A composite oil well intelligent deblocking method

Abstract

The present application relates to the technical field of oilfield development, and more particularly to a composite oil well intelligent unblocking method, comprising: obtaining rock types and plugging types of the oil well; configuring alkaline and acidic unblocking agents; injecting the alkaline unblocking agent, soaking the well, and pulse flowback; delivering the alkaline and acidic unblocking agents to the oil well according to a preset ratio; continuously detecting the temperature in the oil well, adjusting the ratio of the acidic and alkaline unblocking agents according to the backflow pH value and the measured temperature in the oil well; detecting the particle size in the backflow liquid until the particle size is less than a preset particle size; performing hot flushing and pressure recovery testing, calculating the skin coefficient, and determining that unblocking is successfully completed when the skin coefficient decreases to within a standard range. The heat generated by the neutralization reaction can melt the residual paraffin and asphalt, reduce their viscosity, and make them more easily dissolved and discharged by the unblocking agent, thereby improving the unblocking effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield development, and particularly relates to a composite oil well intelligent plugging removal method. BACKGROUND

[0002] In the process of oilfield development, crude oil often needs to be lifted from the well bottom to the ground. In the process of oil and gas flow moving from the well bottom to the well mouth, impurities such as resin and asphaltene contained in the crude oil gradually precipitate as the temperature continuously decreases, and heavy organic and inorganic plugging is easily generated in the formation and wellbore.

[0003] Patent No. CN107558955A discloses a method for removing plugging in oil wells by using microorganisms, which comprises: taking core samples from the oil well to analyze the plugging; determining the concentration of organic and inorganic plugging removal agents; determining the injection amount of organic and inorganic plugging removal agents; determining the injection mode of organic and inorganic plugging removal agents; and conducting field tests and effect evaluation. The method has the disadvantage that the step-by-step process of acid plugging removal agent and alkaline plugging removal agent lacks dynamic regulation, and cannot be flexibly adjusted according to real-time parameters (such as pH, temperature, and plugging changes) in the well, which easily leads to incomplete plugging removal. SUMMARY

[0004] The present application aims to provide a composite oil well intelligent plugging removal method to solve the problem that the step-by-step process of acid plugging removal agent and alkaline plugging removal agent in the prior art lacks dynamic regulation, cannot be flexibly adjusted according to real-time parameters (such as pH, temperature, and plugging changes) in the well, and easily leads to incomplete plugging removal.

[0005] The present application provides a composite oil well intelligent plugging removal method, which comprises:

[0006] obtaining the rock type and the plugging type of the oil well;

[0007] in response to the rock type being sandstone and the plugging type being complex plugging, configuring alkaline plugging removal agent and acid plugging removal agent according to the plugging type;

[0008] injecting the alkaline plugging removal agent into the oil well, soaking for 3-5 hours, and pulse backflowing;

[0009] delivering the alkaline plugging removal agent and the acid plugging removal agent into the oil well at a preset ratio;

[0010] continuously detecting the temperature in the oil well, adjusting the ratio of the acid plugging removal agent and the alkaline plugging removal agent according to the pH value of the backflow and the measured temperature in the oil well, maintaining the pH value in the well within a preset pH value range, and controlling the temperature within a preset temperature range;

[0011] detecting the particle size of the backflow liquid until the particle size is less than a preset particle size;

[0012] The oil well is hot-flushed and pressure recovery test is conducted to calculate the skin factor, and the deblocking is determined to be successfully completed in response to the skin factor being reduced to the standard range.

[0013] As the preferred technical solution of the composite oil well intelligent deblocking method, the alkaline deblocking agent is configured by mass fraction as follows: 5%-10% NaOH, 0.3%-1.0% non-ionic surfactant, 0.5%-2.0% corrosion inhibitor, and 0.2%-0.5% chelating agent.

[0014] The chelating agent is ethylenediaminetetraacetic acid or amino-trimethylene phosphonic acid, and the corrosion inhibitor is imidazoline or quaternary ammonium salt compound.

