RU2388786C2 - Composition for acid treatment of bottom-hole zone of low-permeable terrigenous bed - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: composition for acid treatment of bottom-hole zone of low-permeable terrigenous bed includes the following, wt %: inhibited chlorhydric acid (on HCl) 9.0 - 15.0; fluorine-containing reagent - fluorhydric acid or ammonium bifluoride, or ammonium fluoride (on HF) 4.0 - 7.4; neonol and/or phosphonic acid 0.1-2.0; organic solvent - oxal T-66 5.0- 30.0; water - the rest.

EFFECT: increasing efficiency of acid treatment of low-permeable terrigenous beds owing to slowing down the velocity of reaction with rock at bed temperature.

3 ex, 4 tbl, 1 dwg

Description

The invention relates to the oil industry, in particular to the technology of oil production using chemicals based on clay-acid compositions by the integrated impact on the bottom-hole zone of the terrigenous reservoir, in order to intensify the flow of oil and gas from it and can be used to increase oil recovery of low-permeable terrigenous reservoirs.

Known methods of acid treatment of terrigenous reservoirs, which use clay-acid compositions containing monohydric alcohols [1], glycols [2], cellosolves [3].

Common disadvantages of the known compositions 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 one is a composition for acidizing the bottom of the formation containing a mixture of hydrochloric acid with hydrofluoric 8.0-75.0 wt.%, Corrosion inhibitor 0.5-2.0 wt.%, Nonionic surfactants and / or phosphonic acid 0.5-2.0 wt.%, the solvent is ethanol or methanol or alcohol-containing waste: ethanol fraction, methanol fraction - the rest [4] is a prototype.

The disadvantages of this composition are the lack of high compatibility with reservoir oil, insufficient slowdown in the rate of interaction with the rock, which reduces its effectiveness when acting on the reservoir.

The objective of this technical solution is to expand the range of acid compositions for low-permeable terrigenous strata, to reduce the cost of the acid composition by using reagents that are by-products of chemical industries (waste), but at the same time increase the efficiency of acid treatment of low-permeability terrigenous reservoirs by significantly slowing down the rate of reaction with the rock at reservoir temperature to increase treatment coverage and reduce the risk of formation secondary precipitation, as well as increasing the penetration of the acid composition into the low permeability reservoir and improving the removal of spent acid and reaction products from the treated zone.

The problem is solved in that the composition for acidizing the bottom-hole zone of a low permeable terrigenous reservoir, including inhibited hydrochloric acid and a fluorine-containing reagent, a nonionic surfactant Neonol and / or phosphonic acid, an organic solvent and water, according to the invention, contains hydrofluoric acid as a fluorine-containing reagent , or ammonium bifluoride, or ammonium fluoride, as an organic solvent, a mixture of heterocyclic alcohols, diols, alcohol esters - oxal l T-66, in the following ratio of components, wt.%:

Inhibited hydrochloric acid (on Hcl) 9.0-15.0 Fluorine Reagent (on HF) 4.0-7.4 Nonionic surfactants and / or phosphonic acid 0.1-2.0 Specified Organic Solvent 5.0-30.0 Water rest.

A comparative analysis of the claimed invention with a prototype and analogues allows us to conclude that the proposed solution meets the criterion of "novelty", as it contains a new reagent for acidic compounds - a mixture of heterocyclic alcohols, diols, alcohol ethers. In addition, the proposed composition also meets the criterion of "significant differences", since the reagent used in it significantly improves the technological properties of the acid solution.

Flotoreagent - oxal T-66 is a mixture of heterocyclic alcohols, diols, alcohol esters and is a product of processing by-products of dimethyldioxane production, is produced according to TU 2452-029-05766801-94 and is used as a plasticizer in the paint and varnish industry, when drilling oil wells to control properties water based drilling fluids.

The requirements for the properties of the flotation reagent - oxal T-66 according to TU are given in table 1.

The following substances produced by domestic industry were also used to prepare the compositions of working solutions:

Inhibited hydrochloric acid (Hcl) is produced according to TU 2122-131-05807960-97;

Hydrofluoric acid containing 50 wt.% HF is available in accordance with TU 48-5-184-78;

Ammonium bifluoride - a white powder containing 97 wt.% Of the basic substance, is produced according to TU 113-08-544-83;

Ammonium fluoride - a white powder containing 97 wt.% Of the basic substance, is produced according to GOST 4518-75;

Nonionic surfactants - monoalkylphenols based on propylene trimers, hydroxyethylated - neonols AF _9-6 , AF _9-12 , are produced according to TU 38-507-63-171-91.

