A method suitable for in situ hydrogen production in an oil reservoir

Abstract

The application discloses a method suitable for hydrogen production in situ in an oil reservoir underground, and belongs to the technical field of oil and gas development. The method comprises the following steps: arranging three horizontal wells, i.e., upper, middle and lower horizontal wells, and a temperature detection well in the same reservoir, the temperature detection well is used for detecting the temperature of the middle horizontal well, and a hydrogen gas filter membrane is arranged at the upper horizontal well; a heating device is arranged at the middle horizontal well, a close cutting volume fracturing is carried out around the well, and a reaction zone is formed by filling a catalyst and a heat-conducting agent; in-situ ignition is carried out at the lower horizontal well, and an oxygen-containing gas is injected, so that the oxygen-containing gas is incompletely combusted to generate CO and CO2 and form a gasification zone; a heating device is used for heating to above 450 DEG C, when the gas in the gasification zone enters the reaction zone, water vapor is injected to carry out high-efficiency hydrogen production; and the upper horizontal well is opened, and the hydrogen gas filter membrane is used for extracting hydrogen gas. The hydrogen production block is separated, the underground hydrogen production efficiency is greatly improved, the energy utilization rate is improved, and therefore the method has good application value.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and specifically to a method for in-situ hydrogen production in underground reservoirs. Background Technology

[0002] Hydrogen energy, as a clean energy source, can be used in various ways, such as for heating and power generation. Hydrogen is present in very low concentrations in the air, and the most common method for producing hydrogen is water electrolysis, which converts electrical energy into chemical energy. However, water electrolysis is energy-intensive and costly, thus limiting its production. To address this issue, researchers are currently exploring new methods for hydrogen production.

[0003] Underground hydrogen production using oil, gas, and coal is a relatively new method. It typically involves injecting oxygen-containing gas into the reservoir, causing some of the oil, gas, or coal in the reservoir to burn. This provides the temperature required for hydrogen production and the carbon dioxide and other gases needed in the process. High-temperature steam is also injected, and the hydrogen is then produced through a reaction under high-temperature conditions. Other methods also incorporate external heating devices to reduce the loss of oil, gas, or coal in the reservoir.

[0004] However, current underground hydrogen production methods all utilize one or two wells. When using a single well for huff and puff production, this well serves as both a combustion heating well and a gas production well. Its production zone is limited to the combustion front, resulting in low hydrogen blending efficiency and the need to prevent gas channeling during combustion. Furthermore, the process is lengthy with low thermal efficiency, requiring reheating for subsequent production runs, leading to significant heat loss. When using two wells, one typically generates heat through combustion, while the other injects steam. Similarly, in this process, the production zone is limited to the combustion front, resulting in low fuel utilization and hindering the expected profitability of current underground hydrogen production projects. Summary of the Invention

[0005] To address at least one of the aforementioned problems, this invention provides a method for in-situ hydrogen production in underground reservoirs.

[0006] The technical solution of this invention is: a method for in-situ hydrogen production in underground reservoirs, comprising the following steps:

[0007] Three horizontal wells (upper, middle, and lower) and one temperature monitoring well are set up in the same reservoir. The temperature monitoring well is used to detect the temperature of the middle horizontal well. A hydrogen filter membrane is installed at the upper horizontal well and a heating device is installed at the middle horizontal well.

[0008] In the lower horizontal well, ignition is performed at the source and oxygen-containing gas is injected to allow for incomplete combustion, producing CO and CO2 and forming a gasification zone.

[0009] The temperature is raised to above 450°C using a heating device. When the gas in the gasification zone enters the middle horizontal well, water vapor is injected to produce hydrogen, thus forming a reaction zone.

[0010] Open the upper horizontal well and extract hydrogen using a hydrogen filter membrane.

[0011] One embodiment of the present invention is that the oxygen concentration in the oxygen-containing gas is not less than 10%.

[0012] One embodiment of the present invention involves performing close-cut volumetric fracturing on the middle horizontal well before production, with the fracturing proppant including rock cuttings and thermally conductive metal particles; and performing single-fracture fracturing on the upper horizontal well.

[0013] Furthermore, the mass ratio of the thermally conductive metal particles to the rock fragments is 1:1 to 10.

[0014] Furthermore, the temperature detection well is used to detect the temperature in the fracture network.

[0015] Furthermore, a heating device is installed between the casing and tubing in the production section of the central horizontal well for heating; at the same time, the root end of the central horizontal well is sealed.

[0016] One embodiment of the present invention is that the above-mentioned production process continues until the extracted hydrogen is no longer economical.

