CN118498929B - A water plugging and profile control process for heavy oil wells - Google Patents

Abstract

The present invention relates to the technical field of heavy oil storage and development, and in particular to a process method for water plugging and profile control in heavy oil wells. The process comprises the following steps: injecting a modified polymer water plugging agent into a heat injection well in a heavy oil block, cross-linking to form a stable gel in a high temperature and high pressure environment underground, and plugging a high permeability channel; after the injection of the modified polymer water plugging agent is completed, continuing to inject a composite profile control agent, dispersing in the reservoir pores and forming a uniform profile control layer, improving the fluidity of the reservoir, and balancing the flow of oil and water; adopting a segmented injection process, injecting the modified polymer water plugging agent and the composite profile control agent respectively, so that the water plugging and profile control effects of each reservoir section are balanced; and using downhole monitoring equipment to monitor the injection pressure and flow in real time; after the water plugging and profile control are completed, regular maintenance injection is performed. Beneficial effects are: the present invention has significant gel stability in the reservoir environment of steam channeling, water channeling and high temperature and high pressure, effectively solving the problems of water channeling and interlayer interference in heavy oil wells, and improving the recovery rate of heavy oil wells.

Description

A water plugging and profile control process for heavy oil wells

Technical Field

The invention relates to the technical field of heavy oil storage and development, and in particular to a water plugging and profile control process for heavy oil wells.

Background Art

Heavy oil production is difficult and costly. So far, heavy oil reservoirs at home and abroad have formed a production pattern of steam injection thermal recovery as the main method and "heat +" technology as the auxiliary method. Among them, steam injection thermal recovery mainly refers to steam thermal huff and puff, steam drive and other technologies. Under this technical pattern, steam channeling and hot water channeling occur from time to time, which seriously affects the thermal recovery effect of heavy oil. For steam thermal huff and puff, with the increase of huff and puff rounds, the oil saturation in the near-wellbore area of heavy oil wells continues to decline, the steam heating radius, daily oil production level and oil-gas ratio will reach the limit, and the huff and puff effect is extremely poor. For steam drive, under the combined effect of steam overburden and condensation, the reservoir sweep efficiency is also limited, and the steam thermal energy utilization efficiency is low. In the middle and late stages of thermal recovery, steam channeling and overburden will only become more serious, and the development effect will continue to deteriorate. In view of this, the conversion of heavy oil reservoir development mode becomes necessary. Hot water drive is usually an effective alternative to steam injection thermal recovery in the late stage of development. Hot water flooding can fully utilize the residual heat of steam flooding in the oil formation to a certain extent, extend the economic life of steam flooding, and increase the vertical sweep coefficient of the reservoir, but it will cause serious hot water channeling. Therefore, the key focus should be on the water plugging and profile control process when switching to hot water flooding after steam injection development.

The water plugging and profile control process when converting to hot water flooding after steam injection development needs to consider steam channeling, water channeling and high temperature and high pressure reservoir environment in the design and optimization of profile control agents and the improvement of water plugging and profile control processes, so as to ensure that the water plugging agent can still play a good role in the hot water flooding environment. At present, water plugging agents mostly use unmodified polyacrylamide or simple chemically modified polyacrylamide. The modification means are relatively simple, and the cross-linking agents are mostly ordinary organic cross-linking agents, such as formaldehyde and chromium compounds. The cross-linking reaction is simple, and the improvement of water plugging performance is limited. It cannot provide more reliable technical support for the effective development of heavy oil resources after steam injection development and hot water flooding. In view of this, it is necessary to propose a water plugging and profile control process method for heavy oil wells in view of the development environment of hot water flooding after steam injection development.

Summary of the invention

The purpose of the present invention is to provide a water plugging and profile control process method for heavy oil wells in view of the above-mentioned defects in the prior art. The modified polymer water plugging agent used in the present invention is cross-linked in a high temperature and high pressure environment underground to form a stable gel, thereby plugging high permeability channels; the composite profile control agent used is dispersed in the reservoir pores to form a uniform profile control layer, thereby improving the fluidity of the reservoir in the low permeability area and balancing the flow of oil and water; and through a segmented injection process, dynamic monitoring of injection pressure and flow rate, regular maintenance injection, etc., the water plugging and profile control process in a hot water drive environment after steam injection development of heavy oil reservoirs is finally achieved, which has important practical significance for improving the effect of thermal recovery development of heavy oil.

