RU2323243C1 - Solid reagent for acid treatment of well and process of acid treatment of well, preferably water-supply well - Google Patents

Abstract

FIELD: mining industry.

SUBSTANCE: invention preferably relates to treatment of water-supply wells exposing sand producing formation and producing drinking, mineral, and industrial waters, mineral solutions, etc. Solid reagent used in this operation contains 37.5-73.2% of nitric acid/urea reaction product and 24.4-61.5% of oxygen-containing sulfur compound, the rest being sodium polyphosphate. Process solution, which is 10-30% solution of above-indicated solid reagent, is supplied to well provided with filter descended by means of tubing string, injected into formation through reagent conduit, and held in formation during a certain time, after which the well is pumped through. When process solution is held in formation, it is made to reciprocate with the aid of compressed air periodically injected to pressure-sealed wellbore, after which wellbore is depressurized. During the period of time when compressed air is injected, level of fluid in wellbore is lowered below static level at a distance not exceeding length of filter and time point when fluid reaches lower end of the filter is recorded. When this time point is stabilized, reciprocation of process solution is ended. When performing subsequent pumping of well, specific electrical resistance value of fluid pumped out of well is also measured and, when this value approaches or attains the value of specific electrical resistance of the formation fluid, pumping is terminated.

EFFECT: increased dissolving capacity of solid reagent for dehydrated ferruginous mudding deposits and prevented subsequent deposition thereof within near-filter zone, enhanced treatment efficiency due to increased permeability near-filter zone of formation, and intensified dissolution of mudding deposits.

6 cl, 6 tbl, 2 ex

Description

The inventions relate to the mining industry, namely, solid reagents for acid treatment of a well and methods of its use for treating wells, mainly water intakes, opening a sand producing formation and extracting drinking, mineral, industrial waters, mineral solutions, etc. from this formation. , and can be used to intensify the influx of useful formation fluid from a productive formation composed of sandy rocks, including carbonates. The invention can be used in utilities, agriculture and the oil and gas industry at water facilities based on groundwater, etc.

Currently, the vast majority of acid well treatments use reagents in the liquid phase, from which technological (working) solutions are prepared directly at the well or in the factory. Numerous well treatment methods are known in field practice, involving the injection into the well of various technological solutions prepared on the basis of acid reagents, including substances of organic and inorganic origin (US Pat. .).

However, when preparing technological solutions in the liquid phase directly at the well, a large amount of equipment is required. In this case, difficulties arise with the dosage, the exact observance of which depends on the qualifications of the attendants. The probability of unproductive losses of a number of components appears (due to the large volumes of using acidic compositions at the well, it is quite difficult to supply the components in the quantity required by the formulation, usually due to packaging peculiarities, a number of components are in excess, which leads to unjustified losses).

The preparation of liquid acid compositions in the factory eliminates the above disadvantages, but leads to increased costs during transport and storage of such a composition due to the presence of ballast - water.

This makes it necessary to use reagents in the solid phase during acid treatment, which could be prepared in the factory and which would not lose their active properties during storage and transportation.

Known composition for acid treatment of the well, the basic basis of which contains the product of the interaction of nitric acid with urea and sodium nitrite (Aut. Certificate of the USSR No. 1739014, CL EV 43/27, from 1989).

However, this known composition is designed to remove sediment deposits and can chemically affect (dissolve) only materials that make up the carbonate reservoir. Aluminosilicates and quartz materials that are part of the terrigenous collector, the aforementioned known composition can not dissolve. It is also not effective in dissolving clay colmatants.

The closest to the proposed technical solution - a solid reagent in terms of its technical essence and purpose - is a solid reagent - a solid base for acid treatment of a well containing the product of the interaction of nitric acid with urea and additives: the product of the interaction of tertiary amines with hydrogen peroxide - a complex cationic surfactant (Surfactant), organic derivatives of phosphonic acid and a nitrogen-containing corrosion inhibitor (RF Patent No. 2257467, CL EV 43/27, from 2004).

Technological solutions (i.e., aqueous solutions) of this known solid reagent showed high efficiency when used in carbonate reservoirs, however, when working with terrigenous rocks, the dissolution rates of the latter are very low. And given, for example, that the majority of water wells were drilled in sandy (i.e. terrigenous) reservoirs, the effectiveness of acid exposure to them by a known reagent will be insufficient. In addition, technological solutions of the known solid reagent do not provide complete dissolution of dehydrated glandular clogging formations of the well, which has been in long-term operation (more than 3-5 years).

There is a method of acid treatment of a well, according to which a technological solution is injected into the well, which is an aqueous solution of a solid reagent, which includes the product of the interaction of nitric acid with carbamide and sodium nitrite (Authorized certificate of the USSR No. 1739014, class Е21В 43 / 27, from 1989).

However, this known method is not universal, because it is intended only for use in oil producing wells to remove paraffin deposits and is ineffective for water wells in which dehydrated glandular clogging formations are present.

