RU2758371C1 - Composition for removing barium and calcium sulphate scaling and method for application thereof - Google Patents

Abstract

FIELD: petroleum industry.

SUBSTANCE: invention relates to the petroleum and gas industry, namely to a composition and method for application thereof for treatment - cleaning of the bottom and the bottom-hole formation zone (BHFZ) of a borehole from barium and calcium sulphate scaling, and can also be applied for destroying the mud cake in deposits wherein productive formations are drilled and opened on weighted drilling muds containing barium sulphate. The composition for the treatment of the bottom-hole formation zone from barium and calcium sulphates scaling comprises ethylenediaminetetraacetic acid as a complexing substance, potassium hydrate as an alkali metal hydroxide, the surface-active agent "Neftenol VUPAV" and water, at the following ratio of components, % wt.: ethylenediaminetetraacetic acid 25.0, potassium hydrate 20.0, "Neftenol VUPAV" 0.1 to 2.0, fresh water the rest. Also described is a method for treatment of the bottom-hole formation zone, including flushing the borehole, injecting an active reagent, sustaining said reagent for reaction with bridging substances, collecting the spent composition, removing the reaction products from the formation, and putting the borehole into operation, the process of injection and collection of the spent active reagent is executed incycles, until the natural permeability of the bottom-hole formation zone is restored. After collection, the spent active reagent is regenerated by adding a solution of an acid. A composition containing ethylenediaminetetraacetic acid, potassium hydrate, "Neftenol VUPAV" and fresh water in the above amount is used as an active reagent, taken diluted with water in a ratio from 1:0 (without dilution) to 1:40 by weight.

EFFECT: provided dissolution and extraction of the bridging agents from the BHFZ – barium and calcium sulphate scale, possibility of reusing the active reagent, elimination of the corrosive and aggressive effects on surface and downhole equipment, since the proposed alkaline solutions are stable in storage and do not have a corrosive effect on equipment made of carbon and stainless steels in the used concentrations, reduction in the risk of conducting works in terms of safety regulations, since strong mineral acids are not used in the proposed method, increase in the effectiveness of treatment of the BHFZ represented by carbonate rocks or those having carbonate cement, since the active reagent dissolves CaSO₄ and CaCO₃ as well as barium sulphate.

2 cl, 1 tbl, 7 ex

Description

The invention relates to the oil and gas industry, namely to the composition and method of its application for processing - cleaning the bottom of the well and the bottomhole formation zone (BHZ) from scale deposition of barium and calcium sulfates, and can also find application for the destruction of the mud crust in the fields where drilling and the opening of productive formations is carried out on weighted drilling fluids containing barium sulfate.

Known composition for cleaning radiators from salt deposits [1 - analog], including tetrasodium salt of ethylenediaminetetraacetic acid at a concentration of 10-30% wt., Sodium tripolyphosphate (inorganic complexing reagent) in an amount of 70-50%, sodium sulfite (10-40% by weight .) and a surfactant based on polyglycol fatty acid esters, pH 6.5-10. The composition is produced in dry form; for the described purposes, its solution in water at a concentration of 2-4% is used.

The patent [2 - analogue] discusses compositions based on a salt of ethylenediaminetetraacetic acid with the inclusion of various surfactants. It is indicated that salt solutions with an alkaline medium successfully cope with the destruction of water-oil emulsions that block pores; for better destruction of emulsions, surfactants are added, preferably of the nonionic type due to their high resistance to the pH of the medium (sorbitan oleates and palmiates, polyglycol and tallic acid esters), but it is also possible to use cationic and anionic surfactants, in particular alkyl and arylsulfonates and sulfated alcohols. The concentration of the salt of ethylenediaminetetraacetic acid in the proposed composition is 1-10%, the contact time with barium sulfate deposits is 1-24 hours.

The disadvantage of the known compositions is their limited solubility in relation to barium sulfate.

A known composition includes 45% Trilon B (disodium salt of ethylenediaminetetraacetic acid), 6.0% alkali metal hydroxide, 3.0% surfactants (nonionic, anionic, cationic, as examples are given by NPAS Neonol AF 9-12, OP-10 , APAV Neonol RHP-20, KSAV Neftenol K) and water - the rest, while the commercial form is diluted with water in a ratio of 1: 0.6-111 [3 - prototype No. 1].