The present invention provides a method for water plugging and profile control in a heavy oil well, and the technical scheme thereof comprises the following steps:

S1: injecting a water plugging agent into a heat injection well: injecting a modified polymer water plugging agent into a heat injection well in a heavy oil block, wherein the modified polymer water plugging agent is made of 75-87 parts of modified polyacrylamide, 6-8 parts of modified clay, 3-5 parts of a cross-linking agent, 2-3 parts of a stabilizer, 1-2 parts of a composite slow-release agent and 100 parts of water, and cross-links underground to form a gel to plug high permeability channels;

S2: injecting a profile control agent into the heat injection well: after the injection of the modified polymer water plugging agent is completed, continue to inject a composite profile control agent, which is made of 3 parts of nano-microspheres, 2 parts of water-soluble polymers and 100 parts of water, and is dispersed in the reservoir pores to form a profile control layer;

S3: The segmented injection process includes the following steps:

(1) Determine the location of high permeability channels and low permeability areas in the water plugging and profile control reservoir section through well logging data analysis;

(2) Inject modified polymer water plugging agent into the high permeability channel, with the injection volume of 100-200 liters each time and the injection pressure controlled at 10-15 MPa;

(3) Inject composite profile control agent into low permeability sections, with an injection volume of 150-250 liters each time and injection pressure controlled at 8-12 MPa;

(4) Switch the injection section every 2 to 4 hours to ensure effective injection into each reservoir section;

S4: Dynamic monitoring, including the following steps:

(1) Use downhole monitoring equipment to monitor injection pressure and flow in real time and record data;

(2) According to the real-time monitoring data, the injection pressure and injection flow rate are adjusted to ensure that the modified polymer water plugging agent and composite profile control agent are evenly distributed in the reservoir section;

S5: Subsequent maintenance: After water plugging and profile control are completed, maintenance and re-injection are carried out every 3-6 months;

In step S1, the modified polyacrylamide matrix uses 70-80 parts of polyacrylamide with a molecular weight of 10 million to 15 million; the modifier uses 5-7 parts of nano-graphene oxide, and the nano-graphene oxide is combined with the polyacrylamide chain by chemical grafting;

The modified clay is organically modified with alkyl trimethyl ammonium chloride or ion-exchanged with aluminum sulfate;

The cross-linking agent is polysiloxane or tetraisopropoxy titanium;

The stabilizer is a mixture of aluminum sulfate and ethylenediaminetetraacetic acid, and the mass ratio of aluminum sulfate to ethylenediaminetetraacetic acid is 1:1;

The composite sustained-release agent uses natural attapulgite or composite material polylactic acid;

In step S2, the nanospheres are made of the following components in parts by weight: 60-70 parts of polystyrene-acrylate nanospheres, 5-10 parts of polyethylene glycol octylphenyl ether, 10-15 parts of γ-methacryloxypropyltrimethoxysilane, and 5-10 parts of a mixed solution of high-purity water and ethanol;

The water-soluble polymer is made of the following components in parts by weight: a polymer matrix adopts 50-60 parts of a copolymer of sodium polyacrylate and polyethylene glycol, 5-10 parts of methacryloyloxyethyltrimethylammonium chloride, 15-20 parts of a mixture of guar gum and xanthan gum, and 5-10 parts of a mixture of potassium sulfate and dilauryl thiodipropionate, wherein the mass ratio of potassium sulfate to dilauryl thiodipropionate is 1:1.

Preferably, the preparation process of the modified polymer water plugging agent comprises the following steps:

(1) Matrix dissolution: Dissolve 70-80 parts of polyacrylamide with a molecular weight of 10 million to 15 million in deionized water to form a solution with a weight percentage concentration of 1%, and stir evenly;

(2) Nano-modification: Disperse 5-7 parts of nano-graphene oxide in water, add surfactant Tween 80 and perform ultrasonic treatment for 30 minutes to evenly disperse;

(3) Chemical grafting: Add the nano-graphene oxide dispersion into the polyacrylamide solution, keep stirring, add 1 part of ammonium persulfate, and react at 60°C for 2 hours to complete the grafting modification;

(4) Add 6-8 parts of modified clay, dissolve 3-5 parts of tetraisopropoxytitanium in ethanol, add to the modified polyacrylamide solution, and stir evenly;

(5) Dissolve 2-3 parts of a mixture of aluminum sulfate and ethylenediaminetetraacetic acid in ethanol, with the mass ratio of aluminum sulfate to ethylenediaminetetraacetic acid being 1:1, and then add the mixture to the modified polyacrylamide solution, keep stirring, and evenly disperse.

