Material and method for cleaning biogas residues produced by anaerobic digestion of waste oil reservoir

Abstract

The invention provides a material and a method for cleaning biogas residues produced by anaerobic digestion of waste oil reservoirs. The method comprises the following steps: (1) determining required anaerobic digestion methanogens and substrates according to the types of biogas residues produced by anaerobic digestion of the waste oil reservoir; (2) the oil reservoir is screened according to the requirements of the anaerobic digestion methanogens and the substrate for temperature, mineral substances, pH value and permeability, and a standard rock core is obtained; (3) adopting a physical simulation method, injecting anaerobic digestion methanogens and different organic matters into the standard rock core to clean in a manner of producing biogas residues through anaerobic digestion, and performing biogas residue cleaning test on the biogas residues generated by the different organic matters to obtain a cleaning scheme; and (4) cleaning the biogas residues produced by anaerobic digestion of the waste oil reservoir according to the cleaning scheme. A classification cleaning strategy is designed according to the blocking risk of organic matter biogas residues of different sources, the method for preparing the biogas through anaerobic digestion of the waste oil reservoir can be achieved, and the in-situ biogas preparation efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield development, and particularly relates to a cleaning material and method for biogas residue produced by anaerobic digestion of abandoned oil reservoirs. BACKGROUND

[0002] With long-term development, a large number of blocks in China have entered the late stage of high water cut, and the proportion of difficult-to-produce reserves continues to rise. Under this background, the in-situ anaerobic digestion of oil reservoirs to produce biogas technology can utilize the geological characteristics of abandoned oil reservoirs such as high permeability, high water content, natural temperature and sealing, and achieve efficient methane production by injecting organic matter and methanogenic bacteria, becoming an important direction of resource comprehensive utilization and low-carbon development.

[0003] However, the large-scale application of this technology faces core challenges such as oil reservoir pore plugging and formation pollution caused by biogas residue. Therefore, it is an urgent need to provide a cleaning material and method for biogas residue produced by anaerobic digestion of abandoned oil reservoirs to improve resource comprehensive utilization and low-carbon development of abandoned oil reservoirs. SUMMARY

[0004] To solve the above technical problems, the present application provides a cleaning material and method for biogas residue produced by anaerobic digestion of abandoned oil reservoirs.

[0005] To achieve the above purpose, the technical solution adopted by the present application is as follows:

[0006] The present application provides a cleaning material for biogas residue produced by anaerobic digestion of abandoned oil reservoirs, wherein the biogas residue produced by anaerobic digestion of abandoned oil reservoirs includes lignin residue, kitchen waste residue and municipal sludge residue; the cleaning material includes material A for cleaning lignin residue and material B for cleaning kitchen waste residue; wherein the material A includes 2wt%-4wt% NaOH and 0.3wt%-0.7wt% OP-10 surfactant, and nano-SiO2-CO2 foam and 40-60U / g lignin peroxidase complex inoculant; the material B includes supercritical CO2 extraction stripping grease biofilm, and 2500-3500U / mL protease and 0.8%-1.2% cationic surfactant.

[0007] The application also provides a method for cleaning biogas residue produced by anaerobic digestion of waste oil reservoirs, which comprises the following steps: (1) determining the required anaerobic digestion methanogen and substrate according to the type of biogas residue produced by anaerobic digestion of waste oil reservoirs; (2) screening the oil reservoir according to the requirements of the anaerobic digestion methanogen and substrate for temperature, minerals, pH value, and permeability to obtain a standard core; (3) using a physical simulation method, injecting anaerobic digestion methanogen and different organic matter into the standard core to produce biogas residue by anaerobic digestion, and performing biogas residue cleaning test on the biogas residue generated by different organic matter to obtain a cleaning scheme; and (4) cleaning the biogas residue produced by anaerobic digestion of the waste oil reservoir according to the cleaning scheme; wherein, when the biogas residue produced by anaerobic digestion of the waste oil reservoir is lignin biogas residue, the cleaning material used is 3wt% NaOH and 0.5wt% OP-10 surfactant, and nano-SiO2-CO2 foam and 50U / g lignin peroxide complex bacteria agent; when the biogas residue produced by anaerobic digestion of the waste oil reservoir is kitchen waste biogas residue, the cleaning material used is supercritical CO2 extraction to strip grease biofilm, and protease-cationic surfactant; and when the biogas residue produced by anaerobic digestion of the waste oil reservoir is municipal sludge biogas residue, ultrasonic treatment is performed. 2- CO2 foam and 50U / g lignin peroxide complex bacteria agent; when the biogas residue produced by anaerobic digestion of the waste oil reservoir is kitchen waste biogas residue, the cleaning material used is supercritical CO2 extraction to strip grease biofilm, and protease-cationic surfactant; and when the biogas residue produced by anaerobic digestion of the waste oil reservoir is municipal sludge biogas residue, ultrasonic treatment is performed.

