RU2808778C1 - Method for treating bottomhole zone of formation with hydrogen peroxide with phlegmatization during development - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method of treating the bottomhole zone of a formation with hydrogen peroxide with phlegmatization, which includes pumping a solution of hydrogen peroxide through the tubing, its decomposition in the formation with the release of heat, during development, the well is washed with the tubing lowered to the bottom, tightness of the pipe string is assessed, and well injectivity is determined. With injectivity of ≥ 50 m³/day, process tubing with a packer is lowered, while the packer is installed above the perforation interval, then fresh water is injected as a buffer fluid in a volume equal to 1.2 volumes of the tubing, after which a 37 wt.% hydrogen peroxide solution is injected. Then the said hydrogen peroxide solution is forced into the formation with fresh water with a volume of 1 m³, then with process water, a total of 1.2 times the volume of tubing, while the entire volume of injection is carried out in less than 5 hours, provided that the chemicals supply rate is uniform. Next, the well is shut in for reaction while pressure at the wellhead is recorded. At a pressure of 60-65 atm. and no increase in pressure for more than 2 hours, the decomposition reaction of hydrogen peroxide is considered complete. If there is no increase in pressure during decomposition of hydrogen peroxide in the formation, an aqueous solution of the catalyst - 5 wt.% potassium permanganate - is injected in a volume equal to the volume of the injected hydrogen peroxide. Then the catalyst solution is pressed with process water in a volume equal to 1.2 times the volume of the tubing. Then, at a pressure of 60-65 atm. and no pressure increase for more than 2 hours, nitrogen is injected. At the wellhead, liquid and separated gas are released into the oil carrier and disposed of, while during the process of nitrogen injection, oxygen in the composition of the separated gas is measured. After complete bleeding, the well is swabbed with a volume of at least 2 times the volume of the injected liquid. Next, to clarify the well flow rate, studies are carried out to restore the fluid level in the tubing and the tubing is lifted with a packer. Then the pump is lowered with the calculated flow rate according to the study results. In this case, development of the well is accompanied by the measurement of oxygen in the composition of the produced liquid into the oil tanker; at the minimum permitted concentration of oxygen in the liquid, development is switched to the oil pipeline.

EFFECT: safety of treatment of the bottomhole zone of the formation using hydrogen peroxide.

1 cl, 1 dwg, 5 tbl, 2 ex

Description

The invention relates to the oil industry, in particular, it can be used when treating the bottomhole zone of wells in gas and oil fields with highly viscous oil and the presence of free gas in the produced product.

During the exploitation of fields, the need arises to carry out treatment of the bottom-hole zone of the formation in order to restore and/or improve the productivity of wells. In conditions of high-viscosity oils, it is advisable to use thermal treatment methods that make it possible to clean the bottom-hole well of asphaltene-resin-paraffin deposits by means of their thermal destruction and to increase the mobility of oil by reducing its viscosity.

One of the methods for heating the formation is to inject aqueous solutions of hydrogen peroxide H ₂ O ₂ (HP) into the formation. Warming up is carried out due to the exothermic reaction of the decomposition of PV with the release of oxygen (O ₂ ):

2H ₂ O ₂ → 2H ₂ O + O ₂ + Q,

where Q is the heat released due to the exothermic reaction (98 kJ/mol).

In order to significantly increase the temperature, it is necessary that the decomposition of the PV occurs at a rate exceeding the rate of heat removal from the reaction area. This high rate of decomposition can be achieved due to the presence of catalysts. Organic and inorganic acids, oxides of iron and a number of other metals are usually used as the latter.

When treating wells using PV, if there is free gas in the produced product, the formation of an explosive mixture of oxygen and hydrocarbon gases is possible.

Table 1 shows data on explosion limits (lower and upper) for hydrocarbon gases - methane, ethane, propane, butane - according to the “Safety Rules for Processes for the Production or Use of Metals”. Approved by order of the Federal Service for Environmental, Technological and Nuclear Supervision dated December 9, 2020 N 512.