(6) Add 1-2 parts of the composite sustained-release agent to the modified polyacrylamide solution, keep stirring, and evenly disperse;

(7) Final preparation: After all ingredients are mixed evenly, adjust the pH value of the solution to 7.0 and let it stand for 12 hours to allow all components to fully react and form a stable modified polymer water plugging agent.

Preferably, the polystyrene-acrylate nanospheres have a particle size of 50-100 nanometers.

Preferably, the preparation process of the composite profile control agent comprises the following steps:

(1) Using a mixed solution of high-purity water and ethanol as a dispersion medium, with the mixed solution using 5-10 parts, the mass ratio of high-purity water to ethanol being 3:2, and then adding 50-60 parts of a copolymer of sodium polyacrylate and polyethylene glycol, stirring evenly until all dissolved;

(2) adding 60-70 parts of polystyrene-acrylate nanospheres with a particle size of 50-100 nanometers to the above solution and stirring to make them evenly dispersed;

(3) While stirring, add 5-10 parts of polyethylene glycol octylphenyl ether and continue stirring evenly;

(4) While stirring, add 10-15 parts of γ-methacryloxypropyltrimethoxysilane and stir to mix thoroughly;

(5) Add 5-10 parts of methacryloyloxyethyltrimethylammonium chloride to the mixed solution and continue stirring to make it evenly distributed;

(6) While stirring, add 15-20 parts of a mixture of guar gum and xanthan gum, with the mass ratio of guar gum to xanthan gum being 1:1, and stir until the mixture of guar gum and xanthan gum is completely dissolved and evenly dispersed;

(7) Add 5-10 parts of a mixture of potassium sulfate and dilauryl thiodipropionate, with the mass ratio of potassium sulfate to dilauryl thiodipropionate being 1:1, and stir evenly;

(8) Stir the mixture to ensure that all components are evenly mixed, and then use a high shear mixer to homogenize it.

Compared with the prior art, the beneficial effects of the present invention are as follows:

(1) The nano-graphene oxide used in the present invention is used to hydrophobically modify polyacrylamide, thereby improving the high temperature resistance, salt resistance and mechanical strength of polyacrylamide; the combination of polyethylene glycol octylphenyl ether and γ-methacryloxypropyltrimethoxysilane enhances the dispersibility and mechanical strength of nano-microspheres; the water-soluble polymer composed of sodium polyacrylate and polyethylene glycol copolymer has excellent water solubility and rheological properties; the introduction of the cross-linking monomer methacryloxyethyltrimethylammonium chloride enhances the structural stability of the profile control agent;

(2) The present invention has significant gel stability under the reservoir environment of steam channeling, water channeling and high temperature and high pressure, and can form a stable plugging layer and profile control layer in the well, effectively solving the problems of water channeling and interlayer interference in heavy oil wells, improving the recovery rate of heavy oil wells, and expanding the application feasibility of hot water flooding after steam injection development of heavy oil reservoirs;

(3) The two-way management concept of "oil well plugging and water well regulation" combined with the formula and production process of modified polymer water plugging agent and composite profile control agent makes the process simple, low-cost and easy to operate, providing more reliable technical support for the effective development of heavy oil resources after steam injection development and then hot water flooding.

DETAILED DESCRIPTION

The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

Example 1, a water plugging and profile control process for heavy oil wells mentioned in the present invention comprises the following steps: The following are by weight:

S1: injecting a water plugging agent into a heat injection well: injecting a modified polymer water plugging agent into a heat injection well in a heavy oil block, wherein the modified polymer water plugging agent is made of 75 parts of modified polyacrylamide, 6 parts of modified clay, 3 parts of a cross-linking agent, 2 parts of a stabilizer, 1 part of a composite slow-release agent and 100 parts of water, and cross-links underground to form a gel to plug high permeability channels;

S2: injecting a profile control agent into the heat injection well: after the injection of the modified polymer water plugging agent is completed, continue to inject a composite profile control agent, which is made of 3 parts of nano-microspheres, 2 parts of water-soluble polymers and 100 parts of water, and is dispersed in the reservoir pores to form a profile control layer;

S3: The segmented injection process includes the following steps:

(1) Determine the location of high permeability channels and low permeability areas in the water plugging and profile control reservoir section through well logging data analysis;

(2) Inject modified polymer water plugging agent into the high permeability channel, with the injection volume of 100-200 liters each time and the injection pressure controlled at 10-15 MPa;

