Environmentally and technically suitable salt rock goaf abandoning method and system

Abstract

The invention relates to the field of application of methods and systems for filling, sealing and discarded (abandoned) salt rocks, in particular goaf located in a heterogeneous salt structure (in which a porous / permeable formation is present), or a goaf close to a geological fault, or even a goaf experiencing collapse at the top of the goaf, or in particular a goaf in a non-homogeneous salt structure (in which a porous / permeable formation is present), or even a goaf undergoing collapse at the bottom of the goaf. These can be performed simultaneously with and integrated with the disposal of field facilities. More specifically, the invention is used for the disposal of civil engineering structures in rock salt production and / or storage sites by applying a dissolution mining process, where the goaf needs to be filled by filling solid material, where the recovered solid material is produced by comminuting demolition waste from the disposal civil engineering structures (in-situ) or other areas of the project facility, and where the solid material is recovered from the disposal civil engineering structures (in-situ) or other areas of the project facility. Through its on-site or off-site mobile recovery device (grinding / comminution / screening), larger particle size waste (gravel) is added to the bottom of the SRC, while smaller particle size waste (sand) is added at the end of SRC filling to block voids and faults.

Description

Technical Field

[0001] The present invention is applicable to methods and systems for filling, sealing and abandoning (discarding) goafs constructed in salt rock, particularly goafs located in heterogeneous salt structures (with porous / permeable rock layers within the salt layer), or goafs near geological faults, or even goafs that have experienced top collapse, all of which can be carried out simultaneously with and integrated with the abandonment of on-site facilities.

[0002] More specifically, by applying a dissolution mining process, this invention is used for the disposal of civil structures in rock salt production and / or storage sites, where it is necessary to fill the goaf with solid materials, wherein the recovered solid materials are obtained by crushing the discarded civil structures from the project facility. On the spot Waste generated from demolition in other areas is collected through on-site or off-site mobile recycling units (grinding / crushing / screening), where larger particles (gravel) are added to the bottom of the SRC, while smaller particles (sand) are added at the end of the SRC filling to seal voids and faults. Background Technology

[0003] Rock salt is a rock primarily composed of rock salt (NaCl). It is one of the most widely used raw materials for the production of chlorine, caustic soda, hydrochloric acid, and sodium bicarbonate. It is also a component of various products in the pharmaceutical, personal hygiene (soap, detergent, and toothpaste), clothing, footwear, and civil engineering piping industries. Furthermore, it is widely used in the textile, military, paper, pulp and glass industries, as well as in water treatment.

[0004] Rock salt can generally be mined in two ways. When the deposit is at the surface, rock salt is mined underground using mechanical methods. However, when the deposit is deep or vertically distributed, rock salt is mined using a dissolution mining method. This can be summarized as follows: constructing a channel well; injecting water; then dissolving the rock salt and pumping it to a surface processing facility. This method has advantages over methods that obtain rock salt through seawater evaporation and purification, as the purity and concentration are much higher (up to ten times higher).

[0005] It is worth mentioning that the solution mining method is called leaching, which involves dissolving and removing the chemical components of the salt rock with water (fresh water or NaCl saturated water) [(PEREIRA JC, Solution Mining Research Institute (SMRI). Research Report RR2012-03. Common Practices – Gas Cavern Site Characterization, Design, Construction, Maintenance, and Operation. 2012)], which creates voids in the host rock, called salt caverns (SRC).

[0006] Specifically, the process begins by drilling one or more channel wells, drilling into the rock until reaching an area near the top of a goaf formed by a leaching process. Then, the drill string is removed and a steel casing (casing) is inserted and cemented to provide a seal between the drilled rock layers.

[0007] Two concentric tubing strings are lowered to near the bottom of the channel well. One is used for water injection, and the other for brine reflux. Compared to the outer tubing string, the innermost tubing string has a smaller diameter and a slightly larger length (tens of meters) to optimize rock salt production.

[0008] Rock salt production and SRC formation begin with the circulation of fresh or seawater to dissolve the salt rock walls. It is important to note that the higher the temperature and flow rate of the injected water, the more efficient the salt dissolution. When the injected water becomes saturated, it is replaced with new unsaturated water. By circulating a high flow rate of unsaturated water through the salt, this process dissolves a large amount of salt, leaving a large space to be filled with water, thus forming the SRC.

[0009] Once the rock salt mining life of the deposit ends, due to the inherent properties of salt rock such as negligible porosity and permeability, and compressive strength similar to concrete (POIATE Jr E), Mecânica das Rochas e Mecânica Computacional para Projeto de Poços de Petróleo em Zonas de Sal(RockMechanics and Computational Mechanics for the Design of Oil Wells in SaltZones). Doctoral dissertation, Pontifical Catholic University of Rio de Janeiro, PUC Rio, December 2012), SRC produced by the leaching process can be used to store compressed air, hydrocarbons, hydrogen, waste, etc. (CROTOGINO et al., HUNTORF CAES: More than 20 Years of Successful Operation, Solution Mining Research Institute, Spring Meeting, Orlando, Florida, USA, 2001; USDEPARTMENT OF ENERGY, Strategic Petroleum Reserve Storage Sites. Available at: http: / / www.fossil.energy.gov / programs / reserves / spr / spr-sites.html; EVANS DJ, CHADWICK RA (EDS). Underground gas storage: Worldwide experiences and future development in the UK and Europe. Geological Society, London, Special Publication, 313, 93-128. 2009; LORD, AS Overview of geological storage of natural gas with emphasis on assessing the feasibility of storing hydrogen. SAND2009-5878. SandiaNational Laboratories. 2009; MUNSON et al., Approach to first principles model prediction of measured WIPP (Waste Isolation Pilot Plant) in-situ room closure in salt.Tunneling and Underground Space Technology, 5, 135, 1990; VEIL et al. Disposal of NORM-contaminated oil field wastes in Salt Caverns. UnitedStates: N. p., 1998. Web.doi:10.2172 / 808431).

[0010] However, it is only possible to use SRCs for storage purposes if prior research has been conducted and the dimensions of the SRCs have been carefully confirmed using sonar to analyze the actual conditions using appropriate global technical standards and recommendations. Otherwise, a decommissioning plan for the SRCs and channel wells must be implemented, which must include risk mitigation measures, the provision of dismantling equipment, sealing of the channel wells, and monitoring of the area to confirm settlement over time.