Table 1 - Explosion limits of hydrocarbon gases for gas-oxygen and gas-air mixtures Flammable gases Concentration limits of explosion of mixtures, % by volume Explosion limit range for flammable gases, % by volume _O2 range,
% by volume NPV* ERW** (gas-oxygen) ERW** (gas-air) Methane ( _CH4 ) 5.1 61 14 1.8-66 (gas-oxygen mixture)
1.8-14 (gas-air mixture) 98.2-34 (gas-oxygen mixture)
19.6-17.2 (gas-air mixture) Ethane _{( C2H6} ) 3.0 66 12.5 Propane (C ₃ H ₈ ) 2.3 55 9.5 Isobutane (iC ₄ H ₁₀ ) 1.8 48 8.4 N-butane (nC ₄ H ₁₀ ) 1.8 49 8.5 *LEL is the limit of concentration of gases in a mixture with an oxidizer, below which the gas mixture cannot ignite.
**LEV is the limit of concentration of gases in a mixture with an oxidizer, above which the gas mixture cannot ignite.

According to Table 1, it is possible to distinguish a “dangerous zone” (ignition area), in which the content of oxidizer (oxygen) and hydrocarbon gas (Fig.) is in the range of 17.2-19.6% oxygen, 1.8-14% on flammable gases for gas-air mixtures. To minimize the risk of separation gas ignition, nitrogen injection was considered to reduce the oxygen concentration below 17%.

The invention “Extraction of viscous oil from a geological reservoir using hydrogen peroxide” is known (US patent No. 4867238, IPC C09K 8/84 E21B 43/243, published 09/19/1989).

The essence of the method is: 1) the decomposition of hydrogen peroxide in a formation containing residual oil saturation in order to generate heat, water and oxygen in sufficient quantities to cause an oxidation reaction of hydrocarbons with the generation of heat, water and carbon dioxide;

2) injection of an aqueous solution of hydrogen peroxide into the formation in an amount sufficient to move the decomposition front from the injection site and to displace hydrocarbons within the specified formation;

3) extraction of hydrocarbons after decomposition of hydrogen peroxide in the formation and generation of heat, water and carbon dioxide.

The disadvantages of the known technical solution are the need to inject large volumes of hydrogen peroxide solution, long-term exposure, and the possibility of the formation of an explosive mixture of oxygen and hydrocarbon gases due to the lack of control over the oxygen content in the gas mixture.

There is a known method for the production of viscous oil (patent RU No. 2522690, MPK E21B 43/24, E21B 43/22, published July 20, 2014, Bulletin No. 20), which consists of first entering the bottom-hole zone of the formation for formation at the bottom catalyst pad with a permeability not lower than the permeability of the bottom-hole zone of the formation, an aqueous suspension of clayey drill cuttings containing clay particles - a catalyst for the decomposition of hydrogen peroxide and sand particles that ensure the permeability of the catalyst pad, or an aqueous suspension of a mixture of a catalyst for the decomposition of hydrogen peroxide - two- or three-oxide powder is pumped in , or tetravalent metal and sand or proppant, then a 10-40% solution of hydrogen peroxide, a water buffer and a solution of a nonionic surfactant - demulsifier are sequentially pumped into the formation, after which water is supplied from the formation pressure maintenance system and oil is pumped out .

The disadvantage of the known technical solution is the possibility of the formation of an explosive mixture of oxygen and hydrocarbon gases due to the lack of control over the oxygen content in the gas mixture.

There is a known method for developing an oil field" (patent RU No. 2278250, MPK E21B 43/22, published June 20, 2006, Bulletin No. 17), including drilling vertical wells according to a given pattern into the productive formation, pumping water and producing oil, drilling at a late stage of field development, horizontal lateral trunks between vertical production wells. After drilling at least two wells with horizontal lateral trunks located in parallel planes, hydrogen peroxide with a concentration of 18 to 50% with a stabilizer is supplied to one of them, and 5% sodium permanganate is supplied to the other in volumes equal to the volumes of horizontal wells. well bores, then using water, hydrogen peroxide and sodium permanganate are forced into the productive formation, backpressure is created at the wellheads of wells with horizontal sidetracks, technological holding is carried out with oil displacement due to the release of reaction products, after which additional oil displacement is carried out through production wells with using water supplied from the surface through injection wells with horizontal lateral trunks.

