Slow-speed automatic gas generation foam gel base solution and preparation method thereof

Abstract

The invention discloses a slow automatic gas generation foam gel base fluid and a preparation method thereof, and relates to the technical field of oil exploitation and profile control and water plugging. The slow-speed gas self-generating foam gel base solution comprises a gas generating agent, a thickening agent, a pH stabilizer, a cross-linking agent, a foaming agent and water, the gas generating agent comprises an amine substance and a nitrous acid oxidizing agent, the pH stabilizer is a buffer solution, the cross-linking agent is a cross-linking agent, and the foaming agent is a foaming agent. The cross-linking agent is a coordination compound formed by one or more of titanium ions, chromium ions, aluminum ions, zirconium ions or boron ions and organic acid. The slow-speed gas self-generating foam gel base fluid provided by the invention realizes controllability and slow speed of cross-linking reaction and gas generation reaction, and can improve the stability of the base fluid at normal temperature, prolong the cross-linking time and the gas generation period and improve the gas generation efficiency during application. The safety of the system can be enhanced, the injection pressure of the base fluid can be reduced, the plugging strength can be improved, deep profile control and plugging can be realized, and the crude oil recovery rate can be improved.

Description

Technical Field

[0001] The present invention belongs to the field of profile control and water plugging in oilfields, and specifically, relates to a retarded self-generating gas foam gel base fluid and a preparation method thereof. Background Art

[0002] As a fluid for oil displacement, foam has a relatively high apparent viscosity and good oil-water selectivity. It can break the foam when encountering oil under formation conditions and be stable when encountering water, effectively increasing the seepage resistance in the areas with a relatively high water saturation, thereby improving the recovery rate of high-water-cut oil reservoirs. However, its poor stability results in a short action period. Dai Caili combined foam with gel components in the paper "Application of Gel Foam in Water Plugging of Fractured Oil Wells in Huoshaoshan Oil Reservoir" (see "Journal of Oil and Gas Technology", 2007(01)), introducing the composition of gel foam, whose formula is 0.3% foaming agent YG240 + 0.2% - 0.4% thickener HPAM + crosslinking agent (0.09% sodium dichromate + 0.16% sodium sulfite), and the gas is nitrogen. It is confirmed that the gel can significantly improve the stability of the foam, thus greatly increasing the recovery rate. However, it requires special gas storage, gas injection, and foaming equipment, with complex operating processes, high injection pressure, and great construction difficulty.

[0003] The self-generating gas foam gel system uses a gas-generating agent to generate gas through a chemical reaction underground and then generate foam gel, effectively solving the problems of conventional foam gel. Currently, the commonly used self-generating gas system is a mixture of sodium nitrite and ammonium chloride, and the main reactions are as follows.

[0004]

[0005] Research shows that acid solution is the key factor affecting the gas generation rate and gas production efficiency. Conventional acid solutions, such as hydrochloric acid, acetic acid, etc., will significantly increase the gas generation reaction rate, resulting in an explosion risk during construction and generating toxic nitrogen oxides. At the same time, the too-fast gas generation speed is also not conducive to reducing the injection pressure and realizing deep profile control and displacement.

[0006] Wang Yefei pointed out in the paper "Reaction Characteristics of Sodium Nitrite and Ammonium Chloride" (see "Acta Petrolei Sinica", 2024, 41(02)) that the reaction kinetic equation under this self-generating gas is: dc / dt = -7.103×107c(H + ) 1.3291 c0 2.0949 *e (-51.28 / RT) , so reducing the acid solution concentration or using organic acids with low dissociation degrees helps to delay the gas generation reaction. However, the complex formation conditions will consume the acid solution and affect the actual acid solution concentration, so it has no application value.

[0007] Generating acid through the high-temperature hydrolysis reaction of in-situ acid in the high-temperature environment of the formation is another commonly used measure to control the gas production reaction. Such as organic acid esters, ammonium chloride-formaldehyde, sulfamic acid, etc. Chinese Patent CN102899012A discloses a preparation method and use of in-situ acid. The in-situ acid includes paraformaldehyde, ammonium chloride and water, and its applicable condition is high-temperature carbonate rock reservoirs. The paraformaldehyde and ammonium chloride in the in-situ acid react to generate hydrochloric acid. However, the action time of the in-situ acid in this invention is short, and the acid-rock reaction time is only 1 hour and 40 minutes, which cannot meet the requirements of deep profile control and flooding. Patents CN101712864A and CN1524922A utilize the hydrolysis of phosphate esters to delay the generation of acid solution. Its acid production rate is relatively fast at high temperature, and there will be poor environmental protection and poor biodegradability after the reaction, resulting in serious environmental pollution problems. Wang Yefei summarized and compared several common in-situ acids in the paper "A Novel In-situ N2 Generation System Assisted by In-situ Acid to Improve Formation Energy in Oilfields" (see "RSC Advances", 2024, Issue 30), such as methyl acetate (MA), ethyl acetate (EA), paraformaldehyde (PRF) and ammonium persulfate (APS). Through the hydrolysis of esters or salts at high temperature, H + is slowly released to control the purpose of gas production. However, the hydrolysis reaction rate of in-situ acid accelerates at high temperature, and the heat released by the gas production reaction further accelerates the hydrolysis, gas production and cross-linking reactions, making it impossible to achieve the purpose of retarding the rate.

[0008] The prior art discloses an indoor study of an in-situ foam gel composite plugging agent. Ammonium chloride and sodium nitrite are selected as reactants, and a large amount of N2 is released through a chemical reaction under the control of an acid catalyst. In this in-situ foam / gel system, when the addition amount of the acid catalyst is 2.0% of the strong acid and weak base sodium salt and the temperature is 60 °C, a large amount of gas can be produced after 12 h, and the gelation time is more than 16 h. Core flow experiments show that this in-situ foam / gel system can effectively plug the water-bearing core with a plugging rate of 88.1%, but the plugging effect on the oil-bearing core is poor. The application field is the conventional water shutoff and profile control operation in oilfields, and the gas production cycle of the in-situ gas does not need to be too long, making it difficult to adapt to the application field of deep profile control and flooding.

[0009] Therefore, it has important research significance and application value to develop a retarding in-situ gas-generating foam gel base fluid with appropriate strength and delayed cross-linking gas production. Summary of the Invention

[0010] The primary object of the present invention is to provide a retarding in-situ gas-generating foam gel base fluid for profile control and water shutoff in oil wells, which has appropriate strength and delayed cross-linking gas production, and does not cross-link and produce gas at room temperature, so as to overcome the problem of too fast gas production reaction and cross-linking reaction rate brought by the acid catalyst in the prior art.