[0017] One embodiment of the present invention is that in the three horizontal wells, at least a portion of the horizontal section is in the same vertical direction.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] The proposed three-well hydrogen production method utilizes a modular underground design. The gasification zone primarily focuses on the gasification of liquid hydrocarbons, burning less liquid hydrocarbons to produce more CO and gaseous hydrocarbons, forming the feedstock for hydrogen production. The reaction zone, powered by electric heating and a heat conduction system, creates a high-temperature slit-mesh space where gaseous hydrocarbons, CO, and high-temperature steam react under a catalyst. This large reaction space ensures high efficiency in catalyst and thermal energy utilization. The separation and extraction zone employs a single slit to prevent the complex slit network from easily connecting to the reaction zone, which would allow gas from the reaction zone to directly transfer to the separation and extraction zone. This gives the gas in the reaction zone more time to react before it is filtered by a hydrogen filter membrane within the single slit and extracted. This invention features clearly defined functional areas, significantly improving underground hydrogen production efficiency, increasing energy and catalyst utilization, and creating an underground hydrogen production development model akin to an underground hydrogen factory. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the development well group according to an embodiment of the present invention;

[0021] Figure 2 This is a structural diagram of the central horizontal well and the fractured mesh;

[0022] Figure 3 This is a schematic diagram of the upper horizontal well structure. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0024] Unless otherwise specified, the operating methods used in the following embodiments are all common methods in the art.

[0025] A method for in-situ hydrogen production in underground reservoirs includes the following steps:

[0026] Three horizontal wells (upper, middle, and lower) and one temperature monitoring well are set up in the same reservoir. The temperature monitoring well is used to detect the temperature of the middle horizontal well. A hydrogen filter membrane is installed at the upper horizontal well and a heating device is installed at the middle horizontal well.

[0027] For details, see Figures 1-3 The reason for setting up three horizontal wells (upper, middle, and lower) in this step is to separate the hydrogen production gasification zone, reaction zone, and hydrogen extraction zone.

[0028] In conventional single-well huff and puff hydrogen production, since gasification, reaction, and separation all occur around a single well, there are problems with low hydrogen production efficiency and low heat utilization. For dual-well hydrogen production, one well is usually used for combustion (dry combustion or wet combustion), and the other well is used for hydrogen separation and production. However, the problem with this operation is that there is no fixed reaction zone. The hydrogen production reaction occurs at the fire-driven front, the reaction area is small, and the catalyst cannot adapt to changes in the reaction zone, resulting in a large loss of catalyst. This method requires complete combustion of hydrocarbons to produce hydrogen, which reduces the material basis for hydrogen production reaction. At the same time, when there is excess oxygen, it will also react with the produced hydrogen, reducing the hydrogen production.

[0029] The proposed three-well hydrogen production method utilizes a modular underground design. The gasification zone primarily focuses on the gasification of liquid hydrocarbons, burning less liquid hydrocarbons to produce more CO and gaseous hydrocarbons, forming the feedstock for hydrogen production. The reaction zone, powered by electric heating and a heat conduction system, creates a high-temperature slit-mesh space where gaseous hydrocarbons, CO, and high-temperature steam react under a catalyst. This large reaction space ensures high efficiency in catalyst and thermal energy utilization. The separation and extraction zone employs a single slit to prevent the complex slit network from easily connecting to the reaction zone, which would allow gas from the reaction zone to directly transfer to the separation and extraction zone. This gives the gas in the reaction zone more time to react before it is filtered by a hydrogen filter membrane within the single slit and extracted. This invention features clearly defined functional areas, significantly improving underground hydrogen production efficiency, increasing energy and catalyst utilization, and creating an underground hydrogen production development model akin to an underground hydrogen factory.

[0030] For temperature monitoring wells, which are used to detect the temperature around the central horizontal well, i.e. the hydrogen production reaction site, their setup is a conventional technical method in this field, so it will not be described in detail here.

[0031] Installing a hydrogen filter membrane inside the well is a standard practice in this field, and commercially available hydrogen filter membranes are readily available; therefore, it will not be elaborated upon here.

[0032] To facilitate the collection of produced hydrogen, single-fracture fracturing is performed in the upper horizontal well. Although other fracturing methods can be used, single-fracture fracturing avoids direct communication between the single fracture and the fracture network in the reaction zone. This allows for more reaction time and slows down the gas flow rate as it is transported from the reaction zone to the upper horizontal well. Furthermore, single-fracture fracturing has better conductivity than the matrix, enabling rapid hydrogen extraction.

