A system for co - mining deep brine and shallow soluble salts and a CO₂ sequestration method

Abstract

The present invention relates to a co - mining system for deep brine and shallow soluble salts and a CO2 sequestration method, which includes a deep brine production well extending to a deep brine reservoir, a mobile lithium extraction vehicle arranged at the wellhead of the deep brine production well, a brine pressurization and reinjection station for pressurizing the deep brine discharged by the mobile lithium extraction vehicle, and a group of docking wells arranged in the shallow soluble salt layer. This group of docking wells includes a brine injection end connected to the outlet of the brine pressurization and reinjection station and a brine production end for mining the shallow soluble salts after the dissolution equilibrium of the deep brine injected through the brine pressurization and reinjection station; the deep brine production well, the mobile lithium extraction vehicle, the brine pressurization and reinjection station, and the brine injection end are connected in sequence. It effectively recovers lithium in deep brine resources; reduces water resource waste; utilizes the advantage of the relatively high temperature of deep brine to further improve the extraction efficiency of soluble salts; and can simultaneously construct two different CO2 sequestration geological bodies in the deep and shallow parts to implement CO2 geological sequestration.

Description

Technical Field

[0001] The present invention belongs to the technical field of mineral resource development, and particularly relates to a co-mining system for deep brine extraction and shallow soluble salts and a CO2 sequestration method. Background Art

[0002] Under the new situation, salt lake brine resources are becoming important resources favored by various industries. On the one hand, China is a large agricultural country, and potassium is one of the three important elements for crop growth. Therefore, potassium fertilizer is a key fertilizer for agricultural production, and the rich potassium chloride resources in salt lake brine resources have become key resources to ensure the stable development of agriculture. On the other hand, with the rapid development of the new energy industry, lithium resources have become the core material basis restricting the development of the new energy industry, and the efficient development and utilization of lithium-rich brine are of great significance.

[0003] Over the years, the exploitation of conventional shallow brine resources has gradually tended to exhaustion, and deep salt lake brine has become an important subsequent resource and is being widely concerned. At the same time, there are a large number of soluble salts rich in potassium and lithium, such as carnallite and polyhalite, remaining in the shallow salt lake strata, which need to be exploited by water injection leaching. The Quaternary salt lakes are usually characterized by the coexistence of deep lithium-rich brine and shallow potassium-rich carnallite. Generally, the exploitation technology of deep brine is relatively simple. Mainly in the water-rich area, through drilling construction, extraction can be implemented to achieve the exploitation of brine. However, in the case of multiple aquifers existing in the deep part, the large-scale exploitation of the target layer is likely to cause cross-flow recharge between aquifers, resulting in a decrease in brine quality, and a method is needed to maintain the formation fluid pressure to prevent cross-flow recharge. In addition, for the leaching exploitation of shallow polyhalite and carnallite, a large amount of external water diversion is often required, and it is injected into the soluble salt layer through natural infiltration or artificial drilling to realize the exploitation of solid soluble salts. However, there is little research on the efficient exploitation technology for such coexisting mineral resources.

[0004] In addition, CO2 geological sequestration has attracted more and more attention. Both brine formations and underground salt caverns have important CO2 geological sequestration potential. After the completion of deep brine extraction in this method, the deep brine reservoir can be used for CO2 geological sequestration. After the leaching exploitation of shallow soluble salts, artificial salt caverns can also be formed and CO2 geological sequestration can be implemented.

