Microbial coal seam mining method based on proppant

Abstract

The invention discloses a microbial coal seam mining method based on a proppant, and belongs to the technical field of coal seam hydraulic fracturing. Comprising a proppant A and a proppant B. The proppant A comprises a first particle, and the first particle is wrapped with a nutrient medium. The proppant B comprises a second particle, and the second particle is wrapped with a culture medium. The nutrient medium and the culture medium are in a liquid state at the high temperature (85 DEG C or above) and in a solid state at the normal temperature (45 DEG C or below), the proppant can be filled with the nutrient medium and the culture medium at the high temperature, and the nutrient medium and the culture medium cannot seep after being cooled to the normal temperature; after being added into a coal layer, a large amount of heat is released, so that a nutrient medium and a culture medium are changed into liquid to be released, the effect of the nutrient solution on methanogens is improved, and the methanogens can accelerate proliferation under the condition of sufficient nutrient substances; according to the invention, the effect of the methanogens and the nutrient medium can be improved, and the methanogens can be better propagated.

Description

Technical Field

[0001] The invention relates to the technical field of coal seam hydraulic fracturing, and in particular to a method for coal seam mining based on proppant using microorganisms. Background Art

[0002] Coalbed methane, also known as "gas", is mainly composed of methane (CH4), which is mainly adsorbed on the surface of coal matrix particles, and partially free in coal pores or dissolved in coal seam water. It is a semi-raw mineral resource of coal and an unconventional natural gas. The generation of coalbed methane is a relatively slow process, but it can be continuously generated under certain conditions. Compared with traditional fossil fuels, coalbed methane combustion produces fewer pollutants and is a relatively clean energy option. It has abundant reserves, especially in some coal mining areas, and can be used as an important energy resource for power generation, heating and as a chemical raw material. With the increase in global demand for clean energy, the development and utilization of coalbed methane will receive more and more attention.

[0003] At present, there are two main ways to mine coalbed methane in China, namely underground extraction of coalbed methane and ground drilling. As for the ground drilling technology for coalbed methane, the auxiliary production increase measure adopted is mainly fracturing technology. With the continuous progress of drainage and the gradual closure of the fractures in the fracturing holes, the gas production of coalbed methane wells will decrease day by day until it has no economic value for mining. At the same time, during the mining process, fracturing technology requires a large amount of water resources, which will cause a waste of water resources. Summary of the invention

[0004] The object of the present invention is to provide a method for coal seam mining based on proppant microorganisms, comprising the following steps:

[0005] Directional drilling is set up from the surface to enter the coal seam;

[0006] After the directional drill enters the coal seam, a fracturing pipe is set by drilling holes in the horizontal direction;

[0007] The surface pump station is turned on to hydraulically fracture the coal seam with fracturing fluid and proppant to form fractures on the coal seam;

[0008] Open the ground gas extraction device and extract coalbed methane from the coal seam through the gas extraction pipeline in the directional drilling.

[0009] Among them, a methane concentration detection device is installed in the fracturing pipeline, and the methane concentration detection device is used to detect the methane content in the coal seam.

[0010] Hydraulic fracturing technology is used to form fractures in coal seams, and the proppant after flowback can improve the fracture conductivity.

[0011] The proppant of the present invention comprises proppant A and proppant B. Proppant A comprises first particles coated with nutrient medium; proppant B comprises second particles coated with culture medium, and the culture medium comprises methanogen enrichment solution and carrier culture medium.

[0012] Wherein, the first particles and the second particles are porous particles.

[0013] The internal pore structure of the proppant A is filled with a nutrient matrix storing nutrients.

[0014] The internal pore structure of the proppant B is filled with a culture medium serving as a carrier of methanogens. Highly efficient and heat-resistant methanogens are obtained by domesticating microorganisms and injected into the carrier culture medium to obtain the culture medium.

