Viscosity reduction and plug removal method of composite biological enzyme microorganisms and application of viscosity reduction and plug removal method

Abstract

The invention belongs to the technical field of oil field yield increase, and relates to a viscosity-reducing and plug-removing method of composite biological enzyme microorganisms and application of the viscosity-reducing and plug-removing method. According to the composite bio-enzyme microorganism viscosity reduction and plug removal method, the bio-enzyme preparation liquid and the microorganism bacterium liquid are injected into the oil well to be treated, heavy components can be effectively dissolved, the viscosity of crude oil can be remarkably reduced, and the fluidity of the crude oil can be improved; and the method can effectively solve the problem that heavy components are separated out and block pore channels due to formation temperature and pressure changes, normal productivity of an oil well is recovered, and the crude oil yield is increased. In addition, long-chain components in the crude oil can be reduced by injecting the microorganisms, the deposition of macromolecular substances is reduced, and the freezing point and viscosity of the crude oil are remarkably reduced. Microorganisms metabolize to generate biogas to expand the volume of the crude oil and reduce the viscosity of the crude oil. And a deposited film formed by adhering microorganisms to the rock surface can improve the surface property of rock pores, so that an oil film adhered to the rock surface is easier to fall off, the oil displacement area is enlarged, and the recovery efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of enhanced oil recovery in oilfields, and relates to a method for reducing viscosity and removing plugging of a composite bio-enzyme microorganism and its application. Background Art

[0002] At present, in some oil wells in domestic oilfields, the viscosity of crude oil is high, and the wax content and gum content are high. During the development process, heavy components precipitate due to changes in formation temperature and pressure, and block the pores after deposition, resulting in a decrease in crude oil production. The conventional method is to relieve the plugging of inorganic pollution through measures such as acidification and low-temperature self-generated gas, but the effect of relieving plugging of organic pollution is not ideal.

[0003] Therefore, there is an urgent need for a method for reducing viscosity and removing plugging of a composite bio-enzyme microorganism. Under the condition of not moving the pipe string, a composite bio-enzyme microorganism system is injected through the annulus between the tubing and the casing to dissolve heavy components, reduce the viscosity of crude oil, and restore the productivity of a single well. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art and provide a method for reducing viscosity and removing plugging of a composite bio-enzyme microorganism and its application.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] On the one hand, the present invention provides a method for reducing viscosity and removing plugging of a composite bio-enzyme microorganism, specifically including the following steps:

[0007] Step 1: Prepare a bio-enzyme preparation solution with a specific concentration;

[0008] Step 2: First inject the pre-prepared preflush fluid into the oil well to be treated, and then inject the bio-enzyme preparation solution into the oil well to be treated;

[0009] Step 3: First prepare a microbial inoculum with a specific concentration and inject it into the oil well to be treated in Step 2, then inject a displacement fluid, and shut in the well for a specific reaction time;

[0010] Step 5: After the reaction is completed, conduct a trial pumping on the oil well. After passing the trial pumping, start production.

[0011] Specifically, the volume ratio of the bio-enzyme preparation solution to the microbial inoculum is 1:(1-10).

[0012] Specifically, in Step 1, the concentration of the bio-enzyme in the bio-enzyme preparation solution is 3-5%.

[0013] Specifically, in Step 3, the concentration of the microorganism in the microbial inoculum is 3-5%.

[0014] Specifically, in Step 3, the temperature of the microbial inoculum is 40-50°C.

[0015] Specifically, in step 3, the specific time for the well to stop and react is 120 - 168 h.

[0016] Specifically, both the preflush fluid and the displacement fluid are clear water.

[0017] Specifically, the bio - enzyme in the bio - enzyme preparation solution includes one of rhamnolipid, lipopeptide, and sophorolipid; when preparing the bio - enzyme preparation solution with a bio - enzyme fermentation broth, the concentration of the bio - enzyme fermentation broth is 30 - 90 g / L.

[0018] Specifically, the microorganisms in the microbial liquid include one of Pseudomonas aeruginosa, Bacillus licheniformis, and Bacillus subtilis; the microbial liquid is prepared with a microbial strain concentration of 10 8 -10 9 CFU / ml.