[0005] First, the existing technologies mainly focus on the separate extraction of deep brine or shallow soluble salts, and have not yet involved the technology of co-extraction; second, with the mobile lithium extraction technology, after the deep brine extraction is completed, it can directly enter the adsorption vehicle to complete the extraction of lithium resources, and the treated brine resources are directly discharged. On the one hand, it causes environmental pollution. On the other hand, the deep brine has a relatively high temperature and contains some other useful ions, and direct discharge is also a waste of resources; third, the external water diversion project for shallow solution mining is large in scale and extremely limited by the water resource acquisition conditions, often resulting in huge investment costs; fourth, during the large-scale extraction of deep brine, cross-flow recharge is likely to occur between multiple aquifers, leading to a decrease in the brine quality; fifth, the permeability of the deep brine reservoir is low, the fluidity of the brine is poor, and the sustainable seepage capacity of the brine is poor; sixth, after the shallow solution mining is completed, due to the existence of a large-scale underground cavity, there is a potential risk of surface subsidence. Summary of the Invention

[0006] The object of the present invention is to overcome the deficiencies of the existing technologies, and in particular, to provide a co-extraction system for deep brine and shallow soluble salts and a CO2 sequestration method, which can improve the extraction efficiency, reduce the waste of brine resources and environmental pollution, avoid the occurrence of cross-flow recharge, and at the same time construct deep and shallow CO2 sequestration geological bodies to achieve CO2 sequestration and avoid surface subsidence.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A co-extraction system for deep brine and shallow soluble salts, characterized in that it includes a deep brine extraction well extending to the deep brine reservoir, a mobile adsorption vehicle arranged at the wellhead of the deep brine extraction well, a brine pressurization and reinjection station for pressurizing the deep brine discharged from the mobile adsorption vehicle, and a group of docking wells arranged in the shallow soluble salt layer. This group of docking wells includes a brine injection end connected to the outlet of the brine pressurization and reinjection station and a brine extraction end for extracting the shallow soluble salts after the dissolution balance of the deep brine injected by the brine pressurization and reinjection station.

[0009] The deep brine extraction well, the mobile adsorption vehicle, the brine pressurization and reinjection station and the brine injection end are connected in sequence.

[0010] The aforementioned co-extraction system for deep brine and shallow soluble salts further includes a carbon dioxide injection well and a carbon dioxide pressurization station arranged at the inlet of the carbon dioxide injection well; the carbon dioxide injection well and the deep brine extraction well form a deep brine CO2 displacement extraction system to improve the deep brine extraction efficiency, and at the same time, on the premise that the fluid pressure of the aquifer is balanced with the carbon dioxide injection pressure, prevent the occurrence of cross-flow recharge.

[0011] A carbon dioxide sequestration method applicable to the co-extraction of deep brine and shallow soluble salts, characterized by including the following steps:

[0012] 1) First, a carbon dioxide injection well is constructed in the deep brine reservoir as a brine displacement well and a deep brine production well, and a group of docking wells are constructed in the shallow soluble salt layer; then a carbon dioxide pressurization station is set at the wellhead of the brine displacement well, and a mobile adsorption vehicle is set at the wellhead of the deep brine production well. The mobile adsorption vehicle is a skid-mounted, movable, and efficient lithium ion adsorption integrated equipment that can achieve efficient extraction of brine lithium resources; then a brine pressurization recharge station is added behind the mobile adsorption vehicle. At this point, the deep brine production well, the mobile adsorption vehicle, and the brine pressurization recharge station are connected in sequence using pipes with anti-corrosion coatings inside;

[0013] 2) Open the carbon dioxide booster station to make the wellhead pressure of the brine displacement well reach the preset pressure of the deep brine fluid. After the carbon dioxide begins to be injected into the deep brine reservoir, open the deep brine production well for production;

[0014] 3) After the deep brine production well is opened, a certain flow rate is maintained to keep the pressure of the carbon dioxide pressure station unchanged. By adjusting the flow rate of the deep brine production well, the balance between the carbon dioxide pressure and the aquifer fluid pressure is maintained to prevent overflow recharge;

[0015] 4) Directly extract lithium by adsorption after deep brine mining, selectively adsorb lithium resources in the brine to achieve the extraction of lithium resources in deep brine;

