A method for characterizing a biological nano-deblocking injection-increasing breakthrough point

Abstract

This invention belongs to the field of oil extraction and relates to a method for characterizing the breakthrough point of bio-nano-based unblocking and injection enhancement. The method includes: measuring the porosity and permeability of the core sample; injecting a bio-nano-based unblocking agent using KCl or NH4Cl solution for displacement, and analyzing the breakthrough point of the bio-nano-based unblocking agent; flushing the pipeline with simulated formation water, shutting off the displacement device, injecting the bio-nano-based injection enhancement agent, and measuring the porosity and permeability of the core sample again; dividing the unblocking process into a linear flow model into contaminated and uncontaminated zones, determining the contaminated skin coefficient based on Darcy's formula and the definition of the skin factor, and determining the fluid viscosity in the contaminated zone and the fluid viscosity in the uncontaminated zone at any given time; deriving the relationship between pressure difference and time during the core displacement reaction process based on the fitting relationship between pressure difference and the rising and falling phases of the injected PV number, and the relationship between the unblocking agent propulsion time and the injected PV number; and determining the relationship between fluid viscosity and the unblocking agent injection time based on the relationship between pressure difference and time during the core displacement reaction process.

Description

Technical Field

[0001] This invention relates to the field of oil extraction, and in particular to a characterization method for breakthrough points in bio-nano-based unblocking and injection enhancement. Background Technology

[0002] The Bohai Oilfield has over 700 water injection wells, with as many as 400 requiring pressure reduction and injection enhancement operations annually. Therefore, the market demand for unblocking and injection enhancement systems is enormous. Low-permeability tight oil reservoirs are characterized by densely buried rocks, small pore throats, low porosity, and very poor permeability. During production, long-term water injection in wells leads to hydration and expansion of clay and other materials on the near-wellbore surface, causing scale buildup and throat blockage. This results in high injection pressure, difficulty in replenishing energy, and stagnation of recovery rates. To address the high injection pressure issue in actual production, conventional unblocking measures such as acidizing and micro-fracture are typically employed. However, after multiple rounds of these measures, the amount of rock particles that can be dissolved in the oil reservoir decreases, and the effectiveness of conventional unblocking measures gradually shortens.

[0003] In recent years, with the rapid development of nanotechnology, its application in oil extraction, particularly in areas such as pressure reduction and injection enhancement, and near-wellbore unblocking, has attracted considerable attention. As pressure reduction and injection enhancement agents and unblocking agents for water injection wells in low-permeability reservoirs, they have been extensively studied. Bio-nano unblocking agents possess properties such as fluid diversion and inhibition of secondary precipitation; however, these inhibitions are relative and cannot achieve 100% suppression. Therefore, in core simulation experiments and actual field experiments, a breakthrough point for the unblocking agent will emerge, characterizing the effective range of action of the bio-nano unblocking agent. Determining or predicting this breakthrough point during core experiments is crucial for the practical application of bio-nano unblocking agents in the field. However, currently, there is no corresponding method for characterizing this breakthrough point. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a characterization method for breakthroughs in bio-nano-based unblocking and injection enhancement.

[0005] Specifically, the characterization method for breakthrough points in bio-nano-based unblocking and injection enhancement provided by this invention includes:

[0006] (1) The artificial rock core is cleaned, dried and then saturated.

[0007] (2) Using saturated simulated formation water or clear water displacement, the water drive pressure at a certain flow rate is tested to determine the porosity and permeability of the rock core.

[0008] (3) KCl solution or NH4Cl solution is used for displacement, and bio-nano unblocking agent is injected. The breakthrough point of bio-nano unblocking agent is analyzed based on the change of displacement pressure.

[0009] (4) Flushing the pipes with simulated formation water, turning off the displacement device and letting it stand for a period of time before injecting the bio-nano-injection agent;

[0010] (5) Turn off the displacement device and let it stand for a period of time. Then inject formation water and test the water drive pressure at a certain flow rate to determine the porosity and permeability of the core.

