Method for relieving formation sand production by using microorganisms

Abstract

The invention belongs to the technical field of microbial oil recovery, and particularly relates to a method for relieving formation sand production through microorganisms. The method comprises the following steps: screening test blocks; preliminarily determining biofilm-producing microorganisms and nutrients thereof; determining biofilm-producing microorganisms and nutrients thereof; determining the injection amount of biofilm-producing microorganisms and nutrients thereof; determining the injection speed of biofilm-producing microorganisms and nutrients thereof; and carrying out field test and effect evaluation. According to the method, biofilm-producing microorganisms are injected into the oil reservoir at a specific injection concentration and a specific injection speed by mainly utilizing the characteristic that extracellular polymeric substances in a microbial film have high cohesiveness to consolidate loose sandstone particles, so that the purpose of relieving serious sand production of the loose sandstone oil reservoir is achieved. According to the method, the sand production operation period of the oil producing well is prolonged, the well lying frequency is reduced, the well opening time rate is improved, and long-term stable production of the oil well is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of microbial oil recovery, and particularly relates to a method for using microorganisms to alleviate formation sand production. Technical Background

[0002] Unconsolidated sandstone reservoirs are widely distributed in various oil fields, and there is a serious sand production problem in general. Such reservoirs are usually heavy oil reservoirs, with relatively shallow burial depth, high shale content, and loose cementation. During the production process, sand production is very likely to occur, affecting the normal production of oil wells. Due to the weak cementation and low cement content in unconsolidated sandstone, during the water injection production process, it is continuously scoured by the fluid, the pore throat radius increases, and the porosity and permeability become higher, resulting in more serious sand production. Sand production will not only lead to a reduction or suspension of oil well production and the wear of surface and downhole equipment, but in severe cases, it will cause casing damage and oil well abandonment, posing great harm to oil, gas, and water wells.

[0003] At present, the sand control technologies at home and abroad are mainly divided into three categories: mechanical sand control, chemical sand control, and composite sand control. Mechanical sand control is further divided into screen gravel packing sand control technology, high-pressure packing sand control technology, and fracturing packing sand control technology, etc. Among them, the screen gravel packing sand control technology has problems such as high cost, inapplicability to fine silt sand formations, low shale low-permeability formations, and high-yield wells; the high-pressure packing sand control technology cannot meet the sand control requirements of multiple oil layers and long well sections; the fracturing packing sand control technology has high requirements for downhole pipeline equipment and complex construction processes. Existing mechanical sand control processes all have their own characteristics and adaptabilities, and most of them are difficult to be competent for the sand control tasks of oil wells with relatively serious sand production in the middle and late stages or those that have undergone multiple sand control operations. Compared with mechanical sand control, chemical sand control technology has the characteristics of simple construction and no tools left in the well, and is a low-cost sand control method. By injecting a sand consolidant into the formation to consolidate the formation sand in the near-well area or using chemical agents such as resins to establish an artificial wellbore system, the formation sand production can be prevented. However, at present, chemical sand control generally has problems such as large pollution, short validity period, and great influence on the permeability of the oil layer in the near-well area. Therefore, chemical sand control technology is usually not used alone and is mainly used in combination with mechanical sand control. Therefore, it is necessary to develop a green and feasible method to enhance the cementation between sand bodies, so as to achieve the effect of sand consolidation and sand control.

[0004] In nature, most microorganisms do not exist in a single free state, but colonize on the surface of attachments and secrete extracellular polymers to form microbial aggregates. This kind of microbial aggregate is called a microbial film. The microbial film is mainly composed of microbial cells and extracellular matrix. The extracellular matrix is an extracellular polymer mainly composed of polysaccharides, proteins, nucleic acids, lipids, etc., and has strong adhesiveness, which can effectively consolidate loose sand grains and provide a new way for sand consolidation and sand control.

[0005] After literature retrieval, the publication number "CN110644953B" discloses a method for in-situ microbial sand consolidation in unconsolidated sandstone reservoirs. This invention belongs to the technical field of microbial enhanced oil recovery and specifically relates to a method for in-situ microbial sand consolidation in unconsolidated sandstone reservoirs. The steps of this method include: screening of test blocks; determination method of sand consolidation functional microorganisms and their nutrients; determination of injection process of sand consolidation functional microorganisms and their nutrients. This method uses microbial induced mineral precipitation to cement and deposit the loose sand bodies in the reservoir to improve the sand production problem in unconsolidated sandstone reservoirs. However, this technology has certain requirements for the content of calcium and magnesium ions or ferrous ions in the formation, and its application scope is limited.

[0006] After literature retrieval, the publication number "CN108659805A" discloses an emulsion-type low-temperature sand consolidant and its preparation method. In this invention, a water-soluble melamine formaldehyde resin solution is used as a binder, and nano-silica particles as an emulsion stabilizer are introduced to prepare a stable emulsion with kerosene, obtaining an emulsion-type low-temperature sand consolidant. This sand consolidant can not only meet the sand control requirements of low-temperature formations, but also has good high-temperature resistance, water resistance, oil resistance, alkali resistance, and salt resistance. However, this technology has high pretreatment difficulty, high cost, and high free formaldehyde content, polluting the environment and being harmful to human health.

[0007] After literature retrieval, the publication number "CN110317594A" discloses a sand control agent for realizing self-aggregation of sand grains. This sand control agent includes three parts: self-aggregation liquid, self-aggregation aid, and sand consolidant; among them, the main component of the self-aggregation liquid is a natural polysaccharide compound, and the main component of the self-aggregation aid is an inorganic salt. The mass ratio of the self-aggregation liquid to the self-aggregation aid is 1:1 to 10; the mass ratio of the self-aggregation liquid to the sand consolidant is 1 to 6:1. However, the composition of this sand consolidation reagent is relatively complex, the construction process is cumbersome, the operation cost is high, and it is difficult to be widely promoted and applied on a large scale.

[0008] After literature retrieval, the publication number "CN109540630A" discloses a combined sample preparation device and method for microbial batch reinforcement of sandy soil. This device includes a cementation curing box, which is provided with a partition water tank inside. The partition water tank is internally provided with a temperature-controlled heater and a circulating water pump; a sand loading mold combination placed in the cementation curing box, including a soft plastic tube, the outer wall of the soft plastic tube is wound with gauze, the soft plastic tube has upper and lower openings and air holes on the side wall; it also includes filter paper and permeable stones covering the upper and lower openings of the soft plastic tube in sequence. This invention is only a device for using microorganisms to batch reinforce sandy soil, belonging to the field of calcareous sand foundation reinforcement and involving the use method in geotechnical engineering. It does not involve the application scope of microbial enhanced oil recovery technology. Summary of the Invention

[0009] The object of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a method for using microorganisms to relieve formation sand production. The present invention has the characteristics of reasonable method, simple and easy construction process, safety, environmental protection and low cost. The present invention mainly utilizes the characteristic that the extracellular polymers in the microbial film have strong adhesiveness, and injects biofilm-producing microorganisms into the reservoir at a specific injection concentration and injection rate to consolidate loose sandstone particles, so as to achieve the purpose of relieving serious sand production in loose sandstone reservoirs. This method prolongs the sand production operation cycle of production wells, reduces the frequency of well shutdowns, increases the production rate of open wells, and ensures the long-term stable production of oil wells.

[0010] The present invention discloses a method for using microorganisms to relieve formation sand production, and the method specifically includes the following steps:

[0011] (1) Screening of test blocks

[0012] The screening conditions for test blocks are as follows: reservoir temperature ≤ 80 °C, porosity ≥ 25%, permeability ≥ 500×10 3 μm 2 , the content of clay cementing material is 5-35%, loose sandstone reservoir, and injection wells and production wells have correspondence.