The disadvantages of the known technical solution are the need for a large volume of additional drilling, the possibility of the formation of an explosive mixture of oxygen and hydrocarbon gases due to the lack of control over the oxygen content in the gas mixture.

There is a known method for developing an oil field (patent RU No. 2283949, MPK E21B 43/22, published on September 20, 2006, Bulletin No. 26), including a slug, pumping a solution through an injection well through a tubing pipe (Tubing) and its decomposition in the reservoir with the release of heat followed by water injection, lifting oil through production wells. As a solution, 50% hydrogen peroxide is supplied to the injection well in a volume equal to 0.3 pore volume, and hydrogen peroxide is supplied between two slugs with a liquid neutral to hydrogen peroxide, while the volume of liquid neutral to hydrogen peroxide is taken equal to 1 .1 of the tubing volume, and before the first slug, a pre-skin is carried out with a catalyst - potassium hydroxide, in a volume of 0.1 of the volume of hydrogen peroxide, after two slugs a 5% solution of sodium permanganate is supplied, after which the oil is displaced to production wells using water. Acetate buffer is used as a liquid neutral to hydrogen peroxide.

The disadvantages of the known technical solution are the use of high concentration hydrogen peroxide, as well as the possibility of the formation of an explosive mixture of oxygen and hydrocarbon gases due to the lack of control over the oxygen content in the gas mixture.

Technical objectives of the invention are the safe treatment of the bottomhole formation zone with hydrogen peroxide due to the phlegmatization of an explosive mixture of associated petroleum gas with oxygen using nitrogen.

Technical problems are solved by the method of treating the bottomhole zone of the formation with hydrogen peroxide with phlegmatization during development, which includes injection of a hydrogen peroxide solution - PV through a pump-compressor pipe - tubing, its decomposition in the formation with the release of heat.

What's new is that the well is flushed with tubing allowed to the bottom, the tightness of the pipe string is assessed and the injectivity of the well is determined, if the injectivity is ≥ 50 m³/day, technological tubing with a packer is lowered, while the packer is installed above the perforation interval, then fresh water is injected as a buffer fluid in a volume equal to 1.2 volumes of the tubing, after which an PV solution of 37 wt.% is injected. calculated volume:

V _PV = 4.5 h m + 1.3,

where h is the exposed effective thickness of the formation, m,

m - porosity of the productive interval, units,

then the PV solution is forced into the formation with fresh water with a volume of 1 m³, then with process water, a total of 1.2 volumes of tubing, while the entire volume of injection is carried out in less than 5 hours, provided that the reagent supply rate is uniform, then the well is closed for response, while the pressure at the wellhead is recorded, at a pressure of 60-65 atm and there is no pressure increase for more than 2 hours, the decomposition reaction of the PV is considered complete, if there is no increase in pressure during the decomposition of the PV in the formation perform injection of an aqueous solution of the catalyst - potassium permanganate 5% wt. in a volume equal to the volume of the injected PV, then the catalyst solution is forced with process water in a volume equal to 1.2 volumes of the tubing, then at a pressure of 60-65 atm and no pressure increase for more than 2 hours, nitrogen is injected, at the wellhead the liquid and separated gas are discharged into the oil tanker and disposed of, while in the process of nitrogen injection, oxygen is measured in the composition of the separated gas, after complete bleeding, the well is swabbed with a volume of at least 2 volumes of injected liquid, then, to clarify the well flow rate, studies are carried out to restore the liquid level in the tubing and the tubing is lifted with a packer, then the pump is lowered with the calculated flow rate according to the research results, while the development of the well is accompanied by the measurement of oxygen in the composition of the produced fluid into the oil tanker; with the minimum permitted concentration of oxygen in the liquid, the development is transferred to the oil pipeline.

To implement the method of processing the bottomhole zone of the PV formation with phlegmatization during development, the following is used:

- technical grade B hydrogen peroxide with a mass fraction of hydrogen peroxide of 37% according to GOST 177-88;

- potassium permanganate grade Ch according to GOST 20490-75;

- fresh water and process water for flooding oil reservoirs according to OST 39-225-88;

- technical nitrogen according to GOST 9293-74.