[0011] Another object of the present invention is to provide a preparation method of the retarding in-situ gas-generating foam gel base fluid.

[0012] Another object of the present invention is to provide an application of the slow-release self-generating gas foam gel base fluid in oil and gas exploitation.

[0013] The above object of the present invention is achieved by the following technical solutions:

[0014] The present invention protects a slow-release self-generating gas foam gel base fluid, which comprises components in the following mass percentages:

[0015] The gas-generating agent is composed of 2% - 30% of amine substances and 2% - 30% of nitrous acid oxidants, 0.05% - 1.0% of thickener, 0.2% - 3.0% of pH stabilizer, 0.1% - 0.4% of crosslinking agent, 0.05% - 0.5% of foaming agent, and the balance is water;

[0016] Among them, the crosslinking agent is a coordination compound formed by one or more of titanium ions, chromium ions, aluminum ions, zirconium ions or boron ions and organic acids;

[0017] The pH stabilizer is a buffer solution;

[0018] The pH value of the pH stabilizer is 2.8 - 6.8;

[0019] The NH4 of the amine substance + and the NO2 of the nitrous acid oxidant - and the mass ratio of the pH stabilizer is 8 - 14:10:0.05 - 0.3.

[0020] The main active ingredient of the slow-release self-generating gas foam gel base fluid provided by this application is the gas-generating agent, which is composed of amine substances and nitrous acid oxidants that are stable at room temperature. The reaction between the two components is mainly regulated by temperature and catalyst, and can efficiently produce gas-phase products mainly composed of nitrogen within a specific pH range, with a large gas production volume, and the by-products are common inorganic salts in the formation, without the risk of secondary pollution. By introducing the synergistic pH regulation mechanism of the conjugate acid-base pair of the buffer solution and the amine substance, the former maintains the acid-base stability of the solution through the proton dynamic balance, and the latter, as a strong acid-weak base salt, dissociates to enhance the H+ concentration at high temperature. The two work together to stabilize the pH value of the solution within an appropriate range, enabling the slow-release self-generating gas foam gel base fluid to achieve controllable and slow crosslinking reaction and gas production reaction, improving the stability of the base fluid at room temperature, extending the crosslinking time and gas production cycle, and increasing the gas production efficiency when applied. It helps to enhance the safety of the system, reduce the injection pressure of the base fluid, improve the plugging strength, achieve deep profile control and plugging, and improve the oil recovery rate.

[0021] The retarded self-generated gas foam gel base fluid of the present invention has no cross-linking at room temperature, and the gas-generating component is an inorganic salt solution. The proportion of the thickener in it is small, so it shows a low-viscosity aqueous solution and has good injectability. The finally formed foam gel has both high gel strength and foam stability, forming a stable foam fluid with high viscoelasticity and significantly improving the plugging strength. The stability, viscoelasticity and long gas-generation period of the foam gel endow it with excellent erosion resistance and extend the effective action time of the plugging agent. In addition, this system can be widely applied to fields such as self-generated gas foam drainage gas recovery, foam flooding, foam water plugging and foam fracturing, replacing the traditional nitrogen injection technology. The in-situ generated nitrogen not only provides foaming gas for the foaming agent, but also can supplement formation energy and improve oil displacement efficiency. Since no additional acidic solution needs to be added, the corrosion of the system is significantly reduced. At the same time, the gas-generation rate and gas-generation amount can be conveniently regulated by adjusting the type and concentration of the buffer solution, and the chemical agent cost is low, which is suitable for large-scale on-site applications.

[0022] The retarded self-generated gas foam gel base fluid of the present invention has good stability at room temperature, does not show premature decomposition or generate toxic nitrogen oxide gases; it is safe and environmentally friendly to use, and the reaction can generate a large amount of nitrogen to increase formation energy, forming a stable foam gel system, and having the dual advantages of gel and foam at the same time, becoming a stable foam fluid with high viscoelasticity to improve the plugging strength. Due to the good stability and long gas-generation period of the foam gel, it also has strong erosion resistance and improves the long-term effectiveness of the plugging agent. And it can be used to replace various occasions that require gas injection into the formation. In short, the retarded self-generated gas foam gel base fluid of the present invention has the characteristics of safety, environmental friendliness, good injectability, convenient construction, high gas-generation amount, strong erosion resistance and good plugging effect, and has broad application prospects in the fields of improving oil and gas recovery rate and formation transformation.

[0023] Preferably, the amine substance is one or more of inorganic ammonium salts, organic ammonium salts or organic acid amides.

[0024] Specifically, the inorganic ammonium salt is selected from one or more of ammonium sulfate, ammonium nitrate, ammonium chloride or ammonium carbonate.

[0025] Specifically, the organic ammonium salt is selected from one or more of ammonium lactate, ammonium formate, ammonium acetate or ammonium sulfamate.

[0026] Specifically, the organic acid amide is selected from one or more of formamide, glutamine, lactamide or urea.

[0027] The amine is further preferably ammonium chloride.

[0028] Preferably, the mass fraction of the nitrous acid oxidant is 15% - 25%.

[0029] Preferably, the nitrous acid oxidant is one or more of sodium nitrite, potassium nitrite or nitramine. More preferably, it is sodium nitrite.

[0030] Preferably, the mass fraction of the thickener is 0.05% to 1.0%, preferably 0.4 to 1.0%.

[0031] Preferably, the thickener is one or more of polyacrylamide, partially hydrolyzed polyacrylamide, sodium carboxymethyl cellulose or guar gum. Preferably, it is partially hydrolyzed polyacrylamide.

[0032] Preferably, the pH value of the pH stabilizer is 3 to 5.

[0033] Preferably, the mass fraction of the pH stabilizer is 0.2% to 1.0%, preferably 0.4 to 0.8%.

[0034] Specifically, the pH stabilizer is a buffer solution, generally composed of a weak acid and its conjugate base or a weak base and its conjugate acid.

[0035] Preferably, the pH stabilizer is selected from one or more of acetic acid - sodium acetate, sodium dihydrogen phosphate - disodium hydrogen phosphate, potassium dihydrogen phosphate - dipotassium hydrogen phosphate, disodium hydrogen phosphate - sodium phosphate, citric acid - sodium citrate, ammonium chloride - ammonia water, sodium carbonate - sodium bicarbonate or ammonium carbonate - ammonium bicarbonate.

[0036] Preferably, the mass fraction of the cross - linker is 0.1% to 0.4%, preferably 0.1 to 0.3%.

[0037] Preferably, the organic acid in the cross - linker is one or both of acetic acid or lactic acid.