[0015] As the preferred technical solution of the composite oil well intelligent deblocking method, the acidic deblocking agent is configured by mass fraction as follows: 8%-15% HCl or organic acid, 2%-5% multi-hydrogen acid retarder, 1%-3% iron ion stabilizer, 1%-2% surfactant, and 1%-2% sodium thiosulfate; wherein the surfactant is sodium dodecyl benzene sulfonate or polyoxyethylene ether.

[0016] As the preferred technical solution of the composite oil well intelligent deblocking method, the preset proportion is a proportion that can maintain the pH value in the well within the preset pH value interval and the temperature within the preset temperature interval after the acidic deblocking agent and the alkaline deblocking agent are input into the oil well, and the determination method of the preset proportion is as follows:

[0017] The concentration of the acidic deblocking agent and the alkaline deblocking agent is obtained.

[0018] The temperature, mass, specific heat capacity, and pH value of the well fluid are obtained.

[0019] The preset proportion is calculated according to the concentration of the acidic deblocking agent, the concentration of the alkaline deblocking agent, the temperature of the well fluid, the specific heat capacity, and the mass of the well fluid.

[0020] As the preferred technical solution of the composite oil well intelligent deblocking method, when the alkaline deblocking agent and the acidic deblocking agent are injected, a vibration auxiliary step is further included, in which a downhole low-frequency vibrator is started, the vibration frequency is 10-50 Hz, and the amplitude is 0.5-1.0 mm.

[0021] As the preferred technical solution of the composite oil well intelligent deblocking method, during the soaking process, the bottom hole pressure change is monitored by a downhole pressure sensor every 30 minutes, and when the pressure drop rate is >0.05 MPa / h, the soaking time is extended by 1-2 hours.

[0022] As the preferred technical scheme of the composite oil well intelligent unblocking method, the complex blockage includes organic blockage and inorganic blockage, the organic blockage includes asphaltene and wax, and the inorganic blockage includes calcium carbonate and barium sulfate, wherein the proportion of the organic blockage is 30% to 70%, and the proportion of the inorganic blockage is 30% to 70%.

[0023] As the preferred technical scheme of the composite oil well intelligent unblocking method, the parameters of the pulse flowback are as follows: the flowback pressure is 0.3 to 0.5 MPa, the pulse frequency is 5 to 10 times per minute, the single pulse duration is 10 to 30 seconds, and the pulse flowback duration is 2 to 4 hours.

[0024] As the preferred technical scheme of the composite oil well intelligent unblocking method, the hot flushing step adopts hot water or hot oil with a temperature of 60 to 80 DEG C, the flow rate of the flushing liquid is 1 to 3 m 3 / min, and the flushing time is 4 to 8 hours.

[0025] As the preferred technical scheme of the composite oil well intelligent unblocking method, the alkaline unblocking agent is injected through the oil pipe of the oil well, and the acidic unblocking agent is injected through the annulus of the oil well.

[0026] Compared with the prior art, the beneficial effects of the present application are that after the alkaline unblocking agent is injected and the well is stewed and pulse flowback, the acid and alkali unblocking agents are transported to the oil well at a preset ratio, the ratio of the two is accurately adjusted by continuously detecting the temperature and the backflow pH value of the oil well, the pH value in the well is maintained in a preset interval and the temperature is controlled, the temperature of the unblocking agent is reduced due to the temperature of the inner wall of the oil well, thereby reducing the unblocking effect, and the neutralization reaction of the acid and alkali plays a key role in this process. On the one hand, the heat generated by the neutralization reaction can melt the residual paraffin and asphalt, reduce the viscosity thereof, and make the paraffin and asphalt more easily dissolved and discharged by the unblocking agent, thereby improving the unblocking effect. On the other hand, by accurately controlling the acid-alkali ratio, the situation of excessive reaction or insufficient reaction is avoided, the blockage is effectively dissolved, and the damage to the formation is reduced. At the same time, the particle size in the backflow liquid is detected, and hot flushing and pressure recovery tests are performed after the particle size meets the requirements, thereby further improving the unblocking effect.

