A method for combined storage of CO2 in deep and shallow formations

Abstract

The present invention provides a method for combined CO2 storage in deep and shallow strata. The method comprises first selecting a stratum according to certain conditions, then deploying wells in a specific pattern based on the selected stratum, and then storing the CO2. This method fully utilizes both deep and shallow geological bodies to improve storage efficiency. Furthermore, by combining the deep saline water layer with the shallow basalt, the shallow basalt forms a precipitate after carbon fixation, effectively preventing CO2 stored in the deep saline water layer from leaking to the surface. Furthermore, the deep saline water is utilized in situ, resolving environmental issues associated with saline water extraction and saving high water treatment costs.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection technology, and in particular to a method for jointly storing CO2 in deep and shallow strata. Background Art

[0002] CO2 geological storage technology is considered an effective means of large-scale CO2 disposal. This technology uses oil and gas reservoirs, deep saline water, and unminable coal seams as storage sites, and has carried out a large number of demonstration projects. In these geological bodies, the storage of CO2 relies on a series of storage mechanisms, including structural storage, residual gas storage, dissolution storage, and mineral storage. Among them, converting CO2 into solid minerals is the safest storage mechanism with the lowest leakage risk. However, the mass fraction of minerals that can be used for carbon sequestration in conventional geological bodies (such as deep saline water layers) is relatively low. Most of the injected CO2 will exist in the storage reservoir in a free state for a long time. It is highly dependent on the sealing conditions of the geological structure and has a high risk of CO2 leakage. Necessary monitoring measures need to be taken during the injection period and for a long time after the injection is stopped to ensure the safety of CO2 storage, which greatly increases the cost of CO2 geological storage projects.

[0003] In addition, the injection of CO2 into conventional geological bodies (such as deep saline water layers) for storage will increase the formation pressure to a certain extent. On the one hand, the increase in formation pressure may bring about geological instability factors; on the other hand, in order to prevent the formation pressure from increasing excessively, measures will be taken to reduce the injection volume, so that the CO2 storage / injection volume will be limited by the formation pressure. In order to reduce the rise in formation pressure and at the same time increase the geological body's CO2 storage / injection volume, CO2 displacement saline water technology can be used, that is, by injecting CO2 into deep saline water layers, the saline water is driven out of the deep saline water layers through the displacement effect, the capacity of the underground space is increased, and then the extracted saline water is subjected to saline water treatment. The process is as follows: Figure 1 However, the current practice of desalinating saline water extracted from deep saline aquifers before discharge results in high costs for saline water treatment, which in turn significantly increases the cost of CO2 geological storage. Summary of the Invention

[0004] In light of this, the present invention provides a method for combined CO2 storage in deep and shallow strata. This method fully utilizes both deep and shallow geological bodies, improving storage efficiency. Furthermore, the method fully utilizes saline water without requiring surface extraction, reducing saline water treatment costs and environmental issues associated with wastewater discharge.

[0005] The present invention provides a method for combined storage of CO2 in deep and shallow strata, comprising the following steps:

[0006] S1. Select stratum:

[0007] The geological storage area is selected according to the following criteria:

[0008] 1) There is a deep saline layer below 800m;

[0009] 2) The integrity of the overburden above the deep saline layer is good;

[0010] 3) There is a shallow basalt reservoir above the upper cover layer;

[0011] S2. Well layout:

[0012] A CO2 deep storage injection well 1 is arranged above the deep saline water layer, and the lower end of the CO2 deep storage injection well 1 is connected to the deep saline water layer;

[0013] A CO2 shallow storage injection well 2 is provided above the stratum of the shallow basalt reservoir, and the lower end of the CO2 shallow storage injection well 2 is connected to the shallow basalt reservoir;

[0014] A well section 3 is arranged below the shallow basalt reservoir, and the lower end of the well section 3 is connected to the deep saline water layer;

[0015] S3. Storage of CO2:

[0016] Injecting CO2 into the deep saline water layer through the CO2 deep storage injection well 1, and driving the saline water in the deep saline water layer into the shallow basalt reservoir through the well section 3;

[0017] CO2 is injected into the shallow basalt reservoir through the CO2 shallow storage injection well 2 to react with the saline water in the shallow basalt reservoir.

[0018] Preferably, the distance between the CO2 deep storage injection well 1 and the CO2 shallow storage injection well 2 is 2~4km.

[0019] Preferably, in step S1, the porosity of the deep saline water layer is 15% to 40%, and the permeability is 30 to 1000 mD.