[0038] Preferably, the cross - linker is one or more of titanium acetate, chromium acetate, aluminum acetate, zirconium acetate, boron acetate, titanium lactate, chromium lactate, aluminum lactate, zirconium lactate or boron lactate.

[0039] The cross - linker is a coordination compound formed by pre - chelating metal ions and organic acids.

[0040] Preferably, the mass fraction of the foaming agent is 0.05% to 0.5%, preferably 0.2 to 0.5%.

[0041] Preferably, the foaming agent is one or more of sodium alkylbenzene sulfonate, sodium alkyl sulfate, petroleum sulfonate, betaine surfactant, fluorocarbon surfactant, silicone surfactant or sodium fatty alcohol polyoxyethylene ether sulfate. Further preferably, it is betaine surfactant.

[0042] Specifically, the water used in the present invention is tap water.

[0043] The indoor preparation method of the above-mentioned retarded self-generated gas foam gel base fluid is as follows:

[0044] At room temperature, take an appropriate amount of tap water, and successively add an appropriate amount of pH stabilizer, amine and nitrite oxidants, dissolve them in the water and stir evenly. Then add dry thickener and completely dissolve it. Finally, add foaming agent and crosslinking agent, and mix evenly to obtain the foam gel base fluid.

[0045] After mixing and stirring at room temperature, it is a uniform and stable system. The crosslinking agent in the foam gel base fluid can be prepared separately from other components and mixed evenly before use, which is convenient for long-term storage of the base fluid.

[0046] When applying the retarded self-generated gas foam gel base fluid, pump the base fluid into the core or sand-filled tube, seal both ends of the model, and heat it with an oven. The heating temperature is 70-90 °C and the time is 4-8 hours, and the self-generated gas foam gel starts to be slowly generated.

[0047] The on-site preparation method of the above-mentioned retarded self-generated gas foam gel base fluid is as follows:

[0048] Prepare the foam gel base fluid except the crosslinking agent in the liquid mixing station in advance, and add the crosslinking agent to the base fluid and mix well before construction. Transfer the prepared foam gel base fluid to the tanker; disassemble the wellhead valve of the injection well and connect the pipe manifolds of the pump truck and the tanker; open the wellhead valve and inject the retarded self-generated gas foam gel base fluid into the formation at a fixed displacement; change the water injection process, and use the injection water to clean the pipeline and the wellbore, and push the retarded self-generated gas foam gel base fluid into the formation; restore the wellhead device and disassemble the pipe manifold; when used for deep profile control, water injection can be directly started, and when used for oil well water plugging, it needs to be shut in for 4-8 hours and then the well is reopened for production.

[0049] When the retarded self-generated gas foam gel base fluid is pumped into the wellbore, the low-temperature wellbore environment can be used to avoid premature gas generation reaction and crosslinking reaction; after it enters the formation and contacts with the high-temperature rock, the temperature gradually rises to the threshold values (25 °C - 70 °C) of the gas generation reaction and crosslinking reaction, and the gas generation reaction and crosslinking reaction are started to be activated, and foam gel is gradually generated to produce a plugging effect;

[0050] Plugging high-permeability layers: The gel stays in the formation pores, plugs the high-permeability channels, forces the subsequent displacement fluid to turn to the low-permeability area, and improves the sweep efficiency.

[0051] The application of the above-mentioned retarded self-generated gas foam gel base fluid in oil and gas exploitation is also within the protection scope of the present invention.

[0052] The retarded self-generated gas foam gel base fluid is used alone or in combination with other agents, including but not limited to applications in occasions where nitrogen gas needs to be controllably generated in the formation for self-generated gas foam profile control technology, self-generated gas gas drive technology, self-generated gas foam drainage gas production, self-generated gas foam drive, and self-generated gas foam fracturing.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] The retarded self-generating gas foam gel base fluid of the present invention comprises: a gas-generating agent, a thickening agent, a pH stabilizer, a cross-linking agent, a foaming agent and water. Among them, the gas-generating agent comprises an amine substance and a nitrous acid oxidant, the pH stabilizer is a buffer solution, and the cross-linking agent is a coordination compound formed by one or more of titanium ions, chromium ions, aluminum ions, zirconium ions or boron ions and an organic acid. The retarded self-generating gas foam gel base fluid of the present invention realizes the controllability and retardation of the cross-linking reaction and the gas-generating reaction, can improve the stability of the base fluid at normal temperature during application, extend the cross-linking time and the gas-generating cycle, and improve the gas-generating efficiency. It helps to enhance the safety of the system, reduce the injection pressure of the base fluid, improve the plugging strength, realize deep profile control and plugging, and improve the crude oil recovery rate. Description of the Drawings

[0055] Figure 1 It is a graph showing the change of RF / RRF with the number of injected PVs during the injection process of the self-generating gas foam gel in Example 13 into a low-permeability model;

[0056] Figure 2 It is a graph showing the change of RF / RRF with the number of injected PVs during the injection process of the self-generating gas foam gel in Example 14 into a medium-permeability model;

[0057] Figure 3 It is a graph showing the change of RF / RRF with the number of injected PVs during the injection process of the self-generating gas foam gel in Example 15 into a high-permeability model;

[0058] Figure 4 It is a graph showing the change of the gas-generation rate and the gas-generation amount of the self-generating gas foam gel in Comparative Example 1 during strong acid catalysis;

[0059] Figure 5 It is a graph showing the change of the gas-generation amount with time of the self-generating gas foam gel in Comparative Example 2 during weak acid catalysis;

[0060] Figure 6 It is a graph showing the change of the gas-generation amount with time of the self-generating gas foam gel in Comparative Example 3 during sulfamic acid catalysis;

[0061] Figure 7 It is a graph showing the change of the gas-generation amount with time of the self-generating gas foam gel in Comparative Example 4 during organic acid ester catalysis;

[0062] Figure 8 It is a graph showing the change of temperature and pressure of the high-concentration gas-generating agent without a pH regulator in Comparative Example 7;

[0063] Figure 9 It is a graph showing the change of temperature and pressure of the high-concentration gas-generating agent with a pH stabilizer in Comparative Example 9;

[0064] Figure 10 This is a physical picture of the self-generated gas foam gel sample. Specific embodiments

[0065] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw material reagents used in the embodiments of the present invention are conventionally purchased raw material reagents.

[0066] (1) Method for evaluating the performance of foam gel:

[0067] Preheat the constant temperature water bath to 70 °C. Take 100 g of the prepared foam gel base liquid and add it to a 1000 mL graduated cylinder, and place the graduated cylinder in the water bath for heating to promote the cross-linking reaction and gas generation reaction of the foam gel base liquid, and generate a viscoelastic foam gel. Record the volume of the foam gel in the graduated cylinder every hour, and the foam gel strength is evaluated by the following code method.