[0016] 5) After the lithium resource is extracted, the remaining brine enters the brine pressure recharge station and is pressurized before being injected into the shallow soluble salt layer through the injection end of the docking well to dissolve the soluble salt;

[0017] 6) Finally, the brine resources after dissolution equilibrium are mined through the mining end of the docking well to the ground and enter the salt field or treatment terminal to realize the leaching mining of shallow soluble salt resources;

[0018] 7) During the exploitation of shallow soluble salt layers, the development degree of shallow salt caverns is explored using surface transient electromagnetic or micro-seismic exploration methods. After exploration and evaluation, carbon dioxide is injected into salt caverns with sealing conditions suitable for carbon dioxide storage to implement carbon dioxide salt cavern sealing.

[0019] As mentioned above, lithium extraction by adsorption is carried out through a mobile adsorption vehicle; or by means of strong evaporation, the salt resources in the brine are concentrated and collected, and then the evaporated water is cooled and collected in a brine pressure reinjection station and then injected into the shallow soluble salt layer and solution mining is carried out.

[0020] The advantages of the present invention are as follows: By using CO2 to displace deep brine, while achieving efficient exploitation of deep brine, CO2 geological sequestration is completed. In addition, it is possible to use CO2 to supplement the underground fluid pressure, thereby preventing the occurrence of cross-flow recharge. At the same time, the mobile lithium extraction technology is used to recover the main useful resources in the deep brine resources. After that, the treated brine is injected into the soluble salt layer through the shallow docking well, making full use of the deep brine resources to implement leaching mining of the shallow soluble salts, which not only reduces the unnecessary waste of water resources, but also takes advantage of the relatively high temperature of the deep brine to further improve the mining efficiency of the soluble salts. Thirdly, through the leaching mining of the shallow soluble salts, a shallow cavity with excellent tightness can be constructed, which can be used as a CO2 geological sequestration body. After implementing CO2 geological sequestration, the internal pressure can prevent the occurrence of surface subsidence. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of a co-mining system for deep brine extraction and shallow soluble salts.

[0022] Figure 2 is a schematic diagram of the wellbore structure and the corresponding system composition of a carbon dioxide sequestration method applicable to the co-mining of deep brine extraction and shallow soluble salts.

[0023] DESCRIPTION OF THE REFERENCE NUMERALS:

[0024] 1, deep brine reservoir; 2, shallow soluble salt layer; 3, deep brine production well; 4, mobile adsorption vehicle; 5, brine pressurization station; 6, brine injection end; 7, brine production end; 8, docking well; 9, carbon dioxide injection well; 10, carbon dioxide pressurization station; 11, aquifer; 12, salt cavern; 13, aquitard; 14, loose formation. SPECIFIC EMBODIMENTS

[0025] In order to overcome the deficiencies of the prior art, this embodiment provides a system that can realize the co-mining of deep brine and shallow soluble salts, improve the mining efficiency and reduce the waste of brine resources. This example provides a Figure 1 co-mining system for deep brine extraction and shallow soluble salts as shown in the figure, including a deep brine production well 3 extending to the deep brine reservoir 1, a mobile lithium extraction vehicle arranged at the wellhead of the deep brine production well 3, a brine pressurization station 5 for pressurizing the deep brine discharged by the mobile lithium extraction vehicle (i.e., the mobile adsorption vehicle 4), a group of docking wells arranged in the shallow soluble salt layer 2, and this group of docking wells includes a brine injection end 6 connected to the outlet of the brine pressurization station 5 and a brine production end 7 for mining the shallow soluble salts after the dissolution equilibrium of the deep brine injected by the brine pressurization station 5; among them, the deep brine production well 3, the mobile lithium extraction vehicle, the brine pressurization station 5 and the brine injection end 6 are connected in sequence.