[0011] (6) Divide the unblocking and linear flow model into a contaminated zone and an uncontaminated zone. Determine the contaminated skin coefficient according to Darcy's formula and the definition of the skin coefficient, and derive the relationship between fluid viscosity and pressure drop. Then determine the fluid viscosity in the contaminated zone and the fluid viscosity in the uncontaminated zone at any time.

[0012] (7) Based on the fitting relationship between pressure difference and the rising and falling phases of injected PV number and the relationship between the unblocking agent propulsion time and the injected PV number, the relationship between pressure difference and time during the core displacement reaction is derived;

[0013] (8) Determine the relationship between fluid viscosity and unblocking agent injection time based on the relationship between pressure difference and time during the core displacement reaction, so as to judge the best unblocking turning time and realize dynamic prediction of the turning breakthrough process.

[0014] In the above-mentioned characterization method of the breakthrough point of biological nano-unblocking and injection, in step (1), the artificial core is cleaned with chloroform and methanol, and the artificial core is saturated with simulated formation water.

[0015] In the above-mentioned characterization method of the breakthrough point of bio-nano unblocking and injection, in steps (2) and (5), the porosity and permeability of the core are calculated by liquid measurement method.

[0016] The porosity calculation method for the aforementioned bio-nano unblocking and injection breakthrough point is as follows:

[0017] Porosity = (mass of saturated core - mass of dry core) / (density of saturated liquid × core volume).

[0018] The permeability is calculated using the following method for characterizing the breakthrough point of the above-mentioned bio-nano-based unblocking and injection enhancement:

[0019] K we =q w μ w L / A(P1-P2)×100%

[0020] in:

[0021] K we —Penetration rate

[0022] q w —Water flow rate, mL / min;

[0023] μw —The viscosity of water at the measured temperature, in mPa·s;

[0024] L—The numerical value of the core length, in cm;

[0025] A—The numerical value of the cross-sectional area of ​​the rock core, in cm² 2 ;

[0026] p1—Value of core inlet pressure, MPa;

[0027] p2 — The numerical value of the core outlet pressure, in MPa.

[0028] The characterization method for the breakthrough point of bio-nano unblocking and injection, in step (6), the determination method for the fluid viscosity in the contaminated area and the fluid viscosity in the uncontaminated area is as follows:

[0029] when At that time, the viscosity μ of the fluid in the contaminated area s for:

[0030]

[0031] when At that time, the viscosity μ of the uncontaminated area is:

[0032]

[0033] in:

[0034] —Initial porosity of the core, %;

[0035] —Porosity of a certain area of ​​the core sample, %;

[0036] —Pore volume of the contaminated area, %;

[0037] μ s —Volume of fluid in the contaminated area, MPa·s;

[0038] μ0 — Initial core viscosity, MPa·s;

[0039] R p— Dimensionless directional pressure difference, MPa;

[0040] S—epidermal coefficient, dimensionless;

[0041] ΔP s —Displacement pressure difference of core samples in the contaminated area, MPa;

[0042] ΔP0—Initial core displacement pressure difference, MPa;

[0043] μ—fluid viscosity when the contaminated zone breaks through to the uncontaminated zone, MPa·s;

[0044] —The pore volume (%) of the unblocking agent as it penetrates from the contaminated area to the uncontaminated area;

[0045] ΔP s —Displacement pressure difference of core samples in the contaminated area, MPa;

[0046] ΔP—Displacement pressure difference of core samples in the uncontaminated area, MPa.

[0047] In the characterization method of the breakthrough point of bio-nano unblocking and injection described above, in step (7), the fitting relationship between the pressure difference and the rising and falling stages of the injected PV number is as follows:

[0048]

[0049] Where ω represents the number of injected PVs, which is dimensionless.

[0050] In the characterization method of the breakthrough point of bio-nano unblocking and injection described above, in step (7), the relationship between the unblocking agent propulsion time and the injected PV number is as follows:

[0051]

[0052] in:

[0053] t—propulsion time of the unblocking agent, s;

[0054] ω — number of injected PVs, dimensionless;

[0055] V p —Initial core pore volume, cm³ 3 ;

[0056] Q—Permeation propulsion flow rate, mL / min.