[0015] Among them, the role of the culture medium is to configure the carrier culture medium for the domesticated methanogens so that the methanogens can be filled into the proppant B. Proppant A and proppant B are filled with different substances, the nutrient base is suitable for the reproduction and growth of methanogens, and the culture medium is used to carry methanogens. In actual use, during hydraulic fracturing, proppant A and proppant B are mixed and sent to the coal seam. The nutrient base on proppant A can make methanogens have sufficient nutrients in the coal seam and proliferate rapidly, effectively realizing the efficient exploitation of coalbed methane using microorganisms.

[0016] Furthermore, a fiber cross-linked film is provided on the nutrient medium of the first particles; and a fiber cross-linked film is provided on the culture medium of the second particles.

[0017] The fiber cross-linked film coated on the surface of the second particle can prevent some exogenous bacteria from infecting the methanogenic bacteria inside the second particle. At the same time, the fiber cross-linked film coated on the surface of the first particle and the second particle can enhance the hydrophilicity and support strength of the pore proppant.

[0018] On the other hand, the nutrient medium includes the following components: agar, peptone, yeast extract, sodium formate, sodium acetate, methanol, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, magnesium chloride, ammonium chloride, cysteine ​​hydrochloride, and SL-10 trace metal element solution.

[0019] The culture medium comprises a methanogen enrichment solution and a carrier culture medium, and the carrier culture medium comprises the following components: agar, tryptone, yeast extract, sodium chloride, sodium hydroxide and antibiotics.

[0020] The above-mentioned nutrient medium and culture medium are liquid at high temperature (above 85°C) and solid at room temperature (below 45°C). Therefore, the nutrient medium and culture medium can be made liquid by high-temperature heating, and the first particles and the second particles can be filled into the gaps inside the particles by immersion and stirring. After cooling to room temperature, the nutrient medium and culture medium will not seep out, and the first particles and the second particles can better bring the nutrient medium and culture medium into the coal seam.

[0021] In coal seams, methanogens release a large amount of heat in the process of decomposing coal. The temperature generated in narrow spaces such as cracks is sufficient to cause the nutrient medium and culture medium inside proppant A and proppant B to seep out in liquid form, allowing methanogens to contact the nutrient medium and obtain nutrients. Methanogens will proliferate faster under conditions of sufficient nutrients, thereby improving gas discharge efficiency.

[0022] Specifically, a method for coal seam mining based on proppant microorganisms comprises the following steps:

[0023] The preparation of proppant A comprises the following steps:

[0024] Heat the nutrient medium to above 85°C using a heating furnace to make the nutrient medium in a liquid state;

[0025] Immerse the first particle in the liquid nutrient medium, stir for 2 hours, and then turn off the heating furnace;

[0026] When the heating furnace is cooled to 60°C, filter out the nutrient medium in the heating furnace;

[0027] When the heating furnace is cooled to 20°C-25°C, the nutrient base on the surface of the first particles is removed;

[0028] The preparation of proppant B comprises the following steps:

[0029] The carrier culture medium is heated to above 85° C. by a heating furnace to make the carrier culture medium in a liquid state, and a methanogen enrichment solution is added to obtain a culture medium;

[0030] The second particle was immersed in the culture medium and stirred for 3 h before the heating furnace was turned off;

[0031] When the heating furnace is cooled to 60°C, filter out the culture medium in the heating furnace;

[0032] When the heating furnace is cooled to 20°C-25°C, the culture medium on the surface of the second particle is removed;

[0033] The proppant A and the proppant B are immersed in a fiber cross-linking solution, and after drying, the proppant A and the proppant B provided with a fiber cross-linking film are obtained.

[0034] In another aspect, the present invention provides a fiber cross-linking solution, the fiber cross-linking solution comprising the following steps:

[0035] The soaked soybeans are dissociated into a fiber mixture using a wall breaking machine;

[0036] Mix the fiber mixture and potassium periodate in a beaker and adjust the pH to 3.0-3.5 with acetic acid;

[0037] After heating in a water bath for 3 hours, the mixture was separated by filtration and washed with distilled water until neutral to obtain dialdehyde cellulose;

[0038] The dialdehyde cellulose was prepared into a solution, and glycerol was added, and the solution was subjected to ultrasonic treatment for 10 minutes after oscillation mixing to obtain a fiber crosslinking solution, wherein the weight ratio of the dialdehyde cellulose to the glycerol was 5:1.

