permeability terrigenous reservoirs, including inhibited hydrochloric acid, fluorine-containing reagent - hydrofluoric acid, or ammonium bifluoride, or ammonium fluoride, an organic solvent, a surfactant - surfactant and water, characterized in that it contains an organic solvent polyethylene glycol-4 or "Reagent-Glycoil", as a surfactant - Neonol AF _9-12 in the following ratio of components, wt.%:
Inhibited hydrochloric acid 9.0-15.0 The specified fluorine-containing reagent 4.0-7.4 Polyethylene glycol - 4 or "Reagent-Glycoil" 5.0-30.0 Neonol AF _9-12 0.1-0.2 Water Rest