Method for preparing composite microbial oil-displacement system having dual functions of produced water treatment and oil displacement

Abstract

Provided is a method for preparing a composite microbial oil-displacement system having the dual functions of produced water treatment and oil displacement. The preparation method comprises: mixing composite microorganisms with oil-containing produced water, performing an expanding culture, and then bringing the expanded material into contact with an oil reservoir to be subjected to oil displacement, wherein the composite microorganisms comprise Candida viswanathii with a deposit number of CGMCC No. 3456, Bacillus subtilis with a deposit number of CGMCC No. 21860, and Pseudomonas aeruginosa with a deposit number of CGMCC No. 23170. The composite microorganisms can significantly reduce interfacial tension and have a good oil displacement effect.

Description

Preparation method of composite microbial oil recovery system with dual functions of produced water treatment and oil recovery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202311279605.4 filed on September 28, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of microbial oil recovery, and in particular to a method for preparing a composite microbial oil recovery system with the dual functions of produced water treatment and oil recovery. Background Art

[0004] Globally, water availability and ecological conservation have significantly constrained the development of oil and gas resources. Furthermore, fracturing and acidizing during reservoir waterflooding, as well as the application of chemical flooding technologies such as polymer and composite flooding, result in a complex composition of oil-bearing produced water, posing significant risks to the environment and formations. Reuse after treatment, such as sedimentation and filtration, is costly and complex, and can even result in secondary pollution. Microbial flooding, with its environmentally friendly nature and the need for no special treatment of produced water, has demonstrated promising potential for improving oilfield recovery. With the rapid advancement of biotechnology and the increasing ability to manipulate microorganisms, microbial oil recovery is poised to make significant contributions to the development of the petroleum industry.

[0005] At present, domestic and foreign microbial flooding technologies (throughput, plugging removal, profile adjustment, oil recovery, etc.) mainly inject one or more microbial fermentation liquids / nutrient systems directly into the formation to recover oil. There is no ground treatment of produced water and expansion and proliferation process, which leads to high transportation costs and ineffective utilization of oilfield produced water resources.

[0006] CN112374701A provides an oilfield produced water treatment process using an oleophilic bacterial group to remove oil. The biological bacterial agent contains Bacillus licheniformis, Bacillus brevis, and Pseudomonas in a compound ratio of 2:1:1. The oil in the produced water is decomposed into non-toxic carbon dioxide and water, and then the effluent is filtered through a membrane to meet the water quality standards for oilfield injection. However, the microorganisms in the water are also filtered out after treatment and cannot be reused.

[0007] CN104312561A discloses a composite microbial strain for use in tertiary oil recovery. A mixed fermentation liquid of Halobacterium salinarium, Brevibacillus brevis, and Bacillus cereus in a weight ratio of 1:1:1 is used in tertiary oil recovery. The strain survives in a high-salt oil recovery environment with a salt content higher than 12%. The crude oil viscosity is reduced by 15.4%, 26.4%, and 35.2%, respectively, and the oil-water interfacial tension is reduced by 91.3%, 76.5%, and 58.6%, respectively. The strain has significant beneficial effects in reducing crude oil viscosity and oil-water interfacial tension, and exhibits wide application value. However, the mixed fermentation liquid needs to be fermented and expanded in large quantities in a factory and transported to the test site, which is costly.

[0008] Under the background of "low-cost, green and efficient" energy development requirements, how to combine produced water microbial treatment with microbial flooding to enhance oil recovery technology, effectively utilize produced water resources, improve oil field recovery, and achieve dual environmental protection on the surface and underground, is of great strategic significance to the "quality, efficiency and sustainable development" of oil reservoirs.

[0009] Summary of the Invention

[0010] The purpose of the present invention is to overcome the problems of the prior art in that the bio-bacterial agent oil recovery effect is not ideal, the ground strain fermentation process is cumbersome, the bacterial liquid needs to be transported over long distances, and the produced water after oil recovery cannot be reinjected into the formation for oil recovery. A preparation method of a composite microbial oil recovery system with the dual functions of produced water treatment and oil recovery is provided. The composite microorganisms used in the preparation method can significantly reduce interfacial tension and have a good oil recovery effect. The microbial oil recovery device can, on the one hand, utilize the growth and metabolism of the composite microorganisms to remove oil from the produced water, and on the other hand, utilize the produced water after proliferation and expansion to be injected into the formation for oil recovery.

[0011] In order to achieve the above-mentioned object, the present invention provides a method for preparing a composite microbial oil recovery system having the dual functions of produced water treatment and oil recovery, wherein the preparation method comprises: mixing the composite microorganism with oil-containing produced water for expansion, and then contacting the expanded material with the oil reservoir to be recovered; wherein,

[0012] The composite microorganism comprises Candida vesiculosus with a preservation number of CGMCC No.3456, Bacillus subtilis with a preservation number of CGMCC No.21860 and Pseudomonas aeruginosa with a preservation number of CGMCC No.23170.

[0013] Through the above technical solution, the beneficial effects of the present invention are:

[0014] The composite microorganisms used in the preparation method of the composite microbial oil displacement system with the dual functions of produced water treatment and oil displacement provided by the present invention can significantly reduce interfacial tension and have a good oil displacement effect.