[0026] The deep brine mining and shallow soluble salt co-mining system provided by this embodiment constructs a deep brine production well 3 extending to the deep brine reservoir 1 in the brine reservoir, and at the same time constructs a set of butt-joint wells in the shallow soluble salt layer, including a brine injection end 6 and a brine production end 7. Then, a mobile lithium extraction vehicle is set at the wellhead of the deep brine production well 3. As a skid-mounted, movable, and highly efficient lithium-ion adsorption integrated equipment, it can achieve the efficient extraction of lithium resources from brine.

[0027] After that, a brine pressure station 5 is added behind the mobile lithium extraction vehicle. This device can be set as a semi-permanent or temporary movable equipment according to the resource volume situation, and specific evaluation needs to be based on the comparison of comprehensive costs.

[0028] After connecting the deep brine production well 3, the mobile lithium extraction vehicle, the brine pressure station 5, the brine injection well, that is, the brine injection end 6, etc. in sequence by using pipes with anti-corrosion coatings inside, the whole system starts to operate.

[0029] After the deep brine is mined to the mobile lithium extraction vehicle through the production well, the lithium extraction vehicle selectively adsorbs the lithium resources in the brine, thus realizing the extraction of lithium resources from the deep brine. The remaining brine after lithium resource extraction enters the pressure station, and relies on the pressure station to be pressurized and enter the brine injection well to dissolve the soluble salt. Among them, the adsorption lithium extraction process can be replaced by a strong evaporation means to achieve the concentration and collection of salt resources in the brine, and then the evaporated water is cooled and collected in the pressure station and then injected into the soluble salt layer to implement solution mining.

[0030] Finally, the brine resources after dissolution equilibrium are mined to the ground through the production end of the butt-joint well, that is, the brine production end 7, and enter the salt field or treatment terminal to realize the solution mining of shallow soluble salt resources.

[0031] During the shallow soluble salt mining process, it is necessary to carry out necessary exploration of the development degree of artificial salt caverns. By using methods such as surface transient electromagnetic and microseismic exploration, the development degree of shallow salt caverns is explored. After exploration and evaluation, for salt caverns 12 with suitable sealing conditions for CO2 storage, CO2 salt cavern storage can be implemented.

[0032] It can be seen that the system can realize the co-mining of deep brine and shallow soluble salt. In order to solve the problems of difficult mining of deep brine and low mining efficiency of shallow soluble salt, a typical salt lake in the Qaidam Basin was taken as an example. Through drilling construction, a CO2 injection well was completed as a brine displacement well, a deep brine mining well and two shallow soluble salt leaching mining wells. The deep brine mining was strengthened by gas injection displacement, and the treated deep brine was injected into the shallow soluble salt layer after the useful ions were adsorbed by a mobile adsorption vehicle on the ground, so as to realize the efficient mining of shallow soluble salt. On the one hand, this system improves the mining efficiency of deep brine, and at the same time solves the water source problem of shallow soluble salt leaching mining in cold and arid areas to a certain extent, realizing the efficient utilization of geothermal resources and the co-mining of solid and liquid mineral resources. At the same time, underground CO2 storage space can be constructed. On the one hand, deep brine exploitation can achieve brine displacement by injecting CO2, thereby enhancing the efficiency of brine exploitation and realizing the geological storage of CO2 in the brine reservoir; on the other hand, by making full use of the closed nature of rock salt formations and through the leaching and exploitation of shallow soluble salts, artificial salt caverns can be formed for the geological storage of CO2.

[0033] In addition, based on the aforementioned embodiment, a deep brine exploitation and shallow soluble salt co-exploitation system is also provided, which is characterized in that it also includes a carbon dioxide injection well 9 and a carbon dioxide pressure station 10 arranged at the entrance of the carbon dioxide injection well 9; the carbon dioxide injection well 9 and the deep brine exploitation well 3 constitute a deep brine CO2 displacement exploitation system, which is used to improve the deep brine exploitation efficiency, and at the same time prevent the occurrence of overflow recharge under the premise that the aquifer fluid pressure is balanced with the carbon dioxide injection pressure.