The disadvantages of this prototype is the use of Trilon B, which is a disodium salt of ethylenediaminetetraacetic acid, which complicates the process of obtaining the composition (heating is required to dissolve in alkali), as well as the use of sodium hydroxide as an alkali, which reduces the efficiency of dissolution of barium sulfate.

A known method for treating the bottomhole formation zone containing a composition comprising 0.35-28% wt. Trilona B, 0.05-7% wt. alkali metal hydroxide and water. It is shown that at a Trilon B concentration of 15% and an NaOH concentration of 4.50%, the solubility of barite is 9.3 g / l, which is 3000 times higher than the solubility of barium sulfate in water. The method for treating the bottomhole formation zone includes sequential injection of an alkaline buffer fluid, an active reagent, holding them for reaction with formation rocks and substances clogging them, selection of the spent active reagent, removal of reaction products from the formation and putting the well into operation. The process of pumping and withdrawing the spent active reagent is carried out cyclically until the natural permeability of the bottomhole formation zone is restored. Moreover, after selection, the spent active reagent is regenerated, and the ratio of the volume of the alkaline buffer liquid to the volume of the active reagent is taken from the condition: K = 1.0-1.5. Soluble complexes exist only under alkaline conditions and are destroyed with the precipitation of barium sulfate with a decrease in the pH of the solution, which makes it possible to regenerate the used solution by adding hydrochloric acid, separating the formed precipitate and then adding alkali to increase the pH. Exposure of the active reagent in the PZP is 8-12 hours [4 - prototype No. 2].

The disadvantages of this method are the use of Trilon B solution, which is a disodium salt of ethylenediaminetetraacetic acid, the use of sodium hydroxide as an alkali, which reduces the percentage of dissolution of barium sulfate, due to the presence of sodium ions in the solution, as well as the absence of surfactants in the composition, contributing to the washing off of oil from the surface of the sediments, which also reduces the efficiency of this method, and the use of an additional buffer fluid complicates the well treatment process.

The invention is aimed at creating a composition for removing scale deposits of barium and calcium sulfates, containing ethylenediaminetetraacetic acid, potassium oxide hydrate and a surfactant, and a method for its use, providing for the injection of the composition, holding it for reaction with clogging substances, selection of the spent composition, removal of reaction products from the reservoir and putting the well into operation. The process of injection and withdrawal of the spent composition is carried out cyclically until the natural permeability of the bottomhole formation zone is restored, and after the withdrawal, the spent composition is regenerated, lowering the pH by adding an acid solution and separating the formed precipitates of barium and calcium sulfates.

The features of the invention are

1. Ethylenediaminetetraacetic acid.

2. Alkali.

3. Potassium oxide hydrate is used as alkali.

4. Surfactant.

5. As a surfactant used zwitterionic (ampholytic) surfactant "Neftenol VUPAV", consisting mainly of oleylamidopropyl betaine.

6. The method of preparation of the composition provides for the preparation of an aqueous solution of alkali, adding to it with stirring ethylenediaminetetraacetic acid, then adding a surfactant.

7. The method of application consists in bringing the composition to the bottom of the well or injecting it into the bottomhole formation zone, holding for at least 5 hours, then removing the reaction products, regenerating the composition by adding an acid solution for subsequent use.

Features 2,4,7 are common with the prototype, and features 1,3,5-6 are essential distinctive features of the invention.

SUMMARY OF THE INVENTION

A composition is proposed for treating the bottomhole formation zone based on a chelate complex, including an alkali metal hydroxide, surfactant and water, prepared from a commercial form (concentrate), which contains ethylenediaminetetraacetic acid as a chelate complex, potassium oxide hydrate as an alkali metal hydroxide, and Surfactant can be used zwitter-ionic (ampholytic) surfactant "Neftenol VUPAV", consisting mainly of oleylamidopropyl betaine with the following ratio of components in the concentrate, wt%:

Ethylenediaminetetraacetic acid - 25.0,

Potassium oxide hydrate - 20.0,

Surfactant "Neftenol VUPAV" - 0.0-2.0,

Fresh water - the rest,

by diluting the concentrate with water in a ratio of up to 1:41,

and a method for treating the bottomhole formation zone using the above composition, including pumping and bringing the active agent to the bottom of the well, or pumping it into the bottomhole formation zone, holding it for reaction with clogging substances, selecting the spent composition, removing the reaction products from the formation and introducing the well into operation, the process of pumping and withdrawing the spent active reagent is carried out cyclically, until the natural permeability of the bottomhole formation zone is restored, and after the withdrawal, the spent active reagent is regenerated by adding an acid solution.