Known methods of acid treatment of a water well, including injecting into the formation a solution of sulfamic acid prepared by dissolving its granules in water, keeping it in the formation and then pumping the well (Jonson EE Ground Water and Wells. Fitst Edition. Saint Paul, Minnisota. 1966, 440 p .; Auth. certificate of the USSR No. 314883, class ЕВВ 43/27, dated 1966).

These known methods do not provide complete dissolution of dehydrated glandular clogging formations of the well, which has been in long-term operation (more than 3-5 years).

Also known is a method of acid treatment of a well, including injecting a solution of a weak acid (acetic, citric, tartaric, tetraboric) into the well with a dissociation constant K _d = 10 ^-3 , holding the solution under pressure for 10-48 hours, then pumping the well to remove acid the solution and its reaction products, the subsequent injection of a solution of potassium bicarbonate, or potassium hypochlorite, or a mixture thereof, the exposure of the alkaline solution for 1-36 hours with the final pumping of the well to remove the alkaline solution and its products Ktsii (US Patent No. 4541488).

The disadvantages of this method include the possibility of secondary deposition of already dissolved collating formations at the first stage of acid treatment, incomplete dissolution of dehydrated ferruginous clogging formations of a well that has been in continuous operation (more than 3-5 years), and the absence of sufficiently justified criteria for determining the time for completion of well treatment. The latter is based on the duration of the interaction of the technological solution with the clogging formations. With insufficient time for processing the well, the permeability of the treated zone, as practice shows, is not fully restored, which leads to insufficient restoration of the productivity of the well. Excessive time for processing a well in itself is uneconomical, negatively affects the structural elements of the well and can lead, under certain conditions, to a deterioration in the permeability of the treated zone of the formation due to the secondary formation of various types of solid and semi-solid compounds.

A known method of reagent treatment of a well, comprising injecting a solution of a strong acid salt into the well, heating the solution in the well filter and then pumping the well (Auth. Certificate No. 610980, class E21B 43/27, 1975).

However, this known method does not ensure complete removal of the clogging formations in the formation under conditions of low (4-8 ° C) reservoir temperatures due to insufficient heating of the accumulated filter zone due to the heating method (in the well filter). So, for example, when the solution is heated in the well filter 80 ° C higher than the temperature of the formation water in the filter zone at a distance of 220 mm from the filter wall, the temperature increase is not recorded (Thesis for the degree of candidate of technical science Tarabarinova P.V. Thermoreagent regeneration water wells. - M., 1986, p.90, Fig. 3.17).

Closest to the proposed invention by technical essence is a method of acid treatment of a well, mainly water intake, which includes feeding into a well equipped with a filter lowered on tubing, and pumping into the formation a preheated first technological solution - an aqueous solution of sodium polyphosphates with a concentration of 1 -3% and subsequent injection into the filter zone of a preheated second technological solution - an aqueous solution of sodium polyphosphates (0.05-0.1% con centration) and salts of a strong acid (10-12% concentration), after which they create a reciprocating movement of the technological solution in the treated zone for 4-6 hours and maintain it in the formation for 8-12 hours (RF Patent No. 2042802 , CL E21B 43/27, 1992).

The disadvantages of this known method are the inadequate increase in the degree of dissolution of dehydrated clogging formations, the absence of control operations that reasonably determine the sufficient time for processing the well and pumping it after processing. In addition, the technological operation used in the known method for heating technological solutions before pumping them into the reservoir is very laborious and does not provide sufficient heating of the filter zone of the reservoir due to the short duration of the effect. All these disadvantages reduce the effectiveness of acid treatment.

When creating the invention - a solid reagent for acid treatment of the well, the task was to increase its dissolving ability in relation to dehydrated glandular clogging formations and to prevent their secondary precipitation in the prefiltered zone, while at the same time ensuring high solubility in relation to both glandular and clay clogging formations.

An additional technical result is the preservation of the manufacturability and stability of the solid reagent for a long time.

To solve this problem, a solid reagent for acid treatment of the well is proposed, including the product of the interaction of nitric acid with urea and additives, while it contains oxygen-containing sulfur compound and sodium polyphosphate as additives in the following ratio of components, wt.%:

the product of the interaction of nitric acid with urea 37.5-73.2 oxygen-containing sulfur compound 24.4-61.5 sodium polyphosphate up to 100

As a product of the interaction of nitric acid with urea, it contains urea nitrate in the form of the ammonium salt CO (NH ₂ ) ₂ · HNO ₃ and / or the oxonium salt (NH ₂ ) ₂ CO · HNO ₃ .

As an oxygen-containing sulfur compound, it contains aqueous sodium bisulfate NaHSO ₄ · H ₂ O, and / or sodium pyrosulphate Na ₂ S ₂ O ₇ , and / or potassium pyrosulphate K ₂ S ₂ O ₇ , and / or ammonium peroxodisulphate (NH ₄ ) ₂ S ₂ O ₈ .