[0015] In the device used in the preparation method of the composite microbial oil recovery system with the dual functions of produced water treatment and oil recovery provided by the present invention, microbial oil recovery is carried out. By adding the composite microorganisms into the microbial oil recovery device, on the one hand, the oil-containing impurities in the produced water of the oil reservoir can be removed by utilizing the growth metabolism of the microorganisms; on the other hand, the water treated by microbial expansion is injected into the formation to recover oil, which not only purifies the water quality to meet the oil field reinjection standard, but also avoids the tedious process of industrial fermentation of single strains on the ground and the inconvenience of long-distance transportation of microbial agent products; that is, the method of the present invention is used to remove oil from the oil-containing produced water, and then reinject it into the oil reservoir to be recovered for oil recovery, thereby recycling water resources while improving the recovery rate of the oil reservoir, achieving multiple goals at one stroke, having the advantages of low cost, simple operation, and being green and environmentally friendly, and having broad prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a schematic diagram of a microbial oil recovery device in a preferred embodiment of the present invention.

[0017] DESCRIPTION OF REFERENCE NUMERALS 1 Primary expansion tank 2 Secondary expansion tank 3 Tertiary expansion tank 4 Sedimentation tank 5 Water inlet 6 Water outlet 7 Overflow port 8 Filler 9 Liquid distribution tank 10 Buffer tank 11 Dosing pump 12 Aeration pump DETAILED DESCRIPTION

[0018] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0019] The present invention provides a method for preparing a composite microbial oil recovery system having the dual functions of produced water treatment and oil recovery, wherein the preparation method comprises: mixing the composite microorganism with oil-containing produced water for expansion, and then contacting the expanded material with the oil reservoir to be recovered; wherein,

[0020] The composite microorganism comprises Candida vesiculosus with a preservation number of CGMCC No.3456, Bacillus subtilis with a preservation number of CGMCC No.21860 and Pseudomonas aeruginosa with a preservation number of CGMCC No.23170.

[0021] The inventors have discovered that a specific combination of Candida viswanathii with a preservation number of CGMCC No. 3456, Bacillus subtilis with a preservation number of CGMCC No. 21860, and Pseudomonas aeruginosa with a preservation number of CGMCC No. 23170 has a good oil displacement effect.

[0022] Candida vesiculosus with a deposit number of CGMCC No. 3456 has been disclosed in CN101781624B, Bacillus subtilis with a deposit number of CGMCC No. 21860 has been disclosed in CN116200285A, and Pseudomonas aeruginosa with a deposit number of CGMCC No. 23170 has been disclosed in CN116445316A.

[0023] According to the present invention, preferably, in the composite microorganism, the ratio of the viable counts of Candida vesiculosus (CGMCC No. 3456), Bacillus subtilis (CGMCC No. 21860), and Pseudomonas aeruginosa (CGMCC No. 23170) is 1:(1-3):(1-5). When the ratio of the viable counts of yeast, Bacillus, and Pseudomonas falls within this range, the oil displacement effect of the composite microorganism can be further improved.

[0024] Furthermore, in the composite microorganism, the ratio of the number of viable bacteria of Candida vesiculosus with a preservation number of CGMCC No. 3456, Bacillus subtilis with a preservation number of CGMCC No. 21860, and Pseudomonas aeruginosa with a preservation number of CGMCC No. 23170 is 1: (1.5-2.5): (2-4).

[0025] The composite microorganisms and their metabolites in the present invention can reduce interfacial tension and have a good oil displacement effect, especially in low-permeability oil reservoirs.

[0026] The permeability of low permeability reservoirs is (0.1-50)×10 -3 μm 2 According to the actual production characteristics, low permeability oil layers can be further divided into general low permeability oil layers, ultra-low permeability oil layers and ultra-low permeability oil layers according to the average permeability of the oil layers. The average permeability of the oil layers is (10-50)×10 -3 μm 2 、(1-10)×10 -3 μm 2 and (0.1-1)×10 -3 μm 2 .

[0027] According to the present invention, preferably, the contacting conditions include: a temperature of 28-42°C.

[0028] According to the present invention, preferably, the oil content in the oil-containing produced water is not higher than 50 mg / L.

[0029] According to the present invention, preferably, the expansion is carried out in the presence of a nutrient.

[0030] In a preferred embodiment of the present invention, the nutrient comprises molasses, peptone, ammonium sulfate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate and sodium citrate.

[0031] In a more preferred embodiment of the present invention, based on the volume of the nutrient agent being 1 L, the nutrient agent comprises 1-2 g of molasses, 0.1-1 g of peptone, 0.1-0.5 g of ammonium sulfate, 0.1-0.5 g of sodium dihydrogen phosphate, 0.01-0.05 g of dipotassium hydrogen phosphate and 0.1-0.5 g of sodium citrate.

[0032] According to the present invention, preferably, the temperature of the expansion culture is 28-42°C.

[0033] Furthermore, the expansion culture temperature is 30-37°C.

[0034] According to the present invention, preferably, the dissolved oxygen content DO is above 2 mg / L during the expansion culture.