[0039] Cellulose can be used as a good biomaterial due to its excellent renewability and degradability. However, membrane materials prepared with cellulose as raw material have performance defects such as weak mechanical strength and easy contamination by bacteria. Dialdehyde cellulose is an oxidized cellulose derivative with the advantages of biodegradability and good antibacterial properties.

[0040] Compared with the existing cellulose films, the cellulose film of the present invention has the advantages of good antibacterial property, stable membrane pore structure, good hydrophilicity and better compressive strength.

[0041] In order to ensure that the proppant containing the nutrient base delivered by one hydraulic fracturing can fully meet the nutrients required for the growth and reproduction of methanogens, there is no need to set up steps or devices for delivering nutrients to the coal seam, and the ratio of proppant A to proppant B is 2:1. Under this ratio, the nutrient base in one grain of proppant A can meet the nutrients required for the growth and reproduction of methanogens contained in one grain of proppant B for one to one and a half years.

[0042] At the same time, the ratio of the average particle size of the first particles to the average particle size of the second particles is 1:2-4. Preferably, the average particle size of the first particles is 0.15 mm, and the average particle size of the second particles is 0.5 mm. Under the microscope, it is shown that multiple particles of proppant A are attached to the outer surface of proppant B. The nutrient base flowing out of proppant A can better act on the methanogens of proppant B, providing a nutrient base for methanogens in an all-round way, ensuring better reproduction of methanogens, and further improving the efficiency of gas extraction.

[0043] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0044] The present invention discloses a method for mining coal seams by using microorganisms based on proppants. The nutrient medium and culture medium of the present invention are in liquid state at high temperature (above 85° C.) and in solid state at normal temperature (below 45° C.), so they can be filled into the proppant by high temperature heating, immersion and stirring, and the nutrient medium and culture medium will not seep out after being cooled to normal temperature. After being added into the coal seam, a large amount of heat will be released in the process of decomposing the coal, so that the nutrient medium and culture medium will be released into liquid state, thereby improving the effect of the nutrient solution on methanogens, and accelerating the proliferation of methanogens under the condition of sufficient nutrients.

[0045] At the same time, the outer surface of the proppant B of the present invention is attached with multiple particles of proppant A, and the nutrient medium flowing out of the proppant A can better act on the methanogens of the proppant B, further improving the interaction between the methanogens and the nutrient medium, and ensuring better reproduction of the methanogens. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0047] Figure 1 Schematic diagram of underground operation structure.

[0048] Among them, 1-directional drilling, 2-exhaust pipeline, 3-sealing device, 4-methane concentration detection device, 5-fracture gap, 6-fracture pipeline, 7-rock layer, 8-coal seam. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and drawings, but the present invention is not limited to the scope of the embodiments. The experimental methods in the following embodiments without specifying specific conditions are selected according to conventional methods and conditions, or according to the product instructions.

[0050] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0051] Example 1

[0052] like Figure 1 As shown, a coal seam 8 is located between two rock layers 7. A method for mining a coal seam based on proppant microorganisms comprises the following steps:

[0053] Setting a directional drilling well 1 from the ground to enter the coal seam 8;

[0054] After the directional drilling 1 enters the coal seam 8, a fracturing pipe 6 is set by drilling in the horizontal direction;

[0055] The surface pump station is turned on to hydraulically fracture the coal seam 8 with the fracturing fluid and the proppant, thereby forming a fracture gap 5 on the coal seam 8;

[0056] The ground gas extraction device is turned on to extract coalbed methane from the coal seam 8 through the gas extraction pipeline 2 in the directional drilling well 1.

[0057] A sealing device 3 is provided between the exhaust pipe 2 and the fracturing pipe 6. A methane concentration detection device 4 is provided in the fracturing pipe 6. The methane concentration detection device 4 is used to constantly monitor the methane content in the coal seam 8 and observe the coal seam gas production.