[0033] Regarding the orientation of the three horizontal wells, at least a portion of the horizontal sections of the three wells must be in the same vertical direction. For example, in the upper, middle, and lower horizontal wells, there are sections whose vertical projections overlap. These overlapping horizontal sections can serve as the gasification zone, reaction zone, and hydrogen extraction zone.

[0034] In the lower horizontal well, ignition is performed at the source and oxygen-containing gas is injected to allow for incomplete combustion, producing CO and CO2 and forming a gasification zone.

[0035] In this invention, the first step is to incompletely burn the thin oil in the reservoir to generate CO and CO2. As those skilled in the art know, oxygen-containing gas needs to be injected to make the thin oil burn. In this invention, the oxygen content of the injected oxygen-containing gas is greater than 10%. The higher the oxygen content of the oxygen-containing gas, the more oxygen-containing gas is required, but the faster the reaction rate is. From an economic cost perspective, air can be used as the oxygen-containing gas.

[0036] The temperature is raised to above 450°C using a heating device. When the gas in the gasification zone enters the middle horizontal well, water vapor is injected to produce hydrogen, thus forming a reaction zone.

[0037] In this step, the reaction zone is the main site for hydrogen production. The main reaction occurring during this process is: CO + H₂O → H₂ 2 +CO2;CH4+H2O→3H2+CO;Gaseous hydrocarbon C n H m +nH₂O→{n+1 / 2m}H₂+nCO, these two hydrogen production reactions require lower temperatures. The reaction of CO₂ with gaseous hydrocarbons requires a higher temperature, 900-1275℃, as shown in the following reaction equation C. n H m +nCO2→1 / 2mH2+2nCO Therefore, in this step, the two reactions mentioned above mainly occur.

[0038] Whether the gas in the gasification zone has entered the middle horizontal well can be determined by numerical simulation, which is common knowledge in this field, so its specific operation will not be described in detail here.

[0039] Meanwhile, because incomplete combustion is required in the gasification zone, the temperature during combustion is relatively low. The flue gas produced after combustion loses some heat during its transport in the reaction zone, making it difficult to achieve the required temperature for hydrogen production. Therefore, this invention uses a heating device in the reaction zone to raise the temperature. These heating devices can be common in the art, such as cable heating. Specifically, to better utilize the heat generated by the heating device, it is installed between the casing and tubing in the production section of the central horizontal well.

[0040] To ensure the periphery of the central horizontal well becomes a better reaction zone, close-cut volumetric fracturing can be performed on the central horizontal well before hydrogen production. This development method is a conventional technique in this field, and its specific operation will not be elaborated upon. As mentioned above, the temperature monitoring well is used to detect the temperature around the central horizontal well, i.e., the hydrogen production reaction site. Therefore, in this step, the temperature monitoring well is used to detect the temperature within the fracturing network.

[0041] Specifically, during fracturing, the proppant used consists of rock cuttings and thermally conductive metal particles. The rock cuttings have a catalytic effect on the hydrogen production reaction, while the thermally conductive metal particles effectively transfer the heat generated by the heating device, resulting in a faster temperature rise around the wellbore in the middle horizontal section. The thermally conductive metal particles can be made of materials such as copper, aluminum, or iron, which have high thermal conductivity. To balance the catalytic activity of the rock cuttings and the thermal conductivity of the thermally conductive metal particles, the mass ratio of thermally conductive metal particles to rock cuttings is limited to 1:1 to 10 in this step. Under this condition, the proppant serves both catalytic and thermal conductivity purposes.

[0042] To prevent injected water vapor from returning to the wellhead, a packer is installed at the root end of the horizontal well in the middle section for sealing. This packer needs to have a certain temperature resistance and is a conventional device in this field with mature commercial products available.

[0043] The purpose of injecting water vapor is to react carbon dioxide, carbon monoxide, and water vapor to produce hydrogen. Therefore, the amount of water vapor injected can be selected according to the actual situation. For example, the amount of gas entering the vicinity of the central horizontal well can be calculated based on the numerical simulation results. Then, appropriate water vapor can be injected according to the amount, and the amount of water vapor added can be adjusted appropriately according to the hydrogen production results.

[0044] Open the upper horizontal well and extract hydrogen using a hydrogen filter membrane.

[0045] When hydrogen is extracted using a hydrogen filter membrane, the pressure around the upper horizontal well decreases relatively due to the extraction of hydrogen. This causes gases produced by combustion in the lower horizontal well and hydrogen production in the middle horizontal well to rise continuously. Simultaneously, after hydrogen extraction, residual gases such as carbon dioxide, carbon monoxide, and light hydrocarbons remain in the reservoir. When these gases accumulate excessively, the pressure around the upper horizontal well increases. However, because the pressure in the middle and lower sections is relatively higher, these accumulated gases will enter the area around the upper horizontal well. Under the influence of gravity, they will displace the light oil around the upper horizontal well to the bottom of the reservoir.