[0027] Further, by acquiring the rock type and the blockage type of the oil well, the alkaline unblocking agent and the acidic unblocking agent are ingeniously configured to achieve efficient removal of organic and inorganic blockage for complex blockage of sandstone formation. When the skin factor is reduced to within the standard range, it is determined that the unblocking is successful, the whole process is efficient and accurate, and a strong guarantee is provided for stable production of the oil well.

[0028] Further, by using the alkaline plugging remover to dissolve inorganic plugging (such as calcium carbonate) and disperse organic matter first, stewing the well for 3-5 hours can make the plugging remover fully penetrate into the plugging; the pulse flowback can take out the loose plugging particles from the wellbore through the periodic pressure change. Then the acidic plugging remover is injected to further dissolve the residual inorganic plugging and increase the wellbore temperature through the heat generated by the neutralization reaction, so as to promote the softening and dissolution of the organic matter (such as wax), thereby further improving the plugging removal effect.

[0029] Further, when the acidic plugging remover is injected into the oil well, if the temperature of the acidic plugging remover is too low, it will damage the bottom structure, especially in winter when the temperature is low, the temperature of the plugging remover will be significantly reduced after the acidic plugging remover is injected, and an external heat source is needed to heat the plugging remover. The application increases the wellbore temperature through the heat generated by the neutralization reaction, reduces the use of additional heat sources to heat the acidic plugging remover, saves energy consumption, and reduces emissions. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The step flow chart of the composite oil well intelligent plugging removal method of the embodiment of the application. DETAILED DESCRIPTION

[0031] The features and exemplary embodiments of various aspects of the present application will be described in detail below, in order to make the purposes, technical solutions and advantages of the present application more clear and apparent, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, but not to limit the present application. The present application can be implemented without some of these specific details for those skilled in the art. The following description of the embodiments is only to provide a better understanding of the present application by showing examples of the present application.

[0032] It should be noted that in this paper, relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitation, the elements defined by the statement "include" do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0033] Please refer to Figure 1As shown, it is a step flow chart of the composite oil well intelligent plugging method of the embodiment of the present application, including:

[0034] Step S1, obtaining the rock type and the plugging type of the oil well;

[0035] Step S2, in response to the rock type being sandstone and the plugging type being complex plugging, configuring the alkaline plugging agent and the acidic plugging agent according to the plugging type;

[0036] Step S3, injecting the alkaline plugging agent into the oil well, soaking for 3-5 hours, and pulse backflow;

[0037] Step S4, transporting the alkaline plugging agent and the acidic plugging agent to the oil well according to a preset ratio;

[0038] Step S5, continuously detecting the temperature in the oil well, adjusting the ratio of the acidic plugging agent and the alkaline plugging agent according to the pH value of the backflow and the measured temperature in the oil well, maintaining the pH value in the well within a preset pH value interval and controlling the temperature within a preset temperature interval;

[0039] Step S6, detecting the particle size in the backflow liquid until the particle size is less than a preset particle size;

[0040] Step S7, performing hot flushing on the oil well and performing pressure recovery test, calculating the skin coefficient, and determining that the plugging is successfully completed when the skin coefficient is reduced to between-3 and +2.

[0041] In detail, in the embodiment, the X-ray diffraction (XRD) analysis is performed through core sampling to determine that the quartz content in the sandstone is >70%. After sampling the plugging material, the organic / inorganic component ratio (such as asphaltene 40%, CaCO3 35%, barium sulfate 25%) is identified through thermogravimetric analysis (TGA) and infrared spectrum (FT-IR). In actual application, in order to prevent excessive corrosion of the inner wall of the pipeline due to too low pH value and incomplete plugging due to high pH value, the pH value of the acidic plugging agent is generally between 1.5 and 3.0; and the temperature of the plugging agent is to avoid insufficient softening of organic matter such as asphalt due to too low temperature or carbonization of asphalt due to too high temperature, and the temperature during oil well plugging generally needs to be controlled between 60-80 degrees Celsius, and considering the influence of temperature change on the stability of the formation structure, the best temperature is not more than the initial temperature of the formation by 10 degrees above and below. Preferably, the preset pH value interval of the embodiment of the present application is 1.0-3.0, and the preset temperature interval is 60-75 degrees Celsius. The particle size threshold is selected according to the actual situation, and in the embodiment, according to the regulation in the particle control standard of the backflow liquid in the specification "Oil and gas well plugging technical specification", the particle size should be less than 50 μm, and preferably the particle size threshold is 45 μm. The temperature detection can be detected by the distributed optical fiber deployed in advance in the annular part of the oil pipe and the casing.