[0068] Table 1 Evaluation criteria of visual inspection code method

[0069]

[0070] (2) Method for evaluating the profile control performance:

[0071] Fill 1% sodium chloride solution and foam gel base liquid in the intermediate container respectively. Pack quartz sand in the sand-packed tube, and set the back pressure at the outlet end to 3 MPa. Measure the initial permeability K1, pore volume of the sand-packed tube by water flooding and calculate the porosity. Use a peristaltic pump to perform water flooding at a speed of 1 mL / min, and record the pre-water flooding pressure difference ΔP1; then inject 0.4 PV of the slow-release self-generated gas foam gel base liquid, and record the maximum injection pressure difference ΔP2; then seal the tube and heat it in an oven at 70 °C for 8 hours. After the reaction is completed, perform subsequent water flooding and record the subsequent water flooding pressure difference ΔP3. Calculate the permeabilities K1, K2, K3 at each stage according to Darcy's formula, and calculate the resistance coefficient, residual resistance coefficient and plugging rate, where RF is used to reflect the injectability of the foam gel base liquid, and RRF reflects the long-term water plugging ability of the foam gel;

[0072] Among them, Darcy's formula: K = 100×QμL / 60×A×△P

[0073] Resistance coefficient: RF = K1 / K2

[0074] Residual resistance coefficient: RRF = K1 / K3

[0075] Plugging rate: η = (K1 - K3) / K1

[0076] In the formula

[0077] Q—the flow rate through the core under the pressure difference of △P, cm 3 / s;

[0078] A——Cross-sectional area of the core, cm 2 ;

[0079] L——Length of the core, cm;

[0080] μ——Fluid viscosity, mPa ● s;

[0081] △P——Pressure difference before and after passing through the core, atm;

[0082] K1——Permeability before plugging, mD;

[0083] K2——Permeability during the injection of the foam gel base fluid, mD;

[0084] K3——Permeability after plugging, mD;

[0085] η——Plugging rate, %.

[0086] (3) Gas production measurement method:

[0087] At atmospheric pressure: Conduct an experiment on the gas production of the self-generated gas system under atmospheric pressure using a graduated cylinder. Preheat the constant temperature water bath to 70°C in advance. Take 100 g of the prepared foam gel base fluid and add it to a 1000 mL graduated cylinder, and then place the graduated cylinder in the water bath for heating to promote the cross-linking reaction and gas production reaction of the foam gel base fluid, and generate viscoelastic foam gel. Record the volume of the foam gel in the graduated cylinder every hour. Stop the experiment when the volume of the foam gel is basically stable. The final gas production is reflected by the foam volume;

[0088] At high pressure: Conduct an experiment on the gas production of the self-generated gas system under high pressure using a high-temperature and high-pressure reaction kettle. Add 150 mL of the reaction solution to a 250 mL high-temperature and high-pressure reaction kettle, and set the heating rate to 10°C / min to start heating. Stop the experiment when the temperature and pressure are basically stable. Record the temperature and pressure changes during the gas production process. When the temperature drops to 25°C, relieve the pressure and clean the reaction kettle.

[0089] (4) Gas production efficiency measurement method:

[0090] Calculated by the ratio of the actual gas production to the theoretical gas production:

[0091] Among them, the formula for theoretical gas production: V0 = n0RT / P

[0092] The formula for gas production efficiency: η = (V1 / V0) × 100%

[0093] In the formula:

[0094] P——Pressure, Pa;

[0095] V0——Theoretical gas production volume, m 3 ;

[0096] V1——Actual gas production volume, m 3 ;

[0097] n0——Theoretical amount of gas-producing substance, mol;

[0098] R——Molar gas constant, R = 8.314 J / (mol·K);

[0099] T——Thermodynamic temperature, K;

[0100] η——Gas production efficiency, %.

[0101] Example 1 A retarded self-generating gas foam gel base fluid and its preparation method

[0102] A retarded self-generating gas foam gel base fluid, with a total amount of 100 g, and each component is in mass percentage,

[0103] including: 5% amine substance ammonium chloride, 5% nitrite oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.36% pH stabilizer (pH = 6), 0.3% cross-linking agent chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance is tap water. The pH stabilizer is a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with pH = 6.

[0104] The preparation method of the retarded self-generating gas foam gel base fluid includes the following steps:

[0105] In a 250 mL beaker, add tap water and then turn on the stirrer. Set the stirrer speed to 150 - 300 rad / min. Sequentially add the phosphate buffer system with pH = 6, amine substance, nitrite oxidant, thickener, and foaming agent into the beaker and stir evenly to fully dissolve them. Add the cross-linking agent before use and stir and mix evenly to obtain the foam gel base fluid.

[0106] The pH stabilizer of Example 1 is a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with pH = 6. There is no reaction at room temperature for 24 h. After 2 h of water bath heating at 70 °C, the foam volume is 50 mL, and its foam has all gelled. After 24 h of water bath heating, the foam height reaches 800 mL.

[0107] Example 2 A retarded self-generating gas foam gel base fluid and its preparation method

[0108] A retarded self-generating gas foam gel base fluid, with a total amount of 100 g, and each component is in mass percentage,

[0109] Comprising: 5% amine substance ammonium chloride, 5% nitrous acid oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.36% pH stabilizer (pH = 3), 0.3% crosslinking agent chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance being tap water. Different from Example 1, the pH stabilizer is a phosphate buffer system composed of phosphoric acid - sodium dihydrogen phosphate with pH = 3.

[0110] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0111] When Example 2 uses a phosphate buffer system with pH = 3, due to its relatively low pH and high hydrogen ion concentration in the system, weak bubbles slowly emerge at room temperature, but not significantly. The gas generation period is 2 h at 70 °C.

[0112] Example 3 A retarded self - generating gas foam gel base fluid and its preparation method

[0113] A retarded self - generating gas foam gel base fluid, with a total amount of 100 g, and each component is calculated by mass percentage.

[0114] Comprising: 5% amine substance ammonium chloride, 5% nitrous acid oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.36% pH stabilizer (pH = 5), 0.3% crosslinking agent chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance being tap water. Different from Example 1, the pH stabilizer is a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with pH = 5.

[0115] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0116] When Example 3 uses a phosphate buffer system with pH = 5, the system is more stable than the phosphate buffer system with pH = 3. It can be stored at room temperature for 24 h without obvious gas generation, and the gas generation period is 24 h at 70 °C.