(3) Inject composite profile control agent into low permeability sections, with an injection volume of 150-250 liters each time and injection pressure controlled at 8-12 MPa;

(4) Switch the injection section every 2 to 4 hours to ensure effective injection into each reservoir section;

S4: Dynamic monitoring, including the following steps:

(1) Use downhole monitoring equipment to monitor injection pressure and flow in real time and record data;

(2) According to the real-time monitoring data, the injection pressure and injection flow rate are adjusted to ensure that the modified polymer water plugging agent and composite profile control agent are evenly distributed in the reservoir section;

S5: Subsequent maintenance: After water plugging and profile control are completed, maintenance and re-injection are carried out every 3-6 months;

In step S1, the modified polyacrylamide matrix uses 70 parts of polyacrylamide with a molecular weight of 10 million to 15 million; the modifier uses 5 parts of nano-graphene oxide, and the nano-graphene oxide is combined with the polyacrylamide chain by chemical grafting;

The modified clay is organically modified with alkyl trimethyl ammonium chloride or ion-exchanged with aluminum sulfate;

The cross-linking agent is polysiloxane or tetraisopropoxy titanium;

The stabilizer is a mixture of aluminum sulfate and ethylenediaminetetraacetic acid, and the mass ratio of aluminum sulfate to ethylenediaminetetraacetic acid is 1:1;

The composite sustained-release agent uses natural attapulgite or composite material polylactic acid;

In step S2, the nanospheres are made of the following components in parts by weight: 60 parts of polystyrene-acrylate nanospheres, 5 parts of polyethylene glycol octylphenyl ether, 10 parts of γ-methacryloxypropyltrimethoxysilane, and 5 parts of a mixed solution of high-purity water and ethanol;

The water-soluble polymer is made of the following components in parts by weight: a polymer matrix adopts 50-60 parts of a copolymer of sodium polyacrylate and polyethylene glycol, 5-10 parts of methacryloyloxyethyltrimethylammonium chloride, 15-20 parts of a mixture of guar gum and xanthan gum, and 5-10 parts of a mixture of potassium sulfate and dilauryl thiodipropionate, wherein the mass ratio of potassium sulfate to dilauryl thiodipropionate is 1:1.

Preferably, the preparation process of the modified polymer water plugging agent comprises the following steps:

(1) Matrix dissolution: Dissolve 70 parts of polyacrylamide with a molecular weight of 10 million in deionized water to form a solution with a weight percentage concentration of 1%, and stir evenly;

(2) Nano-modification: 5 parts of nano-graphene oxide were dispersed in water, and a surfactant Tween 80 was added for ultrasonic treatment for 30 minutes to uniformly disperse the nano-graphene oxide.

(3) Chemical grafting: Add the nano-graphene oxide dispersion into the polyacrylamide solution, keep stirring, add 1 part of ammonium persulfate, and react at 60°C for 2 hours to complete the grafting modification;

(4) Add 6 parts of modified clay organically modified with alkyl trimethyl ammonium chloride, dissolve 3 parts of tetraisopropoxy titanium in ethanol, add to the modified polyacrylamide solution, and stir evenly;

(5) Dissolve 2 parts of a mixture of aluminum sulfate and ethylenediaminetetraacetic acid in ethanol, with the mass ratio of aluminum sulfate to ethylenediaminetetraacetic acid being 1:1, and then add the mixture to the modified polyacrylamide solution, keep stirring, and evenly disperse the mixture;

(6) Add 1 part of the composite sustained-release agent to the modified polyacrylamide solution, keep stirring, and evenly disperse;

(7) Final preparation: After all ingredients are mixed evenly, adjust the pH value of the solution to 7.0 and let it stand for 12 hours to allow all components to fully react and form a stable modified polymer water plugging agent.

The particle size of the polystyrene-acrylate nanospheres is 50-100 nanometers.