[0019] Specifically, when injecting the preflush fluid, bio - enzyme preparation solution, microbial liquid, and displacement fluid into the oil well to be treated, the construction pressure will be slightly higher than the pressure of the oil well to be treated to ensure that the injected fluid can effectively enter the oil well to be treated.

[0020] On the other hand, the present invention provides an application of the viscosity - reducing and plug - removing method of composite bio - enzyme microorganisms, which is an application of the viscosity - reducing and plug - removing method of composite bio - enzyme microorganisms in restoring the productivity of oil wells.

[0021] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0022] The viscosity - reducing and plug - removing method of composite bio - enzyme microorganisms of the present invention injects the bio - enzyme preparation solution and the microbial liquid into the oil well to be treated respectively, which can effectively dissolve heavy components, significantly reduce the viscosity of crude oil, and help improve the fluidity of crude oil; moreover, this method can effectively address the problem of blockage of pore channels caused by the precipitation of heavy components due to changes in formation temperature and pressure, restore the normal productivity of oil wells, and increase the crude oil production.

[0023] Furthermore, the bio - enzyme injected into the oil well to be treated first adsorbs with the heavy components in the oil well to form an enzyme complex, then the enzyme complex decomposes into an enzyme - oil intermediate, and precipitates solid particles. Subsequently, the enzyme - oil intermediate decomposes, separating crude oil and the bio - enzyme restored to its original state; the bio - enzyme restored to its original state adsorbs and combines with the heavy components again for a new round of reaction until the bio - enzyme loses its activity; therefore, the bio - enzyme effectively dissolves heavy components, reduces the viscosity of crude oil, and improves the productivity of oil wells.

[0024] In addition, microorganisms can utilize crude oil as the sole nutrient source for growth and reproduction, effectively catalyzing the cleavage and degradation of long carbon chain components such as paraffin, asphalt, and resin in crude oil into short carbon chain components, reducing the long chain components in crude oil, thereby reducing the deposition of macromolecular substances, and significantly decreasing the freezing point and viscosity of crude oil. Further, during the metabolic process, microorganisms produce biogas, causing the volume of crude oil to expand, thus reducing the viscosity of crude oil. Additionally, microorganisms will adhere to the sedimentary film formed on the rock surface, which can improve the surface properties of rock pores, making the oil film attached to the rock surface easier to fall off, and facilitating the survival and extension of cells in the pores of the oil reservoir, expanding the oil displacement area, and increasing the recovery rate.

[0025] In summary, by injecting bioenzymes first, the plugging removal effect is initially achieved, and a better living environment is also created for the subsequently injected microorganisms. Using microbial strains adapted to the oil well environment can better adapt to the complex and changeable environment of the oil well, ensuring the effectiveness and long-term nature of viscosity reduction and plugging removal. Microorganisms reproduce using crude oil as the sole nutrient source, while ensuring the plugging removal effect, also reducing the possibility of underground pollution. Brief Description of the Drawings

[0026] The accompanying drawings here are incorporated into the specification and form a part of this specification, and are used together with the specification to explain the principles of the present invention.

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the accompanying drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a flowchart of the method for reducing viscosity and removing plugging of the composite bioenzyme microorganism of the present invention;

[0029] Figure 2 It is a schematic diagram of the adsorption of bioenzyme in a porous medium;

[0030] Figure 3 It is a schematic diagram of the retention of bioenzyme in a porous medium;

[0031] Figure 4 It is a schematic diagram of microorganisms in a natural state;

[0032] Figure 5 It is a schematic diagram of microorganisms adhering to the core surface;

[0033] Figure 6 It is a schematic diagram of the reduction of the surface tension of crude oil after the mixture of bioenzyme and crude oil;

[0034] Figure 7 It is a schematic diagram of the reduction of the viscosity of crude oil after the mixture of bioenzyme and crude oil. Detailed implementation manners

[0035] Here, exemplary embodiments will be described in detail, and examples thereof are shown in the accompanying drawings. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present invention. On the contrary, they are merely examples consistent with some aspects of the present invention detailed in the appended claims.

[0036] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] The present invention calculates the dosage of the composite bio-enzyme microorganism using the following formula:

[0038] Q = πR 2 HΦ Formula 1

[0039] Wherein: Q is the dosage of the composite bio-enzyme microorganism, with the unit of m 3 ; π is the pi, taking 3.14; R is the radius of plug removal, with the unit of m; H is the effective thickness of the oil layer, with the unit of m; Φ is the porosity, with the unit of %.