[0042] Specifically, in the above technical solution, by step injection of alkaline / alkaline + acid plugging remover, the organic plugging (asphalt, waxy) and inorganic plugging (calcium carbonate, barium sulfate) are cooperatively removed, and during the neutralization reaction, the pH and temperature are dynamically controlled to avoid the out-of-control of acid-base neutralization reaction, reduce the risk of secondary plugging, and reduce the use of external heat source and energy consumption. Combined with hot flushing and skin coefficient evaluation, the plugging removal effect can be quantitatively verified, thereby improving the plugging removal effect.

[0043] Further, the alkaline plugging remover is configured by mass fraction as follows: 5%-10% NaOH, 0.3%-1.0% non-ionic surfactant, 0.5%-2.0% corrosion inhibitor, and 0.2%-0.5% chelating agent.

[0044] The chelating agent is ethylenediaminetetraacetic acid (EDTA) or amino trimethylene phosphonic acid (ATMP) for complexing Ca 2+ , Mg 2+ and other metal ions in the formation, and the corrosion inhibitor is imidazoline or quaternary ammonium salt compound, with a corrosion rate less than or equal to 0.1 mm / a in acidic environment and less than or equal to 0.076 mm / a in alkaline environment.

[0045] Further, the acid plugging remover is configured by mass fraction as follows: 8%-15% HCl or organic acid, 2%-5% polyhydroxy acid retarder, 1%-3% iron ion stabilizer, 1%-2% surfactant, and 1%-2% sodium thiosulfate; the surfactant is sodium dodecyl benzene sulfonate or polyoxyethylene ether, for enhancing the dispersibility of asphaltene.

[0046] In detail, the polyhydroxy acid retarder (such as fluoroborate) in the acid plugging remover can delay the reaction speed of HCl with formation rock, so that the acid liquid can penetrate deep into the formation for plugging removal, avoiding premature consumption, which is particularly important for treating deep plugging (such as plugging more than 50 meters away from the wellbore).

[0047] Further, the preset proportion is that, after the acid plugging remover and the alkaline plugging remover are input into the oil well, the proportion of maintaining the pH value in the well within the preset pH value range and the temperature within the preset temperature range, wherein the determination method of the preset proportion is as follows:

[0048] Obtain the concentration of the acid plugging remover and the concentration of the alkaline plugging remover;

[0049] Obtain the temperature, mass, specific heat capacity and pH value of the well fluid;

[0050] Calculate the preset proportion according to the concentration of the acid plugging remover, the concentration of the alkaline plugging remover, the temperature of the well fluid, the specific heat capacity and the mass of the well fluid.

[0051] Specifically, the determination method of the preset ratio in the embodiment of the present application is based on neutralization reaction heat and material balance calculation, a machine learning algorithm can be introduced to establish a dynamic prediction model of pH value, temperature and ratio of the plugging remover, historical operation data is used to optimize adjustment parameters, and control precision is improved. Or directly according to the basic common sense: in a dilute solution, when 1 mol of liquid water is generated by the neutralization reaction of a strong acid and a strong base, the heat released is called neutralization heat, which is usually about 57.3 kJ / mol, and the neutralization heat is approximately calculated by combining Q=Cm(t1-t2) and other physical and chemical formulas.