Nitrile-trimethylphosphonic (NTF) acid according to TU 6-09-5065-82, TU 6-09-5283-86, hydroxyethylene diphosphonic (OEDP) acid according to TU 6-02-1215-81 was used as phosphonic acid.

Hydrochloric and hydrofluoric acids dissolve and disperse the carbonate and clay constituents of the formation rock.

Ammonium bifluoride or ammonium fluoride is used instead of hydrofluoric acid in order to reduce the water content in the proposed composition.

Nonionic surfactants contribute to the dispersion of clay components in the composition, dispersion of asphalt-resin-paraffin deposits, increases the oil-displacing properties of the composition, reduces the surface tension of the acid composition at the border with hydrocarbons to almost zero, in combination with the proposed solvent, eliminates the possibility of the formation of oil-acid emulsions.

The introduction of NTF or HEDP into the acid composition avoids contamination of the formation with secondary sediments.

The solvent mixture, which is part of the flotation reagent - oxal T-66, reduces the surface tension of aqueous solutions at the border with hydrocarbons by 2-3 times, which contributes to the creation of a homogeneous system when mixing formation and injected fluids, i.e. prevents the formation of emulsions that block filtration channels.

Also, the solvent flotoreagent - oxal T-66 is unlimitedly soluble in water and oil, therefore, its introduction into the acidic composition additionally increases the penetrating ability of the composition and allows the proposed composition to be used not only on medium but also on low permeability reservoirs where high filterability of solutions is required, except this, helps to reduce the rate of interaction with the rock, which allows not only to increase the depth of the treated zone, but also to slow down the secondary sedimentation.

Evaluation of the effectiveness of the compositions was checked in laboratory conditions by the rate of dissolution of the rock and the flow rate of hydrofluoric acid. For this, the compositions were prepared according to the invention with a solvent and without introducing a solvent, as well as according to the prototype.

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 21 ml of fresh water, 62.5 g of a 24% HCl solution, 10.0 g of a 50% HF solution, 5.0 g of a solvent, flotation reagent - oxal T- were successively dissolved with a plastic stick. 66, 0.5 g of nonionic surfactants - neonol AF _9-12 and 1.0 g of NTF. 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 - AF _9-12 - 0.5; NTF - 1.0; flotation reagent - oxal T-66 - 5.0; water - the rest (composition No. 1).

Example 2. In a 250 ml Teflon beaker, weighed 68.1 g of a 24% solution of Hcl, 7.4 g of NH ₄ F, 23.0 g of solvent flotoreagent - oxal T-66; 0.5 g of nonionic surfactants - neonol AF _9-12 and 1.0 g of NTF. 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 - 0.5; NTF - 1.0; flotation reagent - oxal T-66 - 23.0, the rest of the water (composition No. 3). Part of the HCl reacts with NH ₄ F to form HF; fresh water is not introduced in the preparation of the composition.

Example 3. In a 250 ml Teflon beaker, weighed 62.8 g of a 24% solution of Hcl, 5.7 g of NH ₄ F · HF, 30.0 g of solvent, flotation reagent - oxal T-66, 0.1 g of nonionic surfactants - Neonol AF _9-12 . After mixing for 5-10 minutes, a composition was obtained with the following content of ingredients, wt.%: Hcl - 11.5, HF - 4.0, nonionic surfactants - neonol AF _9-12 - 0.1, flotation reagent - oxal T-66 - 30.0 (composition No. 4). Part of the HCl reacts with NH ₄ F · HF to form HF; fresh water is not introduced in the preparation of the composition.

Compounds No. 2, 5 of Table 2 were prepared in a similar manner. Methanol was introduced into compositions No. 6 and 7 as a solvent.

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. At a temperature of 20 ° C, clay and argillite taken from the Arlan deposit were dissolved. 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, kept in a thermostat at the test temperature for 10-15 minutes, after which the prepared rock sample was placed in the glass for a specified time, after a specified time, the remaining rock was filtered and washed with distilled water until there were no chlorides in wash water, dried to constant weight and weighed. In the filtrate, the concentrations of hydrofluoric and hydrochloric acids were determined.

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 experimental data obtained by dissolving the rock in an acidic composition without introducing solvents are shown in the drawing.