[0013] (2) Preliminary determination of biofilm-producing microorganisms and their nutrients

[0014] The basis for the preliminary determination of biofilm-producing microorganisms and their nutrients is the bacterial concentration of biofilm-producing microorganisms.

[0015] (3) Determination of biofilm-producing microorganisms and their nutrients

[0016] The basis for the determination of biofilm-producing microorganisms and their nutrients is the weight of the mixture of bacteria and products, the polysaccharide content, and the solution pH value.

[0017] (4) Determination of the injection volume of biofilm-producing microorganisms and their nutrients

[0018] The basis for the determination of the injection volume of biofilm-producing microorganisms and their nutrients is the reduction rate of water-phase permeability and the reduction rate of sand production.

[0019] (5) Determination of the injection rate of biofilm-producing microorganisms and their nutrients

[0020] The basis for the determination of the injection rate of biofilm-producing microorganisms and their nutrients is the reduction rate of water-phase permeability and the reduction rate of sand production.

[0021] (6) Field test and effect evaluation

[0022] The evaluation indexes of the field test effect are to track and analyze the sand production, liquid production and validity period in the produced fluid.

[0023] The present invention mainly injects biofilm - forming microorganisms and their nutrients into a sand - producing reservoir. By utilizing the characteristic that the extracellular polymers produced by the growth and metabolism of the above - mentioned microorganisms have strong adhesiveness, the biofilm - forming microorganisms are injected into the reservoir at a specific injection concentration and injection rate to consolidate loose sandstone particles, thereby solving the problem of severe sand production in loose sandstone reservoirs.

[0024] The present invention has the following advantages and beneficial effects compared with the prior art:

[0025] (1) The present invention has a wide range of applicable reservoirs, especially suitable for blocks with easy sand production, poor wellbore conditions, and many oil wells that are not easy to perform pipe - string movement operations. It has the characteristics of low investment and low cost.

[0026] (2) The present invention utilizes the characteristic that the extracellular polymers produced by microorganisms metabolizing in the formation have strong adhesiveness to consolidate loose sandstone particles to relieve sand production. It reduces the pump - inspection period of oil wells and extends the effective sand - control period by more than 30%, ensuring the normal production of oil wells. The microbial sand - consolidation system can be directly injected into the formation along with the injection well. The process is simple and highly operable, which is conducive to on - site popularization and application.

[0027] (3) The microbial sand - consolidation system injected by the present invention is non - toxic and harmless, will not cause harm to the formation, and avoids the problem of environmental pollution. It has the characteristics of green environmental protection, safety and reliability. Specific embodiments

[0028] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0029] The present invention discloses a method for relieving formation sand production by using microorganisms. The method specifically includes the following steps:

[0030] (1) Screening of test blocks

[0031] The screening conditions for test blocks are as follows: reservoir temperature ≤ 80°C, porosity ≥ 25%, permeability ≥ 500×10 3 μm 2 , the content of argillaceous cementing material is 5 - 35%, loose sandstone reservoir, and the injection well and the production well have correspondence.

[0032] (2) Preliminary determination of biofilm - forming microorganisms and their nutrients

[0033] The basis for the preliminary determination of biofilm - forming microorganisms and their nutrients is the bacterial concentration of biofilm - forming microorganisms.

[0034] (3) Determination of Biofilm Microorganisms and Their Nutrients

[0035] The determination of biofilm microorganisms and their nutrients is based on the weight of the mixture of bacteria and products, the polysaccharide content, and the solution pH value.

[0036] (4) Determination of the Injection Volume of Biofilm Microorganisms and Their Nutrients

[0037] The determination of the injection volume of biofilm microorganisms and their nutrients is based on the reduction rate of water-phase permeability and the reduction in sand production.

[0038] (5) Determination of the Injection Rate of Biofilm Microorganisms and Their Nutrients

[0039] The determination of the injection rate of biofilm microorganisms and their nutrients is based on the reduction rate of water-phase permeability and the reduction in sand production.

[0040] (6) Field Tests and Effect Evaluation

[0041] The evaluation indexes of the field test effect are the sand production, liquid production, and effective period in the produced fluid for tracking and analysis.

[0042] In the present invention, preferably, the preliminary determination of the biofilm microorganisms and their nutrients in step (2) is as follows: Add a total of 10 ml of biofilm microorganisms and their nutrients to 100 ml of formation water in the test block, and measure the bacterial concentration of the biofilm microorganisms in the solution after culturing for 5 - 15 d under the reservoir temperature conditions of the test block, and screen out the biofilm microorganisms with a bacterial concentration higher than 10 8 / ml and the highest bacterial concentration.

[0043] The biofilm microorganisms are microbial strains that can grow and metabolize under reservoir temperature and salinity conditions and can secrete extracellular polymers to form microbial films. Preferably, the biofilm microorganisms are one of Agrobacterium, Acetobacter, Pseudomonas, Alcaligenes, and Staphylococcus aureus.

[0044] More preferably, the biofilm microorganisms are one of Agrobacterium, Acetobacter, and Staphylococcus aureus.

[0045] The formula of the biofilm microorganism nutrients is 2 - 3 wt% carbon source, 0.2 - 0.6 wt% nitrogen source, and 0.03 - 0.05 wt% phosphorus source.

[0046] Preferably, the carbon source is glucose or sucrose, the nitrogen source is one of urea, corn steep liquor powder, and peptone, and the phosphorus source is dipotassium hydrogen phosphate or potassium dihydrogen phosphate.

[0047] In the present invention, preferably, for the determination of the biofilm-forming microorganisms and their nutrients in step (3), the specific method is as follows: Add a total of 10 ml of the biofilm-forming microorganisms and their nutrients to 100 ml of the formation water in the test block. After culturing for 15 - 30 d under the reservoir temperature conditions of the test block, measure the weight of the mixture of thalli and products, the polysaccharide content, and the pH value of the solution, and screen the biofilm-forming microorganisms and their nutrients with the largest weight of the mixture of thalli and products, the highest polysaccharide content, and a pH value > 7.

[0048] Preferably, the method for measuring the weight of the mixture of thalli and products is as follows: Filter all the culture solution using a vacuum filtration device. After filtration, dry the mixture of thalli and products. The initial temperature is 35°C, and then increase the temperature by 5°C every hour, with the highest temperature being 50°C. Weigh after drying to a constant weight.

[0049] The polysaccharide is the main component of the extracellular polymer of the biofilm. Use this index of polysaccharide content to indirectly reflect the difference in the ability of microorganisms to produce extracellular polymers. Preferably, the method for measuring the polysaccharide content is the sulfuric acid - anthrone colorimetric method.

[0050] In the present invention, preferably, for the determination of the injection amount of the biofilm-forming microorganisms and their nutrients in step (4), the specific method is as follows: First, select a natural core from the test block, saturate it with the formation water of the test block, calculate the pore volume and measure the aqueous permeability of the core, and at the same time test the sand content in the displaced water; Inject different amounts of the biofilm-forming microorganisms and their nutrients. After culturing for 15 - 30 d, continue to inject the formation water of the test block, and measure the aqueous permeability of the core and the sand content in the produced liquid; Screen the injection amount corresponding to a reduction rate of the aqueous permeability ≤ 10% and a reduction rate of the sand production amount ≥ 95% as the injection amount of the biofilm-forming microorganisms and their nutrients.

[0051] In the present invention, preferably, for the determination of the injection rate of the biofilm-forming microorganisms and their nutrients in step (5), the specific method is as follows: Select a natural core from the test block, and carry out an evaluation of the injection rate according to the determined injection amount of the biofilm-forming microorganisms and their nutrients; The injection rate is 1.0 - 1.5 ml / min. After injecting the biofilm-forming microorganisms and their nutrients and culturing for 15 - 30 d, displace with the formation water of the test block. By comparing the reduction amplitudes of the aqueous permeability and the sand production amount corresponding to different injection rates, screen the injection rate corresponding to a reduction rate of the aqueous permeability ≤ 10% and a reduction rate of the sand production amount ≥ 95% as the injection rate of the biofilm-forming microorganisms and their nutrients.