For research used

1. Ethylenediaminetetraacetic acid (EDTA) is produced according to TU 6-09-11-1721-83, an organic compound, a tetrabasic carboxylic acid with the chemical formula (HOOCCH ₂ ) ₂ N (CH ₂ ) ₂ N (CH ₂ COOH) ₂ , white fine crystalline powder, slightly soluble in water, insoluble in most organic solvents, soluble in alkalis, forms salts of ethylenediaminetetraacetates with metal cations, the content of the basic substance is not less than 99.0%.

2. Trilon B - disodium salt of ethylenediamine N, N, N1, N1-tetraacetic acid 2-water produced in accordance with GOST 10652-73, is a white crystalline powder or white crystals, readily soluble in water, the content of the basic substance is not less than 98, 5 %.

3. Technical potassium oxide hydrate (caustic potassium), an inorganic compound with the chemical formula KOH, produced in accordance with GOST 9285-78, is green, lilac or gray flakes, the mass fraction of caustic alkalis (KOH + NaOH) in terms of KOH, not less than 95%.

4. Sodium oxide hydrate, technical caustic soda, inorganic compound with the chemical formula NaOH, produced in accordance with GOST R 55064-2012, is white flakes, the mass fraction of NaOH is not less than 98.5%.

5. "Neftenol VUPAV" is produced according to TU 2483-209-54651030-2016, is a water-alcohol solution of ampholytic surfactants, a mobile liquid from yellow to brown.

6. "Neftenol K", grade NK-40, produced according to TU 2483-065-17197708-2002, is a multicomponent mixture of anionic and cationic surfactants of different chemical structures.

7. Technical barite (BaSO ₄ ) is produced in accordance with GOST 4682-84. Barite concentrate, mass fraction of barium sulfate is not less than 95%.

8. Calcium sulfate 2-water (CaSO ₄ * 2H ₂ O), produced according to TU 6-09-5316-87, is a fine-crystalline white powder, with a mass fraction of CaSO ₄ * 2H ₂ O not less than 97.5%.

9. Fresh water.

EXAMPLES

Example 1 (Prototype # 2)

Technical barite (BaSO ₄ ) is a sparingly soluble reagent used in drilling wells for weighting drilling fluids.

An active reagent based on Trilon B, proposed for use in cleaning the bottomhole zone of wells from barite, having a composition (% wt.):

Method for preparing a solution of an active reagent

The composition is prepared by dissolving the calculated amount of alkali metal hydroxide in water. Next, the calculated amount of Trilon B is introduced into the resulting solution and the solution is stirred until it is completely dissolved.

Research methodology for composition No. 1 based on Trilon B.

The purpose of the test: to verify the possibility of dissolution and removal of barite with an active reagent based on Trilon B.

A weighed sample of barite is placed in graduated glass cylinders, 30 ml of an active reagent based on Trilon B is added, the contents of the cylinders are stirred and settled for 20 minutes. After that, the initial height of the formed dense sediment (barite insoluble in water) is measured. The results are recorded as baseline values. Cylinders with sediment are kept for 40 hours at a temperature of 80 ° C with periodic stirring. After 40 hours, the height of the precipitate precipitated from the solution is measured.

Notes (edit)

1. To carry out the reaction with the active composition, weighed portions with the amount of barite close to the calculated one are used, which theoretically reacts with Trilon B contained in 30 ml of the active reagent. Taking into account that 1 molecule of barite reacts with 1 molecule of Trilon B, the calculated amount of barite is 2.8 g.