[0046] In this cycle, the oil and gas in the reservoir are mostly converted into hydrogen until the economic limit is reached. The remaining gases that cannot be converted into hydrogen, such as carbon dioxide and carbon monoxide, are buried in the reservoir to reduce carbon emissions.

[0047] To enable those skilled in the art to further understand the technology of the present invention, specific examples are provided below.

[0048] like Figure 1As shown in this embodiment, for the light oil reservoir 4, three horizontal wells are deployed sequentially from top to bottom. Single-fracture fracturing is performed in the upper horizontal well 3, and a corresponding hydrogen filter membrane 7 is placed between the casing and tubing in the perforated section. Through the hydrogen filter membrane 7, hydrogen in the product can be selectively extracted.

[0049] The middle horizontal well 2 is subjected to close-cut volume fracturing. During the fracturing process, rock cuttings 8 and iron-based thermally conductive metal particles 9 are used as proppant to support the fracture network 5 formed by fracturing. At the same time, a resistance is placed in the production section as a heating device 10, and a corresponding packer is placed at the root of the middle horizontal well 2 for sealing.

[0050] At the same time, a directional well is set up to extend to the fracture mesh 5 as a temperature detection well 11 to monitor the temperature inside the fracture mesh 5.

[0051] After the above operations are completed, the lower horizontal well 1 is opened, and oxygen-containing gas is injected and ignited simultaneously, so that the liquid hydrocarbons in the reservoir 4 near the lower horizontal well are incompletely burned and vaporized, generating carbon monoxide and carbon dioxide. Then, the heating device 10 on the middle horizontal well 2 is opened to heat the fracture network 5 and the reservoir around the middle horizontal well 2. When the temperature detection well 11 detects that the temperature is not less than 450°C, and the simulation prediction shows that the vaporized gas enters the vicinity of the fracture network 5, high-temperature water vapor is injected into the fracture network 5 through the middle horizontal well 2, so that the water vapor reacts with carbon monoxide and carbon dioxide to produce hydrogen. Then, the upper horizontal well 3 is opened, and hydrogen is produced under the action of gravity and hydrogen filter membrane, while the remaining tail gas remains in the upper part of the reservoir.

[0052] As the volume of exhaust gas in the upper part increases, its pressure also gradually increases. Therefore, the pressure difference between the upper part and the reservoir edge gradually increases. As a result, these exhaust gases (including carbon dioxide, carbon monoxide, and light hydrocarbons) displace the light oil at the reservoir edge to the bottom of the reservoir. This process continues until most of the light oil in the entire reservoir 4 has been completely reacted.

[0053] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method suitable for in situ hydrogen production in an oil reservoir, characterized in that, The method comprises the following steps, Three horizontal wells and one temperature detection well are arranged in the same reservoir, the temperature detection well is used to detect the temperature of the middle horizontal well, a hydrogen filter membrane is arranged at the upper horizontal well, and a heating device is arranged at the middle horizontal well; Before production, the middle horizontal well is developed by close-cut volume fracturing, and the fracturing proppant comprises rock debris and heat-conducting metal particles; the upper horizontal well is developed by single-fracture fracturing; In-situ ignition is performed in the lower horizontal well, and an oxygen-containing gas is injected to incompletely burn to produce CO and CO2 and form a gasification zone; The heating device is used to heat to above 450 DEG C, when the gasification zone gas enters the middle horizontal well, steam is injected and hydrogen is produced to form a reaction zone; The upper horizontal well is opened, and hydrogen is extracted by the hydrogen filter membrane.

2. The method of claim 1, wherein, The oxygen concentration in the oxygen-containing gas is not less than 10%.

3. The method of claim 1, wherein, The mass ratio of the heat-conducting metal particles to the rock debris is 1:1-10.

4. The method of claim 1, wherein, The temperature detection well is used to detect the temperature in the fracturing fracture network.

5. The method of claim 1, wherein, The heating device is arranged between the casing and the tubing of the production section of the middle horizontal well to heat; meanwhile, the heel of the middle horizontal well is isolated.

6. The method of claim 1, wherein, The above production process is continuously performed until the extracted hydrogen is not economical.

7. The method of claim 1, wherein, In the three horizontal wells, at least part of the horizontal sections are in the same vertical direction.

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