[0020] Preferably, in step S1, the porosity of the upper covering layer is less than 5%, and the permeability is less than 0.1 mD.

[0021] Preferably, in step S1, the conditions for selecting the stratum also include: 4) there are no major faults in the geological storage area.

[0022] The method provided by the present invention directs salt water from a saline water layer (the rock composition is sandstone) in a deep formation to a basalt reservoir in a shallow formation. Basalt and sandstone are two different types of rocks, and their CO2 storage principles are also different. Sandstone mainly dissolves CO2 through the salt water in the pores, while basalt directly undergoes a mineralization reaction with CO2 to achieve the storage goal. However, salt water is required to dissolve CO2 during the mineralization process to increase the reaction rate. Under the scheme of the present invention, salt water is fully utilized and does not need to be mined from the ground, reducing a series of costs for salt water treatment and environmental issues related to sewage discharge. At the same time, CO2 is mineralized and sealed in the shallow formation, forming a precipitate, which can further improve the sealing of the CO2 storage formation and reduce the possibility of CO2 escape from deep formations. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0024] Figure 1 Schematic diagram of a CO2 storage process in the prior art;

[0025] Figure 2 Schematic diagram of the CO2 storage process of the present invention. DETAILED DESCRIPTION

[0026] The present invention provides a method for combined storage of CO2 in deep and shallow strata, comprising the following steps:

[0027] S1. Select stratum:

[0028] The geological storage area is selected according to the following criteria:

[0029] 1) There is a deep saline layer below 800m;

[0030] 2) There is an overburden layer above the deep saline water layer, and the integrity of the overburden layer is good;

[0031] 3) There is a shallow basalt reservoir above the upper cover layer;

[0032] S2. Well layout:

[0033] A CO2 deep storage injection well 1 is arranged above the deep saline water layer, and the lower end of the CO2 deep storage injection well 1 is connected to the deep saline water layer;

[0034] A CO2 shallow storage injection well 2 is provided above the stratum of the shallow basalt reservoir, and the lower end of the CO2 shallow storage injection well 2 is connected to the shallow basalt reservoir;

[0035] A well section 3 is arranged below the shallow basalt reservoir, and the lower end of the well section 3 is connected to the deep saline water layer;

[0036] S3. Storage of CO2:

[0037] Injecting CO2 into the deep saline water layer through the CO2 deep storage injection well 1, and driving the saline water in the deep saline water layer into the shallow basalt reservoir through the well section 3;

[0038] CO2 is injected into the shallow basalt reservoir through the CO2 shallow storage injection well 2 to react with the saline water in the shallow basalt reservoir.

[0039] About step S1 :Select stratum

[0040] Scenarios for geological storage of CO2 include areas with high concentrations of high-carbon-emitting enterprises, such as thermal power plants, steel mills, and chemical plants. In this method, the address data of the area where geological storage of CO2 is planned is first collected, and the geological storage area is selected according to certain conditions.

[0041] In the present invention, the geological storage area is selected according to the following conditions:

[0042] 1) There is a deep saline layer below 800m;

[0043] 2) The integrity of the overburden above the deep saline layer is good;

[0044] 3) There is a shallow basalt reservoir above the upper cover layer.

[0045] in,

[0046] Regarding condition 1): a saline layer must be present below a depth of 800m, i.e., a deep saline layer must be present. The deep saline layer is primarily composed of sandstone. In the present invention, the saline layer is preferably water-containing and has good porosity and permeability. In the present invention, the porosity of the deep saline layer is preferably between 15% and 40%, specifically 15%, 20%, 25%, 28%, 30%, 35%, or 40%. In the present invention, preferably, the permeability of the deep saline water layer is 30~1000mD, specifically 30mD, 50mD, 100mD, 150mD, 200mD, 250mD, 300mD, 350mD, 400mD, 450mD, 500mD, 550mD, 600mD, 650mD, 700mD, 750mD, 800mD, 850mD, 900mD, 950mD, or 1000mD.

[0047] Regarding condition 2): The overburden above the deep saline layer must be well-integrated. The overburden is primarily composed of mudstone. In the present invention, the overburden preferably has low porosity and low permeability. Specifically, the porosity of the overburden is <5%, and the permeability is <0.1 mD.

[0048] Regarding condition 3): There must be a shallow basalt reservoir above the overburden, that is, a basalt reservoir distributed in the shallow area of ​​the storage area. Basalt and other types of volcanic rocks are widely distributed in and around various sedimentary basins in my country. They can be generally divided into five major regions: Northeast (Wudalianchi, Jingpo Lake, Changbai Mountain, Xilin Gol, and Greater Khingan Range), East (Shandong, Jiangsu, and Zhejiang), Southeast (Leizhou and Qiongzhou), Southwest (Yunnan, Guizhou, and Sichuan), and Northwest (West Qinling, Junggar, and Tarim Basins).