[0052] In the present invention, preferably, the specific steps of the on-site test in step (6) are as follows: Inject the biofilm microorganisms and their nutrients from the injection well. The formula, injection volume, and injection rate of the injected biofilm microorganism strains and their nutrients are determined according to the above steps. After injection, shut in the well for culturing for 15 - 30 days, and after opening the well, evaluate the effect of the oil wells in the test block.

[0053] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, without conflict, they can be combined in any appropriate way. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0054] In addition, any combination can be made among various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

[0055] The present invention will be further described below in conjunction with specific embodiments.

[0056] Example 1

[0057] Block C in Shengli Oilfield 33 The reservoir temperature is 50°C, the porosity is 32.8%, and the average permeability is 3028×10 -3 μm 2 , the shale content of the sand body is 6%, belonging to a loose sandstone reservoir. Before the test, the comprehensive water cut of the block is 90.7%, the daily oil production is 8.0 t / d, the daily liquid production is 86 m 3 / d, and the correspondence between the injection well and the production well is good. Many wells in this block have been sand-producing for a long time, with frequent well failures and low well operating rates, and the development effect is poor. Using the method of the present invention to implement sand control in this block, the specific steps are as follows:

[0058] (1) Screening of the test block

[0059] Test block C 33 has a reservoir temperature of 50°C, a porosity of 32.8%, an average permeability of 3028×10 -3 μm 2 , the shale content of the sand body is 6%, is a loose sandstone reservoir, and the correspondence between the injection well and the production well is good. It meets the reservoir screening criteria of the present invention and the present invention can be implemented.

[0060] (2) Preliminary determination of biofilm microorganisms and their nutrients

[0061] Respectively add to 100 ml of test block C 33The formation water is added with Agrobacterium, Acetobacter, Pseudomonas, Alcaligenes, and Staphylococcus aureus. At the same time, nutrients are added, including 2-3 wt% glucose, 0.2-0.6 wt% corn steep liquor powder, and 0.03-0.05 wt% dipotassium hydrogen phosphate, with a total of 10 ml, in test block C 33 After static cultivation at a reservoir temperature of 50 °C for 10 days, the bacterial concentration of the biofilm-forming microorganisms in the solution is measured. The biofilm-forming microorganism with a bacterial concentration higher than 10 8 / ml and the highest bacterial concentration under the conditions of this test block is Acetobacter. The experimental results are shown in Table 1.

[0062] Table 1 Bacterial Concentrations of Different Biofilm-Forming Microorganisms

[0063] Serial number Biofilm-forming microorganism Bacterial concentration (cells / mL) Rank 1 Pseudomonas <![CDATA[1*10 7 > 4 2 Acetobacter <![CDATA[5*10 8 > 1 3 Alcaligenes <![CDATA[3*10 8 > 2 4 Agrobacterium <![CDATA[9*10 7 > 3 5 Staphylococcus aureus <![CDATA[4*10 6 > 5

[0064] (3) Determination of Biofilm-Forming Microorganisms and Their Nutrients

[0065] Add 10 ml of Acetobacter and its nutrients to 100 ml of the formation water in test block C 33 and culture it at a reservoir temperature of 50 °C in test block C for 20 days. Then, measure the weight of the mixture of bacteria and products, the polysaccharide content, and the pH value of the solution. Screen the Acetobacter and its nutrients with the largest weight of the mixture, the most polysaccharide content, and a pH value > 7. 33 Among them, the method for measuring the weight of the mixture of bacteria and products is as follows: Filter all the culture solutions using a vacuum filtration device. After filtration, dry the mixture of bacteria and products. The initial temperature is 35 °C, and then increase the temperature by 5 °C every hour until the maximum temperature of 50 °C. Weigh it after drying to a constant weight. The method for measuring the polysaccharide content is the sulfuric acid-anthrone colorimetric method.

[0066] The measurement results of the dry weight, polysaccharide content, and pH value of the product mixture with different nutrient formulations are shown in Table 2.

[0067] Table 2 Measurement Results of Dry Weight, Polysaccharide Content, and pH Value of the Product Mixture

[0068] Table 2 Measurement Results of Dry Weight, Polysaccharide Content, and pH Value of the Product Mixture

[0069]

[0070] It can be seen from Table 2 that the product mixture corresponding to the Acetobacter and its nutrient formulation of 3 wt% glucose, 0.5 wt% corn steep liquor powder, and 0.05 wt% dipotassium hydrogen phosphate has the largest dry weight, the most polysaccharide content, and a solution pH = 8, meeting the screening requirements of pH value > 7. Therefore, the screened biofilm-forming microorganism is Acetobacter, and its nutrient formulation is 3 wt% glucose, 0.5 wt% corn steep liquor powder, and 0.05 wt% dipotassium hydrogen phosphate.

[0071] (4) Determination of the injection volume of biofilm - forming microorganisms and their nutrients

[0072] First, select the natural core of test block C 33 and saturate it with the formation water of test block C 33 to calculate the pore volume v 1 and measure the aqueous - phase permeability k of the core 1 . At the same time, test the sand content m in the displaced water 1 ; Inject different amounts of the biofilm - forming microorganism Acetobacter and its nutrient with the formula of 3 wt% glucose, 0.5 wt% dry corn steep liquor, and 0.05 wt% dipotassium hydrogen phosphate. After culturing for 20 d, continue to inject the formation water of the test block, and measure the aqueous - phase permeability k 2 of the core and the sand content m in the produced liquid 2 . Screen out the injection volume corresponding to the reduction rate of aqueous - phase permeability ≤ 10% and the reduction rate of sand production ≥ 95%. This injection volume is the injection volume of the biofilm - forming microorganisms and their nutrients.

[0073] The experimental results of the reduction rate of aqueous - phase permeability and the reduction rate of sand production for different injection volumes of biofilm - forming microorganisms and their nutrients are shown in Table 3.

[0074] Table 3 Experimental results of the reduction rate of aqueous - phase permeability and the reduction rate of sand production

[0075]

[0076] It can be seen from Table 3 that when the injection volume of the system is 0.20 PV, it meets the screening conditions of the reduction rate of aqueous - phase permeability ≤ 10% and the reduction rate of sand production ≥ 95%. Therefore, the injection volume of the biofilm - forming microorganism Acetobacter and its nutrients is determined to be 0.20 PV.

[0077] (5) Determination of the injection rate of biofilm - forming microorganisms and their nutrients

[0078] First, select the natural core of test block C 33 . According to the biofilm - forming microorganism Acetobacter, the nutrient formula of 3 wt% glucose, 0.5 wt% dry corn steep liquor, and 0.05 wt% dipotassium hydrogen phosphate, and the injection volume of 0.20 PV determined above, conduct an injection - rate evaluation experiment; The injection rate is 1.0 - 1.5 ml / min. After injecting the screened microbial sand - fixing system and culturing for 20 d, displace it with the formation water of test block C 33 . Compare the reduction rate of aqueous - phase permeability and the reduction amplitude of sand production corresponding to different injection rates, and screen out the injection rate corresponding to the reduction rate of aqueous - phase permeability ≤ 10% and the reduction rate of sand production ≥ 95%. This injection rate is the injection rate of the biofilm - forming microorganisms and their nutrients.

[0079] The experimental results of the reduction rate of the aqueous phase permeability and the reduction rate of sand production of the microbial sand fixation system with different injection speeds are shown in Table 4.

[0080] Table 4 Experimental results of the reduction rate of the aqueous phase permeability and the reduction rate of sand production of the microbial sand fixation system

[0081]

[0082] As can be seen from Table 4: When the injection speed of the system is 1.2 ml / min, the screening conditions of the reduction rate of the aqueous phase permeability ≤ 10% and the reduction rate of sand production ≥ 95% are met. Therefore, the injection speed of the biofilm-producing microorganism Acetobacter and its nutrients is determined to be 1.2 ml / min.