[0035] According to the present invention, preferably, the expansion time is such that the number of viable bacteria in the expanded material is 1×10 8 CFU / mL or above.

[0036] According to the present invention, preferably, the amount of material added after expansion is such that the number of viable bacteria in the material after contact is 1×10 8 CFU / mL or above.

[0037] The incubated material is used as a microbial oil displacement agent in contact with the oil reservoir to be displaced. Preferably, the pH of the incubated material is 6-8.

[0038] According to the present invention, preferably, the expansion is carried out in an expansion device, wherein the device comprises:

[0039] The first-stage culture tank, the second-stage culture tank and the third-stage culture tank connected in series are used to culture composite microorganisms and remove oil impurities in oil-containing produced water.

[0040] According to the present invention, preferably, the device further comprises: a water inlet provided upstream of the first-stage expansion tank for introducing oil-containing produced water.

[0041] According to the present invention, preferably, the device further comprises: a water outlet arranged downstream of the three-stage expansion tank for leading out the expanded material and the deoiled produced water.

[0042] The composite microorganisms are added to the expansion device, and oil-containing produced water (incoming water) is introduced from the water inlet upstream of the first-stage expansion tank. The composite microorganisms are mixed with the oil-containing produced water for expansion. The growth and metabolism of the microorganisms can be used to remove oil impurities in the oil-containing produced water. The expanded material is then drawn from the outlet downstream of the third-stage expansion tank and injected into the formation to drive oil. The expanded material contains the produced water after the oil impurities are removed, the expanded composite microorganisms, the metabolites of the composite microorganisms, and nutrients. The produced water after the oil impurities are removed meets the oil field reinjection standard. The expanded material is injected into the formation to drive oil, recycling water resources while improving the recovery rate of the oil reservoir.

[0043] The device of the present invention comprises a primary culture tank, a secondary culture tank and a tertiary culture tank, which can culture microorganisms to an appropriate number and fully remove crude oil impurities in water.

[0044] According to the present invention, preferably, fillers are independently installed in the first-stage expansion culture tank, the second-stage expansion culture tank and the third-stage expansion culture tank for microorganisms to attach and grow.

[0045] In a preferred embodiment of the present invention, the material of the filler is selected from one or more of aldehyde-chemical fiber soft materials, suspended ball fillers and fiber ball fillers.

[0046] According to the present invention, preferably, each of the first-stage expansion culture tank, the second-stage expansion culture tank and the third-stage expansion culture tank is independently equipped with an aeration device for providing oxygen required for the growth of microorganisms.

[0047] According to the need of treating oilfield produced water, preferably, the water inlet is located at the lower part of the first-level expansion tank.

[0048] According to the present invention, preferably, the overflow ports of the primary and tertiary expansion tanks are located at the upper portion of the tank body, respectively, and the overflow port of the secondary expansion tank is located at the lower portion of the tank body, so that the liquid flow direction forms a three-dimensional S-shape. This design ensures sufficient hydraulic retention time to meet the needs of microbial growth and reproduction.

[0049] According to the present invention, preferably, the device is further configured with a sedimentation tank for settling solid impurities in the water body.

[0050] In a preferred embodiment of the present invention, the sedimentation tank is located downstream of the tertiary expansion tank.

[0051] According to the present invention, preferably, the water outlet is located on the side wall of the sedimentation tank.

[0052] According to the present invention, preferably, the device is further configured with a buffer tank for buffering the oil-containing produced water (incoming water).

[0053] In a preferred embodiment of the present invention, along the direction of liquid flow, the buffer tank is located upstream of the primary expansion tank.

[0054] According to the present invention, preferably, the device is further equipped with a liquid preparation tank for mixing the composite microorganisms and the nutrient agent.

[0055] In a preferred embodiment of the present invention, along the direction of liquid flow, the liquid preparation tank is located upstream of the first-stage expansion culture tank.

[0056] According to the present invention, preferably, a dosing pump is further arranged between the liquid preparation tank and the primary expansion culture tank for introducing a mixed solution of composite microorganisms and nutrients into the primary expansion culture tank.

[0057] According to the present invention, preferably, the device is further equipped with a composite microorganism dosing device for dosing composite microorganisms.

[0058] According to the present invention, preferably, the device is further equipped with a nutrient dosing device for adding nutrients.

[0059] In order to allow a sufficient amount of microorganisms to grow on the fillers in the expansion tank, the expansion tanks can be connected by injecting oil-containing produced water into the device, the water inlet and outlet of the device are closed, and then the composite microorganisms and nutrients are injected into them for expansion. There is no special restriction on the expansion time. For example, the bacterial concentration in the expansion tank can reach 1×10 8 CFU / mL or above is sufficient. Nutrients can be added during this process, and those skilled in the art can add them as needed.

[0060] After expansion, the device's water inlet and outlet are opened to allow fresh oil-bearing produced water (incoming water) to flow in, and the material containing the bacterial solution to flow out and be injected into the reservoir for oil recovery. The hydraulic retention time can be selected within a wide range, such as 6-8 hours. During operation, the composite microorganisms and nutrient solution can be added.