[0057] The technical solution of the present invention has the following beneficial effects:

[0058] (1) This invention provides a comprehensive method that makes it possible to characterize breakthroughs in bio-nano unblocking and injection enhancement;

[0059] (2) This invention comprehensively utilizes indoor core displacement experimental data and analytical mathematical models to improve the accuracy of the characterization method for breakthrough points of bio-nano unblocking and injection.

[0060] (3) This invention provides a quantitative and operable technical method and implementation steps. Attached Figure Description

[0061] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0062] Figure 1 This is a flowchart of the breakthrough point characterization method for bio-nano unblocking and injection enhancement in this invention;

[0063] Figure 2 This is a photograph of the actual rock core of this invention;

[0064] Figure 3 This is a schematic diagram of the core simulation displacement experimental device of the present invention;

[0065] Among them, 1 is distilled water, 2 is a horizontal flow pump, 3 is a six-way valve, 4 is an intermediate container, 5 is a pressure gauge, 6 is a core holder, 7 is a core, 8 is a confining pressure pump, and 9 is a measuring cylinder.

[0066] Figure 4 This is a schematic diagram illustrating the division of contaminated areas in the core during the core simulation experiment of the bio-nano unblocking agent of this invention;

[0067] Figure 5 The core unblocking and reversing pressure drop curve of this invention (50℃, 0.5mL / min);

[0068] Figure 6 The real-time displacement pressure difference and permeability (20.38 mD) of the core bio-nano unblocking agent of this invention. Detailed Implementation

[0069] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.

[0070] Specifically, such as Figure 1 As shown, the characterization method for breakthrough points of bio-nano-based unblocking and injection enhancement provided by this invention includes:

[0071] (1) The artificial rock core is cleaned, dried and then saturated.

[0072] (2) Using saturated simulated formation water or clear water displacement, the water drive pressure at a certain flow rate is tested to determine the porosity and permeability of the rock core.

[0073] (3) KCl solution or NH4Cl solution is used for displacement, and bio-nano unblocking agent is injected. The breakthrough point of bio-nano unblocking agent is analyzed based on the change of displacement pressure.

[0074] (4) Flushing the pipes with simulated formation water, turning off the displacement device and letting it stand for a period of time before injecting the bio-nano-injection agent;

[0075] (5) Turn off the displacement device and let it stand for a period of time. Then inject formation water and test the water drive pressure at a certain flow rate to determine the porosity and permeability of the core.

[0076] (6) Divide the unblocking and linear flow model into a contaminated zone and an uncontaminated zone. Determine the contaminated skin coefficient according to Darcy's formula and the definition of the skin coefficient, and derive the relationship between fluid viscosity and pressure drop. Then determine the fluid viscosity in the contaminated zone and the fluid viscosity in the uncontaminated zone at any time.

[0077] (7) Based on the fitting relationship between pressure difference and the rising and falling phases of injected PV number and the relationship between the unblocking agent propulsion time and the injected PV number, the relationship between pressure difference and time during the core displacement reaction is derived;

[0078] (8) Determine the relationship between fluid viscosity and unblocking agent injection time based on the relationship between pressure difference and time during the core displacement reaction, so as to judge the best unblocking turning time and realize dynamic prediction of the turning breakthrough process.

[0079] In some preferred embodiments, the characterization method for the breakthrough point of bio-nano-unblocking and injection enhancement of the present invention includes the following core displacement experimental steps:

[0080] (1) Based on the reservoir characteristics of offshore oil fields, select artificial cores of appropriate length and permeability (such as...). Figure 2 The core samples were cleaned with chloroform-methanol and then dried in a 120°C oven. The dry weight was measured, and the diameter (d) and length (L) were determined, and the apparent volume was calculated. The core samples were then saturated in simulated formation water (20000 mg / L salinity) for 12 hours.

[0081] (2) Adopting such Figure 3 The core displacement simulation experimental apparatus shown involves placing the core in a core holder, applying ring pressure, and evacuating for 4 hours. An oven is then opened and set to 50℃ to simulate formation water / clear water displacement until a stable displacement pressure is reached. The water displacement pressure ΔP1 at a certain flow rate is measured to determine the core's pore volume and calculate porosity. The core permeability K0 is then calculated using Darcy's formula. This process ensures that ions in the simulated formation water / clear water are uniformly distributed within the core.