[0083] (6) Field test and effect evaluation

[0084] Inject the formulated glucose 3 wt%, corn steep liquor dry powder 0.5 wt%, and dipotassium hydrogen phosphate 0.05 wt% of the biofilm-producing microorganism Acetobacter and its nutrients determined in the above steps from the injection well, with an injection volume of 0.20 PV and an injection speed of 1.2 ml / min. After injection, shut in the well for 20 days of cultivation, and after opening the well, track and analyze the sand production, liquid production, and effective period in the produced fluid of the test block C 33 in the oil well.

[0085] The test results show that in the test block C 33 the reduction rate of sand production in the produced fluid reaches 95.8%, the normal production cycle of the oil well is extended from 106 days to 384 days, and the number of pump inspections is effectively reduced. At the same time, the liquid production of the block increases from 86 m 3 / d to 201 m 3 / d, and the on-site application effect is good.

[0086] Example 2

[0087] Block Y in Shengli Oilfield 55 The reservoir temperature is 57 °C, the porosity is 30.3%, and the average permeability is 2362×10 -3 μm 2 , the shale content of the sand body is 12.5%, belonging to a loose sandstone reservoir. Before the test, the comprehensive water cut of the block is 85.6%, the daily oil production is 10.8 t / d, the daily liquid production is 75 m 3 / d, and the correspondence between the injection well and the oil well is good. Many wells in this block have long-term sand production, frequent well shutdowns, and low open-hole rates, resulting in poor development effects. Using the method of the present invention to implement sand control in this block, the specific steps are as follows:

[0088] (1) Screening of the test block

[0089] Test block Y 55 has a reservoir temperature of 57 °C, a porosity of 30.3%, and an average permeability of 2362×10-3 μm 2 The shale content of the sand body is 12.5%, which is a loose sandstone reservoir, and the injection wells and production wells have good correspondence. It meets the reservoir screening criteria of the present invention, and the present invention can be implemented.

[0090] (2) Preliminary determination of biofilm-forming microorganisms and their nutrients

[0091] Add Agrobacterium, Acetobacter, Pseudomonas, Alcaligenes, and Staphylococcus aureus to 100 ml of formation water in test block Y 55 simultaneously add 10 ml of nutrients including 2 - 3 wt% glucose, 0.2 - 0.6 wt% peptone, and 0.03 - 0.05 wt% dipotassium hydrogen phosphate. After static cultivation at the reservoir temperature of 57°C in test block Y for 15 days, measure the bacterial concentration of biofilm-forming microorganisms in the solution. Screen out the biofilm-forming microorganisms with a bacterial concentration higher than 10 55 / ml and the highest bacterial concentration, which is Alcaligenes. The experimental results are shown in Table 5. 8 / ml, and the biofilm-forming microorganism with the highest bacterial concentration is Alcaligenes. The experimental results are shown in Table 5.

[0092] Table 5 Bacterial concentrations of different biofilm-forming microorganisms

[0093] Serial number Biofilm-forming microorganism Bacterial concentration (cells / mL) Rank 1 Pseudomonas <![CDATA[2*10 7 > 4 2 Staphylococcus aureus <![CDATA[7*10 6 > 5 3 Alcaligenes <![CDATA[7*10 8 > 1 4 Agrobacterium <![CDATA[4*10 7 > 3 5 Acetobacter <![CDATA[3*10 8 > 2

[0094] (3) Determination of biofilm-forming microorganisms and their nutrients

[0095] Add Alcaligenes and its nutrients to 100 ml of formation water in test block Y 55 for a total of 10 ml. After culturing at the reservoir temperature of 57°C in test block Y for 20 days, measure the weight of the mixture of bacteria and products, the polysaccharide content, and the pH value of the solution. Screen out Alcaligenes and its nutrients with the largest weight of the mixture, the most polysaccharide content, and pH > 7. 55 The method for measuring the weight of the mixture of bacteria and products is as follows: Filter all the culture solutions using a vacuum filtration device. After filtration, dry the mixture of bacteria and products. The initial temperature is 35°C, and then increase by 5°C every hour, with the highest temperature of 50°C. Weigh after drying to a constant weight; the method for measuring the polysaccharide content is the sulfuric acid - anthrone colorimetric method.

[0096] The measurement results of the dry weight of the product mixture, polysaccharide content, and pH value with different nutrient formulations are shown in Table 6.

[0097] The measurement results of the dry weight of the product mixture, polysaccharide content, and pH value are shown in Table 6.

[0098] Table 6 Measurement results of the dry weight of the product mixture, polysaccharide content, and pH value

[0099]

[0100] As can be seen from Table 7, for the Alcaligenes and its nutrient formulation with 3 wt% glucose, 0.6 wt% peptone, and 0.05 wt% dipotassium hydrogen phosphate, the dry weight of the product mixture is the largest, the polysaccharide content is the highest, and the solution pH = 8, meeting the screening requirement of pH > 7. Therefore, the biofilm-producing microorganism screened out is Alcaligenes, and its nutrient formulation is 3 wt% glucose, 0.6 wt% peptone, and 0.05 wt% dipotassium hydrogen phosphate.

[0101] (4) Determination of the injection volume of biofilm-producing microorganisms and their nutrients

[0102] First, select the natural core of test block Y 55 and saturate it with the formation water of test block Y 55 to calculate the pore volume v 1 and measure the aqueous permeability k of the core 1 . At the same time, test the sand content m in the displaced water 1 ; inject different amounts of the biofilm-producing microorganism Alcaligenes and its nutrient with the formulation of 3 wt% glucose, 0.6 wt% peptone, and 0.05 wt% dipotassium hydrogen phosphate. After culturing for 20 days, continue to inject the formation water of the test block, and measure the aqueous permeability k 2 of the core and the sand content m in the produced liquid 2 . Screen out the injection volume corresponding to the reduction rate of aqueous permeability ≤ 10% and the reduction rate of sand production ≥ 95%. This injection volume is the injection volume of the biofilm-producing microorganism and its nutrients.

[0103] The experimental results of the reduction rate of aqueous permeability and the reduction rate of sand production for different injection volumes of biofilm-producing microorganisms and their nutrients are shown in Table 7.

[0104] Table 7 Experimental results of the reduction rate of aqueous permeability and the reduction rate of sand production

[0105]

[0106] As can be seen from Table 7, when the system injection volume is 0.25 PV, it meets the screening conditions of the reduction rate of aqueous permeability ≤ 10% and the reduction rate of sand production ≥ 95%. Therefore, the injection volume of the biofilm-producing microorganism Alcaligenes and its nutrients is determined to be 0.25 PV.

[0107] (5) Determination of the injection rate of biofilm-producing microorganisms and their nutrients

[0108] First, select test block Y 55For natural cores, an injection rate evaluation experiment was carried out according to the above-determined biofilm-forming microorganism Alcaligenes, nutrient formula glucose 3 wt%, peptone 0.6 wt%, dipotassium hydrogen phosphate 0.05 wt%, and injection volume 0.25 PV; the injection rate was 1.0 - 1.5 ml / min. After injecting the selected microbial sand fixation system for 20 d, the formation water of test block Y 55 was used for displacement. By comparing the reduction rate of water-phase permeability and the decrease amplitude of sand production corresponding to different injection rates, the injection rate corresponding to a water-phase permeability reduction rate ≤ 10% and a sand production decrease amplitude ≥ 95% was screened out, and this injection rate was the injection rate of the biofilm-forming microorganism and its nutrients.

[0109] The experimental results of the reduction rate of water-phase permeability and the decrease amplitude of sand production of the microbial sand fixation system at different injection rates are shown in Table 8.