[0061] According to a preferred embodiment of the present invention, the method for culturing composite microorganisms and performing oil recovery on an oil reservoir to be recovered in the microbial recovery device shown in FIG1 includes the following steps:

[0062] S1. Fermentation broths of Candida viswanathii (CGMCC No. 3456), Bacillus subtilis (CGMCC No. 21860), and Pseudomonas aeruginosa (CGMCC No. 23170) were prepared respectively, so that the number of viable cells in the fermentation broths of the three bacteria was independently 1×10 8CFU / mL or more, the fermentation broths of the three bacteria are mixed in a liquid preparation tank 9, and the ratio of the number of viable bacteria of Candida vesiculosus, Bacillus subtilis and Pseudomonas aeruginosa in the mixed fermentation broth is 1:(1-3):(1-5), thereby preparing a composite microbial agent.

[0063] S2. Introduce oil-containing produced water (the oil content is not higher than 50 mg / L) from the water inlet 5 to fill the device with oil-containing produced water, put the nutrient solution into the liquid preparation tank 9, mix it with the fermentation liquid of the three bacteria, and then slowly pump it into the first-level expansion tank 1 by the dosing pump 11 (based on the total volume of the feed liquid in the device, the amount of the fermentation liquid of the three bacteria is 0.5-1.5% by volume, and the amount of the nutrient solution is 0.08-0.12% by volume). Close the water inlet 5 and outlet 6 of the device, turn on the aeration pumps 12 in the first-stage expansion culture tank 1, the second-stage expansion culture tank 2, and the third-stage expansion culture tank 3 to provide oxygen required for microbial growth. Expand and cultivate for 10-15 days (temperature is 28-42°C, and the air intake of the fan ensures that the oxygen content in the device is above 2.0 mg / L). Allow the microorganisms to form biofilms and grow on the fillers 8 in the first-stage expansion culture tank 1, the second-stage expansion culture tank 2, and the third-stage expansion culture tank 3. The expansion time is such that the number of viable bacteria in the material after expansion reaches 1×10 8 CFU / mL or above.

[0064] S3, wait until the total concentration of live bacteria in the device reaches 1×10 8 After the concentration reaches 100 mg / mL or more, the device's water inlet 5 and outlet 6 are opened. Oil-bearing produced water (fresh water) is buffered in the buffer tank 10 and flows from the water inlet 5 into the primary expansion tank 1. The water overflows through the overflow port 7 in an S-shaped pattern, passing through the primary expansion tank 1, the secondary expansion tank 2, the tertiary expansion tank 3, and the sedimentation tank 4. Finally, the water is injected into the reservoir through the water outlet 6 according to the geological allocation of the oilfield. The hydraulic retention time in the expansion tank is 6-8 hours.

[0065] The present invention will be described in detail below through examples.

[0066] 1. Determination of the content of glycolipid surfactants produced by yeast:

[0067] (1) Determination of glucose standard curve:

[0068] ① Prepare a 10 mg / mL glucose solution: Accurately weigh 0.1 g of analytical grade anhydrous glucose, previously dried to constant weight in a 105°C oven, into a 100 mL volumetric flask. Add distilled water to the mark and shake well. The glucose concentration is now 1000 mg / L. Add 0.5 mL, 1 mL, 2 mL, 3 mL, and 4 mL of this solution to the corresponding 100 mL volumetric flasks, bringing the volume to 5 mg / L, 10 mg / L, 20 mg / L, 30 mg / L, and 40 mg / L, respectively.

[0069] ② Preparation of anthrone reagent: Accurately weigh 0.2 g of anthrone reagent, add it to 100 mL of concentrated sulfuric acid, and mix well to obtain the anthrone reagent.

[0070] ③ Plot a glucose standard curve: Accurately measure 4 mL of anthrone reagent and 1 mL of the prepared standard glucose solution into stoppered test tubes (also measure 1 mL of distilled water as a blank control). Quickly cool in an ice-water bath, then heat in a boiling water bath for 10 minutes and continue cooling in an ice bath. Once completely cooled, pipette 200 μl into a 96-well plate and measure the OD value at 620 nm in a microplate reader. Plot a standard curve based on the results.

[0071] (2) Determination of glycolipid content in yeast fermentation broth:

[0072] ① Take 0.5 mL of fermentation broth, add 1 mL of ethanol, vortex to mix, and centrifuge at 12,000 rpm for 9 minutes. Take 20 μL of the supernatant and add it to an EP tube. Then add 980 μL of distilled water and 4 mL of anthrone reagent. Immediately place on ice, then heat in a boiling water bath for 8 minutes. Cool in an ice bath, and measure the OD value (m1) of the reaction solution at 620 nm using a spectrophotometer (using the solution obtained by reacting distilled water with anthrone reagent as a control). The total glycolipid content can be calculated based on the ratio of the molecular weights of glycolipid to glucose (i.e., 1.91 g of glycolipid is equivalent to 1 g of glucose).

[0073] ② Place 0.5 ml of fermentation broth in an EP tube, add an equal volume of 1 ml of ethyl acetate, oscillate to mix, and centrifuge at 12,000 rpm for 9 minutes. Take 20 μL of the supernatant and add it to the EP tube. Then add 980 μL of distilled water and 4 mL of anthrone reagent. Quickly place on ice, then heat in a boiling water bath for 8 minutes. Cool in an ice bath, and measure the OD value (m2) of the reaction solution at 620 nm using a spectrophotometer (using the solution obtained by reacting distilled water with anthrone reagent as a control). This can be used to determine the glycolipid content in the yeast.

