A method for promoting CO2 sequestration and enhanced recovery using biomass fermentation

Abstract

The present application relates to the technical field of biogas fermentation, and discloses a method for promoting CO2 sequestration and improving recovery ratio by biomass fermentation, which comprises the following steps: mixing crop straw, household garbage and animal manure to prepare biogas by fermentation; after the fermentation is completed, separating the fermentation product into gas, liquid and solid to obtain biogas, biogas slurry and biogas residue; after the biogas residue is composted, it becomes bio-organic fertilizer; and the biogas slurry and the biogas are injected into the ground. The method provided by the present application does not need to purify the biogas, and can promote CO2 sequestration while improving the recovery ratio by using microorganisms and ethanol in the biogas slurry, and the method of composting the biogas residue to obtain bio-organic fertilizer has the advantages of low cost, clean treatment and efficient utilization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biogas fermentation, and particularly relates to a method for promoting CO2 sequestration and improving recovery ratio by biomass fermentation. BACKGROUND

[0002] China is a large agricultural country and one of the countries with the most abundant straw resources in the world. With the continuous improvement of the comprehensive production level of China's agriculture, the total amount of crop straw in China is showing an upward trend. How to reasonably and effectively dispose of crop straw has become a top priority.

[0003] The potential of anaerobic fermentation of straw to produce biogas is huge. Biogas is the product of the anaerobic fermentation process, and includes methane (CH4), carbon dioxide (CO2), ammonia (NH3), nitrogen (N2), hydrogen (H2), water vapor and other volatile compounds.

[0004] Before use, the trace gases in the biogas are generally removed to ensure safe use, especially the removal of a large amount of carbon dioxide in the biogas gas mixture to produce biogas rich in methane.

[0005] However, due to current technical reasons, the purification process of purified methane biogas has a long purification time and high cost. The biogas residue is usually incinerated and landfilled, and the biogas slurry is often subjected to anaerobic fermentation for deep oxidation, which has a high treatment cost. Moreover, a large amount of microorganisms in the biogas slurry are not effectively utilized, causing damage to the environment and even endangering personal health.

[0006] Therefore, how to clean and efficiently utilize biogas, biogas slurry and biogas residue is a problem that needs to be solved.

[0007] Methane, carbon dioxide and other gases in biogas can be injected into an oil reservoir for oil displacement, which can improve the recovery ratio of crude oil in the formation while reducing the emission of carbon dioxide. The principle is that the viscosity of crude oil is reduced, the volume of crude oil is expanded, the interfacial tension is reduced, the light hydrocarbons in the crude oil are extracted and vaporized, and a mixed oil zone of injected gas and light oil is formed to expand the sweep efficiency and maintain the formation pressure.

[0008] Microorganisms such as methanogenic bacteria in biogas slurry can also improve the recovery ratio of crude oil. The microorganisms are injected into the underground oil layer, and the microorganisms reproduce in the oil layer. On the one hand, the direct action of the microorganisms on the crude oil improves the properties of the crude oil and the flowability of the crude oil in the formation pores. On the other hand, the gas, biological surfactants, organic acids, polymers and other substances produced by the growth and metabolism of the microorganisms in the oil layer are used to improve the recovery ratio of crude oil.

[0009] The ethanol in the biogas slurry reduces the miscibility pressure of carbon dioxide and crude oil, and makes carbon dioxide more easily dissolved in the crude oil, thereby improving the carbon dioxide storage capacity. SUMMARY

[0010] The present application aims to solve the problems of high cost of existing biogas purification of methane biogas and low utilization efficiency of biogas slurry and biogas residue, while also using biogas slurry to improve the carbon dioxide storage capacity and improve the oil recovery rate.