[0008] Further, the step (4) specifically comprises: when the biogas residue produced by anaerobic digestion of the waste oil reservoir is lignin biogas residue, first injecting 80℃ alkaline steam containing 3wt% NaOH and 0.5wt% OP-10 surfactant into the well, and allowing the well to be treated for 24 hours to make lignin soften and decompose and achieve a viscosity reduction of more than 50%; then performing in-situ degradation of biological enzymes: mixing nano-SiO2-CO2 foam and 50U / g lignin peroxide complex bacteria agent in a stirring tank to form a complex system with a bacteria enzyme concentration of 20%, injecting the complex system into the target oil reservoir through a water injection well, and allowing the complex system to circulate for 48 hours, activating the enzyme activity by using the formation temperature, and directionally degrading lignin for 14 days; and finally applying 10MPa high-pressure hydraulic circulation flushing to the oil reservoir.

[0009] Further, the step (4) specifically comprises: when the biogas residue produced by anaerobic digestion of the waste oil reservoir is kitchen waste biogas residue, using supercritical CO2 extraction to strip grease biofilm, and coupling protease-cationic surfactant to remove protein colloid adhesion; and finally applying 10MPa high-pressure hydraulic circulation flushing to the oil reservoir.

[0010] Further, the step (4) specifically comprises: in the case that the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is municipal sludge type biogas residue, first, the municipal sludge is pretreated to a particle size of 70 μm, second, the produced biogas residue is subjected to ultrasonic treatment, through double-frequency ultrasonic physical crushing, first, the biogas residue is subjected to strong crushing by using 20 kHz low-frequency ultrasonic waves, then, the crushed biogas residue is prevented from agglomeration by using 40 kHz high-frequency ultrasonic waves, and finally, the crushed biogas residue is subjected to high-pressure water flushing to drive out.

[0011] Further, the step (4) further comprises: in the case that the stabilized biogas residue fails to be flushed out, the biogas residue is permanently sealed in the selected abandoned oil reservoir by using geological sealing.

[0012] Further, the step (1) specifically comprises: screening anaerobic digestion methanogenic bacteria capable of degrading organic matter and biogas residue in the abandoned oil reservoir, and matching a suitable substrate according to the type of the biogas residue produced by anaerobic digestion of the abandoned oil reservoir.

[0013] Further, in the case that the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is lignin type biogas residue, the anaerobic digestion methanogenic bacteria are acetic nutrient type methanogenic bacteria, and the substrate is agricultural straw; in the case that the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is kitchen waste type biogas residue, the anaerobic digestion methanogenic bacteria are acetic nutrient type methanogenic bacteria, and the substrate is agricultural straw; in the case that the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is municipal sludge type biogas residue, the anaerobic digestion methanogenic bacteria are hydrogen nutrient type methanogenic bacteria, and the substrate is municipal sludge. It should be noted that there are three types of methanogenic bacteria according to the type of the substrate for methanogenesis, which are acetic nutrient type, hydrogen nutrient type and methyl nutrient type. However, methyl compounds are rare and only exist in special environments, and the proportion in natural environment is less than 5%, and the amount of methanogenesis is also extremely low, so in the present application, the other two types of methanogenic bacteria are mainly used.

[0014] Further, the step (3) further comprises: after the biogas residue cleaning test, quantifying the cleaning and residue removal rate of different organic matters, and screening the optimal cleaning combination to optimize the cleaning scheme.

[0015] Compared with the prior art, the technical scheme provided by the present application has at least the following advantages:

[0016] The present application provides a cleaning material and method for biogas residue produced by anaerobic digestion of abandoned oil reservoirs.