[0040] To verify the effect of the viscosity reduction and plug removal method of the present invention, the following embodiments are provided for verification. Table 1 shows the ratios of the preflush fluid, bio-enzyme preparation fluid, microbial bacterial fluid, and displacement fluid in each embodiment.

[0041] Table 1

[0042]

[0043] Example 1

[0044] Referring to Figure 1 as shown, this embodiment provides a viscosity reduction and plug removal method using a composite bio-enzyme microorganism in Oilfield A, which specifically includes the following steps:

[0045] Step 1: Stop pumping the well to be treated, stop the donkey head of the pumping unit at the top dead center, close all valves at the wellhead of the well to be treated and the packing of the polished rod seal, check whether all screws and fittings at the wellhead of the well to be treated are complete and tightened, close the oil and casing valves, and test the wellhead and surface pipelines at 25 MPa. It is qualified if there is no leakage.

[0046] Step 2: Pour rhamnolipid into an empty tank truck, with the selected rhamnolipid content of 45 g / L, and then add clear water. The process of adding clear water plays a stirring role and can evenly dissolve the rhamnolipid (if adding clear water first and then the medicament, appropriate stirring must be done to make it evenly dissolve), and prepare a rhamnolipid preparation solution with a concentration of 3% and a volume of 21 m 3 ;

[0047] Step 3: For the squeezing operation, the reverse squeezing method through the annulus between the production casing and tubing is adopted. Connect the cement pump truck and the wellhead of the well to be treated with a rigid pipeline, and connect the reverse injection pipeline. First, inject 20 m of the preflush fluid 3 for well flushing, with the pressure ≤ 15 MPa and the displacement > 500 L / min. Flush until the water quality at the wellhead inlet and outlet is the same, which is considered qualified, and promptly report the formation leakage situation during the well flushing process.

[0048] Step 4: Then inject 21 m of 3 the rhamnolipid preparation fluid into the well to be treated, with the pressure ≤ 15 MPa and the displacement > 100 L / min.

[0049] Step 5: Prepare 21 m of 3 Pseudomonas aeruginosa bacterial solution with a concentration of 3% and a temperature of 40 - 43°C. The selected concentration of Pseudomonas aeruginosa is 10 8 CFU / ml.

[0050] Step 6: Inject 21 m of 3 the above-mentioned Pseudomonas aeruginosa bacterial solution into the well to be treated in Step 2. After injection, inject 20 m of the displacement fluid 3 to ensure that the Pseudomonas aeruginosa bacterial solution in the wellbore can completely enter the formation. Close the casing valve and shut in the well for 168 hours. The pressure ≤ 15 MPa and the displacement > 100 L / min.

[0051] Step 7: After the shut-in reaction is completed, open the inlet flow path, loosen the packing of the polished rod seal, start the pumping unit, and after successful trial pumping, put it into production.

[0052] For Well X in Oilfield A, a viscosity reduction and plugging removal construction of composite bioenzyme microorganisms is carried out. The treated oil layer is a sandstone oil and gas reservoir, with a formation pressure of 14.5 MPa, an average porosity of the oil layer of 14.5%, an effective thickness of the oil layer of 10.2 m. Before construction, the daily liquid production is 1.2 t, the daily oil production is 0.7 t, and the water cut is 44.3%. After construction, the initial daily liquid production is 3.1 t, the daily oil production is 1.7 t, and the water cut is 45.2%. In the later stage, the daily liquid production increase is 1.6 t, the daily oil production increase is 0.9 t, the construction effective period is 200 days, and the cumulative oil increase is 180 t.

[0053] The average porosity of the oil layer is 14.5%, the effective thickness is 10.2 m, and the plugging removal radius is 3 m. Calculate the treatment fluid volume according to Equation 1 and round up to an integer to determine that the required treatment fluid volume is 42 m 3 ;

[0054] Calculated based on the bioenzyme and microorganism concentration of 3% (v / v) in the treatment fluid, a total of 1.26 m of 3 the oil displacement agent of composite bioenzyme microorganisms needs to be prepared, with a temperature of 40 - 43°C.