The preparation process of the composite profile control agent comprises the following steps:

(1) Using a mixed solution of high-purity water and ethanol as a dispersion medium, and using 5 parts of the mixed solution, the mass ratio of high-purity water to ethanol is 3:2, and then adding 50 parts of a copolymer of sodium polyacrylate and polyethylene glycol, stirring evenly until all dissolved;

(2) adding 60 parts of polystyrene-acrylate nanospheres with a particle size of 50-100 nm to the above solution and stirring to make them evenly dispersed;

(3) While stirring, add 5 parts of polyethylene glycol octylphenyl ether and continue stirring evenly;

(4) Add 10 parts of γ-methacryloxypropyltrimethoxysilane while stirring, and stir to mix thoroughly;

(5) Add 5 parts of methacryloyloxyethyltrimethylammonium chloride to the mixed solution and continue stirring to make it evenly distributed;

(6) While stirring, add 15 parts of a mixture of guar gum and xanthan gum, with the mass ratio of guar gum to xanthan gum being 1:1, and stir until the mixture of guar gum and xanthan gum is completely dissolved and evenly dispersed;

(7) Add 5 parts of a mixture of potassium sulfate and dilauryl thiodipropionate, with the mass ratio of potassium sulfate to dilauryl thiodipropionate being 1:1, and stir evenly;

(8) Stir the mixture to ensure that all components are evenly mixed, and then use a high shear mixer to homogenize it.

Example 2, a water plugging and profile control process for heavy oil wells mentioned in the present invention, is different from Example 1 in that:

The preparation process of the modified polymer water plugging agent used in this embodiment includes the following steps: The following are in parts by weight:

(1) Matrix dissolution: Dissolve 80 parts of polyacrylamide with a molecular weight of 15 million in deionized water to form a solution with a concentration of 1%, and stir evenly;

(2) Nano-modification: 7 parts of nano-graphene oxide was dispersed in water, and a surfactant Tween 80 was added for ultrasonic treatment for 30 minutes to ensure uniform dispersion;

(3) Chemical grafting: Slowly add the nano-graphene oxide dispersion into the polyacrylamide solution, keep stirring, and add 1 part of initiator ammonium persulfate, react at 60°C for 2 hours to complete the grafting modification;

(4) Add 8 parts of modified clay modified by aluminum sulfate ion exchange to improve its dispersibility in water and compatibility with modified polyacrylamide; dissolve 5 parts of polysiloxane in a small amount of ethanol, slowly add it to the modified polyacrylamide solution, and stir evenly;

(5) Dissolve 3 parts of a mixture of aluminum sulfate and ethylenediaminetetraacetic acid in ethanol in a mass ratio of 1:1, and slowly add the mixture to the solution while stirring to ensure uniform dispersion;

(6) Add 2 parts of the composite slow-release agent to the modified polyacrylamide solution and keep stirring to ensure uniform dispersion. The composite slow-release agent uses natural attapulgite to control the release rate of the water plugging agent and ensure the long-term stability of the water plugging agent underground;

(7) Final preparation: After all ingredients are mixed evenly, adjust the pH value of the solution to 7.0 and let it stand for 12 hours to ensure that all components are fully reacted and form a stable modified polymer water plugging agent.

The preparation process of the composite profile control agent mentioned in this embodiment includes the following steps:

(1) Using a mixed solution of high-purity water and ethanol as a dispersion medium, and using 10 parts of the mixed solution, the mass ratio of high-purity water to ethanol is 3:2, and then adding 60 parts of a copolymer of sodium polyacrylate and polyethylene glycol, stirring evenly until completely dissolved;

(2) gradually adding 70 parts of polystyrene-acrylate nanospheres into the above solution, stirring continuously to ensure uniform dispersion;

(3) While stirring, slowly add 10 parts of polyethylene glycol octylphenyl ether and continue stirring evenly;

(4) Add 15 parts of γ-methacryloxypropyltrimethoxysilane under continuous stirring and stir to mix thoroughly;

(5) Add 10 parts of methacryloyloxyethyltrimethylammonium chloride to the mixture and continue stirring to ensure uniform distribution;

(6) While stirring, slowly add 20 parts of a mixture of guar gum and xanthan gum in a mass ratio of 1:1, and stir until the mixture of guar gum and xanthan gum is completely dissolved and evenly dispersed;

(7) Add 10 parts of a mixture of potassium sulfate and dilauryl thiodipropionate, with the mass ratio of potassium sulfate to dilauryl thiodipropionate being 1:1, and continue stirring to ensure that the stabilizer is evenly distributed;

(8) The mixture is continuously stirred to ensure that all ingredients are evenly mixed, and a high shear mixer is used for homogenization to ensure the uniformity of the final composite profile control agent.