[0117] Example 4 A retarded self - generating gas foam gel base fluid and its preparation method

[0118] A retarded self - generating gas foam gel base fluid, with a total amount of 100 g, and each component is calculated by mass percentage.

[0119] Comprising: 5% amine substance urea, 5% nitrous acid oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.36% pH stabilizer (pH = 6), the pH stabilizer is a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with pH = 6, 0.3% crosslinking agent chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance being tap water. Different from Example 1, the amine substance is urea.

[0120] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0121] The amine substance in Example 4 is urea, and there is no reaction at room temperature for 24 h. After 2 h of water bath heating at 70 °C, the foam volume is 120 mL, and all the foams have formed gels.

[0122] Example 5 A retarded self - generating gas foam gel base fluid and its preparation method

[0123] A retarded self - generating gas foam gel base fluid with a total amount of 100 g, and each component is in mass percentage.

[0124] It includes: 5% amine substance ammonium sulfamate, 5% nitrite oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.36% pH stabilizer (pH = 6), the pH stabilizer is a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with pH = 6, 0.3% cross - linker chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance is tap water. Different from Example 1, the amine substance is ammonium sulfamate.

[0125] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0126] The amine substance in Example 5 is ammonium sulfamate, and there is no reaction at room temperature for 24 h. After 2 h of water bath heating at 70 °C, the foam volume is 60 mL, and all the foams have formed gels.

[0127] Example 6 A retarded self - generating gas foam gel base fluid and its preparation method

[0128] A retarded self - generating gas foam gel base fluid with a total amount of 100 g, and each component is in mass percentage.

[0129] It includes: 5% amine substance acetamide, 5% nitrite oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.36% pH stabilizer (pH = 6), the pH stabilizer is a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with pH = 6, 0.3% cross - linker chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance is tap water. Different from Example 1, the amine substance is acetamide.

[0130] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0131] The amine substance in Example 6 is acetamide, and there is no reaction at room temperature for 24 h. After 2 h of water bath heating at 70 °C, the foam volume is 60 mL, and all the foams have formed gels.

[0132] Example 7 A retarded self - generating gas foam gel base fluid and its preparation method

[0133] A kind of retarded self - generating gas foam gel base fluid, with a total amount of 100 g. Each component is calculated by mass percentage,

[0134] including: 5% amine substance lactic acid amide, 5% nitrous acid - type oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.36% pH stabilizer (pH = 6), the pH stabilizer is a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with pH = 6, 0.3% cross - linker chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance is tap water.

[0135] The difference from Example 1 is that the amine substance is lactic acid amide.

[0136] The liquid - preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0137] When the amine substance in Example 7 is lactic acid amide, there is no reaction at room temperature for 24 h. After 2 h of water - bath heating at 70 °C, the foam volume is 55 mL, and all the foams have formed gels.

[0138] Example 8 A kind of retarded self - generating gas foam gel base fluid and its preparation method

[0139] A kind of retarded self - generating gas foam gel base fluid, with a total amount of 100 g. Each component is calculated by mass percentage,

[0140] including: 5% amine substance ammonium chloride, 5% nitrous acid - type oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.36% pH stabilizer (pH = 6), 0.3% cross - linker chromium acetate, 0.2% foaming agent sodium dodecyl polyoxyethylene sulfate, and the balance is tap water. The difference from Example 1 is that the pH stabilizer is an acetic acid - sodium acetate buffer system with pH = 6, and the foaming agent is sodium dodecyl polyoxyethylene sulfate.

[0141] The liquid - preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0142] The pH stabilizer in Example 8 is an acetic acid - sodium acetate buffer system with pH = 6, and the foaming agent is sodium dodecyl polyoxyethylene sulfate. There is no reaction at room temperature for 24 h. After 2 h of water - bath heating at 70 °C, the foam volume is 50 mL, and all the foams have formed gels.

[0143] Example 9 A kind of retarded self - generating gas foam gel base fluid and its preparation method

[0144] A kind of retarded self - generating gas foam gel base fluid, with a total amount of 100 g. Each component is calculated by mass percentage,

[0145] It includes: 5% of amine substances such as ammonium chloride, 5% of nitrous acid oxidant sodium nitrite, 0.3% of thickener partially hydrolyzed polyacrylamide, 0.36% of pH stabilizer (pH = 6), 0.3% of crosslinking agent chromium acetate, 0.2% of foaming agent sodium dodecyl sulfate, and the balance is tap water. Different from Example 1, the pH stabilizer is a sodium carbonate - sodium bicarbonate buffer system with pH = 6, and the foaming agent is sodium dodecyl sulfate.

[0146] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0147] The pH stabilizer in Example 9 is a sodium carbonate - sodium bicarbonate buffer system with pH = 6, and the foaming agent is sodium dodecyl sulfate. There is no reaction at room temperature for 24 h. After 2 h of water bath heating at 70 °C, the foam volume is 50 mL, and its foam has all gelled.

[0148] Example 10 A retarded self - generating gas foam gel base fluid and its preparation method

[0149] A retarded self - generating gas foam gel base fluid, with a total amount of 100 g, and each component is calculated by mass percentage.

[0150] It includes: 5% of amine substances such as ammonium chloride, 5% of nitrous acid oxidant sodium nitrite, 0.3% of thickener partially hydrolyzed polyacrylamide, 0.36% of pH stabilizer (pH = 6), the pH stabilizer is a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with pH = 6, 0.3% of crosslinking agent chromium acetate, 0.2% of foaming agent fluorocarbon surfactant, and the balance is tap water. Different from Example 1, the foaming agent is fluorocarbon surfactant.

[0151] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0152] The pH stabilizer in Example 10 is a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with pH = 6, and the foaming agent is fluorocarbon surfactant. There is no reaction at room temperature for 24 h. After 2 h of water bath heating at 70 °C, the foam volume is 50 mL, and its foam has all gelled.

[0153] Example 11 A retarded self - generating gas foam gel base fluid and its preparation method

[0154] A retarded self - generating gas foam gel base fluid, with a total amount of 100 g, and each component is calculated by mass percentage.

[0155] It includes: 5% of amine substances such as ammonium chloride, 5% of nitrous acid oxidant sodium nitrite, 0.3% of thickener partially hydrolyzed polyacrylamide, 0.36% of pH stabilizer (pH = 6), 0.3% of crosslinking agent organo - aluminum, 0.2% of foaming agent dodecyl betaine, and the balance is tap water. Different from Example 1, the crosslinking agent is aluminum acetate.

[0156] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0157] When the crosslinking agent is organoaluminum, the gelation strength of the HPAM-organoaluminum system can reach G by the visual inspection code method, but the gelation time is shorter, and the gas production performance is the same as that in Example 1.