[0110] Table 8 Experimental results of the reduction rate of water-phase permeability and the decrease amplitude of sand production of the microbial sand fixation system

[0111]

[0112] It can be seen from Table 8 that when the system injection rate is 1.3 ml / min, the screening conditions of water-phase permeability reduction rate ≤ 10% and sand production decrease amplitude ≥ 95% are met. Therefore, the injection rate of the biofilm-forming microorganism Alcaligenes and its nutrients was determined to be 1.3 ml / min.

[0113] (6) Field test and effect evaluation

[0114] The biofilm-forming microorganism Alcaligenes and its nutrient formula glucose 3 wt%, peptone 0.6 wt%, dipotassium hydrogen phosphate 0.05 wt% determined in the above steps were injected from the injection well, with an injection volume of 0.25 PV and an injection rate of 1.3 ml / min. After injection, the well was shut in for 20 d, and after opening the well, the sand production, liquid production, and effective period in the produced fluid of test block Y 55 were tracked and analyzed.

[0115] The test results show that in test block Y 55 the reduction amplitude of sand production in the produced fluid reached 96.3%, the normal production cycle of the oil well was extended from 120 days to 391 days, and the pump inspection frequency was effectively reduced. At the same time, the liquid production of the block increased from 75 m 3 / d to 137 m 3 / d, and the on-site application effect was good.

[0116] Example 3

[0117] A certain block Q in Shengli Oilfield 5 with a reservoir temperature of 60 °C, porosity of 32.9%, and average permeability of 1158 × 10 -3 μm2 , with a shale content of 10% in the sand body, it belongs to a loose sandstone reservoir. Before the experiment, the comprehensive water cut in the block was 77.7%, the daily oil production was 16.4 t / d, and the daily liquid production was 72 m 3 / d, and the injection wells and production wells corresponded well. There were serious sand production and plugging problems in this block, resulting in ineffective water injection, low oil production and low liquid production in production wells, and a high well lying rate. The sand control method of the present invention was implemented in this block, and the specific steps were as follows:

[0118] (1) Screening of the test block

[0119] The test block Q 5 had a reservoir temperature of 60 °C, a porosity of 32.9%, and an average permeability of 1158×10 -3 μm 2 , with a shale content of 10% in the sand body, was a loose sandstone reservoir, and the injection wells and production wells corresponded well. It met the reservoir screening criteria of the present invention and the present invention could be implemented.

[0120] (2) Preliminary determination of biofilm-forming microorganisms and their nutrients

[0121] Agrobacterium, Acetobacter, Pseudomonas, Alcaligenes, and Staphylococcus aureus were respectively added to 100 ml of the formation water in the test block Q 5 . At the same time, 10 ml of nutrients including 2-3 wt% glucose, 0.2-0.6 wt% peptone, and 0.03-0.05 wt% dipotassium hydrogen phosphate were added. After static cultivation at the reservoir temperature of 60 °C in the test block Q 5 for 5 d, the bacterial concentration of the biofilm-forming microorganisms in the solution was measured. The biofilm-forming microorganisms with a bacterial concentration higher than 10 8 / ml and the highest bacterial concentration under the conditions of this test block were screened out, which was Agrobacterium. The experimental results are shown in Table 9.

[0122] Table 9 Bacterial concentrations of different biofilm-forming microorganisms

[0123] Serial number Biofilm-forming microorganism Bacterial concentration (cells / mL) Rank 1 Pseudomonas <![CDATA[4*10 8 > 2 2 Staphylococcus aureus <![CDATA[3*10 7 > 5 3 Alcaligenes <![CDATA[1*10 8 > 3 4 Agrobacterium <![CDATA[6*10 8 > 1 5 Acetobacter <![CDATA[6*10 7 > 4

[0124] (3) Determination of biofilm-forming microorganisms and their nutrients

[0125] Agrobacterium and its nutrients were added to 100 ml of the formation water in the test block Q 5 . After culturing at the reservoir temperature of 60 °C in the test block Q 5 for 20 d, the weight of the mixture of bacterial cells and products, the polysaccharide content, and the pH value of the solution were measured. The Agrobacterium and its nutrients with the largest mixture weight, the most polysaccharide content, and a pH value > 7 were screened out.

[0126] The method for measuring the weight of the cell and product mixture is as follows: Filter all the culture broth using a vacuum filtration device. After filtration, dry the cell and product mixture. The initial temperature is 35°C, and then increase the temperature by 5°C every hour until the maximum temperature of 50°C. Weigh it after drying to a constant weight. The method for measuring the polysaccharide content is the sulfuric acid-anthrone colorimetric method.

[0127] The measurement results of the dry weight, polysaccharide content, and pH value of the product mixture with different nutrient formulations are shown in Table 10.

[0128] Table 10 Measurement results of the dry weight, polysaccharide content, and pH value of the product mixture

[0129]

[0130] It can be seen from Table 10 that the product mixture corresponding to Agrobacterium and its nutrient formulation of 3 wt% glucose, 0.6 wt% peptone, and 0.05 wt% dipotassium hydrogen phosphate has the largest dry weight, the most polysaccharide content, and the solution pH = 8, meeting the screening requirement of pH > 7. Therefore, the biofilm-producing microorganism screened out is Agrobacterium, and its nutrient formulation is 3 wt% glucose, 0.6 wt% peptone, and 0.05 wt% dipotassium hydrogen phosphate.

[0131] (4) Determination of the injection amount of biofilm-producing microorganism and its nutrient

[0132] First, select the natural core of test block Q 5 and saturate it with the formation water of test block Q 5 to calculate the pore volume v 1 and measure the water-phase permeability k 1 of the core. At the same time, measure the sand content m 1 in the produced water; Inject different amounts of the biofilm-producing microorganism Agrobacterium and its nutrient with the formulation of 3 wt% glucose, 0.6 wt% peptone, and 0.05 wt% dipotassium hydrogen phosphate. After culturing for 20 days, continue to inject the formation water of the test block, and measure the water-phase permeability k 2 of the core and the sand content m 2 in the produced liquid. Screen out the injection amount corresponding to the reduction rate of water-phase permeability ≤ 10% and the reduction rate of sand production ≥ 95%. This injection amount is the injection amount of the biofilm-producing microorganism and its nutrient.

[0133] The experimental results of the reduction rate of water-phase permeability and the reduction rate of sand production with different injection amounts of biofilm-producing microorganism and its nutrient are shown in Table 11.

[0134] Table 11 Experimental results of the reduction rate of water-phase permeability and the reduction rate of sand production

[0135]

[0136] As can be seen from Table 11: When the system injection volume is 0.25 PV, the screening conditions of the reduction rate of water-phase permeability ≤ 10% and the reduction rate of sand production ≥ 95% are met. Therefore, the injection volume of Agrobacterium tumefaciens and its nutrients that produce biofilm is determined to be 0.25 PV.

[0137] (5) Determination of the injection rate of biofilm-producing microorganisms and their nutrients

[0138] First, select the natural core of test block Q 5 According to the above-determined Agrobacterium tumefaciens that produces biofilm, the nutrient formula of 3 wt% glucose, 0.6 wt% peptone, and 0.05 wt% dipotassium hydrogen phosphate, and the injection volume of 0.25 PV, carry out an injection rate evaluation experiment; the injection rate is 1.0 - 1.5 ml / min. After injecting the screened microbial sand-fixing system for 20 days, use the formation water of test block Q 5 to displace. Compare the reduction rate of water-phase permeability and the reduction amplitude of sand production corresponding to different injection rates, and screen out the injection rate corresponding to the reduction rate of water-phase permeability ≤ 10% and the reduction rate of sand production ≥ 95%. This injection rate is the injection rate of biofilm-producing microorganisms and their nutrients.

[0139] The experimental results of the reduction rate of water-phase permeability and the reduction amplitude of sand production of the microbial sand-fixing system at different injection rates are shown in Table 12.