[0011] According to API-1114 (American Petroleum Institute (API), Recommended Practice 1114. Recommended Practice for the design of solution-mined underground storage facilities. Second edition, January 2013), in the prior art, the disposal of SRCs at the end of their operational cycle must be carried out in accordance with current regulations. In the absence of regulations, the following procedures may serve as guidance.

[0012] First, when a rock salt production SRC is used for storage, the stored product must be removed by injecting brine into the goaf. If possible, wellhead equipment and all overhead pipelines should be dismantled.

[0013] After removing equipment and materials, the interior of the production string should be filled in the following locations: a mechanical plug (bridge plug) should be placed near the bottom of the production string, and a bottom plug should be placed above it. The top plug should be located approximately 15m above the salt layer; in areas with aquifers, the bottom and top plugs should be installed 30m below the base of the layer and 60m above the top, respectively; the top and bottom plugs should be installed 2m below the surface and 30m below that surface, respectively. The space between cemented zones should be filled with an acceptable weight of saturated brine or non-corrosive drilling fluid.

[0014] Finally, a metal plate was installed on the coating 2m below ground level, and then backfilling was carried out.

[0015] According to API-1170 (American Petroleum Institute (API). Recommended Practice 1170. Design and Operation of Solution Mined Salt Caverns Used for Natural Gas Storage. First edition, July 2015), there is no industry consensus on best practices for SRC decommissioning. Most decommissioning attempts involve processes similar to those implemented in the hydrocarbon exploration and production industry.

[0016] However, some steps should be taken before abandonment: remove stored gas; if the SRC used for rock salt production is used for gas storage, mechanical integrity testing should be performed after gas removal; remove the suspension tubing; inspect the production tubing; sonar inspection; long-term monitoring process (if the access well is not sealed). If unexplained changes occur in the local topography, monitoring of the sealed goaf must include regular settlement assessments and visual inspections.

[0017] According to the recommendations of the Solution Mining Research Institute (SMRI) (PEREIRA, JC, SMRI. Research Report RR2012-03. Common Practices – GasCavern Site Characterization, Design, Construction, Maintenance, and Operation, 2012), the basic concepts of SRC decommissioning that must be met when developing a SRC goaf sealing and decommissioning plan are: providing long-term protection to prevent aquifer contamination and release of hazardous substances to the surface when the SRC used for producing rock salt is used for gas storage; providing long-term stability to the rock surrounding the goaf; requiring no maintenance; allowing the application of methods and materials as much as possible; being accessible; being acceptable to the competent authorities; being able to replenish the stored liquid with brine (preferably) or water; conducting tests and calculations to estimate the hydraulic, thermal, and mechanical properties of the in-situ rock; waiting for the temperature between the brine and the rock to stabilize as needed (in special cases, it may be necessary to heat the brine to reduce the waiting time); decommissioning the goaf (shaft sealing activities); and monitoring the surface.

[0018] It is also recommended to conduct an integrity test on the production tubing shoe before sealing the wellbore to ensure there are no faults that could cause leakage of the stored material. Furthermore, all equipment (packers, overhead lines, etc.) inside the wellbore must be removed before installing the sealing plug. Additionally, proper wellbore cleaning must be performed.

[0019] For the final location of the sealing plug, three options are recommended: the bottom of the production tubing, provided that the integrity and impermeability of that area are guaranteed; the unsleeved area between the production tubing shoe and the top of the goaf, provided that the area has sufficient length and cross-sectional area to allow for packer installation. The sealing plug is installed in a milled opening above the packer. Regardless of which area is ultimately chosen for the sealing plug installation, the area above it must be completely cemented.

[0020] Long-term stability must be ensured by monitoring surface movement to verify whether subsidence has occurred in the area. For mined-out areas used for brine production, this period can last approximately 20-30 years.

[0021] According to the British Geological Survey (BGS) standard, the public report Or / 07023 (An Appraisal of Underground Gas Storage Technologies and Incidents for the Development of Risk Assessment Methodology (2007)) indicates that, in the existing technology, studies must be conducted before decommissioning a SRC to determine strategies for decommissioning, abandoning, and mitigating the risks associated with this step. It is known that pressure within a goaf changes over time. Therefore, analysis / simulation must be performed to predict this change and mitigate the resulting risks. Five possible causes of goaf pressure changes are: rock salt creep; thermal expansion of fluids in the goaf (in some cases, this can be more critical than rock salt creep); fluid loss through porous media (the salt interface with other types of materials); leakage along the wellbore; and further dissolution and precipitation of salt in the goaf.

[0022] According to British Standards Institution (BSI) standard BS EN 1918-3:2016 (Gas infrastructure – Underground gas storage – part 3: Functional recommendations for storage in solution-mined salt caverns, 2016), in the prior art, for the decommissioning of a Storage Reservoir (SRC) at the end of its operational cycle, studies and measurements must be conducted to verify the safety of the site after SRC decommissioning. A specific decommissioning plan must be developed. A plug must be installed in the wellbore to ensure the mechanical stability of the salt layer and maintain the seal between the goaf and the surface. Long-term simulations of evaporite creep and the resulting casing bottom pressure must be performed to confirm the structural stability of the goaf to be decommissioned. SRC decommissioning includes: removing gas from the goaf when the SRC used for gas storage in rock salt production; priming the goaf with water or brine and waiting for temperature stabilization before sealing the wellbore (this process may take several years); monitoring the goaf; installing a plug and decommissioning the wellbore; decommissioning surface facilities; and monitoring.

[0023] In 2006, Crotogino and Kepplinger summarized several foundational R&D projects undertaken by the Solution Mining Research Institute (SMRI) for key aspects of SRC sealing and abandonment, known as Goaf Sealing and Abandonment (CSA), which formed the basis for the development of a general manual for planning and implementing this activity.

[0024] In existing technologies, as SRCs are discarded at the end of their operational cycle, it is possible to permanently encapsulate brine-filled SRCs within homogeneous salt structures, such as salt domes and thick salt layers. Figure 1 a) where stability and integrity are almost entirely guaranteed by the salt rock. In these cases, provided specific site conditions are met, uncontrollable brine eruptions are not expected in the caprock, drinking water aquifer, or surface.