[0082] (3) Select KCl (3%) or NH4Cl (3%) to displace for a period of time until the displacement pressure is stable. Inject the bio-nano unblocking agent at a certain flow rate (0.5-1 mL / min), monitor the displacement pressure of the bio-nano unblocking agent in real time, and analyze the breakthrough point of the bio-nano unblocking agent based on the change of displacement pressure.

[0083] (4) After the bio-nano unblocking agent breaks through, flush the pipeline with simulated formation water (0.2-1 mL) and shut off the displacement device for 4-6 hours. Inject the bio-nano injection agent at a certain flow rate (0.5-1 mL / min);

[0084] (5) After shutting down the displacement device for 72 hours, inject formation water at a certain flow rate (0.5-1 mL / min) and test the water drive pressure ΔP2 at a certain flow rate. Use this to determine the pore volume of the core and calculate the porosity. Calculate the core permeability K1 according to Darcy's formula.

[0085] Further preferably, the core porosity calculation in steps (2) and (5) adopts the liquid saturation method. The principle is as follows:

[0086] Measuring core porosity (connected pore space) using the liquid saturation method involves a weighing analysis of pore volume, including the mass of a clean, dry rock sample, the mass of the core saturated with a liquid of known density, and the mass of the core immersed in a liquid identical to the saturating solution. Core porosity is calculated using the following formula:

[0087] φ=(mass of saturated core - mass of dry core) / (density of saturated liquid × volume of core) (1)

[0088] More preferably, similar to the core porosity determination method, the core permeability calculation in steps (2) and (5) adopts the liquid permeability method. Based on Darcy's formula, the effective permeability of the gas phase and the aqueous phase is calculated as follows:

[0089] K we =q w μ w L / A(P1-P2)×100% (2)

[0090] in:

[0091] q w —Water flow rate, expressed in mL / min;

[0092] μ w —The viscosity of water at the measured temperature, expressed in mPa·s;

[0093] L—The numerical value of the core length, in cm;

[0094] A—The numerical value of the cross-sectional area of ​​the rock core, in cm² 2 ;

[0095] p1—The numerical value of the core inlet pressure, in MPa;

[0096] p2 — The numerical value of the core outlet pressure, in MPa.

[0097] (6) The decongestion relief model is divided into two parts: a contaminated zone and an uncontaminated zone, see [reference needed]. Figure 4 During the displacement process of the bio-nano unblocking agent, the core pressure initially increases, reaches a certain point, and then immediately declines, reaching a trough. The injection of the unblocking fluid creates a breakthrough point, i.e., the point where the pressure suddenly drops. (See...) Figure 5 .

[0098] The displacement in linear seepage cores exhibits a constant plunger rate, as shown in equation (3):

[0099] L s =α s ×t (3)

[0100] In the formula, α s t represents the speed of advance of the contaminated area, in cm / min; t represents time, in min.

[0101] Let the pore volume of the contaminated area be... The pore volume when the unblocking agent penetrates from the contaminated area to the uncontaminated area is: The formula for the average advance speed of the contaminated zone is as follows:

[0102]

[0103] In the formula, Φ0 is the initial porosity of the core, %; Q is the seepage propulsion flow rate, mL / min; and A is the unit cross-sectional area of ​​the seepage flow, cm². 2 V p The pore volume multiple of the unblocking agent injected into the contaminated area, dimensionless.

[0104] The formula for the average advance velocity at the leading edge of the uncontaminated zone is as follows:

[0105]

[0106] In the formula, Φ0 is the initial porosity of the core, %; Q is the seepage propulsion flow rate, mL / min; and A is the unit cross-sectional area of ​​the seepage flow, cm². 2 ; a is the average advancing velocity of the leading edge of the impedance zone, cm / min; L is the location of the leading edge of the uncontaminated zone, cm; V p This is the dimensionless multiple of the pore volume of the unblocking agent injected when it penetrates from the contaminated area to the uncontaminated area.