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 2.0% concentration of HF, the reaction with clay practically does not occur, therefore, the calculated maximum inhibition of the HF reaction is 31% for an initial concentration of 4, 0%, and 45% for an initial HF concentration of 5.0%.

To analyze the experimental data and evaluate the effectiveness of the reagents introduced into the acid composition, the following parameters were adopted: ΔV ₀ — slowing down 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 the decrease in the reaction rate of hydrofluoric acid when a reagent is introduced into the composition relative to the reaction rate of hydrofluoric acid without it, expressed in%.

ΔV - slowing down 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 ° С - 6 hours, at a temperature of 80 ° С - 3 hours).

ΔР is the change in the solubility of the rock when the reagent is introduced into the acid composition relative to the solubility of the rock in the acid composition without it.

The results of the laboratory experiment are shown in table 3.

Table 4 shows the technological characteristics of the acid compositions.

The data presented in table 4 indicate that the use of the proposed composition allows for deep acid treatment of the bottomhole formation zone, composed of terrigenous rocks. The proposed composition in comparison with the known has the following technical and economic advantages:

- maximally reduces the rate of dissolution of the rock, this indicator improves compared with the known by 27-36%;

- allows to reduce the concentration of solvent to 5%;

- large-tonnage production wastes are disposed of;

- improving the technological characteristics of the operation for the SCR through the use of complex action.

Table 1 No. p / p Name of indicator Norm one. Appearance Dark opaque liquid 2. Mass fraction of dimethyldioxane,%, no more 1,5 3. Flash point in an open crucible, ° С, not lower 80 four. Pour point, ° C, not higher minus 40 5. Density, g / cm ³ , within 1,000-1,120 6. Solubility of one part in 50 parts of water Complete, opalescence and slight turbidity are allowed.

Table 3 Composition number The name of the breed 20 ° C 80 ° C ΔV ₀ ,% ΔV,% ΔP,% ΔV ₀ ,% ΔV,% ΔP,% one clay 15.0 0 +6.8 four clay 20.8 28.8 - one Argillite of the Arlan field 20,0 4.4 +9.5 3 "-" 7.7 8.9 +12.5 four "-" 32,3 35.6 +9.5 one Argillite of the Priobskoye field 18.0 9,4 +20 2 "-" 11.5 9,4 - 3 "-" 34.2 7.0 - four "-" 46.0 51.1 - 5 clay 33,2 1.3 +8.3 6 clay 0 0 0 6 (prototype) Argillite of the Arlan field 0 0 0 6 (prototype) Argillite of the Priobskoye field 0 0 0 7 (prototype) Argillite of the Arlan field 22.5 12.0 +8.3 7 (prototype) Argillite of the Priobskoye field 28.8 11.3 +20

Table 4 Composition number The concentration of organic solvent, wt.% Slowdown (%) of the HF reaction at temperature: The increase in solubility,% % slowdown of the maximum possible 20 ° C 80 ° C 20 ° C 80 ° C 20 ° C 80 ° C one 5 fifteen 18.0 9.5 11.5 48,4 40,0 2 10 0 11.5 - 0 0 25.6 3 23 32,3 34.2 12.5 - one hundred 76.0 four thirty 34.0 46.3 9.5 - one hundred one hundred 5 thirty 33,2 - 8.3 - one hundred - 7 prototype 30 (methanol) 22.5 28.8 0 10.8 72.6 64.0

Information sources

1. RF patent №2249101, E21B 43/27, published 03/27/2005.

2. Auth. St. USSR No. 1387547, E21B 43/27, 1986

3. RF patent No. 2213216, E21B 43/27, published 03.01.2002.

4. RF patent 2100587, E21B 43/27, published December 27, 1997 - prototype.

Claims (1)

A composition for acidizing a bottomhole zone of a low-permeable terrigenous formation, including inhibited hydrochloric acid and a fluorine-containing reagent, a nonionic surfactant Neonol and / or phosphonic acid, an organic solvent and water, characterized in that it contains hydrofluoric reagent or ammonium bifluoride , or ammonium fluoride, as an organic solvent - a mixture of heterocyclic alcohols, diols, alcohol esters - oxal T-66 in the following ratio of components s, wt.%:
Inhibited hydrochloric acid (on Hcl) 9.0-15.0 Fluorine Reagent (on HF) 4.0-7.4 Nonionic surfactants and / or phosphonic acid 0.1-2.0 Specified Organic Solvent 5.0-30.0 Water rest

Images