[0058] A separate exhaust pipe 2 is arranged to connect the surface exhaust device and the fracturing pipe 6, and a sealing device 3 is installed to ensure efficient extraction of coalbed methane.

[0059] The present invention can complete the production and extraction of coalbed methane by drilling a directional well and implementing two steps of hydraulic fracturing and coalbed methane extraction, thereby effectively reducing the drilling cost.

[0060] Example 2

[0061] Proppant A and proppant B, proppant A includes first particles, and the first particles are coated with a nutrient medium; proppant B includes second particles, and the second particles are coated with a culture medium.

[0062] The first particles and the second particles can be selected from quartz sand, glass beads, ceramic proppants, etc. Preferably, the first particles and the second particles are porous ceramics, and the internal interconnected porosity of the porous ceramics is generally in the range of about 5% to about 75%, such as about 5% to about 15%, about 15% to about 30%, about 25% to about 45%, about 35% to about 55%, or about 35% to about 70%.

[0063] Considering that the first and second particles need to be filled with nutrient medium and culture medium, the first and second particles need to have a larger internal porosity, so the present invention uses spherical or approximately spherical porous ceramics with an internal porosity of about 35%-70%.

[0064] The nutrient base includes the following components in parts by weight: 18-25 parts of agar, 1-5 parts of peptone, 2-8 parts of yeast extract, 2-8 parts of sodium formate, 3-9 parts of sodium acetate, 2-6 parts of methanol, 0.2-1 parts of dipotassium hydrogen phosphate, 0.1-0.5 parts of potassium dihydrogen phosphate, 0.05-0.6 parts of magnesium chloride, 0.5-2 parts of ammonium chloride, 0.2-1 parts of cysteine ​​hydrochloride and 0.5-3 parts of SL-10 trace metal element solution.

[0065] The culture medium includes a methanogen enrichment solution and a carrier culture medium, wherein the carrier culture medium includes the following components: 18-25 parts of agar, 6-15 parts of tryptone, 3-8 parts of yeast extract, 8-15 parts of sodium chloride, and 0.01-0.1 parts of antibiotics. Sodium hydroxide is used to adjust the pH to 7.4.

[0066] The preparation of proppant A comprises the following steps:

[0067] Heat the nutrient medium to above 85°C using a heating furnace to make the nutrient medium in a liquid state;

[0068] Immerse the first particle in the liquid nutrient medium, stir for 2 hours, and then turn off the heating furnace;

[0069] When the heating furnace is cooled to 60°C, filter out the nutrient medium in the heating furnace;

[0070] When the heating furnace is cooled to 20°C-25°C, the nutrient base on the surface of the first particles is removed;

[0071] The preparation of proppant B comprises the following steps:

[0072] The carrier culture medium is heated to above 85° C. by a heating furnace to make the carrier culture medium in a liquid state, and a methanogen enrichment solution is added to obtain a culture medium;

[0073] The second particle was immersed in the culture medium and stirred for 3 h before the heating furnace was turned off;

[0074] When the heating furnace is cooled to 60°C, filter out the culture medium in the heating furnace;

[0075] When the heating furnace is cooled to 20°C-25°C, the culture medium on the surface of the second particle is removed;

[0076] The proppant A and the proppant B are immersed in a fiber cross-linking solution, and after drying, the proppant A and the proppant B provided with a fiber cross-linking film are obtained.

[0077] In some embodiments, the ratio of the average particle size of the first particles to the average particle size of the second particles is 1:2-4. Preferably, the average particle size of the first particles is 0.15 mm, and the average particle size of the second particles is 0.5 mm.

[0078] In some embodiments, the ratio of proppant A to proppant B is 2:1.

[0079] Example 3

[0080] On the basis of the above embodiment, a fiber cross-linked film is provided on the nutrient medium of the first particles; and a fiber cross-linked film is provided on the culture medium of the second particles.