[0074] 2. Determination of yeast oil removal rate:

[0075] ① The national standard HJ 637-2018 "Determination of Petroleum and Animal and Vegetable Oils - Infrared Spectrophotometry" is used to detect the oil content in oilfield produced water.

[0076] ② Mix the oilfield produced water with a certain oil content with 2% bacterial fermentation liquid, and place it in a constant temperature shaking incubator at 50℃ for shaking culture for 48 hours.

[0077] ③ The national standard HJ 637-2018 "Determination of Petroleum and Animal and Vegetable Oils by Infrared Spectrophotometry" was used to detect the oil content in oilfield produced water treated with microorganisms.

[0078] Oil removal rate = (① measured oil content - ② measured oil content) / ① measured oil content × 100%

[0079] 3. Determination of the content of biopolymer produced by Bacillus:

[0080] The fermentation broth was centrifuged at 12000 rpm for 10 minutes, and the formed white precipitate was placed at 3°C ​​for 12 hours, and then centrifuged at 5000 rpm for 30 minutes. The precipitate was collected and suspended with a minimum amount of distilled water. The pH value was adjusted to 7.0 with NaOH until at least a portion of the precipitate was dissolved. The crude biopolymer was dried and frozen at low temperature and weighed.

[0081] 4. Determination method of emulsification rate E24 of Pseudomonas fermentation broth:

[0082] Take the fermentation liquid of the strain and kerosene (2:3, V / V) and add it to a graduated colorimetric tube. Shake and stir it thoroughly for a period of time and let it stand at room temperature for 24 hours. After standing, measure the emulsion layer and total liquid height, and calculate the emulsification coefficient of each sample.

[0083] Emulsification rate E24 = (emulsified layer height / total liquid height) × 100%

[0084] After the mixture was left to stand for a period of time, the originally uniform emulsion gradually separated into layers. By measuring the height of the emulsion layer and the total liquid, the emulsification rate E24 of Pseudomonas was calculated.

[0085] Composition of the nutrient solution: Based on a total volume of 1 L of the nutrient solution, the nutrient agent includes 1 g of molasses, 0.5 g of peptone, 0.2 g of ammonium sulfate, 0.3 g of sodium dihydrogen phosphate, 0.02 g of dipotassium hydrogen phosphate and 0.2 g of sodium citrate.

[0086] Before the experiment, microorganisms that did not significantly inhibit Candida vesiculosus or had no antagonistic relationship with it were screened, and strains with relatively good performance were further screened, and experiments were conducted based on the screened microorganisms. Table 1 shows the strains used in the following examples and their sources.

[0087] Table 1

[0088] Preparation Example 1

[0089] This preparation example is used to illustrate the preparation of microbial fermentation broth.

[0090] Strains 1-11 in Table 1 were subjected to pure culture fermentation. After resuscitation with warm water, the frozen strains were streaked onto sterile LB solid plates and placed in a 37°C constant temperature incubator for 24 hours. Single colonies were then picked and placed in Erlenmeyer flasks containing LB liquid medium. The plates were shaken in a 37°C constant temperature shaker for 48 hours at 180 rpm. After 48 hours, the bacterial concentration in the fermentation broth of each strain was measured. Based on the measured bacterial concentration of each strain, the bacterial concentration in the fermentation broth of strains 1-11 was adjusted with sterile water to 1×10 8 CFU / mL.

[0091] Example 1: Screening of composite microorganisms

[0092] Collect the fermentation broth of strains No. 1-11 obtained by fermentation in Preparation Example 1, use the fermentation broth of the above strains as described in Table 2 or mix and prepare, stir evenly, and prepare microbial oil-displacing agents, and then measure their interfacial tensions respectively, and compare the sizes of their interfacial tensions. Wherein, v represents volume. If not marked, Bacillus subtilis is Bacillus subtilis CGMCC No. 21860, and Pseudomonas aeruginosa is Pseudomonas aeruginosa CGMCC No. 23170. Method for measuring interfacial tension: Use a rotating drop interfacial tension meter, select dehydrated and degassed crude oil, and measure the interfacial tension value of each group of oil-displacing bacteria agents at a volume concentration of 1% at 50°C.

[0093] Table 2

[0094] From the above results, it can be seen that the interfacial tension value of the fermentation broth of a single strain is the lowest for yeast, which is 0.8626 mN / m, followed by Bacillus subtilis and Pseudomonas aeruginosa, with interfacial tensions of 1.5248 mN / m and 1.3654 mN / m, respectively.

[0095] When yeast and other bacterial solutions were combined one by one, the interfacial tension values ​​of combinations 20 and 25, and Candida combined with Bacillus subtilis and Pseudomonas aeruginosa, respectively, were 0.0114 and 0.0564 mN / m, respectively. All other combinations exceeded these values. Combination 20 showed the strongest ability to reduce oil-water interfacial tension. This suggests that a microbial oil displacement agent prepared with a viable cell count ratio of 1:(1.5-2.5):(2-4) of Candida vesii CGMCC No. 3456, Bacillus subtilis CGMCC No. 21860, and Pseudomonas aeruginosa CGMCC No. 23170 can achieve a better synergistic effect.