[0011] The common biogas fermentation process in the prior art is generally to mix straw, animal manure and household garbage with water, adjust the fermentation system, and then perform biogas fermentation. Since the solid content is generally less than 10 wt.%, a large amount of water is required, which increases the treatment cost of the biogas slurry and the production cost of the biogas. At the same time, the biogas obtained by fermentation contains a large amount of gas impurities, and the concentration of methane may not meet the standard, so secondary treatment is required to remove carbon dioxide, nitrogen and other gas impurities, increasing the use cost. Therefore, it is not a completely energy-saving, emission-reducing, low-cost and green process. In view of the above problems, the present application combines the products of biogas fermentation with carbon dioxide storage and microbial oil recovery. The biogas gas does not need to be subjected to secondary impurity removal, the microorganisms in the biogas slurry do not need to be treated harmlessly, and the ethanol in the biogas slurry can be injected into the formation to promote carbon dioxide storage, and the biogas residue can be converted into biological fertilizer through composting, which can reduce the use cost of biogas and improve the oil recovery rate. Based on this idea, the inventors provide the scheme of the present application.

[0012] To achieve the above-mentioned purpose, the present application provides a method for promoting CO2 storage and improving recovery rate by using biomass fermentation, which comprises:

[0013] (1) under the condition of biological fermentation, the biomass fermentation raw material is subjected to fermentation treatment to obtain a fermentation product; the biomass fermentation raw material is a mixture of crop straw, household garbage and animal manure with a content weight ratio of 10:1-5:2-6; the initial conditions of the reaction system of the fermentation treatment meet: the solid concentration is 5-15 wt.%, and the pH value in the system is 7.5-8.5;

[0014] (2) the fermentation product is subjected to gas-liquid-solid separation to obtain biogas, biogas slurry and biogas residue;

[0015] (3) the biogas residue is subjected to composting treatment to prepare a biological organic fertilizer;

[0016] (4) the biogas slurry is injected into the underground at a volume of 0.1-1 PV to perform in-situ emulsification of crude oil;

[0017] (5) the biogas is injected into the underground alone or mixed with carbon dioxide for oil displacement, and the volume ratio of the carbon dioxide to the biogas is 0-1:1.

[0018] The method can provide a new idea for conversion and utilization of waste resources such as straw, animal manure and household garbage and improve the practicability of biogas economy.

[0019] The method provided by the application does not need to purify biogas, and preferably, the method of the application can promote carbon dioxide sequestration while utilizing microorganisms in biogas slurry and ethanol EOR, and the method of biogas residue composting to obtain bio-organic fertilizer has the advantages of reducing cost, clean treatment and efficient utilization. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a process flow chart shown in a preferred embodiment of the application;

[0021] Figure 2 is an effect diagram of improving the EOR degree after oil displacement under different volume ratios of carbon dioxide to biogas by applying the method of the application;

[0022] Figure 3 is an effect diagram of the amount of carbon dioxide sequestration under miscible pressure and immiscible pressure by applying the method of the application; wherein PVI is the injected pore volume;

[0023] Figure 4 is an effect diagram of in-situ emulsification of crude oil under different biogas slurry injection amounts by applying the method of the application to improve the EOR degree. DETAILED DESCRIPTION

[0024] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values should be understood to be approximate. A range includes the endpoints and any values between the endpoints. The endpoints of the ranges and the values between the endpoints are combinable to create new ranges that are not expressly disclosed. Any numerical value can be expressed as approximately or approximately.

[0025] As described previously, the application provides a method for promoting CO2 sequestration and EOR by using biomass fermentation, which comprises:

[0026] (1) under the condition of biological fermentation, the biomass fermentation raw material is subjected to fermentation treatment to obtain a fermentation product; the biomass fermentation raw material is a mixture of crop straw, household garbage and animal manure with a content weight ratio of 10:1-5:2-6; the initial conditions of the reaction system of the fermentation treatment meet: the solid concentration is 5-15 wt.%, and the pH value in the system is 7.5-8.5;

[0027] (2) the fermentation product is subjected to gas-liquid-solid separation to obtain biogas, biogas slurry and biogas residue;

[0028] (3) composting the biogas residue to produce bio-organic fertilizer;

[0029] (4) injecting the biogas slurry into the ground at a volume of 0.1-1 PV to emulsify crude oil in situ;

[0030] (5) injecting the biogas alone or mixed with carbon dioxide into the ground to drive oil, the volume ratio of the carbon dioxide to the biogas being 0-1:1.