Example 3, a water plugging and profile control process for heavy oil wells mentioned in the present invention, is different from Examples 1 and 2 in that:

The preparation process of the modified polymer water plugging agent mentioned in this embodiment includes the following steps: The following are in parts by weight:

(1) Matrix dissolution: Dissolve 75 parts of polyacrylamide with a molecular weight of 12 million in deionized water to form a solution with a concentration of 1%, and stir evenly;

(2) Nano-modification: 6 parts of nano-graphene oxide were dispersed in water, and a surfactant Tween 80 was added for ultrasonic treatment for 30 minutes to ensure uniform dispersion;

(3) Chemical grafting: Slowly add the nano-graphene oxide dispersion into the polyacrylamide solution, keep stirring, add ammonium persulfate, and react at 60°C for 2 hours to complete the grafting modification;

(4) Add 7 parts of modified clay modified by aluminum sulfate ion exchange to improve its dispersibility in water and compatibility with modified polyacrylamide; dissolve 4 parts of tetraisopropoxytitanium in a small amount of ethanol, slowly add it to the modified polyacrylamide solution, and stir evenly;

(5) Dissolve 2.5 parts of a mixture of aluminum sulfate and ethylenediaminetetraacetic acid in ethanol in a mass ratio of 1:1, and slowly add the mixture to the solution while stirring to ensure uniform dispersion;

(6) Add 1.5 parts of the composite slow-release agent to the modified polyacrylamide solution and keep stirring to ensure uniform dispersion. The composite slow-release agent specifically uses a composite material polylactic acid to control the release rate of the water plugging agent and ensure the long-term stability of the water plugging agent underground;

(7) Final preparation: After all ingredients are mixed evenly, adjust the pH value of the solution to 7.0 and let it stand for 12 hours to ensure that all components are fully reacted and form a stable modified polymer water plugging agent.

The preparation process of the composite profile control agent mentioned in this embodiment includes the following steps:

(1) Using a mixed solution of high-purity water and ethanol as a dispersion medium, with 50 parts of the mixed solution and a mass ratio of high-purity water to ethanol of 1:1, 55 parts of a copolymer of sodium polyacrylate and polyethylene glycol are added, and stirred evenly until completely dissolved;

(2) gradually adding 65 parts of polystyrene-acrylate nanospheres into the above solution, stirring continuously to ensure uniform dispersion;

(3) While stirring, slowly add 7 parts of polyethylene glycol octylphenyl ether and continue stirring evenly;

(4) Add 12 parts of γ-methacryloxypropyltrimethoxysilane under continuous stirring and stir to mix thoroughly;

(5) Add 8 parts of methacryloyloxyethyltrimethylammonium chloride to the mixture and continue stirring to ensure uniform distribution;

(6) While stirring, slowly add 17 parts of a mixture of guar gum and xanthan gum in a mass ratio of 1:1, and stir until the mixture of guar gum and xanthan gum is completely dissolved and evenly dispersed;

(7) Add 8 parts of a mixture of potassium sulfate and dilauryl thiodipropionate, with the mass ratio of potassium sulfate to dilauryl thiodipropionate being 1:1, and continue stirring to ensure that the stabilizer is evenly distributed;

(8) The mixture is continuously stirred to ensure that all ingredients are evenly mixed, and a high shear mixer is used for homogenization to ensure the uniformity of the final composite profile control agent.

In addition, a heavy oil well test well was selected to implement the heavy oil well water plugging and profile control process, as follows:

The average porosity of a heavy oil field is 36.7%, the average air permeability is 3109×10 ^-3 μm ² , and the viscosity of degassed crude oil at formation temperature (25.8℃) ranges from 24800 to 42000 mPa·s. It is a high-porosity and high-permeability extra-heavy oil reservoir. Steam stimulation was used in the early stage of reservoir development. The oil production was 2.2 t/d and the average oil-steam ratio was 0.42. However, after high-cycle stimulation, the production decreased seriously. When the steam injection rate was too high, steam and water channeling would occur, resulting in a decrease in steam utilization and an increase in water content from 30.0% to 100%. In order to further improve the development effect of the block at a low cost, the steam stimulation was converted into hot water drive and water plugging and profile control were used for development.