[0025] As a logical first step in developing a CSA procedure for a specific SRC, this concept must meet the following requirements: when an SRC producing rock salt is used to store hydrocarbons or other products, it must be protected against long-term contamination of drinking water aquifers and the release of brine and / or flammable and / or hazardous products into the environment (product residues on the surface); maintain the long-term stability of the rock mass surrounding the goaf; require no maintenance; apply tested and validated methods and materials as much as possible; be accessible; and obtain approval from the authorities.

[0026] The following steps are necessary: ​​assess the pre-sealing conditions of the SRC channel well; replace the storage fluid with brine or water when the SRC producing rock salt is used to store hydrocarbons or other products; assess the minimum waiting time for pressure and temperature stabilization before sealing the SRC; determine and perform the sealing; and monitor the parameters.

[0027] In the first phase of development, the authors analyzed existing experience and regulations for oil and gas wells, aiming to integrate these experiences into the SRC's CSA concept as much as possible, and then analyzed existing SRC regulations (Germany, the United States, the Netherlands, and Poland).

[0028] Specifically, for sealing the SRC, a cement waste plug is used to ensure a long-term seal. Given that most SRCs are relatively shallow compared to oil and gas wells, this means that continuously cementing the casing shoe at the end of the SRC channel to the surface has technical and cost advantages over alternating cement plugs. This process should be carried out after the brine present in the SRC has reached temperature equilibrium with the surrounding rock. Finally, the wellhead of the SRC channel is removed, a concrete slab is placed, and surface conditions such as settlement are identified and monitored.

[0029] according to Política Nacional de Resíduos Sólidos( According to the National Solid Waste Policy (PNRS), Law No. 12,305 of August 2, 2010, waste is a precise term referring to something that has been discarded, is no longer of use, and is classified according to its origin and hazard. However, waste is understood to mean something that becomes useful in other production processes through recycling, such as as an industrial feedstock. The term 'waste' is used to mean something that cannot be reused, recycled, or composted. Therefore, waste is understood to mean solid waste for which no other possibility exists except adequate environmentally sound final disposal after all possible treatment and recycling methods have been exhausted by available and economically feasible technical means.

[0030] According to ABNT standard NBR 10.004 / 04, waste classification in Brazil is determined by considering the potential hazards that waste may pose to the environment and public health. Waste classification involves identifying the processes or activities that generate waste, as well as their composition and characteristics, and comparing these components with a list of wastes and substances known to have health and environmental impacts. In ABNT NBR 10.004 / 04, waste is classified according to the characteristics of hazardous, inert, and non-inert waste: Category I waste – hazardous waste, refers to waste that is hazardous and has characteristics such as flammability, corrosivity, reactivity, toxicity, and pathogenicity; Category IIA waste – non-inert waste, refers to waste that does not belong to Category I – hazardous waste or Category IIB – inert waste, and therefore may have characteristics such as biodegradability, flammability, or water solubility; Category IIB waste – inert waste, refers to any waste whose dissolved concentration of any component, except for appearance, color, turbidity, hardness, and odor, does not exceed drinking water standards when sampled in a typical manner and subjected to dynamic and static contact with distilled or deionized water at room temperature. It is worth noting that ABNT NBR 10004 does not involve radioactive waste, as this falls under the category of... Comissão Nacional de Energia Nuclear( The exclusive jurisdiction of the National Nuclear Energy Commission.

[0031] according to Conselho Nacional do Meio Ambiente (Resolution 307 / 2002 of the National Environment Committee (CONAMA) established guidelines, standards and procedures for the management of structural demolition waste (C&D waste), which is classified as follows (Article 3): Category IA, waste that can be reused or recycled as aggregate, such as: a) soil from the construction, demolition, renovation and repair of paving and other infrastructure works, including earthwork operations; b) Waste from construction, demolition, renovation, and repair of buildings: ceramic components (bricks, blocks, tiles, cladding, etc.), mortar, and concrete; c) Waste from the manufacturing and / or demolition of precast concrete components (blocks, pipes, curbs, etc.) produced on construction sites; waste from the manufacturing and / or demolition of precast concrete components (blocks, pipes, curbs, etc.) produced on construction sites; Class II–B: waste that can be recycled for other purposes, such as plastics, paper, cardboard, metals, glass, wood, and plaster; Class III–C: waste for which no economically viable technology or application has been developed for recycling or reuse; Class IV–D: hazardous waste from construction processes, such as paints, solvents, oils, etc., or polluting or health-hazardous waste from the demolition, renovation, and repair of radiology clinics, industrial facilities, etc., as well as tiles and other articles and materials containing asbestos or other health-hazardous products.

[0032] Existing technology

[0033] As described below, some existing technical literature has addressed the issue of abandoned salt rock goaf (SRC):

[0034] The document from the Brazilian Institute of Mining and Geology Guia para Planejamento do Fechamento de Mina The paper, “Guide for Mine Closure Planning”, Brasília, 2013, addresses post-mining legacy issues and the socio-economic and environmental problems associated with mine closure planning. Presented in a guiding manner, the document offers a series of general recommendations, drawing on contexts and case studies specific to Brazil, to provide a perspective closer to the country's mining realities in managing mineral development involving mine closure steps, with the aim of promoting long-term sustainable development in the regions where mining activities take place.

[0035] However, the aforementioned literature reports that "access to the underground excavation area was blocked by demolition waste from surface facilities." In other words, this simple process of sealing off the mine excavation area access (at the entrance) is equivalent to abandoning SRC in homogeneous salt structures (salt domes or thick ore layers) using existing technology. This is similar to the practice in the hydrocarbon exploration and production industry of applying a sealing plug only at the well passage (entrance) when a well is abandoned. Therefore, all roadways and mining areas lack filling material (leaving only air), which can lead to compaction in the area, causing ground subsidence, especially in areas with SRC.

[0036] It is worth noting that sealing passages in underground excavation areas with demolition waste from surface facilities does not truly seal the passages (it is not a water-chemical-mechanical-biological barrier), as it only provides partial mechanical obstruction for animal and human access; therefore, fluid can pass through (from the outside in) and flood the roadways and mining areas. If this process occurs during the abandonment of SRC, the increased pressure of the fluid within the goaf during SRC closure due to creep (pressure buildup) causes the fluid to seep out through the inlet (from the inside of the SRC to the outside), because the inlet was merely sealed with demolition waste (without mention of classification, particle size, filling sequence, etc.) and not truly sealed. As a result, the integrity of the SRC may be compromised, potentially leading to significant ground subsidence (forming a settlement funnel), causing damage to any civil / mechanical structures and even nature, such as river and road diversions and structural damage. Moreover, over time, SRC closure may lead to the collapse of the SRC roof and even the creation of cavities (sinkholes) on the surface. Additionally, the leakage of SRC fluid through passages blocked only by demolition waste from surface facilities can prematurely trigger environmental problems.