In fig. a diagram of the ignition regions of the lower and upper explosive limits of a gas mixture of hydrocarbons and oxidizer (oxygen, air) (LEL and ERW) is presented.

Method for treating the bottomhole zone of a formation with hydrogen peroxide with phlegmatization during development implemented as follows.

Before starting work, the well is flushed with the tubing allowed to the bottom, the tightness of the pipe string is assessed and the well's injectivity is determined; if the injectivity is ≥ 50 m ³ /day, the technological tubing with a packer is lowered, and the packer is installed above the perforation interval. Then fresh water is injected as a buffer fluid in a volume equal to 1.2 volumes of the tubing.

After that, an PV solution of 37 wt.% is injected. calculated volume, depending on the values of the exposed effective thickness h and the porosity of the productive interval m : V _PV = 4.5 h m + 1.3.

Then the PV solution is forced into the formation with a volume of 1 m ³ of fresh water, then with process water, a total of 1.2 volumes of tubing. In this case, the entire volume of injection is carried out in less than 5 hours, provided that the reagent supply rate is uniform;

Next, the well is closed for response, while the pressure at the mouth is recorded; at a pressure of 60-65 atm and no pressure increase for more than 2 hours, the decomposition reaction of the PV is considered complete.

If there is no increase in pressure during the decomposition of PV in the formation perform injection of an aqueous solution of the catalyst - potassium permanganate 5% wt. in a volume equal to the volume of the pumped PV, then the catalyst solution is forced through with process water in a volume equal to 1.2 times the volume of the tubing.

Then, at a pressure of 60-65 atm and no pressure increase for more than 2 hours, nitrogen is injected. At the mouth, the liquid and separated gas are discharged into an oil tanker and disposed of. At the same time, during the process of nitrogen injection, oxygen is measured in the composition of the separated gas (oxygen content should not exceed 17%).

The rate of pressure drop at the mouth in the first 5 hours is ensured no more than 10 atm per hour.

After complete bleeding, the well is swabbed with a volume of at least 2 volumes of injected liquid.

Next, to clarify the well flow rate, studies are carried out to restore the fluid level in the tubing and the tubing is lifted with a packer,

Then the pump is lowered with the calculated flow rate according to the research results, while the development of the well is accompanied by the measurement of oxygen in the composition of the produced liquid into the oil tanker; at the minimum permitted concentration of oxygen in the liquid, the development is transferred to the oil pipeline.

Examples of specific implementation of the method .

Example 1. Phlegmatization of a gas mixture using nitrogen when treating a well with a PV solution of 1 m ³ volume.

Option 1. Treatment of the well with a 1 m volume of PV solution³ without implementation of phlegmatization during development (control).

The well was flushed to the bottom, the tightness of the pipe string was assessed and the well's injectivity was determined to be 52 m ³ /day. The process tubing and packer were lowered.

We injected 1.2 volumes of fresh water tubing as a buffer fluid, after which we injected a 37% wt. IP solution. volume 1 m ³ (for a productive interval with an exposed effective thickness of 2 m, porosity 0.19 units). The PV solution was forced into the formation with fresh water with a volume of 1 m ³ , then with process water, a total of 1.2 volumes of tubing. The entire injection volume was completed in 4 hours at a uniform reagent supply rate.

Next, the well was closed for response, while the pressure at the wellhead was recorded. The pressure change was 13 atm. Due to the lack of pressure growth, an aqueous solution of potassium permanganate with a concentration of 5 wt.% was injected. in a volume of 1 ^m3 . The catalyst solution was pressed with process water in a volume of 1.2 volumes of tubing.

We ensured a rate of pressure drop at the mouth in the first 5 hours equal to 8 atm per hour. After the pressure stabilized, the liquid and gas were released into the oil tanker. After complete bleeding, the well was swabbed with a volume of 2.3 volumes of injected liquid. Next, to clarify the well flow rate, studies were carried out to restore the fluid level in the tubing.