[0017] The method of the present application is aimed at the plugging risk of different source organic matter biogas residue types, and a classification cleaning strategy is designed to realize the method of anaerobic digestion of waste oil reservoir to produce biogas and improve the efficiency of in-situ biogas production. First, the present application is aimed at lignin biogas residue in waste oil reservoir, and the three steps of thermochemical softening to reduce viscosity, in-situ biodegradation and high-pressure hydraulic flushing are used for cleaning, and the residue removal rate is more than 90%. Second, the present application is aimed at kitchen waste biogas residue in waste oil reservoir, and the method of supercritical CO2 extraction to strip grease biofilm, coupled with protease-cationic surfactant is used to remove protein colloid adhesion, and then the target cleaning of pore plugging caused by high grease is realized, and the residue removal rate is more than 80%. Third, the present application is aimed at kitchen waste biogas residue in waste oil reservoir, and the four steps of particle size pretreatment, dual-frequency ultrasonic physical crushing, hydraulic flushing and stable storage are used for treatment, and efficient residue removal is realized, and the residue removal rate is more than 70%. Finally, the present application also optimizes the injection amount and concentration of injected bacteria by physical experiment, and different injection process optimization is made for different biogas residue types to improve the cleaning efficiency of biogas residue. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the cleaning method flow chart of biogas residue produced by anaerobic digestion of waste oil reservoir of the present application. DETAILED DESCRIPTION

[0019] The present application aims to first systematically describe a cleaning material and method of biogas residue produced by anaerobic digestion of waste oil reservoir, and to realize efficient biological methane conversion in the ground by directional injection of suitable organic matter substrate and composite anaerobic digestion methanogenic bacteria. For the plugging risk of different source organic matter biogas residue types, such as Figure 1 as shown, a classification cleaning strategy is designed:

[0020] Lignin biogas residue: first, 80℃ alkaline steam containing 2wt%-4wt% NaOH and 0.3wt%-0.7wt% OP-10 surfactant (preferably 3wt% NaOH and 0.5wt% OP-10 surfactant) is injected into the well, and the well is treated for 24 hours to make lignin soften and decompose and achieve more than 50% viscosity reduction; then in-situ biodegradation is carried out: nano-SiO2-CO2 foam is mixed with 40-60U / g lignin peroxidase composite bacteria in a stirring pool to form a composite system with a bacteria enzyme concentration of 20%, which is injected into the target oil reservoir through the injection well and circulates for 48 hours, and the enzyme activity is activated by the formation temperature to directionally degrade lignin for 14 days, and the degradation rate is more than 70%; finally, 10MPa high-pressure hydraulic circulation flushing is applied to the oil reservoir, and the final residue removal rate can reach 91.3%.

[0021] Kitchen waste type biogas residue: supercritical CO2 extraction is used to strip the oil film, and protease-cationic surfactant is used to remove the protein colloid adhesion, so as to solve the pore plugging caused by high oil content (plugging rate > 60%); finally, 10 MPa high pressure water circulation flushing is applied to the oil reservoir, and the final residue removal rate can reach 83.6%.

[0022] Municipal sludge type biogas residue: first, the municipal sludge is pretreated, and the particle size is ground to 70 μm; second, the generated biogas residue is treated by ultrasonic wave, which is physically broken by double-frequency ultrasonic wave; first, 20 kHz low-frequency ultrasonic wave is used to strongly break the biogas residue, and then 40 kHz high-frequency ultrasonic wave is used to prevent the broken biogas residue from agglomeration; finally, the broken biogas residue is washed out by high-pressure water, and the stabilized biogas residue that cannot be washed out is safely and permanently sealed in the selected abandoned oil reservoir by geological sealing, and the final residue removal rate can reach 76.2%.

[0023] It should be noted that when the biogas residue produced by anaerobic digestion of abandoned oil reservoir is cleaned, it is known which of the above three types of biogas residue is, and the type of biogas residue is directly related to the organic substrate injected into the oil reservoir in the early stage. For example, if the injected substrate is agricultural straw, lignin type biogas residue is mainly produced after anaerobic digestion; if kitchen waste related organic matter is injected, kitchen waste type biogas residue containing high oil and protein is easy to form; if municipal sludge is injected as the substrate, municipal sludge type biogas residue is generated, and the type of biogas residue can be determined by tracking the source of the injected substrate.