[0052] The embodiment of the present application provides a calculation method of a preset ratio, comprising:

[0053] It is known that the target of this oil well plugging is to raise the liquid temperature in the well from 60 DEG C to 80 DEG C, maintain the pH value in the well as 1 (the pH value is allowed to be deviated upward and downward by less than or equal to 0.5), and maintain the well liquid volume for plugging as 10 m 3 .

[0054] The mass fraction of NaOH in the alkaline plugging remover is 8%, and the molar concentration C 碱 = 2.2 mol / L.

[0055] The mass fraction of HCl in the acidic plugging remover is 12%, and the molar concentration C 酸 = 3.7 mol / L.

[0056] Step 1, set: Substitute the values in the formula into the formula to obtain n 碱 .

[0057] Wherein: c p is the average specific heat capacity of the well liquid, m p is the mass of the well liquid, n 碱 is the concentration of OH - in the alkaline plugging remover, ΔT is the temperature change of the well, and ΔH is the neutralization heat, ΔH = -57.3 kJ / mol.

[0058] It can be understood that the above formula is obtained by combining the acid-base neutralization formula (Q=n 水 × | ΔH |) and the heat calculation formula (Q=c×m× ΔT). In the implementation, the specific heat capacity of the low-concentration sodium chloride solution is approximately the same as that of water, and the purpose of the acid-base neutralization of the present application is to raise the well liquid temperature to the target temperature through the acid-base neutralization reaction, and the generated sodium chloride exists in the form of ions in the solution and is uniformly distributed in the 10000 L well liquid, which has little effect on the specific heat capacity of the well liquid. Although the mass of the substances in the acidic plugging remover and the alkaline plugging remover accounts for a large proportion, they are uniformly dispersed in the 10000 L well liquid due to their large relative molecular mass, and have little effect on the specific heat capacity of the well liquid, that is, the specific heat capacity c pThe specific heat capacity of the same PH value of the HCl plugging agent. The relative molecular mass of NaCl and HCl differs by 22, i.e. 1 mol of NaCl differs from 1 mol of HCl by 22 g, and the mass of the generated NaCl in the implementation is much smaller than the mass of the HCl, and the mass of other components in the alkaline plugging agent is much smaller than the mass of other components in the acidic plugging agent, and thus the mass of the well fluid can be ≈ the mass of the same volume of the acidic plugging agent with the same PH value. In summary, the specific heat capacity c p The mass of the well fluid can be directly obtained through big data or experiments, and ΔH and ΔT are known quantities, and thus there is only one unknown quantity n 碱 in the above formula, which can be obtained by substituting the numerical value. 碱 Given n 碱 , c 碱 , the volume V 碱 can be obtained.

[0059] Step 2, given that the volume of the well fluid in the well fluid is 10000L and the PH value is kept to 1, the amount n + of residual H 残 in the well fluid can be obtained, the volume of the acid and the base consumed in the acid-base neutralization reaction is 1:1, i.e. n 酸 =n 残 +n 碱 . Given n 酸 , c 酸 , the volume V 酸 of the required acidic plugging agent can be obtained.

[0060] Step 3, the preset ratio V 酸 :V 碱 is obtained, but before the alkaline plugging agent is injected, it needs to be diluted until the sum of V 碱 +V 酸 + the water added by the diluted alkaline plugging agent is 10000L.

[0061] In detail, the released heat is calculated to accurately control the temperature, and the ratio is calculated by the neutralization heat formula, which not only avoids local overheating to cause carbonization of asphalt, but also ensures that the temperature is always within the temperature range of asphalt and paraffin softening, thereby further improving the plugging removal effect.

[0062] Further, when the alkaline plugging agent and the acidic plugging agent are injected, a vibration auxiliary step is further included, a downhole low-frequency vibrator is started, the vibration frequency is 10-50Hz, and the amplitude is 0.5-1.0mm.

[0063] Specifically, during the soak period, the downhole pressure sensor is used to monitor the change of the bottom hole pressure every 30 minutes, and when the pressure drop rate > 0.05MPa / h, the soak period is extended by 1-2 hours.