[0055] Among them, the bioenzyme and microorganism are configured in a ratio of 1:1, so both are 0.63 m3 ;

[0056] Table 2 is the statistical table of crude oil physical properties analysis in Example 1

[0057]

[0058] According to Table 2, after construction, the produced oil was detected. For the viscosity detection at 50°C, the viscosity decreased by 21.9%, the wax content decreased by 30.3%, the gum content decreased by 31.5%, and the freezing point decreased by 13.5%. Therefore, the viscosity reduction and plugging removal method using this compound bio-enzyme microorganism has an obvious effect on viscosity reduction and plugging removal of Well X, and can significantly improve the crude oil recovery rate.

[0059] Example 2

[0060] See Figure 1 As shown, this example provides a viscosity reduction and plugging removal method using compound bio-enzyme microorganism in Oilfield B, which specifically includes the following steps:

[0061] Step 1: Stop pumping the well to be treated, stop the donkey head of the pumping unit at the top dead center, close all valves at the wellhead of the well to be treated and the packing of the polished rod seal, check whether all screws and fittings at the wellhead of the well to be treated are complete and tightened, close the oil and casing valves, and test the pressure of the wellhead and surface pipelines at 25 MPa. It is qualified if there is no leakage;

[0062] Step 2: Pour the lipopeptide into an empty tanker truck. The selected lipopeptide content is 60 g / L, and then add clear water. The process of adding clear water plays a stirring role and can make the lipopeptide dissolve evenly (if adding clear water first and then the medicament, appropriate stirring must be done to make it dissolve evenly), and prepare a lipopeptide preparation solution with a concentration of 4% and a volume of 8 m 3 ;

[0063] Step 3: For the squeezing construction, adopt the method of reverse squeezing in the annulus between the oil pipe and the casing. Connect the cement pump truck and the wellhead of the well to be treated with a hard pipeline, and connect the reverse squeezing injection pipeline; first inject 20 m of preflush fluid 3 for well flushing, with the pressure ≤ 16 MPa and the displacement > 500 L / min. Flush until the water quality at the wellhead inlet and outlet is the same, which is qualified, and report the formation leakage situation during the well flushing process in a timely manner;

[0064] Step 4: Then inject 8 m 3 of the lipopeptide preparation solution into the well to be treated, with the pressure ≤ 16 MPa and the displacement > 100 L / min;

[0065] Step 5: Prepare 40 m 3 of bacillus licheniformis bacterial solution with a concentration of 4% and a temperature of 44 - 46°C. The selected concentration of bacillus licheniformis is 5×10 8 CFU / ml;

[0066] Step 6: Inject 40 m3 Inject the Bacillus licheniformis bacterial liquid into the oil well to be treated described in step 2. After injection, inject 20 m of displacement fluid 3 , so that the Bacillus licheniformis bacterial liquid in the oil well borehole can completely enter the formation. Close the casing valve and stop the well for reaction for 144 hours; pressure ≤ 16 MPa, displacement > 100 L / min;

[0067] Step 7: After the well stopping reaction ends, open the inlet process, loosen the packing of the polished rod seal, start the pumping unit, and after qualified trial pumping, enter the production at the station.

[0068] For Well Y in Oilfield B, a viscosity reduction and plugging removal construction of composite bio - enzyme microorganisms is carried out. The treated oil layer is a sandstone oil layer, the formation pressure is 15.6 MPa, the average porosity of the oil layer is 13.8%, the effective thickness of the oil layer is 12.3 m. Before construction, the daily liquid production is 1.5 t, the daily oil production is 0.2 t, and the water cut is 86.7%; after construction, the initial daily liquid production is 2.5 t, the daily oil production is 1.8 t, and the water cut is 28%; in the later stage, the daily increased liquid production is 1.0 t, the daily increased oil production is 1.6 t, the construction effective period is 130 days, and the cumulative increased oil production is 208 t.

[0069] The average porosity of the oil layer is 13.8%, the effective thickness is 12.3 m, and the plugging removal radius is 3 m. Calculate the treatment liquid volume according to formula 1 and round up to an integer. Determine that the required treatment liquid volume is 48 m 3 ;

[0070] Calculated based on the bio - enzyme and microorganism concentration of 4% (v / v) in the treatment liquid, a total of 1.92 m of 3 composite bio - enzyme microorganism oil displacement agent is required, and the temperature is 44 - 46 °C.