Next, we lifted the technological tubing with a packer and lowered the pump with the calculated flow rate (according to the results of level restoration - 3.1 m ³ /day). The development of the well was accompanied by measuring oxygen in the produced fluid into the oil tanker. During the work, liquid and gas samples were taken and the component composition of the gas mixture was determined. The resulting separation gas composition is given in Table 2.

Table 2 - Dynamics of daily changes in the composition of separation gas (calculation) when processing a PV well with a volume of 1 m ³ (% by volume) Component composition Days 1 2 3 4 5 6 7 8 9 10 _CO2 0.7 2.1 3.3 3.9 4.4 4.6 4.7 4.8 4.9 5.0 _O2 87.6 61.9 39.3 27.2 19.5 15.7 13.3 11.1 9.4 7.9 N ₂ 5.6 17.2 27.3 32.8 36.3 38.0 39.1 40.1 40.8 41.5 _H2S 0.6 1.9 3.0 3.6 3.9 4.1 4.3 4.4 4.4 4.5 CH ₄ 1.7 5.3 8.5 10.2 11.3 11.8 12.2 12.5 12.7 12.9 _{C2H6 _} 1.2 3.6 5.8 6.9 7.7 8.0 8.3 8.5 8.6 8.8 C ₃ H ₈ 1.3 3.9 6.3 7.5 8.3 8.7 8.9 9.2 9.3 9.5 iC ₄ H ₁₀ 0.2 0.7 1.1 1.4 1.5 1.6 1.6 1.7 1.7 1.7 nC ₄ H ₁₀ 0.5 1.5 2.4 2.8 3.1 3.3 3.4 3.5 3.5 3.6 iC ₅ 0.2 0.5 0.8 0.9 1.0 1.1 1.1 1.1 1.2 1.2 nC ₅ 0.1 0.3 0.5 0.6 0.7 0.7 0.7 0.8 0.8 0.8 C ₆ 0.1 0.3 0.4 0.5 0.5 0.6 0.6 0.6 0.6 0.6 _H2O 0.3 0.8 1.3 1.6 1.7 1.8 1.9 1.9 2.0 2.0 Σ 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

We obtained an increased oxygen content in the separation gas after treatment (more than 17% in the first 5 days), which leads to the formation of an explosive mixture.

Option 2. Treatment of the well with a 1 m volume of PV solution³ With implementation of phlegmatization during development.

The well was flushed to the bottom, the tightness of the pipe string was assessed and the well's injectivity was determined to be 55 m ³ /day. The process tubing and packer were lowered.

We injected 1.2 volumes of fresh water tubing as a buffer fluid, after which we injected a 37% wt. IP solution. volume 1 m ³ (for a productive interval with an exposed effective thickness of 1.8 m, porosity 0.18 units). The PV solution was forced into the formation with fresh water with a volume of 1 m ³ , then with process water, a total of 1.2 volumes of tubing. The entire injection volume was completed in 4 hours at a uniform reagent supply rate.

Next, the well was closed for response, while the pressure at the wellhead was recorded. The pressure change was 11 atm. Due to the lack of pressure growth, an aqueous solution of potassium permanganate with a concentration of 5 wt.% was injected. in a volume of 1 ^m3 . The catalyst solution was pressed with process water in a volume of 1.2 volumes of tubing.

Then phlegmatization was performed, for which, after stabilizing the pressure at the wellhead, the valve on the blowout control equipment was slightly opened and nitrogen was supplied, while nitrogen was injected with a double reserve. During the operation, the oxygen content of the separated gas was measured using a gas analyzer, and the oxygen content was ensured to be less than 17%.

We ensured a rate of pressure drop at the mouth in the first 5 hours equal to 9 atm per hour. After the pressure stabilized, the liquid and gas were released into the oil tanker. After complete bleeding, the well was swabbed with a volume of 2.1 volumes of injected liquid. Next, to clarify the well flow rate, studies were carried out to restore the fluid level in the tubing.

Next, we lifted the technological tubing with a packer and lowered the pump with the calculated flow rate (according to the results of level restoration - 2.9 m ³ /day). The development of the well was accompanied by measuring oxygen in the produced fluid into the oil tanker. During the work, liquid and gas samples were taken and the component composition of the gas mixture was determined. The resulting separation gas composition is given in Table 3.