As sodium polyphosphate, it contains sodium tripolyphosphate Na ₅ P ₃ O ₁₀ and / or sodium hexametaphosphate (NaPO ₃ ) ₆ .

When creating an invention - a method for acid treatment of a well, mainly water intake, the task was to increase the processing efficiency by increasing the permeability of the colmated prefilter zone of the formation, increasing the intensification of the process of dissolution of the clogging formations, preventing the secondary precipitation of the dissolved clogging formations in the prefilter zone while ensuring an optimally sufficient time for treating the well .

An additional result provided by the claimed method is to reduce the complexity, cost of work and improve the conditions of industrial sanitation.

The problem is solved by the proposed method of acid treatment of the well, mainly water intake, involving the supply of the technological solution to the well, equipped with a filter deflated on the tubing, pumping it into the formation, holding it in the formation and subsequent pumping of the well, while the new one is that as technological solution using a 10-30% aqueous solution of a solid reagent containing in wt.%:

the product of the interaction of nitric acid with urea 37.5-73.2 oxygen-containing sulfur compound 24.4-61.5 sodium polyphosphate up to 100

and the technological solution is injected into the formation through a reagent line, after which, during aging in the formation, the technological solution is reciprocated by periodic supply of compressed air to the sealed wellbore followed by its depressurization, and at the indicated supply of compressed air, the liquid level in the wellbore is reduced below static level at a distance not exceeding the length of the filter, while fixing the indicator of the time the liquid moves to the lower end of the filter, and at To stabilize the mentioned indicator, the reciprocating movement of the technological solution is stopped, and upon subsequent pumping of the well, the specific electrical resistance of the fluid pumped out of the well is additionally measured, and when this value reaches close to or equal to the specific electrical resistance of the formation fluid, pumping is stopped.

Before supplying the technological solution to the well, the latter is equipped with level sensors, which are placed at a depth of the static level of the liquid in the well and at the level of the lower end of the filter.

The proposed technical solutions are based on the revealed regularities of the formation of the clogging formations in the wells during their drilling and operation, the established fact of the influence on the rate of destruction and dissolution of the clogging formations, thermodynamic, redox conditions and the pH of the medium in the filter zone of the well.

To understand the essence of the issue, it should be clarified that during the construction of wells in sedimentary rocks by a rotational method, the pore space of the filter zone is clogged with clay colloid-dispersed particles, which leads to a decrease in well productivity. The composition of clay mud formations is determined both by the composition of the washing liquid itself and by the composition of the natural clay solution formed during drilling. The washing fluid is enriched with colmatizing particles not only in the presence of clay in the roof of the productive formation, but also in the presence of clay interlayers in the productive formation (thickness from 0.5 to 3 m).

When studying the mudding processes, it was found that when drilling wells using natural and clay solutions with a density of more than 1050 kg / m ³ as the washing liquid, the sizes of the zones of intense mudding in the general case do not exceed 150 mm. When using a low-concentration suspension (less than 1050 kg / m ³ ) as a washing liquid, which is typical for opening an aquifer with replacing the washing liquid with clean water, the size of the zone of mudding does not exceed 1 meter. Subsequent construction pumping of the well, at which fluid is pumped out, contributes to a significant removal of clay clogging formations (at least 30-40% by weight), and in practical calculations for these conditions, the size of the zone of clogging can be taken to be no more than 0.5 m. But at the same time, the indicated constructional pumping of the well does not ensure the complete removal of clay formations from the prefilter zone, which significantly reduces the potential of the well.

During well operation, the process of formation fluid selection is accompanied by hydrodynamic disturbance in the prefilter zone, which leads to a violation of the chemical equilibrium state of the main components of the fluid and to the loss of inorganic compounds that clog the pore space. The polymineral composition of these formations is represented by FeOOH limonite, FeOOH · ag hydrogetite, Fe ₂ O ₃ · ag hydrohematite, FeCO ₃ siderite, FeS pyrrhotite, CaCO ₃ calcite, etc. It has been established by practice that the glandular component predominates in the composition of clogging formations ( up to 70% by weight).

The resulting polymineral compounds fill the pore space, adsorbing on clay formations deposited during drilling, which leads to a decrease in the feather space:

n = n ₀ -b,

where n is the current porosity, n ₀ is the initial porosity, b is the specific volume of the clogging formations, which forms the saturation of the pore space with the clogging formations and a decrease in the initial filtration coefficient of the filter zone:

,

,

where k is the current filtration coefficient, k ₀ is the initial filtration coefficient, α is the saturation of the pore space with clogging formations, m is the exponent (m = 2.8-3.3).

Studies have established that the dimensions of the intense zone of colmatization for these conditions for gravel-wire filters are limited by the size of gravel sprinkling, for filters of block construction and gravel-glue filters - by the thickness of the filter block, and for mesh filters, in general, do not exceed 20 mm.