2. After the treatment of barite with an active compound based on Trilon B, a sediment is observed at the bottom of the cylinder, consisting of 2 layers: the bottom layer is dense gray powdery (barite that has not reacted with Trilon B, the top layer is loose, mobile (easily removable reaction product) ...

Example 2 (Prototype # 1)

Technical barite (BaSO ₄ ) is a sparingly soluble reagent used in drilling wells for weighting drilling fluids.

An active reagent based on Trilon B, proposed for use in cleaning the bottomhole zone of wells from barite, having a composition (% wt.):

Method for preparing a solution of an active reagent

Initially, 3.1% wt., Sodium hydroxide, in 46% wt., Water, is dissolved, then, with continuous stirring, 23% wt. Trilon B, heating to 60 ° C, then the residue of Trilon B in 22% wt. Is added to the solution, stirring continuously, until complete dissolution, and at the final stage, the remainder of sodium hydroxide in 2.9% wt. and 3% wt. Surfactant. The preparation time of the commercial form is 1 hour. The resulting concentrate is diluted with water in a ratio of 1: 2 to obtain the required concentration of components.

The research methodology of composition No. 2 based on Trilon B is similar to the research methodology of composition No. 1, but differs in the reaction time, which is 6 hours.

Example 3

Technical barite (BaSO ₄ ) is a sparingly soluble reagent used in drilling wells for weighting drilling fluids.

An active reagent based on ethylenediaminetetraacetic acid (EDTA), proposed for use to clean the bottom of the well and the bottomhole formation zone from barite, having a composition (% wt.):

Since the molecular weight of Trilon B is 372.24, and EDTA is 292.24, in order to maintain an equimolecular amount of the active base in the working composition with respect to barite, the EDTA concentration was proportionally reduced.

Method for preparing a solution of an active reagent:

The composition is prepared by dissolving 20% by weight, potassium hydroxide in 55% by weight, water. Next, 25% wt. Is introduced into the resulting solution. EDTA and stir the solution until it is completely dissolved. The dissolution of alkali and acid in water proceeds with the release of heat, there is no need for additional heating.

The resulting solution is diluted in a ratio of concentrate to water 1: 1.12 to obtain a composition capable of theoretically binding 2.8 g of barite.

The research method for composition No. 3 on the basis of EDTA is similar to the method for researching composition No. 1, but differs in the reaction time, which is 5 hours.

Example 4

Technical barite (BaSO ₄ ) is a sparingly soluble reagent used in drilling wells for weighting drilling fluids.

An active reagent based on ethylenediaminetetraacetic acid (EDTA), proposed for use to clean the bottom of the well and the bottomhole formation zone from barite, having a composition (% wt.):

Since the molecular weight of Trilon B is 372.24, and EDTA is 292.24, in order to maintain an equimolecular amount of the active base in the working composition with respect to barite, the EDTA concentration was proportionally reduced.

Method for preparing a solution of an active reagent

The composition is prepared by dissolving 20% wt. potassium hydroxide in 53% wt. water. Next, 25% wt. Is introduced into the resulting solution. EDTA and stir the solution until it is completely dissolved. The dissolution of alkali and acid in water proceeds with the release of heat, there is no need for additional heating. Then, 2% surfactant is added to the resulting solution with stirring.

The resulting solution is diluted in a ratio of concentrate to water 1: 1.12 to obtain a composition capable of theoretically binding 2.8 g of barite.

The research methodology for composition No. 4 based on EDTA is similar to the methodology for researching composition No. 1, but differs in the reaction time, which is 5 hours.

Example 5

Technical barite (BaSO ₄ ) is a sparingly soluble reagent used in drilling wells for weighting drilling fluids.

An active reagent based on ethylenediaminetetraacetic acid (EDTA), proposed for use to clean the bottom of the well and the bottomhole formation zone from barite, having a composition (% wt.):

Method for preparing a solution of an active reagent: the composition is prepared by dissolving 20% wt., Potassium hydroxide in 53% wt., Water. Next, 25% wt. Is introduced into the resulting solution. EDTA and stir the solution until it is completely dissolved. The dissolution of alkali and acid in water proceeds with the release of heat, there is no need for additional heating. Then, 2% surfactant is added to the resulting solution with stirring.