[0031] The present application mixes crop straw, domestic waste and animal manure in a weight ratio of 10:1-5:2-6 to produce biogas by fermentation, separates the gas, liquid and solid after fermentation to obtain biogas, biogas slurry and biogas residue, composts the biogas residue to produce bio-organic fertilizer, and injects the biogas slurry and biogas into the ground.

[0032] The present application does not have specific requirements for the container for fermentation treatment, and can use conventional methods in the art, for example, a fermentation tank with a volume of 30-40 m 3 .

[0033] The method of the present application can achieve the purpose of oil driving by injecting the obtained biogas slurry and biogas into the ground.

[0034] Preferably, the biogas slurry is injected into the ground at a volume of 0.5-0.8 PV to emulsify crude oil in situ. The inventors have found that the degree of enhanced oil recovery is higher in this preferred case.

[0035] Preferably, the biological fermentation conditions are anaerobic conditions.

[0036] Preferably, the present application mixes crop straw, domestic waste and animal manure in a weight ratio of 10:1-5:2-6, adjusts the solid concentration in the system to 5-15 wt.%, adjusts the pH value in the system to 7.5-8.5, and seals to ferment under anaerobic conditions.

[0037] Preferably, the biological fermentation conditions satisfy: the fermentation temperature is 20-45℃, and the fermentation time is 30-60 days.

[0038] Preferably, the biological fermentation conditions further satisfy: the C / N in the system is 20-30:1. The calculation formula of C / N in the present application is: C / N = weight of fermentation raw material x carbon content / (weight of fermentation raw material x nitrogen content).

[0039] Preferably, in step (1), the conditions of the fermentation treatment are controlled so that the methane content in the obtained biogas is 60-66 vol.%, the carbon dioxide content is 27-35 vol.%, and the nitrogen content is 1-5 vol.%.

[0040] More preferably, in step (1) of the present application, the conditions of the fermentation treatment are controlled to further comprise that the oxygen and the like gas in the obtained biogas is 4-6 vol.%.

[0041] The present application does not have a particular requirement for the determination method of the gas content in the biogas, and those skilled in the art can test by using the known testing method in the art, for example, gas chromatography can be used.

[0042] Preferably, in step (1), the conditions of the fermentation treatment are controlled to further comprise that the concentration of the methanogen in the obtained biogas is 1-5 / ml, and the concentration of the ethanol in the obtained biogas is 60-68 g / L.

[0043] Similarly, the present application does not have a particular requirement for the determination method of the concentration of the methanogen and the ethanol in the biogas, for example, the fluorescence quantitative PCR amplification method can be used.

[0044] Preferably, the methanogen is selected from the group consisting of methanogenic archaea and / or anaerobic sulfate-reducing bacteria.

[0045] Preferably, the crop straw is selected from at least one of corn straw, rice straw and wheat straw; the household garbage is degradable organic garbage and / or wet garbage; and the animal manure is animal manure from which inorganic matter and plastic products and the like organic matter that cannot be fermented are removed.

[0046] More preferably, the crop straw is corn straw. It should be noted that the method further comprises, before the fermentation treatment, using the means known by those skilled in the art to crush the corn straw, and the particle size after crushing is 1-5 mm.

[0047] The present application separates the product after anaerobic fermentation into gas, liquid and solid three phases to obtain biogas, biogas slurry and biogas residue. The present application does not have a particular requirement for the specific method of the three-phase separation, and those skilled in the art can use the commonly used method known in the art, which will not be described herein again, and those skilled in the art should not be understood as a limitation of the present application.

[0048] Preferably, in step (3), the conditions of the composting treatment satisfy that the temperature is 10-35℃ and the time is 10-20 days.

[0049] According to a particularly preferred specific embodiment, in step (3), the biogas residue is composted at 10-30℃ for 10-20 days and then naturally air-dried to obtain the bio-organic fertilizer.

[0050] Preferably, the method of the present application further comprises that the composting treatment is carried out in an open-air condition.