[0140] Table 12 Experimental results of the reduction rate of water-phase permeability and the reduction amplitude of sand production of the microbial sand-fixing system

[0141]

[0142] As can be seen from Table 12: When the system injection rate is 1.3 ml / min, the screening conditions of the reduction rate of water-phase permeability ≤ 10% and the reduction rate of sand production ≥ 95% are met. Therefore, the injection rate of Agrobacterium tumefaciens and its nutrients that produce biofilm is determined to be 1.3 ml / min.

[0143] (6) Field test and effect evaluation

[0144] Inject the Agrobacterium tumefaciens and its nutrient formula of 3 wt% glucose, 0.6 wt% peptone, and 0.05 wt% dipotassium hydrogen phosphate determined in the above steps from the injection well, with an injection volume of 0.25 PV and an injection rate of 1.3 ml / min. After injection, shut in the well for 20 days of cultivation. After opening the well, track and analyze the sand production, liquid production volume, and effective period in the produced fluid of the oil well in test block Q 5

[0145] The test results show that test block Q 5The reduction rate of sand production in the produced fluid reaches 96.2%, the normal production cycle of the oil well is extended from 154 days to 466 days, and the pump inspection frequency is effectively reduced. At the same time, the liquid production of the block is increased from 72 m 3 / d to 187 m 3 / d, and the on-site application effect is good.

[0146] Example 4

[0147] A certain block S in Shengli Oilfield 14 has a reservoir temperature of 65 °C, a porosity of 33.2%, an average permeability of 2648×10 -3 μm 2 , the shale content of the sand body is 7%, and it belongs to a loose sandstone reservoir. Before the test, the comprehensive water cut of the block is 89.4%, the daily oil production is 12.1 t / d, the daily liquid production is 114 m 3 / d, and the injection wells and production wells have good correspondence. Many wells in this block have been producing sand for a long time, the wells have been shut in frequently, the water injection is ineffective, and the development effect is poor. Using the method of the present invention to implement sand control in this block, the specific steps are as follows:

[0148] (1) Screening of the test block

[0149] The test block S 14 has a reservoir temperature of 65 °C, a porosity of 33.2%, an average permeability of 2648×10 -3 μm 2 , the shale content of the sand body is 7%, it is a loose sandstone reservoir, and the injection wells and production wells have good correspondence. It meets the reservoir screening criteria of the present invention and the present invention can be implemented.

[0150] (2) Preliminary determination of biofilm-forming microorganisms and their nutrients

[0151] Add Agrobacterium, Acetobacter, Pseudomonas, Alcaligenes, and Staphylococcus aureus to 100 ml of the formation water of the test block S 14 respectively, and at the same time add 10 ml of nutrients including 2-3 wt% glucose, 0.2-0.6 wt% peptone, and 0.03-0.05 wt% dipotassium hydrogen phosphate. After static culture at the reservoir temperature of 65 °C in the test block S 14 for 15 d, measure the bacterial concentration of the biofilm-forming microorganisms in the solution. Screen out the biofilm-forming microorganisms with a bacterial concentration higher than 10 8 / ml and the highest bacterial concentration, which is Alcaligenes, and the experimental results are shown in Table 13.

[0152] Table 13 Bacterial concentrations of different biofilm-forming microorganisms

[0153] Serial number Biofilm-forming microorganism Bacterial concentration (cells / mL) Rank 1 Pseudomonas <![CDATA[1*10 8 > 3 2 Staphylococcus aureus <![CDATA[6*10 7 > 4 3 Alcaligenes <![CDATA[8*10 8 > 1 4 Agrobacterium <![CDATA[3*10 7 > 5 5 Acetobacter <![CDATA[4*10 8 > 2

[0154] (3) Determination of biofilm-forming microorganisms and their nutrients

[0155] Add 10 ml of Alcaligenes and its nutrients to the formation water of the 100-ml test block S 14 in the test block S 14 After culturing for 30 d at the reservoir temperature of 65 °C, measure the weight of the mixture of bacteria and products, the polysaccharide content, and the pH value of the solution. Screen the Alcaligenes and its nutrients with the largest weight of the mixture, the most polysaccharide content, and pH > 7.

[0156] The method for measuring the weight of the mixture of bacteria and products is as follows: Filter all the culture solutions using a vacuum filtration device. After filtration, dry the mixture of bacteria and products. The initial temperature is 35 °C, and then increase by 5 °C every 1 hour until the maximum temperature of 50 °C. Weigh after drying to a constant weight. The method for measuring the polysaccharide content is the sulfuric acid-anthrone colorimetric method.

[0157] The measurement results of the dry weight, polysaccharide content, and pH value of the product mixture with different nutrient formulations are shown in Table 14.

[0158] Table 14 Measurement results of the dry weight, polysaccharide content, and pH value of the product mixture

[0159]

[0160] It can be seen from Table 14 that the product mixture corresponding to the Alcaligenes and its nutrient formulation of 3 wt% glucose, 0.5 wt% peptone, and 0.04 wt% dipotassium hydrogen phosphate has the largest dry weight, the most polysaccharide content, and the solution pH = 8, meeting the screening requirements of pH > 7. Therefore, the biofilm-producing microorganism screened out is Alcaligenes, and its nutrient formulation is 3 wt% glucose, 0.5 wt% peptone, and 0.04 wt% dipotassium hydrogen phosphate.

[0161] (4) Determination of the injection amount of biofilm-producing microorganisms and their nutrients

[0162] First, select the natural core of the test block S 14 and saturate it with the formation water of the test block S 14 Calculate the pore volume v 1 and measure the aqueous permeability k of the core 1 , and at the same time, measure the sand content m in the displaced water 1 ; Inject different amounts of the biofilm-producing microorganism Alcaligenes and its nutrients with the formulation of 3 wt% glucose, 0.5 wt% peptone, and 0.04 wt% dipotassium hydrogen phosphate. After culturing for 30 d, continue to inject the formation water of the test block, and measure the aqueous permeability k 2 of the core and the sand content m in the produced liquid 2Screen out the injection volume corresponding to the reduction rate of aqueous phase permeability ≤ 10% and the reduction rate of sand production ≥ 95%. This injection volume is the injection volume of biofilm-forming microorganisms and their nutrients.

[0163] The experimental results of the reduction rate of aqueous phase permeability and the reduction rate of sand production with different injection volumes of biofilm-forming microorganisms and their nutrients are shown in Table 15.

[0164] Table 15 Experimental results of the reduction rate of aqueous phase permeability and the reduction rate of sand production

[0165]

[0166] It can be seen from Table 15 that when the system injection volume is 0.25 PV, the screening conditions of the reduction rate of aqueous phase permeability ≤ 10% and the reduction rate of sand production ≥ 95% are met. Therefore, the injection volume of the biofilm-forming microorganism Acetobacterium and its nutrients is determined to be 0.25 PV.

[0167] (5) Determination of the injection rate of biofilm-forming microorganisms and their nutrients

[0168] First, select the natural core of test block S 14 According to the above-determined biofilm-forming microorganism Alcaligenes, nutrient formula glucose 3 wt%, peptone 0.5 wt%, dipotassium hydrogen phosphate 0.04 wt%, and injection volume 0.25 PV, carry out an injection rate evaluation experiment; the injection rate is 1.0 - 1.5 ml / min. After injecting the screened microbial sand fixation system for 30 days, use the formation water of test block S 14 to displace. Compare the reduction rate of aqueous phase permeability and the reduction amplitude of sand production corresponding to different injection rates, and screen out the injection rate corresponding to the reduction rate of aqueous phase permeability ≤ 10% and the reduction rate of sand production ≥ 95%. This injection rate is the injection rate of biofilm-forming microorganisms and their nutrients.