[0037] paper" Descomissionamento e abandono permanente de poços contextualizaç ão do cenário nacional” (“Decommissioning and permanent abandonment of wells: contextualization of the national scenario”) (Castro et al., 2021, in IV CONEPETRO– Congresso Nacional de Engenharia de Petróleo, Gás Natural e Biocombustíveis Presented at the National Conference on Oil, Gas and Biofuels Engineering, this paper outlines the general characteristics of permanent well decommissioning projects (hydrocarbon production unit shutdowns) and presents key international decommissioning standards. It aims to assess the current status and future prospects of this practice in Brazil, along with their temporal and economic context. The paper then describes so-called universally accepted barriers and the main causes of problems arising from improper decommissioning that can lead to environmental damage. Finally, it provides a quantitative assessment of current decommissioning projects in Brazil and potential investments in the coming years.

[0038] Paper "Post-mining Use of Underground Space For Waste Storage" (Dinis daGama C, Paper presented at the 7 th The ISRM Congress, Aachen, Germany, September 1991. Paper No.: ISRM-7CONGRESS-1991-017 describes a method for the (long-term) storage of (municipal, industrial, toxic, and radioactive) waste (recyclable and / or reusable materials) in abandoned or decommissioned underground mines as a means of additional monetization in the mining industry and a reliable environmental solution. Furthermore, it cites the advantages of using underground space, such as: a) near-constant underground temperature, which is advantageous for a range of stored products; b) easy humidity control and easy protection of groundwater quality; c) excellent security, suitable for fire prevention, flood control, hurricane protection, and rain and snow protection; d) better preservation of insect and bacterial growth compared to traditional warehouses; e) significantly reduced material loss and product degradation; f) no solid, liquid, or gaseous contamination of the soil surface, and no deforestation or landscape damage.

[0039] However, in underground mines located in areas with geological faults and / or highly permeable sedimentary layers and / or roof collapses and / or seismic activity, adjustments are necessary to prevent waste (through fractures and faults or permeable sedimentary layers) from moving and contaminating groundwater. Therefore, it would be better (safer and cheaper) to design, construct, and operate dedicated underground storage facilities for the permanent storage of waste (radioactive and / or toxic) in favorable and waterproof geological locations and environments, in the absence of geological faults (fractures) and / or highly permeable sedimentary layers and / or roof collapses, as has been done at the Yucca Mountain Storage Facility (Nevada, USA) and the Waste Isolation Pilot Plant (New Mexico, USA). These facilities include mine access for monitoring and maintaining the storage facilities, as well as multiple protective barriers to prevent leakage of stored products.

[0040] The paper “Design and Management of Salt Solution Caverns for Toxic WasteDisposal” (Davison et al., 1997, Petroleum Society of CIM, paper number 97-151) describes a safe, practical, and cost-effective alternative for managing low-level radioactive waste and toxic industrial waste, which involves disposing of such waste in underground salt caverns (solution cavern disposal - SCD). This ensures long-term isolation of the waste, thus becoming a means of permanent environmental safety, while being more economical than other methods such as landfill, chemical treatment, and incineration. The document also raises questions about the required characteristics of an ideal waste storage facility, such as: 1. Low likelihood of negative interactions with the biosphere; 2. Relatively simple, economical, and flexible waste disposal technologies; 3. Management methods for permanent waste disposal must facilitate social acceptance through a clear understanding of all process aspects; 4. Waste transport, treatment, and disposal processes must be safe, comply with health and occupational safety agency requirements, and address the concerns of affected communities; 5. The storage facility location must be permanent, not impairing current or future surface use, and requiring no permanent follow-up maintenance or any long-term (e.g., >10 years) treatment; 6. The price of the disposal method must enable its economic operation.

[0041] The aforementioned paper defines engineering waste as any waste with low solubility in saturated brine, which should not contain significant amounts of gasoline or ethylene glycol, may contain up to 10 vol% of dry residues of highly viscous immiscible gases (chlorinated hydrocarbons, greases, and high molecular weight aromatic hydrocarbons), should not contain any amount of organic waste, and may contain inert plastics and resin particles. Furthermore, without excluding other suitable wastes, the paper identifies examples of materials suitable for disposal in salt goafs (SCDs): inert solids rich in toxic metals; low- and intermediate-level radioactive wastes; molten wastes and slags containing toxic or hazardous substances, elements, or compounds; cement, gypsum, and other building materials containing asbestos fibers; solids and soil contaminated with small amounts of greases and viscous concentrated hydrocarbons; sludge and other process wastes containing heavy metals; spent ceramic catalysts and contaminated reaction beds; and other insoluble materials from industrial processes, petroleum refining, accidental spills, and mineral processing. These wastes may also contain significant amounts of water, which, when mixed with particulate salt, will form saturated brine. Waste may be in the form of large solid particles, such as asbestos cement. In this case, it must be crushed to meet the specifications required for mixing and injection into the SCD through the channel pipe. The maximum diameter of the solid particles is one-fifth of the inner diameter of the injection pipe to avoid clogging during the process.

[0042] The document further clarifies that there are two types of SCDs that can be used for storage purposes: 1. Goafs specifically designed to meet waste toxicity levels; 2. Goafs previously formed for use as storage caverns (2a) or for saturated brine extraction for industrial purposes (2b). However, it notes that in the latter case, the geometry (size and shape) of the goaf will determine its use. For example, in the case of an SRC for hydrocarbon storage (2a), it may be teardrop-shaped or inverted cone-shaped, with thick tops and bottoms and well-separated from adjacent caverns; if the goaf is intact, it can be used as a storage facility for all toxic wastes; and if the goaf has been damaged and the overlying strata have been exposed or the top of the goaf has collapsed, its use should be limited to the disposal of non-toxic to low-toxic wastes.

[0043] Regarding the filling process of the SCD, the aforementioned paper states that it is implemented through a pipe (with a backflow check valve), in which brine is drawn from the top of the SRC through the annular outside of the SRC channel well and mixed with waste (particulate form with a specific density greater than brine and unable to be suspended colloidally in brine) to be injected into the SRC as a slurry. In this way, the waste settles rapidly at the bottom of the SRC, filling the SRC with an angle of repose of less than 5 degrees, eliminating most of the potential surface subsidence that might occur over time, even among loose rock fragments within the SRC.