[0051] Preferably, in step (3), the purity of the carbon dioxide is 99.9% by volume or more. The inventors have found that in this preferred embodiment, the method of the present application can improve the recovery rate while reducing carbon dioxide emissions, and can harmlessly dispose of the biogas while having certain economic benefits.

[0052] Preferably, the conditions for in-situ emulsification of the crude oil satisfy: a temperature of 100-120°C, and a pressure of 25-35 MPa.

[0053] The method of the present application further comprises, when the concentration of methanogenic bacteria in the biogas slurry is too low, performing secondary processing, such as purification, to achieve the required concentration for the conditions of the fermentation treatment.

[0054] The following will be described in conjunction with Figure 1 The process flow of the method of the present application for promoting CO2 sequestration and improving recovery rate using biomass fermentation will be described in detail as follows:

[0055] (1) Introducing biomass fermentation raw materials into a fermentation tank under biological fermentation conditions to perform fermentation treatment, to obtain a fermentation product; the biomass fermentation raw materials are a mixture of crop straw, household garbage and animal manure, with a content ratio of 10:1-5:2-6; the initial conditions of the reaction system of the fermentation treatment satisfy: a solid concentration of 5-15 wt.%, and a pH value in the system of 7.5-8.5;

[0056] (2) Introducing the fermentation product into a separation unit to perform gas-liquid-solid separation, to obtain biogas, biogas slurry and biogas residue;

[0057] (3) Performing composting treatment on the biogas residue to prepare a bio-organic fertilizer as a bio-fertilizer;

[0058] (4) Injecting the biogas slurry into the ground to achieve in-situ emulsification of the formation crude oil, to improve the recovery rate; and the ethanol contained in the biogas slurry can promote carbon dioxide sequestration;

[0059] (5) Introducing the biogas into the ground to achieve oil displacement in the oil layer, after determining the gas component content of the biogas, alone or together with high-purity carbon dioxide.

[0060] The foregoing scheme provided by the present application has the following specific advantages:

[0061] (1) Compared with the existing utilization method of biogas fermentation products, the product of biogas fermentation is separated into gas, liquid and solid in the present application, and then utilized respectively, so that the cost of biogas is reduced, since there is no need to separate and purify the methane in the biogas, and the biogas gas injected into the oil field can improve the recovery rate of crude oil;

[0062] (2) Preferably, the biogas slurry is injected into the stratum, and the microorganisms in the biogas slurry are used to enhance oil recovery; the ethanol in the biogas slurry is used to reduce the miscibility pressure of carbon dioxide and crude oil, so as to promote the dissolution of carbon dioxide in the crude oil and increase the carbon dioxide storage capacity.

[0063] (3) Meanwhile, the biogas residue is subjected to non-pollution solid fertilizer treatment, and the effective viable bacteria number, organic matter content and pH value of the produced organic fertilizer all reach the national standard, so that the organic fertilizer can become a standard biological organic fertilizer.

[0064] The application will be described in detail below by examples. In the following examples, the raw materials used are all ordinary commercial products without special instructions.

[0065] The crop straw in the following examples is derived from fresh corn stalks after crushing: the particle size is 1-5 mm.

[0066] The household garbage in the following examples is derived from kitchen waste; the main content parameters are: the protein content is 14.45 g / 100 g (dry basis), the total carbon content is 359.37 g / kg (dry basis), the total nitrogen content is 47.47 g / kg (wet basis), and the C / N is 12.85.

[0067] The animal manure in the following examples is derived from commercially available pig manure; the main content parameters are: organic matter 15 wt.%, nitrogen 0.5 wt.%, phosphorus 0.45 wt.%, and potassium 0.35 wt.%.

[0068] The property parameters of the crude oil are: the density at 20℃ is 0.8587 g / m 3 , the kinematic viscosity at 50℃ is 19.5 x 10 -6 m 2 / s, and the freezing point is 32.6℃.

[0069] The implementation site of the following examples is: Erzhan Town, Zhaoyuan County, Daqing City, Heilongjiang Province.

[0070] The volume of the fermentation tank is 36 m 3 .

[0071] The solid-liquid mixture formed by the mixture of the crop straw, household garbage and animal manure and water accounts for 62.5 vol.% of the fermentation tank.