[0158] Example 12 A retarded self-generating gas foam gel base fluid and its preparation method

[0159] The experimental method is the same as that in Example 1, except that the mass concentration of the pH stabilizer is 3%.

[0160] Test results: The pH stabilizer in Example 12 is a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with pH = 6. When the dosage is increased to 3%, there is no reaction at room temperature for 24 h. After 2 h of water bath heating at 70 °C, the foam volume is 125 mL, and all the foams have gelled. After 24 h of water bath heating, the foam height reaches 800 mL.

[0161] Example 13 A retarded self-generating gas foam gel base fluid and its preparation method

[0162] A retarded self-generating gas foam gel base fluid with a total amount of 100 g, and the components are in mass percentages and the liquid preparation method are the same as those in Example 1.

[0163] In the profile control performance evaluation experiment of this Example 13, different permeability core effects are achieved by controlling the mesh number of quartz sand. Example 13 controls the permeability to 80 mD by filling quartz sand with a mesh number of 120 - 150, which belongs to the simulation of the profile control performance experiment of a low-permeability reservoir physical model experiment;

[0164] As Figure 1 shown, for water plugging in low-permeability reservoirs, it can be clearly seen that it can ensure a relatively high displacement pressure difference, and under the subsequent water flooding conditions of more than 10 PV, there is still a plugging rate of 96%, with a resistance coefficient of 12.4 and a residual resistance coefficient of 58.

[0165] Example 14 A retarded self-generating gas foam gel base fluid and its preparation method

[0166] A retarded self-generating gas foam gel base fluid with a total amount of 100 g, and the components are in mass percentages and the liquid preparation method are the same as those in Example 1.

[0167] In the profile control performance evaluation experiment of this Example 14, different permeability core effects are achieved by controlling the mesh number of quartz sand. Example 14 controls the permeability to 200 mD by filling quartz sand with a mesh number of 80 - 100, which belongs to the simulation of the profile control performance experiment of a medium-permeability reservoir physical model experiment;

[0168] AsFigure 2 As shown in the figure, for water plugging in medium-permeability oil reservoirs, it can be clearly seen that it can ensure a relatively high displacement pressure difference. And under the subsequent water flooding conditions of more than 10 PV, the plugging rate can still reach 99.59%. Its resistance coefficient is 6, and the residual resistance coefficient is 326.92.

[0169] Example 15 A retarded self-generating foam gel base fluid and its preparation method

[0170] A retarded self-generating foam gel base fluid with a total amount of 100 g, and the components are in mass percentage and the liquid preparation method is the same as that in Example 1.

[0171] In the profile control performance evaluation experiment of this Example 15, different permeability core effects were achieved by controlling the mesh number of quartz sand. Example 15 filled quartz sand with a mesh number of 50 - 70 to control the permeability to 1500 mD, which belongs to the simulation of the profile control performance experiment of the physical model experiment of high-permeability oil reservoirs;

[0172] As Figure 3 shown in the figure, for water plugging in high-permeability oil reservoirs, it can be clearly seen that it can ensure a relatively high displacement pressure difference. And under the subsequent water flooding conditions of more than 10 PV, the plugging rate can still reach 99.92%. Its resistance coefficient is 14, and the residual resistance coefficient is 551.

[0173] Comparative Example 1 A retarded self-generating foam gel base fluid and its preparation method

[0174] A retarded self-generating foam gel base fluid with a total amount of 100 g, and the components are in mass percentage,

[0175] including: 5% amine substance ammonium chloride, 5% nitrite oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.3% crosslinking agent chromium acetate, dilute hydrochloric acid, 0.2% foaming agent dodecyl betaine, and the balance is tap water. Different from Example 1, no pH stabilizer is added, and 5% hydrochloric acid solution is added instead, so that its concentration in the base fluid is 0.1 mol / L, 0.01 mol / L, and 0.001 mol / L respectively.

[0176] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1. Since the reaction rate between 5% hydrochloric acid and the gas generating agent is too fast during liquid preparation, a peristaltic pump is used for dropping the sample

[0177] Replace the pH stabilizer with 5% hydrochloric acid, so that its concentration in the base fluid is 0.1 mol / L, 0.01 mol / L, and 0.001 mol / L respectively. As Figure 4As shown, it can be clearly observed that gas production starts from the base fluid at room temperature, and as the acid concentration increases, the gas production rate accelerates. The maximum gas production volume is only 165 mL, and the gas production efficiency is only 14.7%. Also, due to the unstable pH value of the base fluid, the gelation speed is relatively fast and the strength is relatively small. The visual code method evaluation is only B;

[0178] Therefore, when using a low-concentration strong acid solution, the gas production process mainly concentrates in the initial stage, the gas production efficiency is relatively low, and it cannot delay gas production and crosslinking.

[0179] Comparative Example 2 A slow-release self-generating gas foam gel base fluid and its preparation method

[0180] A slow-release self-generating gas foam gel base fluid, with a total amount of 100 g, and each component is calculated by mass percentage.

[0181] It includes: 5% amine substance ammonium chloride, 5% nitrite oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 3% organic acid, 0.3% crosslinker chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance is tap water. Different from Example 1, no pH stabilizer is added, and 3% organic acid: acetic acid is used instead.

[0182] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1. Since the reaction rate between the organic acid with a concentration of 10% and the gas-generating agent is too fast during liquid preparation, a peristaltic pump is used for dropping, and the addition amount is 3%;

[0183] When replacing the pH stabilizer with 3% acetic acid by mass percentage, it can be clearly observed that the overall gas production volume of the system is relatively high compared to strong acids, and the gas production rate is relatively slow. However, gas production also starts at room temperature, the gas production volume is 380 mL, the gas production efficiency is 32.4%, the gelation strength is poor, and the visual code method evaluation is only B;

[0184] Therefore, organic acids cannot delay gas production and crosslinking.

[0185] Comparative Example 3 A slow-release self-generating gas foam gel base fluid and its preparation method

[0186] A slow-release self-generating gas foam gel base fluid, with a total amount of 100 g, and each component is calculated by mass percentage.

[0187] It includes: 5% amine substance ammonium chloride, 5% nitrite oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 3% aminosulfonic acid, 0.3% crosslinker chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance is tap water. Different from Example 1, no pH stabilizer is added, and 3% aminosulfonic acid is used instead.

[0188] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1. Since the reaction rate between sulfamic acid with a concentration of 10% and the gas-generating agent is too fast during liquid preparation, a peristaltic pump is used for dropping samples, and the addition amount is 3%.