[0049] Preferably, the conditions for selecting the stratum also include: 4) there are no major faults in the geological storage area.

[0050] About step S2 :Building a well

[0051] In the present invention, the well layout is as follows: a CO2 deep storage injection well 1 is arranged above the deep saline water layer, and the lower end of the CO2 deep storage injection well 1 is connected to the deep saline water layer; a CO2 shallow storage injection well 2 is arranged above the shallow basalt reservoir layer, and the lower end of the CO2 shallow storage injection well 2 is connected to the shallow basalt reservoir layer; a well section 3 is arranged below the shallow basalt reservoir layer, and the lower end of the well section 3 is connected to the deep saline water layer. The above-mentioned well layout is as follows: Figure 2 shown.

[0052] Among them, one end of the CO2 deep storage injection well 1 is connected to the surface, and the other end (lower end) is connected to the deep saline water layer, that is, the lower end is connected to the deep saline water layer. One end of the CO2 shallow storage injection well 2 is connected to the surface, and the other end (lower end) is connected to the shallow basalt reservoir, that is, the lower end is connected to the shallow basalt reservoir. Well section 3 is arranged below the shallow basalt reservoir, one end of which is connected to the shallow basalt reservoir, and the other end (lower end) is connected to the deep saline water layer. Therefore, there is a basalt reservoir between the well section of the CO2 shallow storage injection well 2 and the well section 3, which provides a reaction space for shallow CO2 mineralization storage.

[0053] In the present invention, the distance between the deep CO2 storage injection well 1 and the shallow CO2 storage injection well 2 is preferably 2-4 km, specifically 2 km, 3 km, or 4 km, and more preferably 2-3 km. The distance refers to the horizontal distance between the center points of well 1 and well 2.

[0054] About step S3 : Storage of CO2

[0055] CO2 is injected into the deep saline water layer through the CO2 deep storage injection well 1, and the saline water in the deep saline water layer is driven into the shallow basalt reservoir through the well section 3; and CO2 is injected into the shallow basalt reservoir through the CO2 shallow storage injection well 2 to react with the saline water in the shallow basalt reservoir.

[0056] Specifically, the CO2 deep storage injection well 1 is opened, and CO2 is injected into the deep saline water layer through the CO2 deep storage injection well 1. The saline water in the deep saline water layer enters the shallow basalt reservoir through the well section 3; the CO2 shallow storage injection well 2 is opened, and CO2 is injected into the shallow basalt reservoir through the CO2 shallow storage injection well 2. After continuous injection for a period of time, the well is closed for chemical reaction. The continuous injection time is preferably 1 day. The time for closing the well for chemical reaction is preferably 1 day. Through the above operations, a portion of CO2 enters the deep saline water layer, occupies the space in the deep saline water layer and is sealed therein. At the same time, another portion of CO2 outside and the saline water in the deep saline water layer enter the shallow basalt reservoir, undergoing mineralization reaction (as shown below), generating carbonate precipitation, and thus completing carbon fixation.

[0057] Mineralization reaction process:

[0058] (1) Dissolution:

[0059]

[0060]

[0061] (2) Carbon sequestration:

[0062] Peridot:

[0063] Plagioclase:

[0064]

[0065] When CO2 dissolves in water, the water becomes weakly acidic, dissolving minerals in the basalt and releasing divalent cations. The divalent cations react with bicarbonate in the water to form carbonate precipitates, completing the carbon fixation process.

[0066] The method provided by the present invention directs salt water from a saline water layer (the rock composition is sandstone) in a deep formation to a basalt reservoir in a shallow formation. Basalt and sandstone are two different types of rocks, and their CO2 storage principles are also different. Sandstone mainly dissolves CO2 through the salt water in the pores, while basalt directly undergoes a mineralization reaction with CO2 to achieve the storage goal, but salt water is required to dissolve CO2 during the mineralization process. Under the scheme of the present invention, salt water is fully utilized and does not need to be mined from the ground, reducing a series of costs for salt water treatment and environmental problems related to sewage discharge. At the same time, CO2 is mineralized and sealed in the shallow formation, generating precipitation, which can further improve the sealing of the CO2 storage formation and reduce the possibility of CO2 escape from deep formations.