[0072] Figure 2 The calculation formula of the "enhanced recovery degree" described in the above is: enhanced recovery degree V mix is the oil production volume obtained by mixing the biogas and carbon dioxide and then conducting oil displacement, cm 3 ; V 衰竭V 3 .

[0073] Figure 4 The calculation formula of the enhanced recovery degree is as follows: enhanced recovery degree V 沼液 is the obtained oil production volume, cm, by using the biogas slurry to emulsify the crude oil in situ 3 ; V 衰竭 is the oil production volume, cm, when the method of the present application is not used, i.e., when the oil is developed by depletion 3 .

[0074] Example 1

[0075] (1) Under the condition of biological fermentation, the biomass fermentation raw material is introduced into a fermentation tank for fermentation treatment to obtain a fermentation product;

[0076] The biomass fermentation raw material is a mixture of crop straw, household garbage and animal manure with a content weight ratio of 10:2.9:4.3; the initial conditions of the reaction system of the fermentation treatment satisfy that the solid concentration in the system is 15 wt.% after the mixture is added with water, the pH value in the system is 7.5; the C / N of the system is 25:1, and the fermentation is carried out under anaerobic conditions at 30±5℃ after sealing, and the fermentation time is 30 days;

[0077] (2) The biogas is collected during the fermentation, and the fermentation product is introduced into a separation unit for gas-liquid-solid separation to obtain biogas, biogas slurry and biogas residue;

[0078] (3) The biogas residue is naturally air-dried after open-air composting to obtain a bio-organic fertilizer, and the composting treatment satisfies that the temperature is 20±10℃, and the time is 15 days;

[0079] (4) The concentration of the methanogen (specific species is methanococcus) in the biogas slurry is determined to be 4×106 / ml by using fluorescence quantitative PCR amplification, and the concentration of ethanol is 62.5 g / L; 0.7 PV of the biogas slurry is injected into a core holder for emulsifying the crude oil in situ to improve the recovery, and the temperature is 110℃ and the pressure is 30 MPa.

[0080] (5) The gas component content in the biogas is determined by using a gas chromatograph, and the gas components are as follows: methane 63 vol.%, carbon dioxide 30 vol.%, nitrogen 2 vol.% and other gases such as oxygen 5 vol.%; the biogas is introduced into the underground together with carbon dioxide with a purity of 99.9 vol.% for oil displacement; the volume ratio of the use amount of carbon dioxide to the biogas is 1:1.

[0081] The result of the enhanced recovery degree after the crude oil in situ emulsification is 14.79%, which is shown inFigure 4 ; Step (5) obtained the enhanced oil recovery degree after oil displacement was 25.1%, see Figure 2 .

[0082] Example 2

[0083] (1) Under the condition of biological fermentation, the biomass fermentation raw material was introduced into the fermentation tank for fermentation treatment, to obtain a fermentation product;

[0084] The biomass fermentation raw material was a mixture of crop straw, household garbage and animal manure with a content weight ratio of 10:5:2; the initial conditions of the reaction system of the fermentation treatment met: the solid concentration was 15 wt.%, the pH value in the system was 8.2; the system C / N was 30:1, and the fermentation was carried out under anaerobic conditions at 25±5℃ after sealing, and the fermentation time was 40 days;

[0085] (2) Biogas was collected during the fermentation, and the fermentation product was introduced into a separation unit for gas-liquid-solid separation, to obtain biogas, biogas slurry and biogas residue;

[0086] (3) The biogas residue was naturally air-dried after open-air composting, to obtain a bio-organic fertilizer, and the composting treatment met: the temperature was 20±10℃, and the time was 15 days;

[0087] (4) The concentration of methanogenic bacteria (specific species: methanogenic archaea) in the biogas slurry was determined to be 4×106 / ml by using fluorescent quantitative PCR amplification, and the concentration of ethanol was 65 g / L; 0.7 PV of the biogas slurry was injected into a core holder for in-situ emulsification of crude oil, at a temperature of 110℃ and a pressure of 30 MPa;

[0088] (5) The gas component content in the biogas was determined by using a gas chromatograph, and the gas components were: methane 61 vol.%, carbon dioxide 29 vol.%, nitrogen 3 vol.%, and other gases such as oxygen 7 vol.%; the biogas was introduced into the underground together with carbon dioxide with a purity of 99.9 vol.% for oil displacement; the volume ratio of the use amount of carbon dioxide to the biogas was 0.8:1.