[0044] Therefore, according to ABNT NBR 10004, the aforementioned documents permit the storage of hazardous waste (Category I waste) and non-hazardous waste (Category II A waste). Furthermore, in accordance with CONAMA (Resolution 307 / 2002), the aforementioned documents also mention the possibility of storing Category B, C, and D C&D waste (asbestos fibers) in salt rock goafs. This contradicts National Environment Committee (CONAMA) Resolution 384 of 2004, which, for example, stipulates that products containing asbestos as a raw material may not be disposed of at any location. It recommends that asbestos be disposed of together with hazardous waste in dedicated landfills. This also contradicts global environmental standards.

[0045] In addition, the above documents contain conceptual errors. For example, using the collapsed SRC as a storage facility for low-toxic waste does not guarantee the long-term isolation of waste or environmental safety, because waste will flow through the permeable sedimentary layer (above the top of the collapsed goaf), thus contaminating groundwater, and may even reach the surface through existing geological faults or cracks on site or caused by the collapse of the SRC top (infiltration process).

[0046] Using previously constructed goafs for industrial purposes as storage repositories for all toxic wastes does not guarantee long-term waste isolation or environmental safety. If the goaf contains heterogeneous salt layers (clay mineral interlayers, highly permeable sedimentary layers, and other non-evaporable rocks within the SRC), or if the goaf is near geological faults and / or fractures (whether active or not) within its radius of influence, waste flow through interlayers or faults (reactivated and opened) or fractures can contaminate groundwater and even cause fluid seepage at the surface.

[0047] Specifically, regarding the disposal of the collapsed SRC, only the process of filling the SRC with granular material (with a diameter at most 1 / 5 of the manhole diameter and an average porosity of approximately 42%) to at most 90% of its dissolved volume (the geometric volume of the SRC) is mentioned; therefore, only 37.8% (0.90 x 0.42 = 0.378) of the SRC volume is filled with granular material, while the remaining 62.2% of the SRC volume contains brine. Subsequently, cement is injected into the manhole of the SRC. In this way, due to the creep behavior of the salt rock, the SRC will seal over time (potentially for several years to decades due to inadequate disposal), compacting the granular material, and draining the 62.2% brine volume through geological faults, fissures, and permeable materials, thereby forming a settlement funnel on the ground above the goaf (around the manhole), damaging equipment, structures, etc., the impact of which has been generally described.

[0048] Therefore, under such a scenario and conditions of abandonment of a collapsed SRC, the aforementioned literature does not maximize disposal capacity, nor can it guarantee the long-term isolation of waste, or even guarantee environmental safety.

[0049] This invention addresses the aforementioned problems by sequentially filling SRC (Structured Concrete Reinforced Plastic) with granular materials of varying diameters (e.g., Category A C&D waste), from the largest diameter (crushed stone 3, crushed stone 2, crushed stone 1, crushed stone 0) to the smallest diameter (coarse sand, medium sand, fine sand) to form a structural framework. The SRC is then pressurized, and the channel wells are subsequently sealed with cement. This method achieves a SRC filling volume greater than 95% (higher efficiency) while using non-polluting and harmless C&D waste to plug or seal faults (no reactivation and no openings) or cracks or permeable materials, thereby significantly reducing or eliminating the resulting settling funnels and preventing surface water pollution or leachate formation (more effective problem-solving). Notably, for example, when using Category A C&D waste, these materials are characterized by their non-decomposition and unchanged composition over time, thus preventing pollution because they do not alter the soil or water environment by releasing environmentally harmful substances upon contact with soil or water.

[0050] paper" Reciclagem de Resíduos Sólidos da Construção Civil do Portal Res íduos Sólidos The article "Recycling of Solid Wastes from Civil Construction of the Solid Waste Portal" (https: / / portalresiduossolidos.com) describes how solid waste is recycled from structural demolition waste (C&D waste) and what recycling equipment can be used for this waste. It also reports that the volume and weight of C&D waste generated are enormous, and a large portion of it does not receive adequate final disposal.

[0051] Specifically, the waste mentioned in the paper refers to Category A C&D waste as defined by CONAMA Resolution 307, and according to NR17 01, as defined by the European Waste Inventory. This includes construction, demolition, renovation, and repair waste from paving and other infrastructure works, including soil from earthwork operations and the construction, demolition, renovation, and repair of buildings. The latter three categories consist of ceramic elements (bricks, blocks, tiles, cladding, etc.) as well as mortar and concrete, derived from the construction and / or demolition processes of precast concrete components (blocks, pipes, curbs, etc.) produced on-site. After selective collection, C&D waste undergoes a grinding process. Therefore, the components are mixed together, resulting in low added value. Only after granulation, i.e., separation of the components, can appropriate uses be assigned to the new materials (sand, gravel, pea gravel, crushed stone, etc.) recovered from C&D waste, increasing their value. Additionally, this can reduce pressure on natural resources and extend the lifespan of landfills.

[0052] The aforementioned paper also describes C&D waste recycling units as being categorized into two types based on their mode: stationary and mobile units. Mobile C&D waste recycling units (MRP) essentially consist of three components: a roll-on / roll-off truck, a mobile shredder connected to the truck, and a mobile rotary screen, the latter two powered by diesel or electricity. The biggest advantage of MRP is its mobility to locations requiring service, its versatility, and its ability to improve profitability, particularly through reduced logistics costs. On the other hand, stationary C&D waste recycling units (FRP) have fixed locations, no trucks, but use conveyor belts to transport C&D waste to the shredder, and offer greater processing capacity and higher yields. However, their logistics costs are higher because they must receive C&D waste, process and granulate it, and then transport this waste to the point of use.

[0053] Therefore, the aforementioned literature differs from the present invention in that it does not provide procedures for filling, sealing, and discarding (abandoning) SRC in heterogeneous salt structures, i.e., SRC in elongated salt layers containing clay mineral interlayers (highly permeable sedimentary layers within the SRC) and other non-evaporable rock layers, nor does it provide procedures for discarding SRC within the SRC's influence radius that is close to geological faults and / or fractures (whether active or not). Furthermore, the vast majority of prior art literature does not address SRC with collapsed tops.