[0024] The present application provides a kind of abandoned oil reservoir anaerobic digestion of biogas residue cleaning method produced, including the following steps:

[0025] (1) screening of anaerobic digestion methanogens and their organic matter: screening of anaerobic digestion methanogens with high efficiency of degrading oil reservoir residual organic matter and biogas residue, and matching suitable organic nutrient substrate (such as lignin type biogas residue, kitchen waste type biogas residue, municipal sludge type biogas residue). The bacterial flora should have the characteristics of temperature resistance, salt tolerance and oil tolerance, and the organic matter should meet the appropriate C / N ratio to promote microbial activity and reduce the adhesion of biogas residue.

[0026] (2) selection of oil reservoir: the requirements of anaerobic digestion methanogens and substrate for temperature, mineral, pH value and permeability are used to select the oil reservoir.

[0027] (3) optimization of biogas residue cleaning process: physical simulation method is used for cleaning process optimization, actual oil reservoir core and mineral water of target oil reservoir are used, different organic matter and anaerobic digestion methanogens are injected to produce biogas residue, and the biogas residue generated by different organic matter is tested for biogas residue cleaning. The residue removal rate is quantified, the optimal cleaning combination is selected, and the cleaning process is optimized.

[0028] (4) Field construction: according to the optimized cleaning process obtained in step (3), the abandoned oil reservoir anaerobic digestion biogas residue is cleaned.

[0029] The application will be described in detail below with reference to the specific embodiments.

[0030] Example 1:

[0031] A cleaning material and method for abandoned oil reservoir anaerobic digestion biogas residue, comprising the following steps:

[0032] (1) Screening of anaerobic digestion methanogens and their substrates:

[0033] The anaerobic digestion methanogens are acetic acid trophic methanogens, and the substrates are agricultural straws; the selected acetic acid trophic methanogens grow strictly anaerobically, and the optimum growth temperature is 38-40℃, and the suitable pH is 6.8-7.4.

[0034] (2) Reservoir screening:

[0035] The suitable temperature of the strain is 39.2℃, the suitable pH is 6.9, and the suitable reservoir parameter requirements are combined: the well pattern belongs to the combination of horizontal well and vertical well, the reservoir permeability is above 1000mD; the produced liquid water content is ≥95%; the target layer has a stable and dense lithologic barrier with a thickness of more than 10m.

[0036] The reservoir temperature of block A is 43℃, the permeability is 1311md, the water content of the oil well is 96.1%, the formation water pH is 7.1, and the barrier thickness is 13.4m.

[0037] (3) Optimization of biogas residue cleaning process, the optimization method adopts physical simulation method, and the optimization basis is the residue removal rate.

[0038] First, the natural core of block A is made into a standard core of Φ25x100mm; vacuumize, saturate with block A1 formation water; saturate with target block crude oil; drive the formation water to the produced liquid water content of more than 95%. Inject 20% concentration of acetic acid trophic methanogens, the injection amount is 0.2PV, and the static culture is 10d, and then the produced methane amount is measured; then, the cleaning scheme of different concentrations of NaOH and lignin peroxidase, different pressure hydraulic flushing combination is injected, see table 1. After chemical dewatering for 2d, biodegradation for 10d, and hydraulic flushing for 1d, the residue removal rate is measured by XRD diffraction; finally, the process with the largest residue removal rate ratio is selected as the optimized cleaning scheme.