[0067] The method provided by the present invention has the following beneficial effects:

[0068] 1. Make full use of deep and shallow geological bodies to improve storage efficiency.

[0069] 2. Combining the deep saline water layer with the shallow basalt, the shallow basalt will form precipitation after fixing carbon, which can also effectively prevent the CO2 sealed in the deep saline water layer from leaking to the shallow surface.

[0070] 3. In-situ utilization of deep saline water solves the environmental issues associated with saline water extraction and saves high water treatment costs. It also solves the problem of basalt storage requiring large amounts of water resources at a low cost.

[0071] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0072] Example 1

[0073] S1. Select stratum:

[0074] The geological storage area is selected according to the following criteria:

[0075] 1) There is a deep saline layer (the rock composition is sandstone) at a depth of about 4000m in a certain place. The saline layer contains water and has good porosity and permeability conditions, with an average porosity of 28% and an average permeability of 100mD.

[0076] 2) The overburden above the deep saline layer is well-integrity (mainly mudstone) and has low porosity and low permeability, with an average porosity of 3% and an average permeability of 0.05 mD.

[0077] 3) There is a shallow basalt reservoir above the upper cover layer.

[0078] 4) There are no major faults in the geological storage area.

[0079] S2. Well layout:

[0080] A deep CO2 storage injection well 1 is located above the deep saline layer, with its lower end connected to the deep saline layer. A shallow CO2 storage injection well 2 is located above the shallow basalt reservoir, with its lower end connected to the shallow basalt reservoir. A well section 3 is located below the shallow basalt reservoir, with its lower end connected to the deep saline layer. The distance between the deep CO2 storage injection well 1 and the shallow CO2 storage injection well 2 is 3 km.

[0081] S3. Storage of CO2:

[0082] The CO2 deep storage injection well 1 is opened, and CO2 is injected into the deep saline water layer through the CO2 deep storage injection well 1. The saline water in the deep saline water layer enters the shallow basalt reservoir through the well section 3. The CO2 shallow storage injection well 2 is opened, and CO2 is injected into the shallow basalt reservoir through the CO2 shallow storage injection well 2. After continuous injection for one day, the well is closed for one day for chemical reaction.

[0083] After two days of treatment (one day for injection and one day for well closure), the total amount of CO2 stored in deep and shallow locations reached 180 tons, significantly increasing the amount stored compared to storage using saline aquifers or basalt mineralization alone, thereby improving storage efficiency. Furthermore, after one day of well closure, CO2 leakage was monitored for 30 consecutive days. The results showed that no CO2 leakage was detected in the atmosphere or soil at the injection wellhead, a significant reduction compared to existing technologies. Furthermore, the method of the present invention eliminates the need for saline water extraction, resolving the environmental concerns associated with saline water extraction, saving on high water treatment costs, and reducing the cost of the CO2 storage process.

[0084] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that are not substantially different from the literal description of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for combined storage of CO2 in deep and shallow formations, characterized in that: The following steps are involved: S1. Select stratum: The geological storage area is selected according to the following criteria: 1) There is a deep saline layer below 800m; 2) The integrity of the overburden above the deep saline layer is good; 3) There is a shallow basalt reservoir above the upper cover layer; S2. Well layout: A CO2 deep storage injection well 1 is arranged above the deep saline water layer, and the lower end of the CO2 deep storage injection well 1 is connected to the deep saline water layer; A CO2 shallow storage injection well 2 is provided above the stratum of the shallow basalt reservoir, and the lower end of the CO2 shallow storage injection well 2 is connected to the shallow basalt reservoir; A well section 3 is arranged below the shallow basalt reservoir, and the lower end of the well section 3 is connected to the deep saline water layer; S3. Storage of CO2: Injecting CO2 into the deep saline water layer through the CO2 deep storage injection well 1, and driving the saline water in the deep saline water layer into the shallow basalt reservoir through the well section 3; CO2 is injected into the shallow basalt reservoir through the CO2 shallow storage injection well 2 to react with the saline water in the shallow basalt reservoir.

2. The method according to claim 1, characterized in that The distance between the CO2 deep storage injection well 1 and the CO2 shallow storage injection well 2 is 2 to 4 km.

3. The method according to claim 1, characterized in that In step S1, the porosity of the deep saline water layer is 15% to 40%, and the permeability is 30 to 1000 mD.

4. The method according to claim 1, wherein In step S1, the porosity of the upper covering layer is less than 5%, and the permeability is less than 0.1 mD.

5. The method according to claim 1, characterized in that In step S1, the conditions for selecting the stratum also include: 4) there are no major faults in the geological storage area.

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