[0169] The experimental results of the reduction rate of aqueous phase permeability and the reduction rate of sand production of the microbial sand fixation system with different injection rates are shown in Table 16.

[0170] Table 16 Experimental results of the reduction rate of aqueous phase permeability and the reduction rate of sand production of the microbial sand fixation system

[0171]

[0172] It can be seen from Table 16 that when the system injection rate is 1.3 ml / min, the screening conditions of the reduction rate of aqueous phase permeability ≤ 10% and the reduction rate of sand production ≥ 95% are met. Therefore, the injection rate of the biofilm-forming microorganism Alcaligenes and its nutrients is determined to be 1.3 ml / min.

[0173] (6) Field test and effect evaluation

[0174] Inject the biofilm-producing microorganism Alcaligenes and its nutrient formulation, which are determined in the above steps, i.e., glucose 3 wt%, peptone 0.5 wt%, and dipotassium hydrogen phosphate 0.04 wt%, into the injection well at an injection volume of 0.25 PV and an injection rate of 1.3 ml / min. After injection, shut in the well for 30 days of cultivation, and after opening the well, conduct a follow-up analysis on the sand production, liquid production, and effective period of the test block S 14 Track and analyze the sand production, liquid production, and effective period in the produced fluid of the oil well.

[0175] The test results show that in the test block S 14 The reduction rate of sand production in the produced fluid reaches 96.1%. The normal production cycle of the oil well is extended from 142 days to 590 days, effectively reducing the number of pump inspections. At the same time, the liquid production of the block increases from 114 m 3 / d to 269 m 3 / d, and the on-site application effect is good.

[0176] Example 5

[0177] A certain block H in Shengli Oilfield 22 has a reservoir temperature of 55°C, a porosity of 30.6%, an average permeability of 2140×10 -3 μm 2 , a shale content of 10.8% in the sand body, and belongs to a loose sandstone reservoir. Before the test, the comprehensive water cut of the block is 88.8%, the daily oil production is 10.5 t / d, the daily liquid production is 94 m 3 / d, and the correspondence between the injection well and the production well is good. Many wells in this block have long-term sand production, frequent well shutdowns, a low open-hole rate, and poor development effects. Use the method of the present invention to conduct sand control in this block, and the specific steps are as follows:

[0178] (1) Screening of the test block

[0179] The test block H 22 has a reservoir temperature of 55°C, a porosity of 30.6%, an average permeability of 2140×10 -3 μm 2 , a shale content of 10.8% in the sand body, is a loose sandstone reservoir, and the correspondence between the injection well and the production well is good. It meets the reservoir screening criteria of the present invention and can implement the present invention.

[0180] (2) Preliminary determination of the biofilm-producing microorganism and its nutrients

[0181] Respectively add Agrobacterium, Acetobacter, Pseudomonas, Alcaligenes, and Staphylococcus aureus to 100 ml of the formation water in the test block H 22 , and at the same time add 10 ml of nutrients including glucose 2 - 3 wt%, urea 0.2 - 0.6 wt%, and dipotassium hydrogen phosphate 0.03 - 0.05 wt% in the test block H 22After static cultivation at a reservoir temperature of 55°C for 10 days, the bacterial concentration of the biofilm-forming microorganisms in the solution was measured. The biofilm-forming microorganism with a bacterial concentration higher than 10 8 / ml and the highest bacterial concentration under the conditions of this test block was Pseudomonas, and the experimental results are shown in Table 17.

[0182] Table 17 Bacterial Concentrations of Different Biofilm-Forming Microorganisms

[0183] Serial number Biofilm-forming microorganism Bacterial concentration (cells / mL) Rank 1 Pseudomonas <![CDATA[4*10 8 > 1 2 Staphylococcus aureus <![CDATA[9*10 7 > 3 3 Alcaligenes <![CDATA[2*10 7 > 4 4 Agrobacterium <![CDATA[8*10 6 > 5 5 Acetobacter <![CDATA[2*10 7 > 2

[0184] (3) Determination of Biofilm-Forming Microorganisms and Their Nutrients

[0185] Add 10 ml of Pseudomonas and its nutrients to 100 ml of formation water in test block H 22 After culturing at a reservoir temperature of 55°C in test block H 22 for 15 days, the weight of the mixture of bacteria and products, the polysaccharide content, and the pH value of the solution were measured. The Bacillus with the largest weight of the mixture, the most polysaccharide content, and pH > 7 and its nutrients were screened.

[0186] Among them, the method for measuring the weight of the mixture of bacteria and products is as follows: Filter all the culture solution using a vacuum filtration device. After filtration, dry the mixture of bacteria and products. The initial temperature is 35°C, and then increase by 5°C every 1 hour, with a maximum temperature of 50°C. Weigh after drying to a constant weight; the method for measuring the polysaccharide content is: the sulfuric acid-anthrone colorimetric method.

[0187] The measurement results of the dry weight, polysaccharide content, and PH value of the product mixture with different nutrient formulations are shown in Table 18.

[0188] Table 18 Measurement Results of the Dry Weight, Polysaccharide Content, and PH Value of the Product Mixture

[0189]

[0190] It can be seen from Table 18 that: The dry weight of the product mixture, the most polysaccharide content, and the solution pH = 8 corresponding to the nutrient formulation of Pseudomonas and its nutrients of 2.5 wt% glucose, 0.5 wt% urea, and 0.05 wt% dipotassium hydrogen phosphate meet the screening requirements of pH > 7. Therefore, the screened biofilm-forming microorganism is Pseudomonas, and its nutrient formulation is 2.5 wt% glucose, 0.5 wt% urea, and 0.05 wt% dipotassium hydrogen phosphate.

[0191] (4) Determination of the Injection Amount of Biofilm-Forming Microorganisms and Their Nutrients

[0192] First, select the natural core of test block H 22 and saturate it with the formation water of test block H 22 Calculate the pore volume v1 and measure the aqueous permeability k of the core 1 , and simultaneously test the sand content m in the displaced water 1 ; Inject different amounts of the biofilm-forming microorganism Pseudomonas and a nutrient solution with a formulation of 2.5 wt% glucose, 0.5 wt% urea, and 0.05 wt% dipotassium hydrogen phosphate. After culturing for 15 days, continue to inject the formation water of the test block, and measure the aqueous permeability k of the core 2 and the sand content m in the produced fluid 2 . Screen out the injection amount corresponding to a reduction rate of aqueous permeability ≤ 10% and a reduction rate of sand production ≥ 95%. This injection amount is the injection amount of the biofilm-forming microorganism and its nutrient

[0193] The experimental results of the reduction rate of aqueous permeability and the reduction rate of sand production for different injection amounts of the biofilm-forming microorganism and its nutrient are shown in Table 19

[0194] Table 19 Experimental results of the reduction rate of aqueous permeability and the reduction rate of sand production

[0195]

[0196] It can be seen from Table 19 that when the system injection amount is 0.20 PV, the screening conditions of a reduction rate of aqueous permeability ≤ 10% and a reduction rate of sand production ≥ 95% are met. Therefore, the injection amount of the biofilm-forming microorganism Pseudomonas and its nutrient is determined to be 0.20 PV

[0197] (5) Determination of the injection rate of the biofilm-forming microorganism and its nutrient

[0198] First, select the natural core of test block H 22 , and conduct an injection rate evaluation experiment according to the determined biofilm-forming microorganism Pseudomonas, the nutrient formulation of 2.5 wt% glucose, 0.5 wt% urea, and 0.05 wt% dipotassium hydrogen phosphate, and the injection amount of 0.20 PV; The injection rate is 1.0 - 1.5 ml / min. After injecting the screened microbial sand fixation system and culturing for 15 days, displace it with the formation water of test block H 22 . Compare the reduction rate of aqueous permeability and the reduction amplitude of sand production corresponding to different injection rates, and screen out the injection rate corresponding to a reduction rate of aqueous permeability ≤ 10% and a reduction rate of sand production ≥ 95%. This injection rate is the injection rate of the biofilm-forming microorganism and its nutrient

[0199] The experimental results of the reduction rate of aqueous permeability and the reduction rate of sand production for the microbial sand fixation system at different injection rates are shown in Table 20

[0200] Table 20 Experimental results of the reduction rate of aqueous permeability and the reduction rate of sand production for the microbial sand fixation system

[0201]

[0202] As can be seen from Table 20, when the injection rate of the system is 1.2 ml / min, the screening conditions of the reduction rate of water phase permeability ≤ 10% and the reduction rate of sand production ≥ 95% are met. Therefore, the injection rate of the biofilm-forming microorganism Pseudomonas and its nutrients is determined to be 1.2 ml / min.