[0081] The fiber cross-linking solution comprises the following steps:

[0082] The soaked soybeans are dissociated into a fiber mixture using a wall breaking machine;

[0083] Mix the fiber mixture and potassium periodate in a beaker and adjust the pH to 3.0-3.5 with acetic acid;

[0084] After heating in a water bath for 3 hours, the mixture was separated by filtration and washed with distilled water until neutral to obtain dialdehyde cellulose;

[0085] The dialdehyde cellulose was prepared into a solution, and glycerol was added, and the solution was subjected to ultrasonic treatment for 10 minutes after oscillation mixing to obtain a fiber crosslinking solution. The weight ratio of the dialdehyde cellulose to the glycerol was 5:1.

[0086] Among them, periodate is used to selectively oxidize and cleave the pyranoside ring between C-2 and C-3 of cellulose, oxidizing the hydroxyl groups on C-2 and C-3 to aldehyde groups to produce dialdehyde cellulose.

[0087] Example 4

[0088] On the basis of the above embodiments, LB medium was used in the laboratory under an anaerobic environment to screen out efficient and heat-resistant methanogens, and the bacteria were enriched, separated, purified and cultured to screen out efficient and heat-resistant methanogens that can adapt to the coal seam environment; a nutrient medium was prepared for the domesticated methanogens, and the nutrient medium included the following components in parts by weight: 20 parts of agar, 3 parts of peptone, 4 parts of yeast extract, 5 parts of sodium formate, 5 parts of sodium acetate, 3.5 parts of methanol, 0.4 parts of dipotassium hydrogen phosphate, 0.2 parts of potassium dihydrogen phosphate, 0.1 parts of magnesium chloride, 1 part of ammonium chloride, 0.5 parts of cysteine ​​hydrochloride, and 1 part of SL-10 trace metal element solution.

[0089] The carrier medium is prepared for the domesticated methanogens, and the carrier medium includes the following components: 20 parts of agar, 10 parts of tryptone, 5 parts of yeast extract, 10 parts of sodium chloride, and 0.01 parts of antibiotics. Sodium hydroxide is used to adjust the pH to 7.4.

[0090] 20 parts of soybeans were added to 1000 parts of distilled water and soaked for 1 hour, then completely broken up with a wall breaking machine to dissociate into a 20g / L fiber mixture;

[0091] Mix the fiber mixture and 30 parts of potassium periodate in a beaker and adjust the pH to 3.0-3.5 with acetic acid;

[0092] After heating in a water bath for 3 hours, the mixture was separated by filtration and washed with distilled water until neutral to obtain dialdehyde cellulose;

[0093] The dialdehyde cellulose was prepared into a solution with a mass fraction of 5%, and glycerol was added, and the solution was subjected to ultrasonic treatment for 10 minutes after oscillation mixing to obtain a fiber crosslinking solution. The weight ratio of the dialdehyde cellulose to the glycerol was 5:1.

[0094] The proppant A and the proppant B were immersed in the fiber cross-linking solution for 1 hour, taken out and placed in a 40° C. oven for drying for 2 hours, and after drying, the proppant A and the proppant B provided with the fiber cross-linking film were obtained.

[0095] Example 5

[0096] On the basis of Example 4, a reaction device simulating the coal seam environment was constructed in the laboratory to simulate the pressure, temperature, gas composition and other conditions of the coal seam.

[0097] Proppant A and proppant B were injected into the reaction device, and the amount of methane during the reaction was monitored to obtain Table 1;

[0098] Table 1

[0099]

[0100]

[0101] The methane production of the existing proppant in this embodiment is 81.33±30.64μmol / g. It can be seen from Table 1 that under the action of the proppant A and proppant B of the present invention, the amount of methane is significantly increased. At the same time, when the average particle size ratio of the first particle to the average particle size of the second particle is in the range of 1:2-4, the methane production is greater than 120μmol / g, and when the number ratio of proppant A to proppant B is 2:1 and the average particle size ratio of the first particle to the average particle size of the second particle is in the range of 1:2-4, the maximum methane production reaches 161.89±20.92μmol / g.