In the period of the onset of the action of colmatization processes, loose deposits of visco-plastic consistency with water-colloidal bonds are formed. These precipitates dissolve easily upon contact with solvents. During the diagenesis of colmatizing compounds, water-colloidal bonds of loose plastic formations are replaced by crystallization ones, as a result of which a dense glandular dehydrated fouling cement is formed on the filter and in the filter zone, filling the pore space.

Oxygen-containing sulfur compounds included in the formulation of the inventive solid reagent, interact with glandular dehydrated mating formations as follows.

For sodium bisulfate aqueous NaHSO ₄ × H ₂ O. When it is dissolved in water, hydrolysis of salt and water occurs as follows:

NaHSO ₄ × H ₂ O → NaHSO ₄ + H ₂ O;

NaHSO ₄ ↔Na ⁺ + HSO ₄ ^- ;

HSO ₄ ^- ↔H ⁺ + SO ₄ ^2- ;

H ₂ O↔2H ⁺ + OH ^- ;

SO ₄ ^2- + 2H ⁺ ↔H ₂ SO ₄ (acidic medium).

In the resulting solution of acid action, the glandular colmatating formations dissolve according to the following equations:

Fe ₂ O ₃ · ag + 6H ⁺ → 2Fe ³⁺ + 3H ₂ O;

FeO · ag + 6H ⁺ → 2Fe ²⁺ + H ₂ O;

FeS + 2H ⁺ → Fe ²⁺ + H ₂ S ↑.

For sodium pyrosulfate Na ₂ S ₂ O ₇ . When it is dissolved in water, hydrolysis of salt and water occurs as follows:

Na ₂ S ₂ O ₇ + H ₂ O → 2NaHSO ₄ .

For potassium pyrosulphate K ₂ S ₂ O ₇ . When it is dissolved in water, hydrolysis of the salt occurs similarly to the hydrolysis of sodium salt.

For ammonium persulfate (NH ₄ ) ₂ S ₂ O ₈ . When dissolving ammonium persulfate in water, hydrolysis of the salt occurs and hydrogen peroxide is released according to the following reaction scheme:

(NH ₄ ) ₂ S ₂ O ₈ ↔ (NH ₄ ) ₂ SO ₄ + H ₂ O ₂ .

Hydrogen peroxide released during the reaction destroys the clay mud formations, effectively dispersing them.

Next, there is a dissolution of the glandular compounds according to the above reactions.

At the same time, the dissolution of the glandular compounds occurs due to the redox process:

FeO · ag + S ₂ O ₈ ^- + e → Fe ³⁺ + 2SO ₄ ^2- ;

FeS + S ₂ O ₈ ^{- +} e → Fe3 + + 2SO ₄ ^2- + S ^2-.

Here, in an acidic environment, ferric iron is in the form of ions. In the presence of released hydrogen sulfide, ammonium hydroxide interacts with hydrogen sulfide according to the following equation, as well as hydrogen sulfide oxidation with peroxide:

NH ₄ OH + H ₂ S → (NH ₄ ) ₂ S + 2H ₂ O;

H ₂ S + H ₂ O ₂ → SO ₂ + H ₂ O.

This prevents the release of hydrogen sulfide during well treatment.

At the same time, when the product of the interaction of nitric acid with urea is dissolved in water, free nitric acid and urea are released:

CO (NH ₂ ) ₂ HNO ₃ = CO (NH ₂ ) ₂ + HNO ₃ .

In an aqueous solution, the dissociation of nitric acid is accompanied by the release of a proton, and it can be simplified to write:

HNO ₃ ↔Н ⁺ + NO ₃ ^- .

Then, the glandular and carbonate colmatating compounds are dissolved according to the following equations:

Fe ₂ O ₃ · ag + 6H ⁺ → Fe ³⁺ + 3H ₂ O;

FeO · ag + 6H ⁺ → Fe ²⁺ + H ₂ O;

FeS + 2H ⁺ → Fe ²⁺ + H ₂ S ↑;

FeCO ₃ + 2H ⁺ → Fe ²⁺ + H ₂ O + CO ₂ ↑;

CaCO ₃ + 2H ⁺ → Ca ²⁺ + H ₂ O + CO ₂ ↑;

MgCO ₃ + 2H ⁺ → Ca ²⁺ + H ₂ O + CO ₂ ↑.

The introduction into the solution within the declared ratios of sodium polyphosphate (sodium tripolyphosphate and / or sodium hexametaphosphate) stabilizes the aqueous solution by preventing secondary precipitation of salts at low concentrations. The stabilizing effect of this kind of proposed additives is associated with adsorption processes: phosphate anions are adsorbed on nuclei or growing crystals, block active centers and thereby prevent the precipitation of salts. This property is used to prevent coagulation of already dissolved colmatating formations in solution. Thanks to the above chemical and physico-chemical processes and ensures the achievement of the technical result.