[0064] Specifically, the complex blockage includes organic blockage and inorganic blockage, the organic blockage includes asphaltene and wax, and the inorganic blockage includes calcium carbonate and barium sulfate, wherein the proportion of the organic blockage is 30% to 70%, and the proportion of the inorganic blockage is 30% to 70%.

[0065] Specifically, the parameters of the pulse flowback are as follows: the flowback pressure is 0.3 to 0.5 MPa, the initial pressure is 0.3 MPa, gradually increased to 0.5 MPa, the pulse frequency is 5 to 10 times per minute, the single pulse duration is 10 to 30 seconds, the pulse flowback duration is 2 to 4 hours, and the pulse flowback and the vibration assistance are alternately performed during the operation process.

[0066] Further, the hot flushing step uses hot water or hot oil with a temperature of 60 to 80 ℃, the flow rate of the flushing liquid is 1 to 3 m 3 / min, and the flushing time is 4 to 8 hours.

[0067] Specifically, the alkaline blockage remover is injected through the oil pipe of the oil well, and the acidic blockage remover is injected through the annulus of the oil well, so as to delay the contact time, avoid direct reaction on the inner wall of the pipe, and make the heat unable to dissipate to the accurate position.

[0068] Example 1

[0069] Well condition: well depth 2500 m, sandstone permeability 50 mD, blockage asphalt (60%) + CaCO3 (30%) + FeS (10%); formation temperature 65 ℃, wellbore pressure 15 MPa.

[0070] Implementation steps:

[0071] Alkaline blockage remover injection: formula: 8% NaOH, 1.0% OP-10, 1.5% imidazoline corrosion inhibitor, 0.3% EDTA;

[0072] Injection amount 12 m 3 , soak for 5 hours, pulse flowback pressure 0.4 MPa;

[0073] Acidic blockage remover injection:

[0074] Formula: 12% HCl, 3% HEDP, 2% citric acid, 1.5% sodium dodecyl benzene sulfonate, 1% sodium thiosulfate;

[0075] Injection amount 18 m 3 , vibration assistance (30 Hz, 0.8 mm amplitude);

[0076] Dynamic regulation:

[0077] Maintain pH = 2.0 to 2.5, temperature 65 to 70 ℃, preset ratio of acid:alkali = 1.44:0.97;

[0078] Effect verification: particle size of flowback fluid is less than or equal to 45 μm, skin factor is reduced from +7.2 to +1.5, and daily oil increment is 4.8 tons.

[0079] Pressure buildup test shows that the skin factor is reduced from +6.8 to +1.3, and it is determined that the plugging is successfully removed.

[0080] Example 2

[0081] Well condition: well depth is 1800 m, sandstone permeability is 80 mD, plugging material is calcium carbonate 55% + barium sulfate 25% + asphalt 20%, formation temperature is 55℃, and wellbore pressure is 12 MPa.

[0082] Implementation steps:

[0083] Injection of alkaline plugging remover:

[0084] Formulation: 6% NaOH, 0.5% OP-10, 1.2% quaternary ammonium salt corrosion inhibitor, 0.4% ATMP, and the rest is water;

[0085] Injection amount is 10 m 3 , soak for 4 hours, and pulse flowback pressure is 0.3 MPa;

[0086] Injection of acidic plugging remover:

[0087] Formulation: 15% HCl, 4% HEDP, 2.5% citric acid, 1.0% polyoxyethylene ether, 1.7% sodium thiosulfate, and the rest is water;

[0088] Injection amount is 15 m 3 , vibration assistance (20 Hz, 1.0 mm amplitude);

[0089] Dynamic regulation: maintain pH = 2.5-3.0, temperature 60-65℃, and preset ratio of acid:alkali = 2.17:1.14;

[0090] Effect verification: particle size of flowback fluid is less than or equal to 45 μm, skin factor is reduced from +5.6 to +0.8, and daily gas increment is 12,000 cubic meters.