[0107] when At that time, the dimensionless directional pressure difference R p Set as:

[0108]

[0109] when At that time, the dimensionless directional pressure difference R p Set as:

[0110]

[0111] In the formula, ΔP s ΔP represents the displacement pressure difference of the core in the contaminated area, in MPa; ΔP represents the displacement pressure difference of the core in the uncontaminated area, in MPa.

[0112] Let the initial core viscosity be μ o If the fluid viscosity is μ when it breaks through from the contaminated zone to the uncontaminated zone, then according to Darcy's formula:

[0113]

[0114] Assuming the core length is L, the permeability of the uncontaminated zone is k, and the permeability of the contaminated zone is k... s The pollution depth is L s When a single-phase fluid undergoes unidirectional Darcy flow in a rock core, the core permeability distribution is as follows:

[0115]

[0116]

[0117] In the formula, (p i -p0) represents the formation pressure differential, MPa; μ is the fluid viscosity, mPa·s; A is the unit cross-sectional area of ​​seepage, cm². 2 ;k s (x) represents the permeability of the polluted area, in mD.

[0118] From equation (9) and the definition of the skin coefficient, the contaminated skin coefficient can be obtained:

[0119]

[0120] Combining equations (7) and (10), we get:

[0121]

[0122] Multiplying both the numerator and denominator on the right side of the equation by AΦ, we get:

[0123]

[0124] In the formula, V s The volume of unblocking agent injected to break through the contaminated area, in cm 3 V represents the volume of unblocking agent injected at the inflection point of the pressure drop curve in the uncontaminated area, in cm³. 3 .

[0125] Divide both the numerator and denominator on the right side of the equation by V. p ,have to:

[0126]

[0127] Furthermore, it can be concluded that when At that time, the viscosity μ of the fluid in the contaminated area s for:

[0128]

[0129] Similarly, it can be deduced that when At that time, the viscosity μ of the uncontaminated area was

[0130]

[0131] The fluid viscosity of the contaminated and uncontaminated areas at any given time can be calculated using equations (14) and (15) based on the pressure drop value displayed on the monitor.

[0132] (7) During the unblocking and turning process, the pressure difference change depends on the combined effect of the viscosity and porosity change of the unblocking agent. The relationship curve between the pressure difference ΔP and the number of injected PVs ω needs to be fitted in two parts: the fitting curve of the rising stage in region II and the fitting curve of the falling stage.

[0133] The propulsion time t(s) of the unblocking agent is related to the number of injected PVs ω as follows:

[0134]

[0135] By combining the fitting equations of pressure difference ΔP and the injected PV number ω during the rising and falling phases, and the equations of the relationship between the unblocking agent propulsion time t(s) and the injected PV number, the relationship between pressure difference and time during the core displacement reaction can be obtained.

[0136] (8) The relationship between fluid viscosity and pressure drop is calculated by combining the relationship between pressure difference and time during the core displacement reaction, so as to determine the best time for unblocking and turning, and realize the dynamic prediction of the turning breakthrough process.

[0137] Example

[0138] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, are performed according to conventional methods and conditions.

[0139] The characterization method for breakthrough points of bio-nano-based unblocking and injection enhancement provided in this embodiment includes the following steps:

[0140] (1) Based on the reservoir characteristics of offshore oil fields, artificial cores with a thickness of 6.0 cm and a permeability of 20.38 mD were selected. See Figure 2Core samples were cleaned with chloroform-methanol and then dried in a 120℃ drying oven. The dry weight was measured, and the diameter d and length L were measured to calculate the apparent volume. The core samples were then saturated in simulated formation water (20000 mg / L salinity) for 12 hours (see Table 1).

[0141] Table 1 Core parameters

[0142]

[0143] (2) Place the core in the core holder, apply ring pressure, and evacuate for 4 hours. Open the oven, set the temperature to 50℃, saturate the simulated formation water / clear water displacement until the displacement stabilization pressure is reached, and test the water drive pressure ΔP1 at a certain flow rate. Use this to determine the pore volume of the core, calculate the porosity, and calculate the core permeability k0 according to Darcy's formula. Ensure that the ions in the simulated formation water / clear water are uniformly distributed in the core.