[0189] When replacing the pH stabilizer with 3% sulfamic acid by mass percentage, as Figure 6 shown, it can be observed more obviously that the overall gas production of the system is relatively high compared with strong acids and organic acids, the gas production cycle is extended, and the entire gas production process can be extended to about 7 h. The final gas production volume can reach 415 mL, and the gas production efficiency is 37.5%.

[0190] However, when sulfamic acid is used as an externally added self-generated acid, it has strong acidity (pH = 1). When mixed with the gas-generating agent at room temperature, it will react quickly and be accompanied by the generation of toxic red-brown nitrogen oxide gas. The gel strength formed is poor, and the visual code method is B;

[0191] Through Figure 5 and Figure 6 , it is obtained that sulfamic acid can delay gas production and cross-linking reactions, but the initial gas production rate is very high, toxic gas is generated, and the gel strength is also weak.

[0192] Comparative Example 4 A retarded self-generating gas foam gel base fluid and its preparation method

[0193] A retarded self-generating gas foam gel base fluid with a total amount of 100 g. Each component is calculated by mass percentage,

[0194] including: 5% amine substance ammonium chloride, 5% nitrite oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 3% methyl acetate, 0.3% cross-linking agent chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance is tap water. Different from Example 1, no pH stabilizer is added, and 3% methyl acetate is used instead.

[0195] The liquid preparation method and performance evaluation method of the foam gel are the same as those in Example 1.

[0196] When the added component is self-generated acid methyl acetate, it can be observed more obviously that the overall gas production of the system is relatively high compared with strong acids and organic acids, the gas production cycle is extended to 7 hours, the gas production volume is 430 mL, and the gas production efficiency reaches 38.4%. However, the foam stability and colloid strength are poor.

[0197] Therefore, although ester substances can also delay gas production and cross-linking reactions, the methanol decomposed is not conducive to foam stability, and ester substances have poor water solubility, are flammable and toxic, which is not conducive to on-site construction.

[0198] Comparative Example 5 A retarded self-generating gas foam gel base fluid and its preparation method

[0199] The experimental method was the same as that of Example 1, except that the pH stabilizer was a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with a pH of 2.

[0200] Test results: The pH stabilizer of Comparative Example 5 was a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with a pH of 2. A relatively obvious gas - generating reaction began at room temperature, and the final gas - generated volume could reach 800 mL, with a gas - generating efficiency of 71.4%. However, due to the too - low pH, the gas - generating time was less than 2 h, resulting in no cross - linking reaction occurring at this time, the foam stability becoming poor, and finally the volume of the foam gel decreasing.

[0201] Comparative Example 6 A retarded self - generating gas foam gel base fluid and its preparation method

[0202] The experimental method was the same as that of Example 1, except that the pH stabilizer was a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with a pH of 7.5.

[0203] Test results: The pH stabilizer of Comparative Example 6 was a phosphate buffer system composed of sodium dihydrogen phosphate - disodium hydrogen phosphate with a pH of 7.5. There was no obvious gas - generating reaction. After heating, the viscosity of the system increased slightly, the fluidity became poor, and finally the foam volume was only 50 mL, and the foam gel code was only B.

[0204] Comparative Example 7 A retarded self - generating gas foam gel base fluid and its preparation method

[0205] A retarded self - generating gas foam gel base fluid, with a total amount of 100 g, and each component was calculated by mass percentage.

[0206] It included: 25% amine substance ammonium chloride, 25% nitrite oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.3% cross - linker chromium acetate, 0.2% foaming agent dodecyl betaine, and the balance was tap water.

[0207] The method for preparing the liquid of the foam gel was the same as that of Example 1.

[0208] The method for evaluating the gas - generating performance was as described in the high - pressure gas - generating amount test method in the gas - generating amount test.

[0209] The experimental results were as Figure 8 shown. When there was no pH stabilizer to stabilize the reaction, the reaction heat would accelerate the gas - generating reaction. The temperature in the autoclave could rise rapidly to 280 °C within 1 hour, the gas - generating amount was 7800 mL, and the final gas - generating efficiency was 77.4%.

[0210] Comparative Example 8 A retarded self - generating gas foam gel base fluid and its preparation method

[0211] The experimental method was the same as that of Example 1, except that it included: 35% amine substance ammonium chloride, 35% nitrous acid oxidant sodium nitrite, and 0.1% pH stabilizer (pH = 6).

[0212] Test results: The increased dosage of the substances intensified the reaction. At this time, due to the too small dosage of the pH stabilizer, the reaction heat accelerated the gas generation reaction. The temperature in the autoclave could rise sharply to 280 °C within 1 hour, the gas generation volume was 9316 mL, and the final gas generation efficiency was 81.99%.

[0213] Comparative Example 9 A slow-release self-generating gas foam gel base fluid and its preparation method

[0214] The experimental method was the same as that of Example 1, except that it included: 35% amine substance ammonium chloride, 35% nitrous acid oxidant sodium nitrite, and 4% pH stabilizer (pH = 6).

[0215] The experimental results were as Figure 9 shown. When the pH regulator was added, the gas generation reaction was very stable, and gas was continuously generated within 150 hours. The temperature in the autoclave was basically stable at the set temperature of 60 °C, the gas generation volume was 7200 mL, and the final gas generation efficiency was 71.9%.

[0216] Comparative Example 10 A slow-release self-generating gas foam gel base fluid and its preparation method

[0217] A slow-release self-generating gas foam gel base fluid, with a total amount of 100 g, and each component was in mass percentage,

[0218] including: 5% amine substance ammonium chloride, 5% nitrous acid oxidant sodium nitrite, 0.3% thickener partially hydrolyzed polyacrylamide, 0.36% phosphate buffer system with pH = 6, 0.3% crosslinking agent glutaraldehyde, 0.2% foaming agent dodecyl betaine, and the balance was tap water. Different from Example 1, the crosslinking agent was glutaraldehyde.

[0219] The liquid preparation method and performance evaluation method of the foam gel were the same as those of Example 1.

[0220] Table 1 Detection results of Examples and Comparative Examples

[0221]

[0222]

[0223] It can be seen from Table 1 that Examples 1 to 12 provided a series of slow-release self-generating gas foam gel base fluids with good stability and long gas generation cycles, and Example 1 was the best. The strength of the slow-release self-generating gas foam gel base fluids in Examples 1 to 12 was in the range of F to G, and the strength was appropriate.