[0039] Table 1 Cleaning scheme optimization

[0040]

[0041] (4) Field construction:

[0042] The substrate is first ground to an average particle size of 100 μm and delivered to the stirred tank by a pressurization device. The stirred tank is used to achieve sufficient mixing of the anaerobic digestion methanogen and the substrate, and the concentration of the injected methanogen is controlled at 20%, and the injection volume is set at 0.2 PV, and the target oil layer is injected after pressurization by a plunger pump. The device is equipped with an automatic control system, which can intelligently adjust parameters such as injection concentration and injection volume to improve injection accuracy and ensure operation quality. Finally, the anaerobic digestion methanogen and its substrate are delivered to the target oil layer site through the water well pipe column. After 12 months of anaerobic digestion of the abandoned oil reservoir, the biogas residue is cleaned by first injecting 80°C alkaline steam containing 3% NaOH (wt%) and 0.5% OP-10 surfactant (wt%) into the well, and allowing the well to soak for 24 hours, so that the lignin softens and decomposes, and the viscosity is reduced by >50%. Subsequently, the biogas residue in the abandoned oil reservoir is biologically degraded in situ, and the nano-SiO2-CO2 foam is mixed with 50 U / g of lignin peroxidase complex bacterial agent in the stirred tank, and injected into the target oil layer through the injection well, with the concentration of the bacterial enzyme liquid controlled at 20%, and the injection is repeated for 48 h, and the enzyme activity is activated by the geothermal temperature of the oil reservoir, and the lignin is directionally degraded for 14 days, with a degradation rate of ≥70%. Finally, the abandoned oil reservoir is subjected to 10 MPa high-pressure hydraulic circulation flushing, and the biodegradable biogas residue remaining in the formation is flushed out by hydraulic flushing, and the reservoir space is cleaned, and the final residue removal rate is 91.3%.

[0043] Field test result evaluation: As of December 30, 2024, the cumulative injection of bacterial liquid and nutrient system in C oil reservoir was 56,000 cubic meters, the injection cost was about 5 yuan per cubic meter, 643,000 cubic meters of methane was produced, the biogas residue treatment operation cycle was 60 days, the cumulative treatment cost was 137 yuan per ton of biogas residue, the biochar generated income was 238 yuan per ton, and the permeability recovery improved the methane recovery rate by 17.1%.

[0044] Example 2:

[0045] A method for cleaning biogas residue produced by anaerobic digestion of abandoned oil reservoirs, comprising the following steps:

[0046] (1) Screening of anaerobic digestion methanogen and its substrate:

[0047] The anaerobic digestion methanogen is an acetate nutrition type methanogen, and the substrate is agricultural straw; the selected acetate nutrition type methanogen grows strictly anaerobically, and the optimum growth temperature is 38-40°C, and the suitable pH is 6.8-7.4.

[0048] (2) Oil reservoir selection:

[0049] The suitable temperature of the bacteria is 39°C, the suitable pH is 7.1, and the suitable reservoir parameter requirements are as follows: the well pattern is a combination of horizontal well and vertical well, the reservoir permeability is above 1000 mD, the produced liquid water content is above 95%, and the target layer has a stable and thick (above 10 m) dense lithologic barrier.

[0050] The reservoir temperature of the block B is 42.7°C, the permeability is 1260 md, the water content of the oil well is 96.1%, the formation water pH is 7.2, and the barrier thickness is 15 m.

[0051] (3) Optimization of sludge cleaning process, the optimization method is physical simulation method, and the optimization basis is the sludge removal rate.

[0052] First, the natural core of the block B is made into a standard core with a diameter of 25 mm and a length of 100 mm; vacuum is drawn, and the block B formation water is saturated; the target block crude oil is saturated; the formation water is driven until the produced liquid water content is above 95%. 20% concentration of acetic acid nutrient methanogen is injected at an injection amount of 0.2 PV, and static culture is carried out for 10 days, and then the output methane amount is determined; supercritical CO2 extraction is used to strip the oil film of the sludge adhered to the protein colloid under different pressures of CO2, and then targeted viscosity reduction treatment is carried out on the sludge adhered to the protein colloid, different amounts of bacillus subtilis protease and different concentrations of cetyltrimethylammonium bromide are mixed at a volume ratio of 1:1, and finally the combined cleaning scheme is washed through high-pressure hydraulic circulation, as shown in Table 2. After CO2 is injected for 4 hours, the sludge adhered to the protein colloid is debonded for 2 days, and then the sludge removal rate is determined by XRD diffraction after hydraulic flushing for 1 day; finally, the process with the largest sludge removal rate is selected as the optimized cleaning scheme.