[0096] Example 2

[0097] This example is used to illustrate the indoor core displacement simulation test of the composite microbial oil recovery system:

[0098] A microbial solution or a composite microbial solution was prepared as described in Example 1, and an indoor core flooding simulation test was conducted. The test apparatus used was a gas injection core evaluation system produced by Zhongshi Dashiyi Technology Co., Ltd.:

[0099] The experimental steps are as follows:

[0100] (1) Core saturated water:

[0101] ① Take the test core, place it in a 60℃ constant temperature box and dry it to constant weight, and weigh its weight m0;

[0102] ② Place the core in a vacuum pump, pressurize and saturate it with water overnight, and weigh its weight m1;

[0103] ③ The pore volume (PV) can be calculated as m1-m0;

[0104] (2) Core saturated with oil:

[0105] ①Put the experimental oil sample and water sample into the corresponding intermediate container respectively, turn on the equipment for heating, and set the temperature to 50℃;

[0106] ② Open the core displacement equipment operation interface, enter the basic data such as core length, diameter, void volume, gas permeability, etc., place the core in the middle of the core holder, connect the pipeline, adjust the flow rate, run the instrument to drain and check the pipeline sealing;

[0107] ③ Adjust the flow rate, open the switch of the intermediate container containing the oil sample, place the measuring cylinder at the outlet of the core holder, turn on the equipment operation interface switch, and start the experiment;

[0108] ④Inject 3-5 PV, stop injecting, close the valve of the intermediate container containing the oil sample, measure the total water output m2, and calculate the saturation;

[0109] (3) Water flooding experiment:

[0110] ①Open the valve of the intermediate container filled with water, disconnect the inlet pipeline, and when liquid comes out of the inlet, stop the pump, connect the inlet pipeline, and start the experiment;

[0111] ② Inject 3-5 PVs until the water content at the outlet reaches 98%, then stop the injection and close the valve of the intermediate container containing the water sample. Measure the oil output, pressure difference, and flow rate corresponding to each PV, and calculate the corresponding core flooding efficiency.

[0112] (4) Microbial activation water flooding experiment:

[0113] ①Put the prepared microbial fermentation liquid into the intermediate container, open the valve, disconnect the inlet pipeline, and when liquid comes out of the inlet, stop the pump, connect the inlet pipeline, and start the experiment;

[0114] ②Inject 3-5 PVs, stop injection, close the valve of the intermediate container containing the water sample, measure the oil output, pressure difference and flow rate corresponding to each PV, and calculate the corresponding core displacement efficiency;

[0115] (5) Subsequent water flooding:

[0116] ①Open the valve of the intermediate container filled with water, disconnect the inlet pipeline, and when liquid comes out of the inlet, stop the pump, connect the inlet pipeline, and start the experiment;

[0117] ② Inject 3-5 PVs, stop the injection, close the valve of the intermediate container containing the water sample, and measure the oil output, pressure difference, and flow rate corresponding to each PV. The corresponding core displacement efficiency can be calculated. The results are shown in Table 3.

[0118] Table 3

[0119] As shown in Table 3, the oil displacement efficiencies of Candida vesii CGMCC No. 3456, Bacillus subtilis CGMCC No. 21860, Pseudomonas aeruginosa CGMCC No. 23170, and Combination 20 were 15.87%, 14.17%, 19.6%, and 24.62%, respectively. Combination 20 also achieved the highest overall oil displacement efficiency, at 26.97%. Therefore, the indoor core flooding tests also confirmed that the combined bacterial agents have higher oil displacement efficiency.

[0120] Example 3

[0121] The oil removal rate, glycolipid content, biopolymer content, and emulsification index (E24) of a microbial agent for produced water treatment and oil recovery (Candida vesii CGMCC No. 3456), a biopolymer-producing microbial agent (Bacillus subtilis CGMCC No. 21860), and a hydrocarbon-dissolving oil recovery microbial agent (Pseudomonas aeruginosa CGMCC No. 23170) were measured. The results showed that Candida vesii CGMCC No. 3456 had an oil removal rate of 91% and a glycolipid content of 10.5 g / L. The biopolymer glucuronic acid content of Bacillus subtilis CGMCC No. 21860 was 5.1 g / L, and the E24 index of the fermentation broth of Pseudomonas aeruginosa CGMCC No. 23170 was 75%.

[0122] Based on the original water injection system at the oil field, the expansion device (processing capacity 500m 3 / day) in the expansion culture of composite microorganisms, the expansion culture device comprises a steel buffer tank, a first-level expansion culture tank, a second-level expansion culture tank, a third-level expansion culture tank and a sedimentation tank connected in series, and is also equipped with a composite microbial agent dosing device and a nutrient agent dosing device. Fillers are independently installed in the three expansion culture tanks for microbial attachment and growth, and aeration devices are also independently installed for providing the oxygen required for microbial growth. The water inlet in the first-level expansion culture tank is located at the bottom of the first-level expansion culture tank, and the water outlet is located at the sidewall of the sedimentation tank. The overflow ports of the first-level expansion culture tank and the third-level expansion culture tank are respectively located on the upper part of the tank body, and the overflow port of the second-level expansion culture tank is located on the upper part of the tank body, so that the liquid flow direction is three-dimensional S-shaped.