Table 3 - Dynamics of changes in the composition of the separation gas and the minimum required volume of nitrogen when purging a well with nitrogen (% by volume) for the case of processing PV with a volume of 1 m ³ Component composition Days 1 2 3 4 5 6 7 8 9 10 _CO2 0.1 0.5 1.4 2.2 3.1 4.6 4.7 4.8 4.9 5.0 _O2 16.1 16.3 16.4 15.5 13.8 15.7 13.3 11.1 9.4 7.9 N ₂ 82.7 78.2 69.7 61.8 55.1 38.0 39.1 40.1 40.8 41.5 _H2S 0.1 0.5 1.2 2.0 2.8 4.1 4.3 4.4 4.4 4.5 CH ₄ 0.3 1.4 3.5 5.8 8.0 11.8 12.2 12.5 12.7 12.9 _{C2H6 _} 0.2 1.0 2.4 3.9 5.4 8.0 8.3 8.5 8.6 8.8 C ₃ H ₈ 0.2 1.0 2.6 4.3 5.8 8.7 8.9 9.2 9.3 9.5 iC ₄ H ₁₀ 0.0 0.2 0.5 0.8 1.1 1.6 1.6 1.7 1.7 1.7 nC ₄ H ₁₀ 0.1 0.4 1.0 1.6 2.2 3.3 3.4 3.5 3.5 3.6 iC ₅ 0.0 0.1 0.3 0.5 0.7 1.1 1.1 1.1 1.2 1.2 Continuation of table 3 nC ₅ 0.0 0.1 0.2 0.4 0.5 0.7 0.7 0.8 0.8 0.8 C ₆ 0.0 0.1 0.2 0.3 0.4 0.6 0.6 0.6 0.6 0.6 _H2O 0.0 0.2 0.5 0.9 1.2 1.8 1.9 1.9 2.0 2.0 ∑ 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 V injection N ₂ , m ³ 541.9 98.9 31.3 13.9 6.8 0 0 0 0 0 The minimum required volume of nitrogen to purge the separator on the first day is 541.9 m ³

After phlegmatization during development, an explosion-proof component composition of the separation gas was obtained, in which the oxygen content does not exceed 17%.

Example 2. Phlegmatization of a gas mixture using nitrogen when treating a well with a solution of hydrogen peroxide with a volume of 3.5 m ³ .

Option 1. Treatment of the well with a solution of hydrogen peroxide with a volume of 3.5 m³ without implementation of phlegmatization during development (control).

The well was flushed to the bottom, the tightness of the pipe string was assessed and the well's injectivity was determined to be 63 m ³ /day. The process tubing and packer were lowered.

We injected 1.2 volumes of fresh water tubing as a buffer fluid, after which we injected a 37 wt.% PV solution. volume 3.5 m ³ (for a productive interval with an exposed effective thickness of 3 m, porosity 0.17 units). The PV solution was forced into the formation with fresh water with a volume of 1 m ³ , then with process water, a total of 1.2 volumes of tubing. The entire injection volume was completed in 3 hours at a uniform reagent supply rate.

Next, the well was closed for response, while the pressure at the wellhead was recorded. The pressure change was 63 atm.

After no increase in pressure for 2 hours, the rate of pressure drop at the mouth in the first 5 hours was ensured at 6 atm per hour. After the pressure stabilized, the liquid and gas were released into the oil tanker. After complete bleeding, the well was swabbed with a volume of 2.4 volumes of injected liquid. Next, to clarify the well flow rate, studies were carried out to restore the fluid level in the tubing.

Next, we lifted the technological tubing with a packer and lowered the pump with the calculated flow rate (according to the results of level restoration - 7.3 m ³ /day). The development of the well was accompanied by measuring oxygen in the produced fluid into the oil tanker. During the work, liquid and gas samples were taken and the component composition of the gas mixture was determined. The resulting composition of the separation gas is given in Table 4.