[0053] Table 2 Cleaning scheme optimization

[0054]

[0055]

[0056] (4) Field construction:

[0057] First, the substrate is ground to an average particle size of 100 μm, and is delivered to the stirring tank through a booster device. The stirring tank realizes sufficient mixing of the anaerobic digestion methanogen and the substrate, the injection concentration of the methanogen is controlled to be 20%, the injection amount is set to be 0.2 PV, and the methanogen is injected into the target oil layer after being pressurized by a plunger pump. The device is equipped with an automatic control system, which can intelligently adjust the injection concentration, injection amount and other parameters to improve the injection accuracy and ensure the operation quality. Finally, the anaerobic digestion methanogen and its substrate are delivered to the target oil layer site through the water well pipe column. After the waste oil reservoir is anaerobically digested for 12 months, the sludge is cleaned first by using supercritical CO2 extraction to strip the oil film, CO2 is injected at a pressure of 30 MPa, 10 m 3 / h flow rate is injected into the target oil layer, and CO2 penetrates into the phospholipid bilayer of the biofilm, causing the membrane volume to expand by 26%. Subsequently, a targeted debonding treatment is carried out on the protein colloid-adhered biogas residue in the abandoned oil reservoir: in the ground liquid preparation tank, 3000 U / mL of subtilisin is mixed with 1.0% concentration of cetyltrimethylammonium bromide at a volume ratio of 1:1, 5% of the stratum water compatible additive glycerol is added, and a homogeneous debonding liquid is formed by mechanical stirring at 300 r / min. The debonding liquid is injected into the target oil layer through the water injection wellhead pump set at a displacement of 3 m 3 / h, and the injection is continuously circulated for 36 h to allow the debonding liquid to fully diffuse in the oil reservoir pores and adsorb on the surface of the protein colloid. The oil reservoir ground temperature of 42.7°C is used to activate the protease activity, and the enzyme-catalyzed hydrolysis reaction is used to break the protein peptide bonds, while the cationic surfactant charge is used to destroy the colloid double electric layer, thereby cooperatively removing the protein colloid adhered to the rock surface, with a protein colloid adhesion removal rate of ≥85%. Finally, high-pressure hydraulic flushing is carried out on the abandoned oil reservoir at 20 MPa, and the biodegradable biogas residue remaining in the stratum is flushed out by hydraulic flushing, cleaning the reservoir space, and finally achieving a residue removal rate of 83.6%.

[0058] Field test result evaluation: By December 30, 2024, the cumulative injection of bacterial solution and nutrient system in B oil reservoir was 54,000 cubic meters, the injection cost was about 5.6 yuan / cubic meter, the methane production was 597,000 cubic meters, the biogas residue treatment operation cycle was 60 days, the cumulative treatment cost was 151 yuan / ton of biogas residue, the biochar generated income was 284 yuan / ton, and the permeability recovery improved the methane recovery rate by 15.7%.

[0059] Example 3:

[0060] A method for cleaning biogas residue produced by anaerobic digestion of abandoned oil reservoirs, comprising the following steps:

[0061] (1) Screening of anaerobic digestion methane-producing bacteria and their substrates:

[0062] The anaerobic digestion methane-producing bacteria are hydrogenotrophic methanogens, and the substrate is municipal sludge; the selected hydrogenotrophic methanogens grow strictly anaerobically, with an optimal growth temperature of 40-41°C and an optimal pH of 6.5-7.3.

[0063] (2) Oil reservoir screening:

[0064] The bacteria have an optimal temperature of 40.2°C and an optimal pH of 7, and the appropriate oil reservoir parameters require: the well pattern is a combination of horizontal wells and vertical wells, the reservoir permeability is above 1000 mD; the produced liquid has a water content of ≥95%; and the target layer has a stable and thick (≥10 m) dense lithologic barrier.

[0065] Block C reservoir temperature 42.3℃, permeability 1267md, water content of oil well 95.7%, formation water 6.9pH, barrier thickness 11.6m.

[0066] (3) Optimization of sludge cleaning process, optimization method using physical simulation method, optimization basis being sludge removal rate.