[0123] Expansion culture: Introduce oil-containing produced water from the water inlet to fill the device with oil-containing produced water. Mix the fermentation broth of the three bacteria in combination 20 in a biological stirring tank (the ratio of the number of live yeast, Bacillus subtilis and Pseudomonas aeruginosa in the mixed fermentation broth is 1:2:3), add nutrient solution, and then slowly pump it into the first-level expansion tank by the dosing pump (based on the total volume of the liquid in the device, the amount of fermentation broth of the three bacteria is 1 volume%, and the amount of nutrient solution is 0.1 volume%). Close the water inlet and outlet of the device, open the aeration devices in the first-level expansion tank, the second-level expansion tank and the third-level expansion tank to provide the oxygen required for microbial growth. Expand for 10 days to allow the microorganisms to grow and reproduce on the fillers in the first-level expansion tank, the second-level expansion tank and the third-level expansion tank. The number of live bacteria in the material after expansion is ≥1×10 8 CFU / mL.

[0124] Normal operation: Open the device's water inlet and outlet. Oil-bearing produced water (fresh water) is buffered in the buffer tank and flows from the inlet into the primary expansion tank. The overflow port allows the water to flow in an S-shaped pattern through the primary, secondary, and tertiary expansion tanks, and finally into the sedimentation tank. The overflow port then injects the water into the reservoir as directed by the geological allocation of the oilfield. The hydraulic retention time in the expansion tank is 8 hours.

[0125] Technical requirements:

[0126] ① The oil content of incoming water is ≤50.0mg / L, the suspended matter content is ≤50.0mg / L, and the water inlet flow is stable.

[0127] ②The reaction pool temperature is controlled at 35℃.

[0128] ③ Replenish the bacteria once every week (500kg fermentation liquid), and replenish the nutrient solution once every 3 days (1000kg, containing 1kg molasses, 0.5kg peptone, 0.2kg ammonium sulfate, 0.3kg sodium dihydrogen phosphate, 0.02kg dipotassium hydrogen phosphate, and 0.2kg sodium citrate).

[0129] ④ The air intake of the fan should ensure that the oxygen content in the reaction tank is above 2.0 mg / L.

[0130] ⑤ The incoming water regulating tank, biochemical reaction tank, sewage sedimentation tank, and purified water tank discharge sewage for 3-5 minutes every day.

[0131] ⑥ No bactericides shall be added or bactericidal devices installed in the produced water treatment process.

[0132] ⑦ Test the bacterial concentration in each culture pool weekly. Refer to GB 4789.2 - Determination of Total Colony Count in Food Microbiological Examination for the testing method. The bacterial concentration test results for each culture pool are shown in Table 4 (unit: CFU / mL).

[0133] Table 4

[0134] From the results in Table 4, it can be seen that the number of viable bacteria in the effluent material reached 1×10 8 CFU / mL or above, so the expansion culture device and method can play the role of expanding the added microorganisms.

[0135] Example 4

[0136] An indoor core flooding simulation experiment was conducted using the method and apparatus of Example 2, except that the effluent from the expansion tank of Example 3 was collected for the indoor core flooding experiment. Three parallel effluent samples from the expansion tank were collected and designated as effluent 1, effluent 2, and effluent 3. The parameters and core flooding efficiencies of effluent 1, effluent 2, and effluent 3 are shown in Table 5.

[0137] Table 5

[0138] The results in Table 5 show that the effluent after expansion can indeed improve the oil displacement efficiency of crude oil as verified by indoor microbial displacement experiments.

[0139] Comparative Example 1

[0140] The reservoir is flooded with oil according to the method and device of Example 3, except that the device is composed of two groups of expansion culture pools connected in series. Specifically, the expansion culture device includes a steel buffer pool, a primary expansion culture pool, a secondary expansion culture pool and a sedimentation tank connected in series, and is also equipped with a composite bacterial agent dosing device and a nutrient agent dosing device. The two expansion culture pools are each independently equipped with a filler for microorganisms to attach and grow, and are also each independently equipped with an aeration device for providing the oxygen required for microbial growth. The water inlet in the primary expansion culture pool is located at the lower part of the primary expansion culture pool, the water outlet is located at the side wall of the sedimentation tank, the overflow port of the primary expansion culture pool is located at the upper part of the pool body, and the overflow port of the secondary expansion culture pool is located at the lower part of the pool body, so that the liquid flow direction is three-dimensional S-shaped. The three-stage expansion culture pool is reduced to the secondary expansion culture pool, and the crude oil impurities in the bacterial concentration in the effluent are shown in Table 6.

[0141] Table 6

[0142] The results in Table 6 show that the effluent after the secondary expansion culture did not meet the oilfield water quality treatment standards (oil content ≤ 10.0 mg / L, number of viable bacteria in the effluent material ≥ 1 × 10 8 CFU / mL). The primary, secondary, and tertiary expansion tanks in the expansion device of the present invention are primarily used for the growth and propagation of microorganisms and for the treatment of crude oil contaminants in incoming water. The three expansion tanks are connected in series and are essential. Removing any one expansion tank will result in failure to meet the bacterial growth standards and oilfield water quality treatment standards.