[0203] (6) Field test and effect evaluation

[0204] Inject the formulated glucose 2.5 wt%, urea 0.5 wt%, and dipotassium hydrogen phosphate 0.05 wt% of the biofilm-forming microorganism Bacillus spores and its nutrients determined in the above steps into the injection well. The injection volume is 0.20 PV, the injection rate is 1.2 ml / min, and after injection, shut in the well for 15 days for culturing. After opening the well, track and analyze the sand production, liquid production, and effective period in the produced fluid of Well H in the test block. 22 Track and analyze the sand production, liquid production, and effective period in the produced fluid of the oil well.

[0205] The test results show that in the test block H 22 The reduction rate of sand production in the produced fluid reaches 95.2%. The normal production cycle of the oil well is extended from 146 days to 423 days, effectively reducing the pump inspection frequency. At the same time, the liquid production of the block increases from 94 m 3 / d to 183 m 3 / d, and the on-site application effect is good.

[0206] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for using microorganisms to alleviate formation sand production, characterized in that, the method specifically comprises the following steps: (1) Screening of test blocks The screening conditions for the test block are as follows: reservoir temperature ≤ 80 °C, porosity ≥ 25%, permeability ≥ 500×10 3 μm 2 , the shale content of cement is 5 - 35%, loose sandstone reservoir, and injection wells and production wells are corresponding; (2) Preliminary determination of biofilm-forming microorganisms and their nutrients The basis for the preliminary determination of biofilm-forming microorganisms and their nutrients is the bacterial concentration of biofilm-forming microorganisms; (3) Determination of biofilm-forming microorganisms and their nutrients The basis for the determination of biofilm-forming microorganisms and their nutrients is the weight of the mixture of bacteria and products, the polysaccharide content, and the solution pH value; (4) Determination of the injection volume of biofilm-forming microorganisms and their nutrients The basis for the determination of the injection volume of biofilm-forming microorganisms and their nutrients is the reduction rate of water-phase permeability and the reduction rate of sand production; (5) Determination of the injection rate of biofilm-forming microorganisms and their nutrients The basis for the determination of the injection rate of biofilm-forming microorganisms and their nutrients is the reduction rate of water-phase permeability and the reduction rate of sand production; (6) Field test and effect evaluation The field test effect evaluation indexes are the sand production, liquid production, and validity period in the produced fluid for tracking and analysis.

2. The method for using microorganisms to alleviate formation sand production according to claim 1, characterized in that, The preliminary determination of the biofilm microorganisms and their nutrients described in step (2) is carried out as follows: Add a total of 10 ml of biofilm microorganisms and their nutrients to 100 ml of formation water in the test block. After culturing for 5 - 15 days under the reservoir temperature conditions of the test block, measure the bacterial concentration of the biofilm microorganisms in the solution, and screen out the biofilm microorganisms with a bacterial concentration higher than 10 8 / ml and the highest bacterial concentration.

3. The method for using microorganisms to alleviate formation sand production according to claim 1 or 2, characterized in that, the biofilm-forming microorganisms are one of Agrobacterium, Acetobacter, Pseudomonas, Alcaligenes, and Staphylococcus aureus.

4. The method for using microorganisms to alleviate formation sand production according to claim 3, characterized in that, the biofilm-forming microorganisms are one of Agrobacterium, Acetobacter, and Staphylococcus aureus.

5. The method for using microorganisms to alleviate formation sand production according to claim 1 or 2, characterized in that, the formula of the nutrients for the biofilm-forming microorganisms is 2-3 wt% of carbon source, 0.2-0.6 wt% of nitrogen source, and 0.03-0.05 wt% of phosphorus source.

6. The method for using microorganisms to alleviate formation sand production according to claim 5, characterized in that, the carbon source is glucose or sucrose, the nitrogen source is one of urea, corn steep liquor dry powder, and peptone, and the phosphorus source is dipotassium hydrogen phosphate or potassium dihydrogen phosphate.

7. The method for using microorganisms to alleviate formation sand production according to claim 1, characterized in that, in step (3), for the determination of the biofilm-forming microorganisms and their nutrients, the specific method is as follows: Add a total of 10 ml of biofilm-forming microorganisms and their nutrients to 100 ml of formation water in the test block, and after culturing for 15-30 d under the reservoir temperature conditions of the test block, measure the weight of the mixture of bacteria and products, the polysaccharide content, and the solution pH value, and screen the biofilm-forming microorganisms and their nutrients with the largest weight of the mixture of bacteria and products, the most polysaccharide content, and pH value > 7.

8. The method for using microorganisms to alleviate formation sand production according to claim 7, characterized in that, the method for measuring the weight of the mixture of bacteria and products is as follows: Filter all the culture solutions using a vacuum filtration device. After filtration, dry the mixture of bacteria and products. The initial temperature is 35 °C, and then increase by 5 °C every 1 hour, with the highest temperature of 50 °C. Weigh after drying to a constant weight.

9. The method for alleviating formation sand production by using microorganisms according to claim 7, characterized in that, the method for measuring the polysaccharide content is the sulfuric acid - anthrone colorimetric method.

10. The method for alleviating formation sand production by using microorganisms according to claim 1, characterized in that, for the determination of the injection amount of the biofilm - forming microorganisms and their nutrients in step (4), the specific method is as follows: First, select the natural core of the test block, saturate it with the formation water of the test block, calculate the pore volume and measure the water - phase permeability of the core, and at the same time test the sand content in the produced water; Inject different amounts of the biofilm - forming microorganisms and their nutrients, after culturing for 15 - 30 d, continue to inject the formation water of the test block, and measure the water - phase permeability of the core and the sand content in the produced liquid; Screen out the injection amount corresponding to the water - phase permeability reduction rate ≤ 10% and the sand production reduction rate ≥ 95% as the injection amount of the biofilm - forming microorganisms and their nutrients.

11. The method for alleviating formation sand production by using microorganisms according to claim 1, characterized in that, for the determination of the injection rate of the biofilm - forming microorganisms and their nutrients in step (5), the specific method is as follows: Select the natural core of the test block, and carry out the evaluation of the injection rate according to the determined injection amount of the biofilm - forming microorganisms and their nutrients above; The injection rate is 1.0 - 1.5 ml / min. After injecting the biofilm - forming microorganisms and their nutrients and culturing for 15 - 30 d, displace with the formation water of the test block. By comparing the decline ranges of the water - phase permeability and sand production corresponding to different injection rates, screen out the injection rate corresponding to the water - phase permeability reduction rate ≤ 10% and the sand production reduction rate ≥ 95% as the injection rate of the biofilm - forming microorganisms and their nutrients.

12. The method for alleviating formation sand production by using microorganisms according to claim 1, characterized in that, the specific steps of the field test in step (6) are as follows: Inject the biofilm - forming microorganisms and their nutrients from the injection well. The injected biofilm - forming microorganism strains, their nutrient formulations, injection amounts, and injection rates are determined according to the above steps. After injection, shut - in the well for culturing for 15 - 30 d, and after opening the well, evaluate the effect of the oil wells in the test block.

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