[0054] Therefore, given the difficulties inherent in the prior art, namely the difficulties associated with the disposal of SRCs in heterogeneous salt structures (porous and permeable rock within SRCs) and / or near geological faults and / or with collapsed tops, there is a need to develop a technology capable of implementing the filling, sealing, and disposal (disposal) of SRCs in an environmentally friendly, technically safe, effective, and economically feasible manner. As mentioned above, the prior art does not possess the unique characteristics that will be detailed below. Summary of the Invention

[0055] This invention relates to methods and systems for filling, sealing, and constructing goafs in abandoned salt rock, particularly goafs located in heterogeneous salt structures (with porous / permeable rock layers within the SRC) and / or near geological faults (whether active or not) and / or that have experienced goaf roof collapse. By filling the SRC with Class A recycled demolition waste (C&D waste) (from or not from the civil engineering project itself), the costs of abandonment / disposal are significantly reduced, risks are mitigated, and greenhouse gas (GHG) emissions are decreased, while promoting the environmentally friendly disposal of recycled demolition waste.

[0056] The method of filling the SRC is carried out sequentially, that is, firstly, larger-grained materials (crushed stone 3, crushed stone 2, crushed stone 1, crushed stone 0) are used, followed by smaller-grained materials (coarse sand, medium sand, fine sand) to form a structural framework, seal voids and faults / cracks, pressurize and monitor the SRC, then fill the channel well with cement, and finally complete the permanent disposal of the SRC.

[0057] As described in the prior art, dissolution mining of rock salt extraction in homogeneous salt layers is recommended because the leaching process will create goafs in the salt rock, where the sealing and disposal of the SRC at the end of its service life can be carried out by the brine in the disposed SRC itself, and the goaf passage well can be sealed with or without cement.

[0058] However, it is inappropriate to seal SRCs with air or brine, regardless of whether they are sealed with cement, in cases where SRCs constructed in heterogeneous salt layers (where porous / permeable rock layers exist within the salt layer), and / or near geological faults, and / or where rock salt production has dissolved the SRC protective slab (top) (the rock thickness between the top of the SRC and the rock above the salt layer) and caused the top of the SRC to collapse. Similarly, it is inappropriate to fill the collapsed top of an SRC with non-toxic or low-toxic waste, hazardous waste, or any type of C&D waste.

[0059] If existing processes used for sealing and decommissioning SRCs occur in SRCs located in heterogeneous salt structures (with porous / permeable rock layers within the salt layer) and / or near geological faults, during SRC sealing, increased fluid pressure within the goaf due to creep processes (pressure accumulation) causes fluid to permeate through non-evaporable rock layers present in the SRC (because these layers have high permeability and porosity) and / or through geological faults. Increased fluid pressure can also fracture the non-evaporable rock and cause geological faults to open or reactivate, contaminating the aquifer and potentially causing fluid seepage at the surface. This can compromise the integrity of the SRC, leading to significant surface subsidence (formation of subsidence funnels), which is detrimental to any civil / mechanical structure and even nature, such as river diversion and road detours, and causing structural damage. Over time, SRC sealing can lead to the collapse of the top of the SRC and even the formation of cavities (sinkholes) in the ground.

[0060] In this way, the methods and systems developed by the present invention can implement the filling, sealing and disposal (rejection) of SRCs by gradually and sequentially filling SRCs with recycled solid materials of different particle sizes, said solid materials being generated by crushing and recycling Class A structural demolition waste (C&D waste) from rock salt production or storage projects (in situ) or other location facilities.

[0061] At the end of SRC filling, the casing shoe from the end of the SRC channel well to the ground is sealed and disposed of with a cement plug.

[0062] Through the described process, voids are better filled, and as the SRC closes, the filling material within the SRC compacts more quickly (almost immediately), with negligible ground subsidence. The process also seals geological faults and fluid infiltration through the SRC into the non-evaporating rock layers present in the heterogeneous salt rock layers. Therefore, stability issues, seismic activity, ground subsidence, seepage, and sinkhole formation within the SRC are avoided.

[0063] The method described herein is intended to replace the following applications: (i) precast bricks, which generate high energy consumption, incur transportation costs, require a considerable degree of compaction (15-20%), and are not effective enough in sealing voids and faults (Rolfs et al., 1993: Rock Mechanical Studies on the Post-operational Phase of a DisposalCaverns - 3rd Conference on Mechanical Behavior of Salt, Paliseau, France); or (ii) sand extracted and transported from licensed mines several kilometers away from the SRC, which is costly (long extraction time and high GHG emissions, as a truck can only transport a maximum of 15m³). 3 (SRC may require thousands of transports), and there is also a high risk of noise generation and traffic congestion due to trucks traveling to and from the licensed mine (collecting sand and / or bricks to SRC).

[0064] In addition, this invention makes it possible to avoid the disposal of Class A civil engineering waste (C&D waste) and demolition waste (wreckage) in landfills, and avoids the problems associated with transporting waste from the SRC project to the landfill by truck (thousands of transports).

[0065] Therefore, the SRC filling and disposal method of the present invention can achieve: significantly reduce the total disposal cost, reduce greenhouse gas emissions, shorten implementation time, reduce noise generation, reduce truck traffic, improve efficiency, increase safety and reduce risks (ground subsidence and traffic accidents), provide an environmentally friendly and sustainable final disposal solution for structural demolition waste by recycling structural demolition waste, and also provide an environmentally friendly disposal destination for SRC brine.

[0066] Therefore, the methods and systems described and claimed in this document are not only economically feasible, but also environmentally and technically suitable, enabling the filling, sealing, and disposal processes of SRC to be carried out simultaneously and integrated with the project's (civil structure's) decommissioning, thus exceeding the limitations of existing technologies. This leads to better results. Attached Figure Description

[0067] To make the invention easier to understand, Figure 1-11 (As appended to and forming part of this specification) is given in a descriptive manner and is not intended to limit the invention.