[0143] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a composite microbial oil recovery system having the dual functions of produced water treatment and oil recovery, characterized in that: The preparation method comprises: mixing the composite microorganism with oil-containing produced water for expansion, and then contacting the expanded material with the oil reservoir to be driven; wherein, The composite microorganism comprises Candida vesica with a preservation number of CGMCC No.3456, Bacillus subtilis with a preservation number of CGMCC No.21860 and Pseudomonas aeruginosa with a preservation number of CGMCC No.23170.

2. The preparation method according to claim 1, characterized in that: In the composite microorganism, the ratio of the number of live bacteria of Candida vesica with a preservation number of CGMCC No. 3456, Bacillus subtilis with a preservation number of CGMCC No. 21860 and Pseudomonas aeruginosa with a preservation number of CGMCC No. 23170 is 1: (1-3): (1-5), preferably 1: (1.5-2.5): (2-4).

3. The preparation method according to claim 1 or 2, characterized in that: The contact conditions include: a temperature of 28-42°C; Preferably, the oil content in the oil-containing produced water is not higher than 50 mg / L.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The expansion is carried out in the presence of a nutrient; Preferably, the nutrient comprises molasses, peptone, ammonium sulfate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate and sodium citrate; Preferably, based on a volume of 1 L of the nutrient agent, the nutrient agent comprises 1-2 g of molasses, 0.1-1 g of peptone, 0.1-0.5 g of ammonium sulfate, 0.1-0.5 g of sodium dihydrogen phosphate, 0.01-0.05 g of dipotassium hydrogen phosphate and 0.1-0.5 g of sodium citrate.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The expansion temperature is 28-42°C, preferably 30-37°C; Preferably, the dissolved oxygen content DO is above 2 mg / L during the expansion culture; Preferably, the culture time is such that the number of viable bacteria in the material after culture is 1×10 8 CFU / mL and above.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The amount of material added after expansion is such that the number of viable bacteria in the material after contact is 1×10 8 CFU / mL or above; Preferably, the pH of the material after expansion is 6-8.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The expansion is carried out in an expansion device, wherein the device comprises: The first-stage expansion culture tank, the second-stage expansion culture tank and the third-stage expansion culture tank connected in series are used to expand the composite microorganisms and remove oil impurities in the oil-containing produced water.

8. The preparation method according to claim 7, characterized in that: The device also includes: a water inlet arranged upstream of the first-level expansion tank for introducing oil-containing produced water.

9. The preparation method according to claim 8, characterized in that: The water inlet is located at the lower part of the first-level expansion culture tank.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The device also includes: a water outlet arranged at the downstream of the three-stage expansion tank, which is used to lead out the expanded material and the produced water after de-oiling.

11. The preparation method according to any one of claims 7 to 10, characterized in that: The first-stage expansion culture tank, the second-stage expansion culture tank and the third-stage expansion culture tank are each independently equipped with a filler for microorganisms to attach and grow; Preferably, the material of the filler is selected from at least one of aldehyded cellulose soft material, suspended ball filler and fiber ball filler.

12. The preparation method according to any one of claims 7 to 11, characterized in that: The first-stage expansion culture tank, the second-stage expansion culture tank and the third-stage expansion culture tank are each independently equipped with an aeration device for providing oxygen required for the growth of microorganisms.

13. The preparation method according to any one of claims 7 to 12, characterized in that: The overflow ports of the first-stage expansion culture tank and the third-stage expansion culture tank are respectively located at the upper part of the tank body, and the overflow port of the second-stage expansion culture tank is located at the lower part of the tank body, so that the liquid flow direction is three-dimensional S-shaped.

14. The preparation method according to any one of claims 7 to 13, characterized in that: The device is also equipped with a sedimentation tank for settling solid impurities in the water body; Preferably, the sedimentation tank is located downstream of the tertiary expansion tank.

15. The preparation method according to claim 14, characterized in that: The water outlet is located on the side wall of the sedimentation tank.

16. The preparation method according to any one of claims 7 to 15, characterized in that: The device is also equipped with a buffer tank for buffering the oil-containing produced water; Preferably, along the direction of liquid flow, the buffer tank is located upstream of the primary expansion tank.

17. The preparation method according to any one of claims 7 to 16, characterized in that: The device is also equipped with a liquid preparation tank for mixing the composite microorganisms and the nutrient agent; Preferably, along the direction of liquid flow, the liquid preparation tank is located upstream of the primary expansion culture tank.

18. The preparation method according to claim 17, characterized in that: A dosing pump is also arranged between the liquid preparation tank and the primary culture expansion tank for introducing a mixed liquid of composite microorganisms and nutrients into the primary culture expansion tank.

19. The preparation method according to any one of claims 7 to 18, characterized in that: The device is also equipped with a composite microorganism adding device for adding composite microorganisms.

20. The preparation method according to any one of claims 7 to 19, characterized in that: The device is also equipped with a nutrient agent dosing device for adding the nutrient agent.

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