The resulting solution is not diluted, theoretically it is able to bind 5.9 g of barite, as in previous experiments, a slightly larger amount is taken for research - 6.3 g.

The research method for composition No. 5 on the basis of EDTA is similar to the method for researching composition No. 1, but differs in the reaction time, which is 5 hours and the amount of barite taken - 6.3 g.

Example 6

Technical barite (BaSO ₄ ) is a sparingly soluble reagent used in drilling wells for weighting drilling fluids.

An active reagent based on ethylenediaminetetraacetic acid (EDTA), proposed for use to clean the bottom of the well and the bottomhole formation zone from barite, having a composition (% wt.):

Method for preparing a solution of an active reagent

The composition is prepared by dissolving 20% wt. potassium hydroxide in 55% wt. water. Next, 25% wt. Is introduced into the resulting solution. EDTA and stir the solution until it is completely dissolved. The dissolution of alkali and acid in water proceeds with the release of heat, there is no need for additional heating.

The resulting solution is diluted in a ratio of concentrate to water 1:41 to obtain a composition capable of theoretically binding 0.15 g of barite.

The research method for composition No. 5 on the basis of EDTA is similar to the method for researching composition No. 1, but differs in the reaction time, which is 5 hours and the amount of barite taken - 0.15 g.

Example 7

Calcium sulfate 2-water (CaSO ₄ * 2H ₂ O) is a poorly soluble reagent that is deposited in the pore space of the reservoir and the well.

An active reagent based on ethylenediaminetetraacetic acid (EDTA), proposed for use to clean the bottom of the well and the bottomhole zone of the formation from calcium sulfate, having a composition (% wt.):

Method for preparing a solution of an active reagent: the composition is prepared by dissolving 20% wt. potassium hydroxide in 53% wt. water. Next, 25% wt. Is introduced into the resulting solution. EDTA and stir the solution until it is completely dissolved. The dissolution of alkali and acid in water proceeds with the release of heat, there is no need for additional heating. Then, 2% surfactant is added to the resulting solution with stirring.

The resulting solution is diluted in a ratio of concentrate to water 1: 1.12 to obtain a composition capable of theoretically binding 2.1 g of CaSO ₄ * 2H ₂ O.

The method for investigating composition No. 7 based on EDTA is similar to the method for investigating composition No. 1, but differs in the reaction time, which is 5 hours, and in that a sample of 2-water calcium sulfate in the amount of 2.3 g is taken for dissolution.

The research results are presented in table 1.

As follows from table 1, the proposed composition even does not contain surfactants, has greater solubility at 80 ° C compared to the composition according to prototype No. 1 with a much shorter dissolution time, and when the surfactant content exceeds the composition according to prototype No. 2, both in quantity and and in terms of dissolution time, at the same time, the proposed composition with an equimolecular content of the complexing substance, in percentage terms, contains much less of it (by about 34%), which significantly reduces its cost, this is explained by the lower molecular weight of EDTA (M 292.24) compared to with Trilon B (M 372.24), and when receiving the composition, there is no need to heat the solution, because the reaction of the interaction of acid and alkali occurs with the release of heat.

The composition works well in the stated concentration range, which is confirmed by the results of studies, examples 5 and 6.

Also, the composition dissolves calcium sulfate deposits well, which is demonstrated by the research result, example 7.

At lower temperatures, the solubility of the proposed composition, as well as compositions according to prototypes, decreases, and when the temperature rises to 90 ° C and above, it increases.

Further studies have shown the low-temperature properties of the proposed concentrate, the pour point is minus 30 ° C.

The ratio of EDTA and potassium hydroxide is determined by the maximum ability to dissolve barium and calcium sulfates, and the type and amount of surfactants is determined by its ability to retain precipitates in volume, which explains the somewhat higher than theoretical solubility of barite in compositions containing surfactants (Table 1). Also, the ampholytic surfactant "Neftenol VUPAV" does not form precipitation with multivalent cations at the proposed concentrations in the composition.

The dilution limits of the concentrate are determined by the amount and type of deposits that need to be removed.

The method is carried out as follows.