[0144] (3) Displacement was carried out with simulated formation water (0.5 mL / min) for a period of time. The experimental setup and principle are as follows: Figure 3 , Figure 4 As shown in the figure. To achieve a stable displacement pressure, the bio-nano unblocking agent was injected at a flow rate (0.5 mL / min) in a ratio of 1:2 (w / w) to water, and the displacement pressure of the bio-nano unblocking agent was monitored in real time. The breakthrough point of the bio-nano unblocking agent was analyzed based on the changes in displacement pressure.

[0145] (4) Displace the material with KCl (3%) or NH4Cl (3%) for a period of time until a stable displacement pressure is reached. Inject the bio-nano unblocking agent at a certain flow rate (0.5 mL / min), monitor the displacement pressure of the bio-nano unblocking agent in real time, and analyze the breakthrough point of the bio-nano unblocking agent based on the changes in displacement pressure. See [link to relevant documentation]. Figure 5 ;

[0146] (5) After the bio-nano unblocking agent breaks through, flush the pipeline with simulated formation water (0.2-1 mL) and shut off the displacement device for 4-6 hours. Inject the bio-nano injection agent at a certain flow rate (0.5-1 mL / min);

[0147] (6) After shutting off the displacement device for 72 hours, inject formation water at a certain flow rate (0.5-1 mL / min) and test the water drive pressure ΔP2 at a certain flow rate. Use this to determine the pore volume of the core, calculate the porosity, and calculate the core permeability K1 according to Darcy's formula.

[0148] The graph showing the relationship between differential pressure and injected PV number needs to be fitted in two parts. The fitted curves for the rising phase and the falling phase in Region II are as follows:

[0149]

[0150] In the formula, ω represents the number of injected PVs. The propulsion time t(s) of the unblocking agent and the number of injected PVs ω are related as follows: Initial core pore volume V p =4.16cm 3 Q = 0.5 mL / min.

[0151] By combining the fitting equations of pressure difference ΔP and injected PV number ω during the rising and falling phases, and the equation of unblocking agent propulsion time t(s) and injected PV number, the relationship between pressure difference and time during the core displacement reaction can be obtained as follows:

[0152]

[0153] (7) Pore volume of the contaminated area It is 6.04cm 3 The pore volume when the unblocking agent penetrates from the contaminated area to the uncontaminated area. It is 8.89cm 3 .

[0154] The formula for the average advance speed of the contaminated zone is as follows:

[0155]

[0156] The formula for the average advance velocity at the leading edge of the uncontaminated zone is as follows:

[0157]

[0158] Displacement pressure difference ΔP in core samples from contaminated areas s The displacement pressure difference in the uncontaminated core area is 8.17 MPa; the displacement pressure difference ΔP in the uncontaminated area is 0.94 MPa.

[0159] Dimensionless directional pressure difference R p for:

[0160] The inflection point (S=0) of the pressure drop curve in the uncontaminated zone during the entire core displacement reaction process is the volume viscosity.

[0161]

[0162] By combining the relationship between fluid viscosity and pressure drop with the relationship between pressure difference and time during the core displacement reaction, the relationship between fluid viscosity and injection time is calculated as follows:

[0163]

[0164] The optimal turning point for unblocking was determined at t=75.4min, ultimately achieving dynamic prediction of the turning breakthrough process.

[0165] (8) Core displacement experiments (permeability = 20.38 mD) showed a very clear breakthrough point for the bio-unblocking fluid. After the bio-nano unblocking agent was injected, the pressure initially rose steadily, while the permeability of the core decreased accordingly, reaching a minimum of 5.87 mD. Subsequently, a breakthrough point appeared, the pressure difference between the two ends of the core decreased, the permeability recovered, and showed an increasing trend, with the highest permeability reaching 36.03 mD. Figure 6 In later studies on the optimization of injection parameters for the bio-nano unblocking and injection system, the pressure breakthrough point of the unblocking agent can be used as the main parameter indicator.