Table 4 - Dynamics of daily changes in the composition of separation gas (calculation) when processing a PV well with a volume of 3.5 m ³ (% by volume) Component composition Days 1 2 3 4 5 6 7 8 9 10 _CO2 0.5 0.7 1.2 1.6 2.0 2.4 2.7 3.0 3.3 3.5 _O2 90.1 86.9 78.4 70.8 62.8 56.1 49.4 44.1 39.4 35.6 N ₂ 4.4 5.9 9.7 13.2 16.8 19.8 22.8 25.2 27.3 29.0 _H2S 0.5 0.6 1.1 1.4 1.8 2.2 2.5 2.7 3.0 3.2 CH ₄ 1.4 1.8 3.0 4.1 5.2 6.2 7.1 7.8 8.5 9.0 _{C2H6 _} 0.9 1.2 2.1 2.8 3.5 4.2 4.8 5.3 5.8 6.1 C ₃ H ₈ 1.0 1.3 2.2 3.0 3.8 4.5 5.2 5.8 6.3 6.6 iC ₄ H ₁₀ 0.2 0.2 0.4 0.6 0.7 0.8 1.0 1.1 1.1 1.2 nC ₄ H ₁₀ 0.4 0.5 0.8 1.1 1.5 1.7 2.0 2.2 2.4 2.5 iC ₅ 0.1 0.2 0.3 0.4 0.5 0.6 0.6 0.7 0.8 0.8 nC ₅ 0.1 0.1 0.2 0.3 0.3 0.4 0.4 0.5 0.5 0.6 C ₆ 0.1 0.1 0.1 0.2 0.2 0.3 0.3 0.4 0.4 0.4 _H2O 0.2 0.3 0.5 0.6 0.8 1.0 1.1 1.2 1.3 1.4 Σ 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

We obtained an increased oxygen content in the separation gas after treatment (more than 17% in the first 10 days), which leads to the formation of an explosive mixture.

Option 2. Treatment of the well with a solution of hydrogen peroxide with a volume of 3.5 m³ With implementation of phlegmatization during development.

The well was flushed to the bottom, the tightness of the pipe string was assessed and the well's injectivity was determined to be 58 m ³ /day. The process tubing and packer were lowered.

We injected 1.2 volumes of fresh water tubing as a buffer fluid, after which we injected a 37% wt. IP solution. volume 3.5 m ³ (for a productive interval with an exposed effective thickness of 2.8 m, porosity 0.25 units). The PV solution was forced into the formation with fresh water with a volume of 1 m ³ , then with process water, a total of 1.2 volumes of tubing. The entire injection volume was completed in 4 hours at a uniform reagent supply rate.

Next, the well was closed for response, while the pressure at the wellhead was recorded. The pressure change was 62 atm.

Then phlegmatization was performed, for which, after stabilizing the pressure at the wellhead, the valve on the blowout control equipment was slightly opened and nitrogen was supplied, while nitrogen was injected with a double reserve. During the operation, the oxygen content of the separated gas was measured using a gas analyzer, and the oxygen content was ensured to be less than 17%.

After no increase in pressure for 2 hours, the rate of pressure drop at the mouth in the first 5 hours was ensured at 7 atm per hour. After the pressure stabilized, the liquid and gas were released into the oil tanker. After complete bleeding, the well was swabbed with a volume of 2.5 volumes of injected liquid. Next, to clarify the well flow rate, studies were carried out to restore the fluid level in the tubing.

Next, we lifted the technological tubing with a packer and lowered the pump with the calculated flow rate (according to the results of level restoration - 7.5 m ³ /day). The development of the well was accompanied by measuring oxygen in the produced fluid into the oil tanker. During the work, liquid and gas samples were taken and the component composition of the gas mixture was determined. The resulting separation gas composition is given in Table 5.