The specific implementation process of water plugging and profile control is as follows:

S1: Injection of modified polymer water plugging agent into hot water well

At the designed depth of the MH6279 hot injection well, for example, the sixth layer, the modified polymer water plugging agent mentioned in Examples 1-3 is injected, with an injection volume of 120 liters each time and an injection pressure of 12 MPa; the modified polymer water plugging agent is cross-linked in the high temperature and high pressure environment of the sixth layer of the well to form a stable gel, thereby plugging the high permeability channel;

S2: Injection of composite profile control agent into heat injection well

After the injection of the modified polymer water plugging agent is completed, the composite profile control agent mentioned in Examples 1-3 is continuously injected, with an injection volume of 150 liters each time and an injection pressure of 10 MPa; the composite profile control agent can be dispersed in the reservoir pores and form a uniform profile control layer, improve the fluidity of the reservoir in the low permeability zone, and balance the flow of oil and water;

S3: Segmented injection

The segmented injection process is adopted to inject modified polymer water plugging agent and composite profile control agent into different reservoir sections respectively to ensure balanced water plugging and profile control effects in each reservoir section; specifically: 40m segment length, 15MPa maximum injection pressure limit, 25m³/h injection speed, and the reasonable segment size of water plugging agent is selected as 0.025～0.075PV;

S4: Track and analyze injection dynamic parameters and output dynamic parameters to evaluate the profile control effect when switching to hot water flooding after steam injection development of heavy oil reservoirs;

S5: Subsequent maintenance: After water plugging and profile control are completed, maintenance and re-injection are carried out every 3-6 months.

The industrial profile, water content and oil production changes of the oil well MH6279# before and after hot water flooding are shown in the following table. It can be seen that better production effects can be obtained after adopting the three embodiments of the present invention, which shows that the present invention has significant gel stability under the reservoir environment of steam channeling, water channeling and high temperature and high pressure, and can form a stable plugging layer and profile adjustment layer underground, effectively solve the problems of water channeling and interlayer interference in heavy oil wells, improve the recovery rate of heavy oil wells, and expand the application feasibility of hot water flooding after steam injection development of heavy oil reservoirs.

Table 1 Changes in water content and oil production of the heavy oil hot injection well MH6279# before and after hot water injection

The above are only some preferred embodiments of the present invention. Any person skilled in the art may modify the above technical solutions or modify them into equivalent technical solutions. Therefore, the corresponding simple modifications or equivalent transformations made according to the technical solutions of the present invention shall fall within the scope of protection claimed by the present invention.

Claims (1)

1. A water shutoff and profile control process method for a thickened oil well is characterized by comprising the following steps: the method comprises the following steps: the following components are added in parts by weight,

S1: injecting a water shutoff agent into the heat injection well: injecting a modified polymer water shutoff agent into a heat injection well of a thickened oil block, wherein the modified polymer water shutoff agent is prepared from 75-87 parts of modified polyacrylamide, 6-8 parts of modified clay, 3-5 parts of a cross-linking agent, 2-3 parts of a stabilizing agent, 1-2 parts of a composite slow release agent and 100 parts of water, and is crosslinked in a well to form gel to block a high-permeability channel;

S2: injecting profile control agent into the heat injection well: after the injection of the modified polymer plugging agent is completed, continuously injecting a composite profile control agent, wherein the composite profile control agent is prepared from 3 parts of nano microspheres, 2 parts of water-soluble polymer and 100 parts of water, and is dispersed in the pores of a reservoir to form a profile control layer;

s3: the sectional injection process comprises the following steps:

(1) Determining the positions of a high-permeability channel and a low-permeability zone in a water shutoff profile control reservoir section through logging data analysis;

(2) Injecting a modified polymer water shutoff agent into the high-permeability channel, wherein the injection amount is 100-200 liters each time, and the injection pressure is controlled to be 10-15MPa;

(3) Injecting a compound profile control agent into the low-permeability section, wherein the injection amount is 150-250 liters each time, and the injection pressure is controlled to be 8-12MPa;

(4) Switching injection sections every 2-4 hours to enable each reservoir section to be effectively injected;

s4: dynamic monitoring, comprising the following steps:

(1) Monitoring injection pressure and flow in real time by using underground monitoring equipment, and recording data;

(2) According to the real-time monitoring data, adjusting injection pressure and injection flow to uniformly distribute the modified polymer water shutoff agent and the composite profile control agent in a reservoir section;

S5: and (3) subsequent maintenance: after the water shutoff profile control is completed, maintaining and reinjecting every 3-6 months;

In the step S1, 70-80 parts of polyacrylamide with the molecular weight of 1000-1500 ten thousand is adopted as a matrix of the modified polyacrylamide; the modifier adopts 5-7 parts of nano graphene oxide, and the nano graphene oxide is combined with a polyacrylamide chain through chemical grafting;

the modified clay adopts alkyl trimethyl ammonium chloride for organic modification or aluminum sulfate ion exchange modification;

the cross-linking agent adopts polysiloxane or titanium tetraisopropoxide;

the stabilizer is a mixture of aluminum sulfate and ethylenediamine tetraacetic acid, and the mass ratio of the aluminum sulfate to the ethylenediamine tetraacetic acid is 1:1;