[0071] Among them, the bio - enzyme and microorganism are configured in a ratio of 1:5, so the bio - enzyme is 0.32 m 3 , and the microorganism is 1.6 m 3 ;

[0072] Table 3 is the statistical table of crude oil analysis in Example 2

[0073]

[0074] According to Table 3, it can be seen that the viscosity reduction and plugging removal effect of Well Y using the viscosity reduction and plugging removal method of the present composite bio - enzyme microorganism is obvious, and the oil production significantly increases after the construction of the oil well to be treated.

[0075] Example 3

[0076] Refer to Figure 1 shown. This example provides a viscosity reduction and plugging removal method using composite bio - enzyme microorganisms in Oilfield C, which specifically includes the following steps:

[0077] Step 1: Stop pumping the oil well to be treated. The donkey head of the pumping unit stops at the top dead center. Close all valves at the wellhead of the oil well to be treated and the packing of the polished rod seal. Check whether all screws and fittings at the wellhead of the oil well to be treated are complete and tightened. Close the oil and casing valves. Pressure test the wellhead and surface pipelines at 25 MPa. It is qualified if there is no leakage.

[0078] Step 2: Pour sophorolipid into an empty tanker truck. The selected content of sophorolipid is 75 g / L, and then add clear water. The process of adding clear water plays a stirring role and can evenly dissolve the sophorolipid (if adding clear water first and then the medicament, appropriate stirring must be done to make it dissolve evenly). Prepare 6 m 3 sophorolipid preparation solution with a concentration of 5%.

[0079] Step 3: The squeezing operation is carried out in the annulus between the tubing and the casing in a reverse squeezing manner. Connect the cement pump truck and the wellhead of the oil well to be treated with a hard pipeline, and connect the reverse squeezing injection pipeline. First, inject 20 m of preflush fluid 3 for well flushing. The pressure ≤ 15.5 MPa and the displacement > 500 L / min. Flush until the water quality at the wellhead inlet and outlet is the same, which is qualified. Report the formation loss situation during the well flushing process in a timely manner.

[0080] Step 4: Then inject 6 m 3 of the sophorolipid preparation solution into the oil well to be treated. The pressure ≤ 15.5 MPa and the displacement > 100 L / min.

[0081] Step 5: Prepare 60 m 3 of Bacillus subtilis bacterial solution with a concentration of 5% and a temperature of 47 - 50 °C. The selected concentration of Bacillus subtilis is 10 9 CFU / ml.

[0082] Step 6: Inject the 60 m 3 of the Bacillus subtilis bacterial solution into the oil well to be treated in Step 2. After injection, inject 20 m of displacement fluid 3 to make the Bacillus subtilis bacterial solution in the wellbore of the oil well completely enter the formation. Close the casing valve and stop the well for reaction for 120 hours. The pressure ≤ 15.5 MPa and the displacement > 100 L / min.

[0083] Step 7: After the well stopping reaction is over, open the inlet flow path, loosen the packing of the polished rod seal, start the pumping unit, and after a qualified trial pumping, start production into the station.

[0084] For Well Z in Oilfield C, a viscosity reduction and plugging removal construction of composite bio - enzyme microorganisms was carried out. The treated oil reservoir is a sandstone oil reservoir, with a formation pressure of 15.0 MPa, an average porosity of the oil reservoir of 18.3%, an effective thickness of the oil reservoir of 12.6 m. Before the construction, the daily liquid production was 2.6 t, the daily oil production was 1.0 t, and the water cut was 61.5%; in the initial stage after the construction, the daily liquid production was 5.0 t, the daily oil production was 2.8 t, and the water cut was 44%; in the later stage, the daily increased liquid production was 2.4 t, the daily increased oil production was 1.3 t, the construction validity period was 150 days, and the cumulative increased oil production was 195 t.