The proposed inventions can also be used in injection wells (in the field of oil and gas production), since according to established field practice, surface, groundwater, associated sewage, or various mixtures thereof are used to flood productive formations in order to maintain reservoir pressure. As a rule, in the fields there is no high-performance filtering equipment for purification of injected water from suspended matter, which determines the clogging of the perforated borehole zone and a decrease in the injectivity of the injection well. When river waters are injected into productive strata, the main components of the clogging formations are polyvalent metal oxides and hydroxides, clay minerals (up to 78%) and partially organic substances. The presence of iron, nitrobacteria, and sulfate-reducing bacteria in river waters additionally leads to the formation of mucous glandular biofouling and peptic corrosion of the metal in the injection conduit. When commercial water is injected into injection wells as part of the injected water, the content of mechanical impurities varies over a wide range (from 3.5 to 10.0 mg / l), with up to 90% of mechanical impurities having a size in the range of 1-4 microns. As a rule, iron hydroxides (products of equipment corrosion) predominate in the mineral composition of mechanical impurities. When groundwater is injected into injection wells, the main gumming substance is ferruginous compounds formed in the composition of the injected water as a result of a shift in the equilibrium state of Fe ²⁺ due to changes in temperature, pressure, and hydrodynamic disturbance. Additionally, corrosion processes in the equipment form mechanical impurities that are entirely represented by iron oxides in a wide variety of forms.

The proposed solid acid reagent for well treatment was prepared and tested in laboratory conditions. The following substances were used for its preparation:

- the product of the interaction of nitric acid with urea is a crystalline powder from white to gray, produced according to TU 27081564.042-98 under the brand name Nitrol, characterized by a mass fraction of acids in terms of nitric acid of at least 46%, and a mass fraction of moisture of 5-8% ;

- oxygen-containing sulfur compounds:

- sodium bisulfate aqueous NaHSO ₄ × H ₂ O in accordance with GOST 6053-77;

- sodium pyrosulfate Na ₂ S ₂ O ₇ according to 18344-78;

- potassium pyrosulfate K ₂ S ₂ O ₇ according to GOST 7172-76;

- ammonium peroxodisulfate (NH ₄ ) ₂ S ₇ O ₈ according to GOST 20478-75;

- sodium polyphosphates:

- sodium tripolyphosphate Na ₅ P ₃ O ₁₀ according to TU 2148-037-00194441-02, GOST 13493-86;

- sodium hexametaphosphate (technical sodium polyphosphate NaPO ₃ ) ₆ according to GOST 20291-80.

For its use in the form of a technological aqueous solution when implementing the proposed method was used:

- technical water.

The inventive solid reagent was prepared as follows.

Example. To obtain the inventive solid reagent in laboratory conditions, 56 g of Nitrol was taken and 40 g of aqueous sodium bisulfate and 4 g of sodium tripolyphosphate were added to it, the dry mixture was mixed and a solid reagent of the following composition was obtained, wt.%: Nitrol - 56; sodium bisulfate water - 40; sodium tripolyphosphate - 4. To prepare a technological solution from the obtained solid reagent, 12.5 g of the indicated solid reagent were taken and dissolved in 87.5 g of water, obtaining a solution of 12.5% concentration.

Solid reagents and technological solutions based on them with a different content of components were prepared in a similar way.

In the course of laboratory tests, the solubility of the technological solution prepared by dissolving the solid reagent in water was determined for cemented dehydrated glandular samples taken from the filter zone of well No. 34 of the Zamoskvoretsky drainage. According to the analysis, the chemical composition of the sediments — formations taken from the filter zone of the indicated well, is represented by the following components (wt.%): Fe ₂ O ₃ - 73.02; FeO - 3.66; Al ₂ O ₃ - 0.18; MgO - 0.14; CaO - 3.15; SiO ₂ - 0.12; MnO - 0.15. Loss on ignition is 19.58%. The mineral composition of these formations is represented by limonite FeOOH, goethite α-FeO (OH), calcite CaCO ₃ , polymorphic quartz and illite.

.During the experiments, samples of colmatizing formations were placed in the studied technological solution, subjected to shaking on a shuttle machine for 30 minutes at a temperature of 20 ° C, and the content of dissolved iron in the filtrate was determined by the colorimetric method (ΔFe ₁ ). The residual iron content in the sample was determined by secondary treatment of the sample with heated concentrated hydrochloric acid (37%) for 30 minutes. The content of dissolved iron (ΔFe ₂ ) was also determined in the secondary filtrate, and the solubility was estimated as the ratio of the concentrations of dissolved iron after treatment with the technological solution to the total concentration of dissolved iron after two treatments

.

The determination of the optimal ratios between the components of the proposed solid reagent, as well as the optimal concentration of the solid reagent in the technological solution, was carried out in accordance with the well-known method (see Prince Ruzinov L.P., Slobodchikova R.I. Planning an experiment in chemistry and chemical technology. - M ., Chemistry, 1980. - Series “Chemical cybernetics.” - 280 p.). The results of the experiments are presented in table 1.