The compound slow release agent uses natural attapulgite or a compound material polylactic acid;

In the step S2, the nano microsphere is prepared from the following components in parts by weight: 60-70 parts of polystyrene-acrylic ester nanometer microspheres, 5-10 parts of polyethylene glycol octyl phenyl ether, 10-15 parts of gamma-methacryloxypropyl trimethoxy silane and 5-10 parts of mixed solution of high-purity water and ethanol;

The water-soluble polymer is prepared from the following components in parts by weight: 50-60 parts of a copolymer of sodium polyacrylate and polyethylene glycol, 5-10 parts of methacryloxyethyl trimethyl ammonium chloride, 15-20 parts of a mixture of guar gum and xanthan gum, and 5-10 parts of a mixture of potassium sulfate and dilauryl thiodipropionate, wherein the mass ratio of the potassium sulfate to the dilauryl thiodipropionate is 1:1;

The preparation process of the modified polymer water shutoff agent comprises the following steps: the following components are added in parts by weight,

(1) Dissolving a matrix: 70-80 parts of polyacrylamide with the molecular weight of 1000-1500 ten thousand are dissolved in deionized water to form a solution with the weight percentage concentration of 1%, and the solution is stirred uniformly;

(2) Nano modification: dispersing 5-7 parts of nano graphene oxide in water, adding surfactant Tween 80 for ultrasonic treatment for 30 minutes, and uniformly dispersing;

(3) Chemical grafting: adding the nano graphene oxide dispersion liquid into a polyacrylamide solution, keeping stirring, adding 1 part of ammonium persulfate, and reacting at 60 ℃ for 2 hours to complete grafting modification;

(4) Adding 6-8 parts of modified clay, dissolving 3-5 parts of titanium tetraisopropoxide in ethanol, adding the solution into a modified polyacrylamide solution, and uniformly stirring;

(5) 2-3 parts of a mixture of aluminum sulfate and ethylenediamine tetraacetic acid are dissolved in ethanol, the mass ratio of the aluminum sulfate to the ethylenediamine tetraacetic acid is 1:1, and then the mixture is added into a modified polyacrylamide solution, and stirring is kept, so that the mixture is uniformly dispersed;

(6) Adding 1-2 parts of a composite slow release agent into a modified polyacrylamide solution, stirring and uniformly dispersing;

(7) And (3) final blending: after all the components are uniformly mixed, the pH value of the solution is adjusted to 7.0, and the solution is kept stand for 12 hours, so that all the components fully react and form a stable modified polymer plugging agent;

the particle size of the polystyrene-acrylic ester nanometer microsphere is 50-100 nanometers;

the preparation process of the composite profile control agent comprises the following steps: the following components are added in parts by weight,

(1) Taking a mixed solution of high-purity water and ethanol as a dispersion medium, adopting 5-10 parts of the mixed solution, wherein the mass ratio of the high-purity water to the ethanol is 3:2, adding 50-60 parts of a copolymer of sodium polyacrylate and polyethylene glycol, and uniformly stirring until all the components are dissolved;

(2) Adding 60-70 parts of polystyrene-acrylic ester nanometer microspheres with the particle size of 50-100 nanometers into the solution, and stirring to uniformly disperse the solution;

(3) Adding 5-10 parts of polyethylene glycol octyl phenyl ether under stirring, and continuously stirring uniformly;

(4) Adding 10-15 parts of gamma-methacryloxypropyl trimethoxy silane under stirring, and stirring and fully mixing;

(5) Adding 5-10 parts of methacryloxyethyl trimethyl ammonium chloride into the mixed solution, and continuously stirring to uniformly distribute the mixed solution;

(6) Adding 15-20 parts of a mixture of guar gum and xanthan gum under stirring, wherein the mass ratio of the guar gum to the xanthan gum is 1:1, and stirring until the mixture of the guar gum and the xanthan gum is completely dissolved and uniformly dispersed;

(7) Adding 5-10 parts of a mixture of potassium sulfate and dilauryl thiodipropionate, and uniformly stirring the mixture in a mass ratio of 1:1;

(8) The mixture was stirred to mix all components uniformly and homogenized using a high shear stirrer.