[0224] Table 2 Detection results of the plugging effect of Examples

[0225] Example Permeability / mD Resistance coefficient Residual resistance coefficient Blocking ratio 13# 80 12.4 58.0 96.00％ 14# 200 6.0 326.9 99.59％ 15# 1500 14.0 551.0 99.92％

[0226] Examples 13 to 15 were used to conduct a displacement performance evaluation experiment on the components of the retarded self - generating gas foam gel base fluid in Example 1 to evaluate the plugging effect of the retarded self - generating gas foam gel base fluid under different permeability conditions.

[0227] It can be seen from the data in Table 2 that under different permeability conditions, the RF of the self - generating gas foam gel is relatively small, showing good injectability requirements. The pressure differences in the subsequent water flooding are relatively high. Even when displaced to 10 times the pore volume, excellent plugging effects are still demonstrated, confirming its ability to long - term plug water - channeling channels.

[0228] In Comparative Example 1, strong acid HCl was added. Since hydrochloric acid will completely ionize, gas production in the base fluid began at room temperature after mixing, and as the acid concentration increased, the gas production rate accelerated. The maximum gas production volume was only 165 mL, and the gas production efficiency was only 14.7%. And due to the unstable pH value of the base fluid, the gelation speed was relatively fast and the strength was relatively small. The visual code method evaluation was only B, and it could not achieve the effect of delaying gas production and cross - linking.

[0229] In Comparative Example 2, acetic acid was added. Since acetic acid can continuously ionize H + in the solution, it can be more obviously observed that the overall gas production volume of the system is relatively higher than that of strong acid, and the gas production rate is relatively slow. However, gas production also started at room temperature. The gas production volume was 380 mL, and the gas production efficiency was 32.4%. The gelation strength was poor, and the visual code method evaluation was only B. Therefore, organic acids cannot delay gas production and cross - linking.

[0230] In Comparative Example 3, self - generating acid sulfamic acid was added. Since it can slow down the release rate of hydrogen ions, the gas production rate can be slowed down. It can be more obviously observed that the overall gas production volume of the system is relatively higher than that of strong acid and organic acid, the gas production cycle is lengthened, and the entire gas production process can be extended to about 5 h. The final gas production volume can reach 415 mL, and the gas production efficiency is 37.5%. However, due to its own certain acidity (pH is about 1), the initial gas production rate is relatively high. When mixed with the gas - generating agent at room temperature, it will react quickly and be accompanied by the generation of toxic red - brown nitrogen oxide gas. And due to the instability of pH, the gel strength formed is poor, and the visual code method is B.

[0231] In Comparative Example 4, self - generating acid methyl acetate was added. It can be more obviously observed that the overall gas production volume of the system is relatively higher than that of strong acid and organic acid, the gas production cycle is extended to 7 hours, the gas production volume is 430 mL, and the gas production efficiency reaches 38.4%. Although it can delay gas production and cross - linking reactions, the methanol decomposed from the ester substances is not conducive to foam stability and affects the final foam gel effect.

[0232] In Comparative Example 5, the pH value of the pH stabilizer was too low, the gas generation time was less than 2 h, and the foam stability was poor; in Comparative Example 6, the pH value of the pH stabilizer was too high, and the foam gel strength was low; in Comparative Example 7, no pH stabilizer was added, the gas generation reaction proceeded rapidly, and the delaying effect could not be achieved; in Comparative Example 8, the amount of the pH stabilizer added was too small, resulting in the failure to stabilize the pH; in Comparative Example 9, the amount of the pH stabilizer added was too large, the gas generation amount decreased significantly, and the gel strength was weak; in Comparative Example 10, glutaraldehyde was used as the crosslinking agent, and the gel formation strength of the HPAM-aluminum organic system was only at Grade C by the visual inspection code method, belonging to a weak gel. The gas generation performance was the same as that of Example 1. Because the crosslinking condition of glutaraldehyde was under alkaline conditions, but the influence of alkaline conditions on the gas generation performance was great, which would greatly reduce the gas generation efficiency.

[0233] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A retarded self-generated gas foam gel base fluid, characterized in that, Comprising components in the following mass percentages: The gas-generating agent consists of 2% - 30% of amine substances and 2% - 30% of nitrous acid oxidants, 0.05% - 1.0% of thickener, 0.2% - 3.0% of pH stabilizer, 0.1% - 0.4% of cross-linking agent, 0.05% - 0.5% of foaming agent, and the balance is water; Among them, the cross-linking agent is a coordination compound formed by one or more of titanium ions, chromium ions, aluminum ions, zirconium ions or boron ions and organic acids; The pH stabilizer is a buffer solution; The pH value of the pH stabilizer is 2.8 - 6.8; NH4 of the amine substance + 、NO2 of the nitrous acid oxidant - and the pH stabilizer are in a mass ratio of 8 to 14:10:0.05 to 0.

3.

2. The retarded self-generating foam gel base fluid according to claim 1, characterized in that, The amine substances are one or more of inorganic ammonium salts, organic ammonium salts or organic acid amides.

3. The retarded self-generated gas foam gel base fluid according to claim 1, characterized in that, The nitrous acid oxidants are one or more of sodium nitrite, potassium nitrite or nitrosamine.

4. The retarded self-generating foam gel base fluid according to claim 1, wherein The mass fraction of the pH stabilizer is 0.2% - 1.0%.

5. The retarded self-generating foam gel base fluid according to claim 1, characterized in that The thickener is a water-soluble polymer compound.

6. The retarded self-generating foam gel base fluid according to claim 1, wherein The pH stabilizer is selected from one or more of acetic acid - sodium acetate, sodium dihydrogen phosphate - disodium hydrogen phosphate, potassium dihydrogen phosphate - dipotassium hydrogen phosphate, disodium hydrogen phosphate - sodium phosphate, citric acid - sodium citrate, ammonium chloride - ammonia water, sodium carbonate - sodium bicarbonate or ammonium carbonate - ammonium bicarbonate.

7. The retarded self-generating foam gel base fluid according to claim 1, wherein The foaming agent is a high-temperature resistant water-soluble surfactant.

8. The retarder self-generating gas foam gel base fluid according to claim 1, wherein The organic acid in the cross-linking agent is one or both of acetic acid or lactic acid.

9. A preparation method of the retardant self-generated gas foam gel base fluid according to any one of claims 1 to 8, characterized in that, Including the following steps: Take an appropriate amount of tap water at room temperature, add an appropriate amount of pH stabilizer, amine and nitrous acid oxidants in sequence and dissolve them by stirring evenly, then add the thickener dry powder and dissolve it completely, and finally add the foaming agent and cross-linking agent, and mix evenly to obtain the foam gel base liquid.

10. Application of the retarded self-generating gas foam gel base liquid according to any one of claims 1 - 8 in oil and gas exploitation.

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