[0034] Finally, based on the above system, a carbon dioxide storage method suitable for deep brine mining and shallow soluble salt co-mining is provided, including the following steps:

[0035] 1) First, a carbon dioxide injection well 9 is constructed in the deep brine reservoir 1 as a brine displacement well, and a deep brine production well 3, and a group of docking wells are constructed in the shallow soluble salt layer 2; then a carbon dioxide pressurizing station 10 is set at the wellhead of the brine displacement well, and a mobile adsorption vehicle 4 is set at the wellhead of the deep brine production well 3. The mobile adsorption vehicle 4 is a skid-mounted, movable, and efficient lithium ion adsorption integrated equipment that can achieve efficient extraction of brine lithium resources; then a brine pressurizing recharge station 5 is added behind the mobile adsorption vehicle 4. At this point, the deep brine production well 3, the mobile adsorption vehicle 4, and the brine pressurizing recharge station 5 are connected in sequence using a pipeline with an anti-corrosion coating inside;

[0036] 2) Open the carbon dioxide booster station 10 to make the wellhead pressure of the brine displacement well reach the preset deep brine fluid pressure (assuming that the brine reservoir depth is 1000m and the fluid pressure is 11MPa). After carbon dioxide begins to be injected into the deep brine reservoir 1, open the deep brine production well 3 for production;

[0037] 3) After the deep brine extraction well 3 is opened, maintain a certain flow rate, keep the pressure of the carbon dioxide pressurization station 10 unchanged, and maintain the balance between the carbon dioxide pressure and the fluid pressure of the aquifer 11 by adjusting the flow rate of the deep brine extraction well 3 to prevent cross-flow recharge.

[0038] 4) After the deep brine is extracted, directly perform lithium extraction by adsorption. Selectively adsorb the lithium resources in the brine to achieve the extraction of lithium resources from the deep brine. Here, the lithium extraction by adsorption can be carried out by the mobile adsorption vehicle 4; or by means of strong evaporation, concentrate and collect the salt resources in the brine, and then the evaporated water is cooled and collected in the brine pressurization and reinjection station 5.

[0039] 5) The remaining brine after lithium resource extraction enters the brine pressurization and reinjection station 5, is pressurized and then injected into the shallow soluble salt layer 2 through the injection end 6 of the docking well 8 to dissolve the soluble salt.

[0040] 6) Finally, the brine resources after dissolution equilibrium are mined to the ground through the production end of the docking well 8 and enter the salt field or treatment terminal to achieve the leaching and mining of shallow soluble salt resources.

[0041] Among them, during the mining process of the shallow soluble salt layer 2, use the surface transient electromagnetic or microseismic exploration method to explore the development degree of the shallow salt cavern 12. After exploration and evaluation, for the salt cavern 12 with suitable sealing conditions for carbon dioxide storage, inject carbon dioxide into it to implement carbon dioxide salt cavern storage.

[0042] Among them, the CO2 injection volume is determined by the surrounding rock pressure in the injected salt cavern and the breakthrough pressure of the salt cavern itself. According to the salt cavern burial depth and laboratory experiments, calculate the surrounding rock pressure and the CO2 breakthrough pressure of the salt cavern itself respectively, and take the smaller of the two pressures as the upper limit of the CO2 pressure in the salt cavern. When the CO2 pressure in the salt cavern reaches the injection upper limit, stop injecting, and then seal the docking well connected to the shallow salt cavern with high-strength cement.