[0067] First, the natural core of block C is made into Φ25x100mm standard core; vacuum extraction, saturation of block C formation water; saturation of target block crude oil; formation water drive to output liquid water content above 95%. Inject 20% concentration of acetic acid nutrient methanogen, injection amount 0.2PV, static culture for 10d, then measure the output of methane; then different ultrasonic crushing methods, different pressure hydrocyclone flushing combinations of cleaning schemes for sludge are carried out, see table 3. After ultrasonic crushing for 1d and hydrocyclone flushing for 1d, the sludge removal rate is measured by XRD diffraction; finally, the process with the largest sludge removal rate is selected as the optimized cleaning scheme.

[0068] Table 3 Cleaning scheme optimization

[0069]

[0070] (4) Field construction:

[0071] First, the substrate is ground to an average particle size of 70μm and transported to the mixing tank through a booster device. The mixing tank realizes the full mixing of anaerobic digestion hydrogen-nutrient methanogen and substrate, the injection concentration of methanogen is controlled at 20%, the injection amount is set at 0.2PV, and the target oil layer is injected after boosting by a plunger pump. The device is equipped with an automatic control system, which can intelligently adjust parameters such as injection concentration and injection amount to improve injection accuracy and ensure operation quality. Finally, the anaerobic digestion methanogen and its substrate are transported to the target oil layer site through the water well pipe column. After 12 months of anaerobic digestion of abandoned oil reservoir, 46,000 cubic meters of methanogen and substrate are injected, with an injection cost of about 6.1 yuan / square meter, and 539,000 cubic meters of methane are produced, with good field effect.

[0072] First, install low-frequency ultrasonic transducers in the screen section of the gas injection well, operate intermittently for 2h and stop for 1h, set the frequency at 20kHz and the power at 1kW / group, install 1 group every 5m of well section to perform low-frequency strong crushing on the sludge of abandoned oil reservoir, then switch to high frequency to prevent sludge agglomeration, set the frequency at 40kHz and the power at 2kW / group, and direct the sludge to the sludge. Finally, the abandoned oil reservoir is subjected to 10MPa high-pressure hydrocyclone flushing, and the sludge residue that is difficult to biodegrade in the formation is flushed out by hydrocyclone, the reservoir space is cleaned, and the stabilized sludge that cannot be flushed out is safely and permanently sealed in the selected abandoned oil reservoir, which is considered as a geological sealing method, and the final sludge removal rate reaches 76.2%.

[0073] The field test result evaluation: C oil reservoir accumulative injection of bacteria liquid and nutrient system is 49,000 square meters by December 30, 2024, the injection cost is about 6.1 yuan / square meter, the methane production is 573,000 square meters, the biogas residue treatment operation cycle is 60 days, the accumulative treatment cost is 143 yuan / ton of biogas residue, the biochar income is 270 yuan / ton, and the methane recovery rate is increased by 13.3% after the permeability recovery.

[0074] Those skilled in the art can understand that the above-mentioned embodiments are specific examples for implementing the present application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the present application. Any person skilled in the art can make respective changes and modifications without departing from the spirit and scope of the present application, and therefore the protection scope of the present application should be limited by the scope defined in the claims.

Claims

1. A cleaning material for biogas residue produced by anaerobic digestion of abandoned oil reservoirs, characterized in that: The biogas-producing residues from anaerobic digestion of the abandoned oil reservoirs include lignin-based biogas residues, food waste-based biogas residues, and municipal sludge-based biogas residues; The cleaning materials include material A for cleaning lignin-based biogas residues and material B for cleaning food waste-based biogas residues; The material A comprises 2wt%-4wt% NaOH and 0.3wt%-0.7wt% OP-10 surfactant, as well as nano-SiO2-CO2 foam and 40-60U / g lignin peroxidase composite bacterial agent; The material B comprises supercritical CO2 extraction and stripping of oil biofilm, 2500-3500 U / mL protease and 0.8%-1.2% cationic surfactant.