[0089] Step (4) obtained the enhanced oil recovery degree after in-situ emulsification of crude oil, which was 13.6%; Step (5) obtained the enhanced oil recovery degree after oil displacement, which was 24.8%.

[0090] The same process flow as in Example 1 was used, but a different volume ratio of the use amount of carbon dioxide to the biogas (0-1:1) was used than in Example 1 to repeat the experiment of Example 1, and the experimental data and the obtained experimental results are shown in Figure 2 , that is, the effect diagram of the enhanced oil recovery degree after oil displacement under different volume ratios of the use amount of carbon dioxide to the biogas is shown in Figure 2 .

[0091] In Figure 2 the leftmost end, the volume ratio of carbon dioxide and biogas is 0, which is the condition of no carbon dioxide and pure biogas, while in the rightmost end, the volume ratio of carbon dioxide and biogas is 1, which is the condition of no biogas and all carbon dioxide. Figure 2 It can be known from Figure 2 that when the volume ratio of carbon dioxide and biogas gradually increases, that is, the concentration of carbon dioxide gradually increases, the enhanced oil recovery degree gradually increases.

[0092] In the present application, after the biogas slurry is injected into the underground, the biogas slurry contains ethanol, and the ethanol can reduce the miscibility pressure, so that the carbon dioxide is more easily dissolved in the crude oil; and at the immiscible pressure, the ethanol also has the effect of promoting the dissolution of carbon dioxide.

[0093] Figure 3 The effect of ethanol on the carbon dioxide storage capacity at the immiscible pressure and the miscible pressure is shown in Figure 3 . Whether at the miscible pressure or at the immiscible pressure, the ethanol can significantly increase the carbon dioxide storage capacity, which shows that in the actual oil reservoir, the injection of ethanol does not need to consider whether the pressure of the oil reservoir reaches the miscible pressure of carbon dioxide, so the application range is wider. Figure 3 It can be known from Figure 3 that the biogas slurry provided by the method of the present application can promote the carbon dioxide storage and increase the carbon dioxide storage capacity.

[0094] The same process flow as in Example 1 is applied, but the biogas slurry injection amount is different from that in Example 1, and the experiment of Example 1 is repeated, and the experimental data and the obtained experimental results are shown in Figure 4 , that is, Figure 4 The effect of the method of the present application on the concentration of methanogenic archaea under different biogas slurry injection amounts is shown in

[0095] It can be known from Figure 4 that under the conditions of a temperature of 110℃ and a pressure of 30MPa, as the biogas slurry injection amount increases from 0.1PV to 0.8PV, the enhanced oil recovery degree continuously increases. Therefore, within a certain range, increasing the biogas slurry injection amount can improve the recovery rate of the oil reservoir.

[0096] Comparative Example 1

[0097] The present comparative example is carried out by using a similar process as in Example 1, except that:

[0098] The biomass fermentation raw material in the present comparative example is a mixture of crop straw and household garbage, and the content weight ratio is 10:7.2.

[0099] The rest is the same as in Example 1.

[0100] The result of the enhanced oil recovery degree after the in-situ emulsification of the crude oil in step (4) is 12.25%; the result of the enhanced oil recovery degree after the oil displacement in step (5) is 20.2%.

[0101] Comparative Example 2

[0102] The present comparative example is carried out by using a similar process as that in Example 1, except that:

[0103] The biomass fermentation raw material in the present comparative example is a mixture of crop straw, household garbage and animal manure with a weight ratio of 10:0.5:4.3.

[0104] The rest is the same as in Example 1.

[0105] The result of the enhanced oil recovery degree after the in-situ emulsification of the crude oil in step (4) is 13.34%; the result of the enhanced oil recovery degree after the oil displacement in step (5) is 21.1%.