[0068] Figure 1 a-1e, adapted from Crotogino F & Kepplinger J. Cavern well abandonment techniques guidelines manual. SMRI. 2006, schematically illustrates the current state of technology for SRC abandonment in homogeneous salt formations. In this sense, the figures depict: 1a) the definition of a goaf in homogeneous salt structures (salt domes or thick mineral deposits), and the definition of a goaf in heterogeneous salt structures (elongated layers or those with interlayers and geological faults), and an overview of the areas affected by goafs; 1b) the sealing and abandonment of SRCs in homogeneous salt formations at atmospheric pressure using air and solid particles; 1c) the change in SRC volume over time as a function of the filling material (air or brine) for unsealed SRCs (I-II-III) and sealed SRCs (IV); and 1d) the most common methods for abandoning SRCs in homogeneous salt formations using brine, without brine, and with solid particles. As the internal fluid pressure of the SRC increases, brine is released from the SRC due to its closure; 1e) In a homogeneous salt layer, the SRC is sealed and abandoned with brine at atmospheric pressure, but the casing facing the shallow aquifer has perforations. As the internal fluid pressure of the SRC increases, brine is released from the SRC into the aquifer due to its closure.

[0069] Figure 2 Figure a-2f schematically illustrates the current state of technology for discarding SRC in a homogeneous salt layer, involving the operations necessary to fill the SRC with granular solid material using sand mined from a licensed mining area. In this sense, the figure depicts: 2a) mining sand from a licensed mining area; 2b) loading the sand onto a truck (15 m... 3 2c) Transport the sand to the application site by truck; 2d) Unload the sand at the location of the goaf to be sealed and abandoned; 2e) Load the sand onto a conveyor belt, mix the sand with water, and inject the fluidized sand into the goaf access shaft; 2f) Fill the goaf with solid material (sand) while monitoring pressure, temperature (using differential pressure gauges) and the filling volume in the goaf (applying sonar).

[0070] Figure 33d schematically depicts the current technical status of abandoned facilities (civil infrastructure) at the SRC project site, involving the operations required from demolition to disposal of the debris at a landfill. In this sense, the figure illustrates: 3a) demolishing installed infrastructure or other structures; 3b) loading the civil structure debris (waste) onto trucks (15 m... 3 -28 tons); 3c) Transport the wreckage to a suitable disposal site; 3d) Unload the wreckage and return the truck to the site for the next loading.

[0071] Figure 4 a, adapted from Warren, JK 2017 (Salt usually seals, but sometimes leaks: Implications for mine and cavern instabilities in the short and longterm: Earth-Science Reviews, 2017;165:302-341), illustratively describes application scenarios of the present invention when the SRC is constructed in a heterogeneous salt layer, i.e. when the SRC contains a porous / permeable rock (non-evaporite) layer, or when the SRC is located near a geological fault / fracture. Figure 4 b, adapted from Chen X. et al. 2019 (Study on Sealing Failure of Wellbore in Bedded Salt Cavern Gas Storage. Rock Mechanics and Rock Engineering 2019;52:215–228), schematically describes what might happen to a well-sealed reservoir (SRC) constructed in the application scenario of this invention if the deprecated methods described herein are not implemented. Fluids present in the SRC would permeate through non-evaporable rock layers (present in the SRC) until they reach geological faults, allowing the fluids to reach the surface and cause fluid seepage (not shown). Furthermore, if an aquifer is present at said location, it would also contaminate the aquifer (also not shown).

[0072] Figure 5a - 5c, adapted from Zhang Z et al. 2019 (Study on the mechanism of roof collapse and leakage of horizontal cavern in thinly bedded salt rocks. Environmental Earth Sciences, 2019;78:292), schematically describes another application scenario of the present invention, i.e., when the top of the SRC collapses, it causes more exposed non - salt rocks in the goaf.

[0073] Figure 6 a, adapted from Berést et al. 2019 (Review and analysis of historical leakages from storage salt caverns wells. Oil & Gas Science and Technology - Rev. IFP Energies Nouvelles, 2019;74,27), schematically describes the situation that can be prevented by applying the present invention, i.e., the settlement of the ground above the SRC (due to over - closure of the SRC). Accordingly, Figure 6 b shows the subsidence (ground sinking, formation of subsidence) formed due to the collapse of the top of the SRC and the strata above the SRC.

[0074] Figure 7 a - 7g schematically and detailedly describes the first step of the method of the present invention, in which a method of filling the SRC is given, where particulate solids with determined volume and size are added in sequence:

[0075] 7a) 30 - 40% GVC adds gravel 3 (14a) (25 < MCD < 50 mm);

[0076] 7b) 15 - 25% GVC adds gravel 2 (14b) (19 < MCD < 25 mm);

[0077] 7c) 10 - 15% GVC adds gravel 1 (14c) (9.5 < MCD < 19 mm);

[0078] 7d) 5 - 10% GVC adds gravel 0 (14d) (4.8 < MCD < 9.5 mm);

[0079] 7e) 5 - 25% GVC adds coarse sand (15a) (2.0 < MCD < 4.8 mm);

[0080] 7f) 3 - 10% GVC adds medium sand (15b) (0.42 < MCD < 2.0 mm); and

[0081] 7g) 2-5% GVC added with fine sand (15c) (0.07) <MCD<0.42mm)。

[0082] Figure 8 a-8c schematically illustrates the second step of the method of the present invention, wherein the following processes are performed: 8a) pressurizing the SRC and monitoring the pressure, temperature and liquid level in the SRC; 8b) reinjecting fine sand until the channel well is completed and monitoring the pressure, temperature and liquid level in the SRC; and 8c) injecting cement slurry until the SRC channel well is filled to complete the permanent abandonment of the SRC.

[0083] Figure 9 a-9c schematically depicts the production and use of Class A demolition C&D waste as raw material for SRC filling. In this sense, the figure depicts: 9a) demolishing installed infrastructure or other structures; 9b) adding demolition material to a mobile recycling unit, such as civil engineering waste, using an excavator (29), the unit consisting of a roll-on / roll-off truck (28), a mobile crusher (impact or jaw) connected to the truck, and a mobile rotary screen. Crushing or grinding the waste fragments it, crushing (coarse fragmentation) and grinding (fine fragmentation), followed by granulation (screening) to produce crushed stone (30-blue circle) and sand (31-yellow circle) and / or separating ferromagnetic materials by electromagnetic separation; and 9c) loading the crushed stone and / or sand onto a conveyor belt, mixing the crushed stone or sand with water, and injecting the fluidized crushed stone and / or sand into the goaf access shaft.