[0091] Obviously, the above examples of the present application are only examples for clearly illustrating the present application, and are not limitations on the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A composite oil well intelligent unblocking method, characterized in that, The method comprises the following steps: acquiring the rock type and the plugging type of the oil well; in response to the rock type being sandstone and the plugging type being complex plugging, configuring an alkaline plugging remover and an acid plugging remover according to the plugging type; injecting the alkaline plugging remover into the oil well, soaking for 3-5 hours, and pulse flowback; delivering the alkaline plugging remover and the acid plugging remover into the oil well at a preset ratio; continuously detecting the temperature in the oil well, adjusting the ratio of the acid plugging remover and the alkaline plugging remover according to the pH value of the backflow and the measured temperature in the oil well, maintaining the pH value in the well within a preset pH value range and controlling the temperature within a preset temperature range; detecting the particle size in the backflow until the particle size is less than a preset particle size; performing hot flushing on the oil well and conducting a pressure build-up test, calculating the skin factor, and determining that the plugging is successfully completed when the skin factor is reduced to a standard range; the preset ratio is a ratio at which the pH value in the well can be maintained within a preset pH value range and the temperature can be maintained within a preset temperature range after the acid plugging remover and the alkaline plugging remover are delivered into the oil well, wherein the preset ratio is determined by the following method: acquiring the concentrations of the acid plugging remover and the alkaline plugging remover; acquiring the temperature, mass, specific heat capacity and pH value of the well fluid; calculating the preset ratio according to the concentration of the acid plugging remover, the concentration of the alkaline plugging remover, the temperature of the well fluid, the specific heat capacity and the mass of the well fluid; the complex plugging includes organic plugging and inorganic plugging, the organic plugging includes asphaltene and wax, and the inorganic plugging includes calcium carbonate and barium sulfate, wherein the proportion of the organic plugging is 30%-70% and the proportion of the inorganic plugging is 30%-70%.

2. The combined oil well intelligent unblocking method according to claim 1, characterized in that, the alkaline plugging remover is configured by 5%-10% NaOH, 0.3%-1.0% non-ionic surfactant, 0.5%-2.0% corrosion inhibitor and 0.2%-0.5% chelating agent. The chelating agent is ethylenediaminetetraacetic acid or amino-trimethylene phosphonic acid, and the corrosion inhibitor is imidazoline or quaternary ammonium salt compound.

3. The combined oil well intelligent unblocking method according to claim 1, characterized in that, The acid plugging remover is configured by 8%-15% HCl or organic acid, 2%-5% multi-hydrogen acid retarder, 1%-3% iron ion stabilizer, 1%-2% surfactant and 1%-2% sodium thiosulfate, wherein the surfactant is sodium dodecyl benzene sulfonate or polyoxyethylene ether.

4. The combined oil well intelligent un-plugging method according to claim 1, characterized in that, When the alkaline plugging remover and the acid plugging remover are injected, a vibration auxiliary step is further included, in which a downhole low-frequency vibrator is started, the vibration frequency is 10-50 Hz, and the amplitude is 0.5-1.0 mm.

5. The combined oil well intelligent unblocking method according to claim 4, characterized in that, During the soaking process, the downhole pressure sensor is used to monitor the change of the bottom hole pressure every 30 minutes, and when the pressure drop rate is greater than 0.05 MPa / h, the soaking time is extended by 1-2 hours.

6. The combined oil well intelligent unblocking method according to claim 4, characterized in that, The pulse flowback parameters are as follows: the flowback pressure is 0.3-0.5 MPa, the pulse frequency is 5-10 times per minute, the single pulse duration is 10-30 seconds, and the pulse flowback duration is 2-4 hours.

7. The combined oil well intelligent unblocking method according to claim 6, characterized in that, The hot flushing step uses hot water or hot oil with a temperature of 60-80 ℃, the flow rate of the flushing fluid is 1-3 m³ / min, and the flushing time is 4-8 hours.

8. The combined oil well intelligent un-plugging method of claim 1, wherein, The basic plug remover is injected through the tubing of the oil well, and the acid plug remover is injected through the annulus of the oil well. The basic plug remover is injected through the tubing of the oil well, and the acid plug remover is injected through the annulus of the oil well.

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