As can be seen from the data presented, the solubility of the glandular clogging formations reaches a plateau with the claimed limits of the components of the solid reagent.

A decrease in the concentrations of the components compared with the claimed concentrations does not provide the maximum possible dissolution of the clogging compounds (experiments No. 7 and 8), and their increase does not improve the efficiency of the dissolution process.

The presence in the technological solution obtained from the proposed solid reagent, nitrol, the product of the interaction of nitric acid with urea, ensures the dissolution of carbonate compounds, excluding their decarbonization with oxygen-containing sulfur compounds.

An important property of the technological solution obtained from the developed solid reagent is its high destructive ability of coagulation contacts between clay aggregates filling the pore space of the productive formation, and leaching of aluminosilicates that form the clay minerals framework. As a result, clay mud formations pass into the pelitic phase and are easily removed when pumping the well.

The solution to the above technical problem provided by the proposed method is achieved due to the following.

Based on the basic theoretical principles of the kinetics of the dissolution of salts in porous media, the creation in the inventive method of the reciprocating motion of technological solutions in the colonized zone significantly intensifies the process of dissolution of the clogging formations. In the proposed method, this movement is created by periodically supplying compressed air to the sealed wellbore followed by its depressurization, and the liquid level in the wellbore is reduced from the static level by a distance not exceeding the length of the filter, which is controlled, for example, using level sensors installed on depth of the static level and depth of placement of the lower end of the filter.

The total duration of the well treatment is determined by the dissolution kinetics of the clogging formations, the hydrodynamic, temperature conditions of the dissolution process, and the initial water permeability of the accumulated zone. Therefore, the permeability coefficient of the filter zone, which, in turn, depends on the saturation of the pore space with clogging formations, was adopted as a control indicator during well treatment. This is the basis of the technological operation, which allows reliably and accurately determine the sufficient time for creating the reciprocating motion of the solution in the colmated zone of each particular well.

This operation in the proposed method is implemented as follows. When compressed air is supplied into the annular space of a sealed wellbore, an indicator of the time the fluid level moves from the static level to a distance not exceeding the length of the filter (i.e., not lower than the lower end of the filter) is monitored using level sensors. After that, the well is depressurized, the liquid level in the wellbore rises to static (or may almost reach the static, but only by this time the level recovery curve at this depth goes to a plateau), the well is again sealed and the cycle is repeated. When stabilizing the specified indicator of the crushing time (time from the static level to the lower end of the filter), recorded in each cycle, the reciprocating movement of the solution is stopped. The stabilization of the measured values of time indicates the maximum possible reduction in the saturation of the pore space with clogging formations in specific conditions and the advisability of stopping this kind of treatment.

The legitimacy of the application of this kind of technological operation and its feasibility during the treatment of the well by the proposed method confirm the results of field experiments.

The proposed method was tested in three wells. At the same time, a fluid sample was taken from the well filter with a special minibarometer and the content of dissolved glandular clogging formations (concentration of dissolved iron) was determined in it. The results of the experiments are presented in table 2.

table 2 Data on field trials of the proposed method Processing time, min Well No. 1 Well No. 2 Well No. 3 The time of fluid movement from the static level to the lower end of the filter, s The concentration of dissolved iron, mg / l The time of fluid movement from the static level to the lower end of the filter, s The concentration of dissolved iron, mg / l The time of fluid movement from the static level to the lower end of the filter, s The concentration of dissolved iron, mg / l 0 330 0.61 492 0.15 558 1.05 thirty 276 3.28 480 1,52 414 3.09 60 234 5.13 450 2.48 243 4.64 90 204 6.18 305 3.08 186 5.42 120 168 6.70 336 3.52 150 5.81 150 150 7.05 294 3.68 96 6.10 180 132 7.28 312 3.95 98 6.10 210 120 7.39 352 3.85 96 6.15 240 125 7.45 234 3.97 97 6.17 270 120 7.32 222 4.05 300 123 7.38 204 4.12 330 200 4.08 360 202 4.11

As can be seen from the data presented, the stabilization of the time the fluid level moves in the wellbore when compressed air is supplied under the conditions under consideration corresponds to the stabilization of the concentration of dissolved clogging formations in this fluid, which proves the fact that the indicated solution of clogging formations practically completely dissolves in the reservoir and there is no need for further creating a reciprocating motion of the solution in the well.

To determine the duration of the pumping of the well after processing by the value of the electrical resistivity of the fluid pumped out of the well, three field experiments were carried out, during which, during the pumping of the well, the electrical resistivity of the pumped fluid was measured. The electrical resistance of pure formation water (which is a useful formation fluid of a water well) was 2000 Ohms. The experimental results are presented in table 3.