[0102] The compressive strength tests were carried out on the first particles wrapped with nutrient base, the second particles wrapped with culture medium, the proppant A provided with a fiber cross-linked film, and the proppant B provided with a fiber cross-linked film. The compressive strength of the proppant A provided with the fiber cross-linked film was 7.3 times that of the first particles wrapped with the nutrient base, and the compressive strength of the proppant B provided with the fiber cross-linked film was 7.8 times that of the second particles wrapped with the culture medium.

[0103] In summary, the proppant A and proppant B of the present invention have good compressive strength and good antibacterial properties, which can prevent some exogenous bacteria from infecting the methanogenic bacteria in the second particle. And when the number ratio of proppant A and proppant B of the present invention is 2:1, and the average particle size ratio of the first particle to the average particle size of the second particle is within the range of 1:2-4, the methane yield is the highest. The proppant carried by the primary hydraulic fracturing of the present invention can meet the nutrition required for the proliferation of efficient heat-resistant methanogenic bacteria.

[0104] The present invention uses a proppant A containing a nutrient base and a proppant B containing a methanogen culture medium in a ratio of 2:1, and the mixed fracturing fluid enters the coal reservoir fissure. The proppant remaining after the backflow can increase the permeability of the coal seam on the one hand, and on the other hand, the nutrient base inside the proppant A can provide nutrition for the methanogens carried by the proppant B to proliferate, and generate a continuous supply of biogenic coalbed methane by decomposing coal. The present invention can be used for general coal seam mining or mining of residual coal in goaf areas, and has good environmental benefits.

[0105] The above descriptions are only some specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for coal seam mining based on proppant microorganisms, characterized in that: The following steps are involved: Setting a directional drilling well (1) from the surface and entering the coal seam (8); After the directional drilling (1) enters the coal seam (8), a fracturing pipe (6) is set by drilling a hole in the horizontal direction; Starting a surface pump station to hydraulically fracture the coal seam (8) with a fracturing fluid and a proppant, thereby forming a fracture gap (5) on the coal seam (8); The ground gas extraction device is turned on to extract coal seam gas from the coal seam (8) through the gas extraction pipeline (2) in the directional drilling well (1).

2. A method for coal seam mining based on proppant microorganisms according to claim 1, characterized in that: The proppant includes proppant A and proppant B. Proppant A includes first particles, on which nutrient medium is coated; proppant B includes second particles, on which culture medium is coated.

3. The method for coal seam mining based on proppant microorganisms according to claim 1, characterized in that: A methane concentration detection device (4) is arranged in the fracturing pipeline (6), and the methane concentration detection device (4) is used to detect the methane content in the coal seam (8).

4. A method for coal seam mining based on proppant microorganisms according to claim 2, characterized in that: A fiber cross-linked film is arranged on the nutrient medium of the first particles; and a fiber cross-linked film is arranged on the culture medium of the second particles.

5. The method for coal seam mining based on proppant microorganisms according to claim 2, characterized in that: The ratio of the average particle size of the first particles to the average particle size of the second particles is 1:2-4.

6. A method for coal seam mining based on proppant microorganisms according to claim 5, characterized in that: The average particle size of the first particles is 0.15 mm, and the average particle size of the second particles is 0.5 mm.

7. The method for coal seam mining based on proppant microorganisms according to claim 5, characterized in that: The quantitative ratio of proppant A to proppant B is 2:

1.

8. The method for coal seam mining based on proppant microorganisms according to claim 5, characterized in that: The nutrient medium includes the following components: agar, peptone, yeast extract, sodium formate, sodium acetate, methanol, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, magnesium chloride, ammonium chloride, cysteine ​​hydrochloride, and SL-10 trace metal element solution.

9. The method for coal seam mining based on proppant microorganisms according to claim 5, characterized in that: The culture medium comprises a methanogen enrichment solution and a carrier culture medium, and the carrier culture medium comprises the following components: agar, tryptone, yeast extract, sodium chloride, sodium hydroxide and antibiotics.

10. The method for coal seam mining based on proppant microorganisms according to claim 4, characterized in that: The fiber cross-linked film comprises dialdehyde cellulose and glycerol, and the weight ratio of the dialdehyde cellulose to the glycerol is 5:1.

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