2. A method for cleaning biogas residue produced by anaerobic digestion of abandoned oil reservoirs, characterized in that: The method includes: (1) Determine the required anaerobic digestion methanogens and substrates based on the type of biogas residue produced by anaerobic digestion of abandoned oil reservoirs; (2) screening the oil reservoir using the anaerobic digestion methanogens and substrate requirements for temperature, minerals, pH, and permeability to obtain standard cores; (3) Using a physical simulation method, actual reservoir cores and target reservoir mineral water are used to inject anaerobic digestion methanogens and different organic matter into the standard cores to produce digestate residues for cleaning, and digestate residue cleaning tests are performed on the digestate generated by different organic matter to obtain a cleaning plan; (4) Cleaning the biogas residue produced by anaerobic digestion of abandoned oil reservoirs using the cleaning scheme; Wherein, when the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is lignin-based biogas residue, the cleaning materials used are 3% NaOH and 0.5% OP-10 surfactant, as well as nano-SiO 2- CO2 foam and 50U / g lignin peroxidase compound agent; In the case where the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is food waste-type biogas residue, the cleaning materials used are supercritical CO2 extraction to remove the oil biofilm, and protease-cationic surfactant; When the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is municipal sludge-type biogas residue, it is treated by ultrasonic treatment.

3. The method for cleaning biogas residue produced by anaerobic digestion of abandoned oil reservoirs according to claim 2, characterized in that: The step (4) specifically includes: when the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is lignin-based, first injecting 80°C alkaline steam containing 3wt% NaOH and 0.5wt% OP-10 surfactant into the well, sealing the well for 24 hours to soften and decompose the lignin and reduce the viscosity by more than 50%; then performing in-situ degradation by biological enzymes: fully mixing nano-SiO2-CO2 foam and 50U / g lignin peroxidase composite bacterial agent in a stirring tank to form a composite system with a bacterial enzyme concentration of 20%, injecting the system into the target oil reservoir through a water injection well and circulating the system for 48 hours, using the formation temperature to activate the enzyme activity, and directionally degrading the lignin for 14 days; finally, applying 10MPa high-pressure hydraulic circulation flushing to the oil reservoir.

4. The method for cleaning biogas residue produced by anaerobic digestion of abandoned oil reservoirs according to claim 2, characterized in that: The step (4) specifically includes: when the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is food waste-type biogas residue, supercritical CO2 extraction is used to remove the oil biofilm, and proteinase-cationic surfactant is coupled to remove protein colloid adhesion; finally, 10MPa high-pressure hydraulic circulation flushing is applied to the oil reservoir.

5. The method for cleaning biogas residue produced by anaerobic digestion of abandoned oil reservoirs according to claim 2, characterized in that: The step (4) specifically includes: when the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is municipal sludge-type residue, first pre-treating the municipal sludge and grinding it to a particle size of 70 μm, then ultrasonically treating the generated residue, and physically crushing it through dual-frequency ultrasonic waves, first using 20 kHz low-frequency ultrasonic waves to strongly crush the residue, then using 40 kHz high-frequency ultrasonic waves to prevent the crushed residue from agglomerating, and finally flushing and driving out the crushed residue with high-pressure water.

6. The method for cleaning biogas residue produced by anaerobic digestion of abandoned oil reservoirs according to claim 5, characterized in that: The step (4) further includes: permanently sealing the stabilized biogas residue that cannot be flushed out in a selected abandoned oil reservoir by means of geological sealing.

7. The method for cleaning biogas residue produced by anaerobic digestion of abandoned oil reservoirs according to claim 2, characterized in that: The step (1) specifically includes: screening anaerobic digestion methanogens that can efficiently degrade residual organic matter and biogas residue in oil reservoirs, and matching suitable substrates according to the type of biogas residue produced by anaerobic digestion of the abandoned oil reservoirs.

8. The method for cleaning biogas residue produced by anaerobic digestion of abandoned oil reservoirs according to claim 7, characterized in that: In the case where the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is lignin-based biogas residue, the anaerobic digestion methanogen is an acetotrophic methanogen, and the substrate is agricultural straw; In the case where the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is food waste-type biogas residue, the anaerobic digestion methanogen is acetotrophic methanogen, and the substrate is agricultural straw; In the case where the biogas residue produced by anaerobic digestion of the abandoned oil reservoir is municipal sludge-type biogas residue, the anaerobic digestion methanogens are hydrogenotrophic methanogens, and the substrate is municipal sludge.

9. The method for cleaning biogas residue produced by anaerobic digestion of abandoned oil reservoirs according to claim 2, characterized in that: The step (3) further includes: after the biogas residue cleaning test, quantifying the cleaning and slag removal rates of different organic matter, screening the optimal cleaning combination, and optimizing the cleaning scheme.

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