[0085] The average porosity of the oil reservoir is 18.3%, the effective thickness is 12.6 m, and the plugging removal radius is 3 m. Calculate the treatment liquid volume according to Equation 1 and round up to an integer. Determine that the required treatment liquid volume is 66 m 3 ;

[0086] Calculated based on the bio - enzyme and microorganism concentration of 5% (v / v) in the treatment liquid, a total of 3.3 m 3 of composite bio - enzyme microorganism oil displacement agent is required, and the temperature is 47 - 50 °C.

[0087] Among them, the bio - enzyme and microorganism are configured in a ratio of 1:10, so the bio - enzyme is 0.3 m 3 , and the microorganism is 3 m 3 .

[0088] Table 4 is the statistical table of crude oil analysis in Example 3

[0089]

[0090] According to Table 4, it can be seen that the viscosity reduction and plugging removal effect of Well Z using the viscosity reduction and plugging removal method of this composite bio - enzyme microorganism is obvious. After the construction of the oil well to be treated, the oil production has increased significantly.

[0091] The reaction mechanism of the bio - enzyme and microorganism of the present invention in the oil well to be treated: The bio - enzyme is a biological agent for improving crude oil recovery formed by compounding according to the utilization functions and uses of microbial metabolites; it mainly consists of glycolipids and lipopeptide surfactants; the specific reaction process is as follows:

[0092] See Figure 2 and 3 As shown, the bio - enzyme injected first adsorbs or remains in the porous medium of the oil reservoir and forms an enzyme complex with the crude oil plugging body; the enzyme complex is further decomposed into an enzyme - oil intermediate, and the solid particles in the crude oil plugging body are precipitated; then the enzyme - oil intermediate decomposes, separating the crude oil, and the bio - enzyme returns to its original state; the bio - enzyme then adsorbs and binds to the plugging body again and continues the above cycle; the bio - enzyme adsorbs and binds to different plugging bodies multiple times until the bio - enzyme loses its activity.

[0093] It should also be noted that the microbial flora can utilize crude oil as the sole nutrient source for growth and reproduction, effectively catalyze the cleavage of long carbon chain components such as paraffin, asphalt, and gum in crude oil, degrade them into short carbon chain components, reduce the long chain components in crude oil, reduce the deposition of macromolecular substances, and significantly lower the freezing point and viscosity of crude oil. Further, the microbial metabolism produces biogas, which expands the volume of crude oil and reduces its viscosity. The deposition film formed by the adhesion of microorganisms to the rock surface can improve the surface properties of the rock pores, make the oil film attached to the rock surface easier to fall off, and is conducive to the survival and extension of cells in the pores of the oil layer, expanding the oil displacement area and increasing the recovery rate. The present invention preferably selects a composite bioenzyme-microorganism system composed of a bioenzyme that can dissolve blockages multiple times and a specific microbial flora using crude oil as the sole nutrient source, meeting the requirements of viscosity reduction and plugging removal.

[0094] The present invention provides a method for optimizing the bioenzyme concentration, which is as follows:

[0095] 1. First, dilute the bioenzyme with water without preservatives into solutions with concentrations of 5%, 3%, 1%, 0.5%, 0.1%, and 0.01% respectively, then add them into the dehydrated crude oil separated from the oilfield samples respectively. After stirring with a glass rod, seal the bottle mouth with plastic wrap, place it in a constant temperature incubator (under formation temperature conditions), stir once every 2 hours, and measure its surface tension after 48 hours.

[0096] See Figure 6 As shown, the results show that when the bioenzyme concentration is 5%, it has a good effect on reducing the surface tension of crude oil; when the bioenzyme concentration is 3%, the reduction rate of the surface tension of crude oil can reach 55.4%; when the bioenzyme concentration is 0.1%, the reduction rate of the surface tension of crude oil can reach 52.1%.

[0097] 2. First, dilute the bioenzyme with water without preservatives into solutions with concentrations of 5%, 3%, 1%, 0.5%, 0.1%, and 0.01% respectively, then add them into the dehydrated crude oil separated from the oilfield samples respectively. After stirring with a glass rod, seal the bottle mouth with plastic wrap, place it in a constant temperature incubator (under formation temperature conditions), stir once every 2 hours, and measure its viscosity after 48 hours.

[0098] See Figure 7 As shown, the results show that when the bioenzyme concentration is 5%, it can reduce the crude oil concentration by 94.5%, and when the bioenzyme concentration is 3%, it can reduce the viscosity of crude oil by more than 90%.