[0043] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A co-mining system for deep brine extraction and shallow soluble salts, characterized in that: The invention comprises a deep brine production well (3) extending to a deep brine reservoir (1), a mobile adsorption vehicle (4) arranged at the wellhead of the deep brine production well (3), a brine pressure reinjection station (5) for pressurizing the deep brine discharged by the mobile adsorption vehicle (4), and a group of docking wells (8) arranged in a shallow soluble salt layer (2), wherein the group of docking wells (8) comprises a brine injection end (6) connected to the outlet of the brine pressure reinjection station (5) and a brine production end (7) for producing shallow soluble salt after the deep brine injected through the brine pressure reinjection station (5) has reached a dissolution equilibrium; The deep brine extraction well (3), the mobile adsorption vehicle (4), the brine pressure reinjection station (5) and the brine injection end (6) are connected in sequence.

2. The deep brine extraction and shallow soluble salt co-extraction system according to claim 1, wherein It also includes a carbon dioxide injection well (9) and a carbon dioxide pressure station (10) arranged at the entrance of the carbon dioxide injection well (9); the carbon dioxide injection well (9) and the deep brine production well (3) constitute a deep brine CO2 displacement production system for improving the deep brine production efficiency and preventing the occurrence of overflow recharge under the premise that the fluid pressure of the aquifer (11) is balanced with the carbon dioxide injection pressure.

3. A carbon dioxide sequestration method applicable to the co - extraction of deep brine and shallow soluble salts, characterized in that, The following steps are involved: 1) First, a carbon dioxide injection well (9) is constructed in the deep brine reservoir (1) as a brine displacement well, and a deep brine production well (3), and a group of docking wells are constructed in the shallow soluble salt layer (2); then, a carbon dioxide pressurizing station (10) is set at the wellhead of the brine displacement well, and a mobile adsorption vehicle (4) is set at the wellhead of the deep brine production well (3). The mobile adsorption vehicle (4) is a skid-mounted, movable, and highly efficient lithium ion adsorption integrated equipment that can realize efficient extraction of brine lithium resources; then, a brine pressurizing recharge station (5) is added behind the mobile adsorption vehicle (4), and thus, the deep brine production well (3), the mobile adsorption vehicle (4), and the brine pressurizing recharge station (5) are sequentially connected using a pipeline with an anti-corrosion coating inside; 2) Opening the carbon dioxide boosting station (10) to make the wellhead pressure of the brine displacement well reach the preset pressure of the deep brine fluid, and after starting to inject carbon dioxide into the deep brine reservoir (1), opening the deep brine production well (3) for production; 3) After the deep brine production well (3) is opened, a certain flow rate is maintained to keep the pressure of the carbon dioxide pressure station (10) constant. By adjusting the flow rate of the deep brine production well (3), the balance between the carbon dioxide pressure and the fluid pressure of the aquifer (11) is maintained to prevent overflow recharge; 4) Directly extract lithium by adsorption after deep brine mining, selectively adsorb lithium resources in the brine to achieve the extraction of lithium resources in deep brine; 5) After the lithium resource is extracted, the remaining brine enters the brine pressure reinjection station (5) and is pressurized before being injected into the shallow soluble salt layer (2) through the injection end (6) of the docking well (8) to dissolve the soluble salt; 6) Finally, the brine resources after dissolution equilibrium are mined through the mining end of the docking well (8) to the ground and enter the salt field or treatment terminal, realizing the leaching mining of shallow soluble salt resources; 7) During the exploitation of the shallow soluble salt layer (2), the development degree of the shallow salt caverns (12) is explored by using surface transient electromagnetic or microtremor exploration methods. After exploration and evaluation, for the salt caverns (12) with suitable sealing conditions for carbon dioxide storage, carbon dioxide is injected into them to implement carbon dioxide salt cavern storage.

4. A carbon dioxide sequestration method applicable to the co - mining of deep brine and shallow soluble salts according to claim 3, characterized in that, Lithium extraction by adsorption is carried out by a mobile adsorption vehicle (4); or by means of strong evaporation, the concentration and collection of salt resources in the brine are realized, and then the evaporated water is cooled and collected in the brine pressurized reinjection station (5) and then injected into the shallow soluble salt layer (2) to implement solution mining.

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