[0106] Comparative Example 3

[0107] The present comparative example is carried out by using a similar process as that in Example 1, except that:

[0108] In step (4), the biogas slurry is injected into the underground with an injection amount of 1.5 PV;

[0109] The rest is the same as in Example 1.

[0110] In the present comparative example, the result of the enhanced oil recovery degree after the oil displacement in step (5) is 14.84%; the result of the enhanced oil recovery degree after the in-situ emulsification of the crude oil in step (4) is 25.1%, which indicates that the excessive addition of the biogas slurry not only cannot obviously improve the enhanced oil recovery degree, but also increases the cost.

[0111] The method provided by the present application mixes crop straw, household garbage and animal manure to prepare biogas by fermentation, separates the fermentation products into gas, liquid and solid after the fermentation is completed, obtains biogas, biogas slurry and biogas residue, and turns the biogas residue into bio-organic fertilizer after composting treatment. The biogas is injected into the underground to improve the recovery degree, and the biogas slurry and the microorganisms in the biogas slurry are injected into the underground to promote the carbon dioxide sequestration and the in-situ conversion of the crude oil in the stratum, thereby improving the recovery degree of the crude oil.

[0112] The present application realizes the pollution-free treatment of waste such as crop straw, household garbage and animal manure by biogas fermentation, and injects the fermentation products into the stratum to improve the recovery degree of the crude oil by in-situ emulsification of the crude oil, and at the same time, promotes the carbon dioxide sequestration.

[0113] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for enhancing CO2 sequestration and recovery using biomass fermentation, characterized in that, The method comprises: (1) fermenting biomass fermentation raw materials under biological fermentation conditions to obtain fermentation products; the biomass fermentation raw materials are a mixture of crop straw, household garbage and animal manure, with a content weight ratio of 10:1-5:2-6; the initial conditions of the reaction system of the fermentation treatment meet: a solid concentration of 5-15 wt.%, a pH value in the system maintained at 7.5-8.5, and a C / N in the system of 20-30:1; (2) performing gas-liquid-solid separation on the fermentation products to obtain biogas, biogas slurry and biogas residue; the conditions of the fermentation treatment are controlled so that the concentration of methanogenic bacteria in the obtained biogas slurry is 3-5 cells / ml, and the concentration of ethanol in the obtained biogas slurry is 60-68 g / L; (3) performing composting treatment on the biogas residue to prepare bio-organic fertilizer; (4) injecting the biogas slurry into the ground at a volume of 0.1-1 PV to perform in-situ emulsification of crude oil; (5) injecting the biogas into the ground alone or mixed with carbon dioxide to perform oil displacement, and the volume ratio of the carbon dioxide to the biogas is 0-1:

1.

2. The method of claim 1, wherein, The biogas slurry is injected into the ground at a volume of 0.5-0.8 PV to perform in-situ emulsification of crude oil.

3. The method of claim 1 or 2, wherein, The biological fermentation conditions are anaerobic conditions.

4. The method of claim 1 or 2, wherein, The biological fermentation conditions meet: a fermentation temperature of 20-45℃ and a fermentation time of 30-60 days.

5. The method of claim 1 or 2, wherein, In step (1), the conditions of the fermentation treatment are controlled so that the methane content in the obtained biogas is 60-66 vol.%, the carbon dioxide content is 27-35 vol.%, and the nitrogen content is 1-5 vol.%.

6. The method of claim 5, wherein, The methanogenic bacteria are selected from at least one of methanogenic archaea and anaerobic sulfate-reducing bacteria.

7. The method of claim 1 or 2, wherein, The crop straw is selected from at least one of corn straw, rice straw and wheat straw; the household garbage is degradable organic garbage and / or degradable wet garbage; and the animal manure is animal manure from which inorganic substances and plastic products that cannot be fermented are removed.

8. The method of claim 1 or 2, wherein, In step (3), the conditions of the composting treatment meet: a temperature of 10-35℃ and a time of 10-20 days.

9. The method of claim 1 or 2, wherein, In step (5), the purity of the carbon dioxide is above 99.9 vol.%.

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