First, the bottomhole formation zone is cleaned from extraneous liquid (solution, industrial water) and mechanical impurities by flushing it. Then, the estimated volume of the active reagent (of the proposed composition) is pumped into the bottomhole zone.

After holding the active reagent at the bottom of the well or in the bottomhole formation zone for 5-10 hours, it is extracted together with dissolved barium and / or calcium sulfates to the surface and regenerated in the field conditions.

Regeneration of the used solution is carried out by processing it with vigorous stirring by adding concentrated hydrochloric acid until the pH of the medium reaches 7-8, followed by settling. In this case, precipitation from solution and precipitation of crystalline barium and / or calcium sulfate occurs. The settled solution is separated from the precipitate and after adding potassium hydroxide to the required values, it is ready for reuse.

After regeneration, the solution is again injected into the well or bottomhole formation zone, held for reaction and again withdrawn to the surface for subsequent regeneration.

The process of pumping and withdrawing the spent active reagent is carried out cyclically until the permeability of the bottomhole formation zone is restored, which is judged by the results of gas-hydrodynamic studies for gas and hydrodynamic studies for an oil well, for example, according to the pressure recovery curve, productivity coefficient or filtration resistance coefficients.

Preparation of solutions is carried out as follows. The container is loaded with fresh water in a calculated amount, into which, while stirring, the calculated amount of the concentrate is loaded and the composition continues to be mixed until homogeneous. After mixing, the solution is ready for use.

The advantages of the proposed composition and method of its application:

- allows to dissolve and extract from the bottomhole formation zone bridging agents - deposits of barium and calcium sulfate, which leads to a decrease in the development and operation costs of the field and, accordingly, to an increase in profits;

- allows multiple use of the active reagent, which significantly reduces the cost of treatment of wells; this is due to the fact that the active reagent can be regenerated in the field conditions and transported from well to well;

- no corrosive effect on surface and downhole equipment is excluded, since the proposed alkaline solutions are stable during storage and do not have a corrosive effect on equipment made of carbon and stainless steel in the concentrations used;

- the danger of work is reduced from the point of view of safety regulations, since the proposed method does not use strong mineral acids;

- the efficiency of treatment of the bottomhole formation zone, represented by carbonate rocks or with carbonate cement, increases, since the active reagent, in addition to barium sulfate, transforms CaSO ₄ and CaCO ₃ into a dissolved state. This eliminates the need for hydrochloric acid treatment, which eliminates the cost of these works.

Sources of information

1. US Patent No. 2,802,788 "Cleaning compositions for automotive cooling systems", 1957.

2. US Patent No. 2,877,848 "Process for cleaning permeable formations", 1959.

3. RF patent No. 2232879, E21B 43/22 "Method of treatment of the bottomhole formation zone", Priority dated 01.04.2003. Published on 20.07.2004 - prototype No. 1.

4. RF patent No. 2581859 "Composition for treatment of the bottomhole formation zone", Priority dated 20.03.2015. Published on 04/20/2016. Bulletin No. 11 - prototype No. 2.

Claims (6)

1. A composition for treating the bottomhole formation zone from scale deposits of barium and calcium sulfates, containing a complexing agent, an alkali metal hydroxide, surfactant and water, characterized in that it contains ethylenediaminetetraacetic acid as a complexing agent, and potassium oxide hydrate as an alkali metal hydroxide, and as a surfactant - zwitter-ionic (ampholytic) surfactant "Neftenol VUPAV", with the following ratio of components, wt%: Ethylenediaminetetraacetic acid - 25.0, Potassium oxide hydrate - 20.0, Surfactant "Neftenol VUPAV" - 0.1-2.0, Fresh water - the rest. 2. A method for treating the bottomhole formation zone, including flushing a well, pumping an active reagent, holding it for reaction with clogging substances, selecting a spent composition, removing reaction products from a formation and putting a well into operation, the process of pumping and selecting a spent active reagent is performed cyclically, up to restoration of the natural permeability of the bottomhole formation zone, and after sampling, the spent active reagent is regenerated by adding an acid solution, characterized in that the composition according to claim 1 is used as an active reagent, when diluted with water from 1: 0 (without dilution) to 1:40 by weight ...