[0099] Therefore, the present invention selects the bioenzyme concentration to be 3 - 5% to ensure better reduction of the surface tension of crude oil and the viscosity of crude oil.

[0100] The present invention provides a method for optimizing the microorganism concentration, which is as follows:

[0101] The crude oil after different dehydration and degassing treatments was mixed with *Bacillus subtilis* and cultured in a shaker at 150 r / min for 7 days. Through observation, it was found that the desorption ability and solubility of the crude oil with the addition of the microbial inoculant to the bottle wall were enhanced, and the oil and water could form a uniform emulsion. After standing, there was no stratification between the upper and lower layers, indicating that *Bacillus subtilis* had a good emulsifying effect and would have important application value in the microbial enhanced oil recovery with composite bioenzymes.

[0102] Determination of the emulsification coefficient: *Bacillus subtilis* and kerosene were mixed (2:3, V / V) and added to a graduated colorimetric tube, shaken and stirred thoroughly for a period of time, and then left to stand at room temperature for 24 h. After standing, the heights of the emulsified layer and the total liquid were measured, and the emulsification coefficient of each sample was calculated as shown in Equation 2:

[0103] Emulsification coefficient = (height of emulsified layer / height of total liquid) × 100% Equation 2

[0104] After the mixed liquid stood for a period of time, the originally homogeneous emulsion gradually stratified. By measuring the heights of the emulsified layer and the total liquid, the emulsification coefficient of the microbial inoculant was calculated to be 70.11%, as shown in Table 5.

[0105] Table 5 Emulsification coefficient of the microbial inoculant

[0106] Pharmaceutical Total liquid height / cm Emulsion layer height / cm Emulsification coefficient (%) Microorganism 8.7 6.1 70.11

[0107] Artificial cores simulating the main reservoir of a certain oilfield were used. The test temperature was controlled at the reservoir temperature. The crude oil and water used in the test were taken from the oil-water samples retrieved from the production wells and metering stations in the block, and the microorganisms used in the experiment were 5%.

[0108] Test steps: Core vacuuming - water saturation - porosity calculation - water flooding to measure water-phase permeability - simulation of plugging - measurement of permeability after plugging - injection of 5% microorganisms - reaction for 7 days - water flooding - measurement of restored permeability - calculation of plugging removal efficiency. The results of the physical simulation of microbial plugging removal experiments showed that the recovery rate of the permeability of the cores plugged with organic matter was above 80%, as shown in Table 6.

[0109] Table 6 Statistical table of the results of microbial plugging removal experiments

[0110]

[0111] Similarly, when the microbial concentration was 3 - 5% using the above experimental method, the recovery rate of the permeability of the cores plugged with organic matter was above 70%.

[0112] The present invention also provides a preparation method of a bioenzyme, and the specific steps are as follows:

[0113] Step 1: Inoculate the Candida yeast strain into a shake flask containing a culture medium, and culture it at a temperature of 35 - 37°C and a stirring speed of 180 - 220 rpm for 20 - 24 h to obtain a shake flask seed solution;

[0114] Step 2: Inoculate the shake flask seed solution into a shake flask containing a culture medium, and culture it at a temperature of 35 - 37°C, a stirring speed of 180 - 220 rpm, an aeration rate of 2.8 - 3.2 vvm, and a tank pressure of 0.1 - 0.2 MPa for 16 - 20 h to obtain a secondary seed solution;

[0115] Step 3: Inoculate the secondary seed solution into a tank containing a fermentation medium, and ferment it at a temperature of 35 - 37°C, a stirring speed of 200 - 300 rpm, an aeration rate of 3.0 - 4.0 vvm, and a tank pressure of 0.1 - 0.2 MPa for 118 - 124 h to obtain sophorolipid fermentation broth;

[0116] Step 4: Filter the sophorolipid fermentation broth through a ceramic membrane, collect the filtered clear liquid, and the concentration of sophorolipid after filtration is 30 - 90 g / L. The present invention can also use the sophorolipid fermentation broth to prepare a biological enzyme preparation solution.

[0117] It should be added that the formula of the culture medium is: containing 1.0 g of yeast extract, 1.0 g of glucose, 0.1 g of dipotassium hydrogen phosphate, 0.1 g of potassium dihydrogen phosphate, and 0.02 g of magnesium sulfate in every 100 ml of water, and the pH value is 4.8.