Table 5 - Dynamics of changes in the composition of the separation gas and the minimum required volume of nitrogen when purging a well with nitrogen (% by volume) for the case of processing PV with a volume of 3.5 m ³ Component composition Days 1 2 3 4 5 6 7 8 9 10 _CO2 0.1 0.1 0.2 0.4 0.5 0.7 0.9 1.1 1.4 1.6 _O2 16.2 16.0 16.5 16.5 16.3 16.3 16.2 16.3 16.4 16.3 N ₂ 82.8 82.6 81.0 79.8 78.3 76.7 74.7 72.4 69.7 67.5 _H2S 0.1 0.1 0.2 0.3 0.5 0.6 0.8 1.0 1.2 1.4 CH ₄ 0.2 0.3 0.6 1.0 1.4 1.8 2.3 2.9 3.5 4.1 _{C2H6 _} 0.2 0.2 0.4 0.6 0.9 1.2 1.6 2.0 2.4 2.8 C ₃ H ₈ 0.2 0.2 0.5 0.7 1.0 1.3 1.7 2.1 2.6 3.0 iC ₄ H ₁₀ 0.0 0.0 0.1 0.1 0.2 0.2 0.3 0.4 0.5 0.6 nC ₄ H ₁₀ 0.1 0.1 0.2 0.3 0.4 0.5 0.6 0.8 1.0 1.2 iC ₅ 0.0 0.0 0.1 0.1 0.1 0.2 0.2 0.3 0.3 0.4 nC ₅ 0.0 0.0 0.0 0.1 0.1 0.1 0.1 0.2 0.2 0.3 Continuation of table 5 C ₆ 0.0 0.0 0.0 0.0 0.1 0.1 0.1 0.1 0.2 0.2 _H2O 0.0 0.1 0.1 0.1 0.2 0.3 0.4 0.4 0.5 0.6 Σ 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 V injection N ₂ , m ³ 908.3 645.8 317.9 190.2 124.9 88.2 64.4 47.8 35.5 27.9 The minimum required volume of nitrogen for purging the separator on the first day is 908.3 m ³

After carrying out phlegmatization during development, an explosion-proof component composition of the separation gas was obtained, in which the oxygen content does not exceed 17%.

Thus, from the above we can conclude that safe treatment of the near-wellbore formation zone using PV has been achieved due to the phlegmatization of an explosive mixture of associated petroleum gas with oxygen using nitrogen.

Claims (5)

A method for treating the bottomhole zone of a formation with hydrogen peroxide with phlegmatization during development, including pumping a hydrogen peroxide solution through the tubing tubing, its decomposition in the formation with the release of heat, characterized in that the well is flushed with tubing allowed to the bottom, the tightness of the pipe string is assessed and the injectivity of the well is determined, if the injectivity is ≥50 m³/day, technological tubing with a packer is lowered, while the packer is installed above the perforation interval, then fresh water is injected as a buffer fluid in a volume equal to 1.2 volumes of the tubing, after which a 37 wt.% solution of hydrogen peroxide of the calculated volume is injected V _PV =4.5⋅ h ⋅ m +1.3, where h is the exposed effective thickness of the formation, m, m - porosity of the productive interval, units, then the hydrogen peroxide solution is forced into the formation with fresh water with a volume of 1 m ³ , then with process water, a total of 1.2 volumes of tubing, while the entire volume of injection is carried out in less than 5 hours, provided that the reagent supply rate is uniform, then the well is closed for reaction, when In this case, the pressure at the wellhead is recorded, at a pressure of 60-65 atm and no pressure increase for more than 2 hours, the decomposition reaction of hydrogen peroxide is considered complete; if there is no increase in pressure during the decomposition of hydrogen peroxide in the formation, an aqueous solution of the catalyst - 5 wt.% permanganate is injected potassium in a volume equal to the volume of injected hydrogen peroxide, then the catalyst solution is forced with process water in a volume equal to 1.2 volumes of the tubing, then at a pressure of 60-65 atm and no pressure increase for more than 2 hours, nitrogen is injected, the liquid and separated gas are vented at the wellhead into the oil tanker and disposed of, while in the process of injecting nitrogen, oxygen is measured in the composition of the separated gas; after complete bleeding, the well is swabbed with a volume of at least 2 volumes of injected liquid; then, to clarify the well flow rate, studies are carried out to restore the liquid level in the tubing and carry out lifting the tubing with a packer, then lowering the pump with the calculated flow rate according to the research results, while the development of the well is accompanied by the measurement of oxygen in the composition of the produced fluid into the oil tanker; at the minimum permitted concentration of oxygen in the liquid, the development is transferred to the oil pipeline.