[0166] Table 2 Summary of parameters in Example 1

[0167]

[0168] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art should understand that these embodiments are merely illustrative of the invention and should not be construed as limiting its scope. It should be noted that any variations and substitutions equivalent to these embodiments should be considered to be covered within the scope of the claims. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for characterizing a breakthrough point of a biological nano-plugging and injection-increasing, characterized in that, include: (1) After cleaning and drying the artificial rock core, it is subjected to saturation treatment; (2) Using saturated simulated formation water or clear water displacement, the water drive pressure at a certain flow rate is tested to determine the porosity and permeability of the core. (3) KCl solution or NH4Cl solution is used for displacement, and bio-nano unblocking agent is injected. The breakthrough point of bio-nano unblocking agent is analyzed based on the change of displacement pressure. (4) Flush the pipeline with simulated formation water, turn off the displacement device and let it stand for a period of time before injecting the bio-nano-injection agent; (5) After turning off the displacement device and letting it stand for a period of time, the formation water was injected and the water drive pressure at a certain flow rate was tested to determine the porosity and permeability of the core. (6) Divide the unblocking and linear flow model into a contaminated zone and an uncontaminated zone. Determine the contaminated skin coefficient according to Darcy's formula and the definition of the skin coefficient, and derive the relationship between fluid viscosity and pressure drop value. Then determine the fluid viscosity in the contaminated zone and the fluid viscosity in the uncontaminated zone at any time. (7) Based on the fitting relationship between pressure difference and the rising and falling phases of injected PV number and the relationship between the unblocking agent propulsion time and the injected PV number, the relationship between pressure difference and time during the core displacement reaction is derived; (8) Determine the relationship between fluid viscosity and unblocking agent injection time based on the relationship between pressure difference and time during the core displacement reaction, so as to judge the best unblocking turning time and realize dynamic prediction of the turning breakthrough process.

2. The method of claim 1, wherein the method is characterized by, In step (1), the artificial core is cleaned with chloroform and methanol, and the artificial core is saturated with simulated formation water.

3. The method of claim 1, wherein the method is characterized by, In steps (2) and (5), the porosity and permeability of the core are calculated using the liquid measurement method.

4. The method of claim 3, wherein the method is characterized by, The porosity is calculated as follows: Porosity = (mass of saturated core - mass of dry core) / (density of saturated liquid × core volume).

5. The method of claim 3, wherein the method is characterized by, The permeability is calculated as follows: K we = q w µ w L / A(P 1- P 2 ) ×100% in: K we permeability q w - the value of the water flow, mL / min; μ w - the value of the viscosity of water at the assay temperature, mPa.s; L — Numerical value of the core length, cm; A - the value of the core cross-sectional area, cm2 2 ; p 1 - Numerical value of the core inlet pressure, MPa; p 2 — The value of the core outlet pressure, in MPa.

6. The method of claim 1, wherein the method is characterized by, In step (6), the methods for determining the fluid viscosity in the contaminated area and the fluid viscosity in the uncontaminated area are as follows: When φ0< φ (x) < φ s the contaminated zone fluid viscosity μ s is: When φ s < φ (x) < φ, the viscosity of the uncontaminated zone μ is: in: φ0—Initial porosity of the core, % φ (x) porosity of a certain region of the core; φ s - pore volume of the contaminated zone, %; μ s - Contaminated zone fluid viscosity, MPa s; μ 0 — Initial core viscosity, MPa s; R p — Dimensionless turning pressure difference; S— Epidermal coefficient, dimensionless; ΔP s — Contaminated zone core displacement pressure differential, MPa; ΔP 0 — Initial core displacement pressure differential, MPa; μ - fluid viscosity at breakthrough of the contaminated zone into the non-contaminated zone, MPa s; φ—Pore volume when the unblocking agent penetrates from the contaminated area to the uncontaminated area, % ΔP - Core displacement pressure differential, MPa, in the uncontaminated zone.

7. The method of claim 1, wherein the method is characterized by, In step (7), the fitting equations for the pressure difference and the rising and falling phases of the injected PV number are as follows: wherein, ω represents the number of injections, dimensionless.

8. The method of claim 1, wherein the method is characterized by, In step (7), the relationship between the unblocking agent propulsion time and the injected PV number is as follows: in: t - plug breaking agent push time, s; ω — Injected PV, dimensionless; V p Initial core pore volume, cm 3 ; Q—Permeation propulsion flow rate, mL / min.

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