Table 3 No. Indicators Well No. 1 Well No. 2 Well No. 3 one The flow rate of pumping fluid from the well, m ³ / hour 10.9 8.9 13.0 2 Electrical resistivity in the first samples of liquid during pumping, Ohm 64 32 130 3 The fixation time of the electrical resistivity of 2000 Ohms in the pumped liquid after ..., hour 13 10.5 6.5

After fixing in the samples of the pumped-out liquid the value of the specific electrical resistance of 2000 Ohms (or a value close to this), which corresponds to pure formation waters, water samples were taken for analysis. The analyzes found that the indicators of the selected samples are in full compliance with the indicators of pure formation water. Thus, the measurement of the above values of specific electrical resistance of the pumped liquid during the implementation of the proposed method allows you to accurately and reliably determine the time of completion of work.

Examples of specific performance of the method.

The proposed method was tested at eleven water wells of the Zarechensky water intake. Wells capitate an aquifer confined to paleogenous medium-grained sands. The thickness of the aquifer is 13-18 m. The wells were drilled to a depth of 45-80 m by a rotary method and equipped with gravel-wire filters with a diameter of 245 mm. The thickness of the gravel sprinkling is 100-150 mm. Groundwater composition of sodium bicarbonate with a salinity of 0.5 g / l and an iron content of from 0.5 to 1.5 mg / l. The static groundwater level is at a depth of 8 m.

Over the period of operation within 5–7 years, the specific production rates of the wells decreased to 19.4–43.1% relative to the initial values due to mud formation by various formations. In the composition of the clogging formations in the reservoir, glandular compounds predominate (on average 72%), calcium and magnesium compounds are represented in small quantities. The polymineral composition of the clogging formations is represented mainly by limonite, hydrohematite, montmorillonite, illite.

The size of the treated zone was taken equal to 0.5 m from the borehole wall with a sand porosity of 20%. The volume of technological solution for processing wells adopted 3.4 m ³ .

The characteristics of the wells in which the inventive method was tested are shown in table 4.

Table 4 Characteristics of the wells in which the inventive method was tested Well number Depth, m Filter length m The specific flow rate of the well, m ³ / (hour × m) Initial Before processing the claimed method one fifty 10 7.2 1.4 2 54 10 5.8 2,5 3 72 12 7.7 2,4 four 78 12 5.5 1.7 5 46 10 5,6 1.8 6 62 12 7.9 2,8 7 68 12 5,4 1.9 8 75 12 7.0 2,4 9 48 10 4.6 1.3 10 55 10 4.6 1,6 eleven 68 12 3,5 1,2

The composition of the solid reagent and the concentration of the prepared from it technological solution used in the implementation of the proposed method are presented in table 5.

Table 5 The composition of the solid reagent and the concentration of the prepared from it technological solution used in the implementation of the proposed method in specific wells Well number (from table 4) The ratio of components in the solid reagent, wt.% The concentration of solid reagent in the technological solution,% Oxygen-containing sulfur compounds Nitrol Sodium Polyphosphates one 60,2 37.5 2,3 15.5% 2 60.0 38,0 2.0 20.0% 3 31.7 63.5 4.8 15.75% four 34.1 63.8 2.1 23.5% 5 38.8 58.1 3,1 25.8% 6 35.9 61.5 2.6 19.5% 7 52,2 43.5 4.3 23.0% 8 24.4 72.3 3.3 20.75% 9 54.5 40.9 4.6 22.0% 10 41.9 55.8 2,3 21.5% eleven 37.0 51.9 11.1 13.5%

Example. Well No. 1 with a depth of 50 m was selected as an object for illustrating the proposed method. The well is equipped with a gravel-wire filter with a diameter of 245 mm and a length of 10 m. The thickness of the gravel sprinkling is 100-150 mm. The static groundwater level is at a depth of 8 m. The life of the well is 6 years. The initial specific rate, i.e. when putting the well into operation, it was 7.2 m ³ / (hour × m), and before implementing the proposed method, it was 1.4 m ³ / (hour × m). The electrical resistivity of the formation fluid — pure water — was 2000 ohms.

After dismantling the water-lifting equipment, a reagent line is installed, level sensors are installed at 8.15 m (0.15 m below the static level, because by this time the level recovery curve at this depth will reach a plateau, and to reach the full static level at least 30% of the total level recovery time will be required, which will significantly increase the well treatment time) and at around 18 m (corresponds to the lower end of the filter). The reagent line is connected to the sealing head of the wellhead. The well is sealed and checked for leaks with compressed air. A compressor with a capacity of 6 m ³ / min, a pump unit and a flow line is connected to the well head.

A technological solution with a volume of 3.4 m ³ is prepared in the pumping unit with the following components (wt.%): Aqueous sodium bisulfate 9.3, nitrol 5.8, sodium tripolyphosphate 0.4 and water 84.5 (the specified technological solution was prepared by preparing a 15.5% aqueous solution of a solid reagent of the following composition, wt.%: aqueous sodium bisulfate - 60.2, nitrol - 37.5, sodium tripolyphosphate - 2.3). To dissolve the components of the solid reagent, the unit is switched on in a circulating mode. The resistivity of the solution was 75 ohms. Next, the solution is injected into the aquifer with an injection rate of 5.5 m ³ / h.