[0118] The present invention also provides a preparation method of a microorganism, and the specific steps are as follows:

[0119] Step 1: Inoculate the Bacillus subtilis strain into a liquid culture medium, and culture it at a temperature of 35 - 37°C and a stirring speed of 200 - 240 rpm for 22 - 25 h to obtain a shake flask seed solution;

[0120] Step 2: Inoculate the shake flask seed solution into a liquid culture medium, and culture it at a temperature of 35 - 37°C, a stirring speed of 180 - 220 rpm, an aeration rate of 1.0 - 2.0 vvm, and a tank pressure of 0.08 - 0.095 MPa for 16 - 20 h to obtain a secondary seed solution;

[0121] Step 3: Inoculate the secondary seed solution into a tank containing a fermentation medium, and ferment it at a temperature of 35 - 37°C, a stirring speed of 120 - 160 rpm, an aeration rate of 0.2 - 0.6 vvm, and a tank pressure of 0.08 - 0.095 MPa for 36 - 48 h until the bacterial concentration reaches 10 8 -10 9 CFU / ml, then the preparation of Bacillus subtilis is completed.

[0122] It should be supplemented and explained that the formula of the liquid medium is as follows: containing 0.5 g of yeast extract, 2 g of glucose, 0.8 g of dipotassium hydrogen phosphate and 0.05 g of potassium dihydrogen phosphate in every 100 ml of water, and the pH value is 6.8.

[0123] Finally, it should be noted that during actual use, the temperature of the microbial bacterial liquid can be adjusted according to the actual situation of the oil well to meet the production requirements.

[0124] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0125] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A composite bio-enzyme microbial viscosity reduction and plugging removal method, characterized in that: The specific steps include: Step 1, preparing a biological enzyme preparation solution of a specific concentration; Step 2, first injecting the pre-prepared pre-fluid into the oil well to be treated, and then injecting the biological enzyme preparation solution into the oil well to be treated; Step 3, first prepare a microbial liquid of a specific concentration and inject it into the oil well to be treated in step 2, then inject a displacement fluid, and stop the well for a specific reaction time; Step 4: After the reaction is completed, the oil well is tested for pumping, and production is carried out after the test pumping is qualified.

2. The viscosity reduction and plugging removal method of composite bio-enzyme microorganisms according to claim 1, characterized in that: The volume ratio of the biological enzyme preparation liquid to the microbial bacterial liquid is 1:(1-10).

3. The viscosity reduction and plugging removal method of composite bio-enzyme microorganisms according to claim 1, characterized in that: In step 1, the concentration of the biological enzyme in the biological enzyme preparation solution is 3-5%.

4. The viscosity reduction and plugging removal method of composite bio-enzyme microorganisms according to claim 1, characterized in that: In step 3, the concentration of microorganisms in the microbial liquid is 3-5%.

5. The viscosity reduction and plugging removal method of composite bio-enzyme microorganisms according to claim 1, characterized in that: In step 3, the temperature of the microbial culture liquid is 40-50°C.

6. The viscosity reduction and plugging removal method of composite bio-enzyme microorganisms according to claim 1, characterized in that: In step 3, the specific time for shutting down the well for reaction is 120 to 168 hours.

7. The viscosity reduction and plugging removal method of composite bio-enzyme microorganisms according to claim 1, characterized in that: The pre-fluid and displacement fluid are both clean water.

8. The viscosity reduction and plugging removal method of composite bio-enzyme microorganisms according to claim 1, characterized in that: The biological enzyme in the biological enzyme preparation solution includes one of rhamnolipid, lipopeptide and sophorolipid.

9. The viscosity reduction and plugging removal method of composite bio-enzyme microorganisms according to claim 1, characterized in that: The microorganisms in the microbial liquid include one of Pseudomonas aeruginosa, Bacillus licheniformis and Bacillus subtilis.

10. Application of the viscosity reduction and plugging removal method based on the composite bio-enzyme microorganism according to any one of claims 1 to 9, characterized in that: The composite bio-enzyme microorganism viscosity reduction and plugging removal method is used in restoring oil well productivity.

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