Then, compressed air is supplied into the annulus of the well and the indicator of the time of movement of the liquid level from the level of 8.15 m to a depth of 18 m is fixed (the installation location of the lower sensor). After that, the well is depressurized, the liquid level in the wellbore rises to static, the well is again sealed and the cycle is repeated. When stabilizing the said indicator of the passage time of the liquid to the lower end of the filter, fixed in each cycle, the reciprocating movement of the solution is stopped. The stabilization of the measured values of the time indicator occurred after 5 hours of processing.

Then the well is depressurized, the room of the pumping station is purged with compressed air for 30 minutes, the processing equipment is dismantled and the water-lifting equipment for pumping the well is mounted.

Next, a well is pumped to remove the reaction products of the solutions. During pumping, the electrical resistance of the pumped liquid is measured. After 3.5 hours of pumping, the specific electrical resistance of the pumped-out fluid was 1955 Ohms, which is approximately equal to (close) the electrical resistance of the useful formation fluid - formation water (≈2000 Ohms), and pumping of the well was stopped.

The specific production rate after treatment was determined to be 6.1 m ³ / (hour × m), which is 85% relative to the original.

Other wells were treated in a similar manner. The results of the well treatments are presented in table 6.

Table 6 Data on the results of processing wells by the proposed method Well number The specific flow rate after processing the proposed method, m ³ / (hour m) The increase in specific rate, times The increase in the specific rate relative to the original,% Well treatment time, hour Well pumping time after treatment, hour one 6.1 4.3 85 5 3,5 2 5.75 2,3 one hundred 4,5 4.0 3 6.9 2.9 90 3,5 5.5 four 4.8 2,8 87 6 2,5 5 5,4 3.0 96 3 4.2 6 7.4 2.6 94 6.5 3.6 7 5.9 3,1 109 3,5 5.2 8 6.2 2.6 88.5 7 2,8 9 4.2 3.2 91.3 4,5 4.1 10 4.8 3.0 104 5 3.2 eleven 3.8 3.2 108 6 2,8

As a result of treatment of eleven water intake wells with the proposed method using the inventive solid reagent, the specific production rate of the wells was increased from 2.3 to 4.3 times, and the water supply to the consumer increased by 79%. In this case, the specific production rate of the wells relative to the initial values was 85-108%, which indicates a high degree of dissolution of the glandular and clay clogging formations of the proposed solid reagent in the implementation of the proposed method.

Claims (6)

1. Solid reagent for acid treatment of the well, including the product of the interaction of nitric acid with urea and additives, characterized in that as additives it contains an oxygen-containing sulfur compound and sodium polyphosphate in the following ratio, wt.%: product of nitrogen interaction acids with carbamide 37.5-73.2 oxygen-containing sulfur compound 24.4-61.5 sodium polyphosphate up to 100 2. The solid reagent according to claim 1, characterized in that as the product of the interaction of nitric acid with urea it contains urea nitrate in the form of ammonium salt CO (NH ₂ ) ₂ * HNO ₃ and / or oxonium salt (NH ₂ ) ₂ CO · HNO ₃ . 3. The solid reagent according to claim 1, characterized in that, as an oxygen-containing sulfur compound, it contains aqueous sodium bisulfate NaHSO ₄ · H ₂ O, and / or sodium pyrosulphate Na ₂ S ₂ O ₇ , and / or potassium pyrosulphate K ₂ S ₂ O ₇ , and / or ammonium peroxodisulfate (NH ₄ ) S ₂ O ₈ . 4. The solid reagent according to claim 1, characterized in that as sodium polyphosphate it contains sodium tripolyphosphate Na ₅ P ₃ O ₁₀ and / or sodium hexametaphosphate (NaPO ₃ ) ₆ . 5. The method of acid treatment of the well, mainly water intake, involving the supply of the technological solution to the well, equipped with a filter deflated on the tubing, pumping it into the formation, holding it in the formation and subsequent pumping of the well, characterized in that 10- 30% aqueous solution of a solid reagent according to claim 1, and the technological solution is injected into the formation through a reagent line, after which, when holding in the formation, a reciprocating movement is created the technological solution by periodically supplying compressed air to the sealed wellbore followed by its depressurization, and with the specified supply of compressed air, the liquid level in the wellbore is reduced below the static level by a distance not exceeding the length of the filter, while fixing the indicator of the passage of fluid to the lower end of the filter , and upon stabilization of the aforementioned indicator, the reciprocating movement of the technological solution is stopped, and upon subsequent pumping of the well to olnitelno measured value of electrical resistivity of the wellbore fluid pumped out, and when it reaches this value close or equal to the electrical resistivity of the formation fluid, the pumping is stopped. 6. The method according to claim 5, characterized in that before supplying the technological solution to the well, the latter is equipped with level sensors that are placed at a depth of the static level of the liquid in the well and at the lower end of the filter.