[0084] Figure 10 a-10b respectively schematically illustrate the extent to which the prior art and the present invention have progressed in the abandonment of SRC. In this sense, Figure 10 A describes existing technology in which sand is transported by truck from a licensed mining area to the location of abandoned SRC (up to 15m per truck). 3 Thousands of vehicles traveling tens of kilometers, and transporting demolition waste from the SRC facility to the permitted landfill by truck (up to 15m per vehicle). 3 (Thousands of vehicles traveling tens of kilometers). Accordingly, Figure 10 b describes the invention of filling SRCs with solid materials recovered on-site from Class A demolition waste (C&D waste) from SRC projects and / or locations of civil structures affected by SRCs (which were demolished due to the risk of forming sinkholes). In this way, the invention avoids the displacement of thousands of trucks carrying sand and waste for tens of kilometers.

[0085] Figure 11 This illustration depicts a method of disposing of brine in a technically and economically suitable manner, wherein the brine is treated by filling SRC (such as) with gravel and sand. Figure 7(as shown in a-7g and 8a-8c) are replaced in SRC.

[0086] Purpose of the invention

[0087] This invention aims to provide a method for filling, sealing, and abandoning (discarding) salt reservoirs (SRCs) constructed in heterogeneous salt structures (with porous / permeable layers within the SRC) and / or near geological faults or / or where the top of the SRC has collapsed. In a preferred embodiment, the method is used for salt reservoirs (SRCs) constructed in salt rock, particularly those located in heterogeneous salt structures (with porous / permeable rock layers within the salt layer) and / or near geological faults or where the top (roof) of the SRC has collapsed. This can be carried out simultaneously with and integrated with the abandonment of SRC project site facilities or the abandonment of civil structures or other areas that are at risk of being demolished due to the SRC (due to the formation of settlement funnels). This embodiment applies to project facilities including the SRC itself ( On the spot Recycled aggregate from other civil structures affected by the SRC or from other nearby hazardous areas designated for demolition, or from Class A structural demolition waste (C&D waste).

[0088] A second objective of the present invention is to provide a system capable of filling, sealing, and constructing goafs (SRCs) in abandoned salt rock, wherein the goafs are located in heterogeneous salt structures (with porous / permeable layers within the SRC), and / or near geological faults or / or where the top of the goaf has collapsed. Detailed Implementation

[0089] This invention relates to methods and systems for filling, sealing, and abandoning (discarding) salt reservoirs (SRCs) constructed in salt rock, particularly in SRCs located in heterogeneous salt structures (with porous / permeable rock layers within the salt layer) and / or near geological faults, and / or in SRCs where the top (roof) has collapsed. These SRCs can be decommissioned simultaneously with and integrated with the decommissioning of SRC project site facilities and / or the decommissioning of civil structures or other areas at risk of being demolished due to the SRC's influence (due to the formation of settlement funnels). More specifically, in the decommissioning of rock salt production and / or storage projects where SRCs are constructed through a dissolution mining process, it is necessary to fill the SRCs with solid materials.

[0090] This invention can be described by the following reference numerals:

[0091] 01 – Evaporite or salt rock layer;

[0092] 02 – Non-salt rock (porous / permeable rock) layers between salt rock layers;

[0093] 03 – SRC (Salt Coal Mine) in Salt Rock;

[0094] 04 – The area of ​​influence of SRC;

[0095] 05–SRC channel well;

[0096] 06 – Geological faults existing near SRC;

[0097] 07 – SRC fluid leakage in non-salt rock layers present in SRC;

[0098] 08 – SRC fluid leakage through geological faults near the SRC;

[0099] 09–SRC above non-salt rock (porous / permeable rock) layer;

[0100] The top of 10–SRC collapsed;

[0101] The closure of 11–SRC;

[0102] 12 – A settlement funnel forms on the ground above the SRC;

[0103] 13 – Ground subsidence occurs;

[0104] 14a – Add 3 pieces of gravel to SRC;

[0105] 14b – Add 2 pieces of gravel to SRC;

[0106] 14c – Add 1 piece of gravel to SRC;

[0107] 14d – Add 0 gravel to SRC;

[0108] 15a – Add coarse sand to SRC;

[0109] 15b – Add medium sand to SRC;

[0110] 15c – Add fine sand to SRC;

[0111] 16 – The SRC fill level decreases due to displacement of the filler material caused by applied pressure;

[0112] 17 – Flow of smaller particles (15c) filling the hollow volume of SRC(03);

[0113] 18 – After leakage, the non-evaporable rock layer (02) present in SRC (03) is sealed;

[0114] 19 – After leakage, seal the geological fault (08) near SRC (03).

[0115] 20 – Add fine sand (15c) to SRC (1) to complete the displacement volume (16);

[0116] 21 – The channel well from the end casing shoe of the channel well to the surface is filled with SRC(03) using cement grout;

[0117] 22 – Complete the permanent abandonment of the SRC;

[0118] 23 – Sea Area;

[0119] 24 – Brine discharge hose leading to the sea;

[0120] Shallow brine aquifer near the location of the 25–SRC channel well;

[0121] 26 – Brine discharge hose that allows water to be discharged into a brine aquifer via a shallow well.

[0122] 27 – Demolition of civil engineering structures;

[0123] 28 – Mobile recycling units for structural demolition waste, such as those consisting of roll-on / roll-off trucks, mobile crushers (impact or jaw) connected to the trucks, and mobile rotary screens.

[0124] 29 – An excavator that loads demolition materials into a shredder for a mobile recycling unit;

[0125] 30 – Demolition materials, after being crushed and screened, are thrown out by a conveyor belt;

[0126] 31 – Sand that is thrown out by a conveyor belt after the demolition materials have been crushed and screened;

[0127] 32 – Use a truck (up to 15 m) 3 Transporting sand from the permitted mining site to the location of the abandoned SRC involves thousands of transports over tens of kilometers (existing technology);

[0128] 33 – Use a truck (up to 15 m) 3 Transporting demolition waste from SRC facilities to licensed landfills involves thousands of transports covering tens of kilometers (existing technology);

[0129] 34 – As described in this invention, the SRC is filled with recycled solid material from on-site demolition waste, eliminating the need for thousands of truck trips over tens of kilometers.

[0130] When SRC is built in a heterogeneous salt layer ( Figure 4 a) That is, when the SRC contains porous / permeable rock (non-evaporable rock) layers, the SRC is located near a geological fault / fracture, or when the top of the SRC collapses ( Figure 5 (a-5c) can lead to more exposed non-salt rock in the goaf, and the method of the present invention can be applied.

[0131] If the abandonment method described in this invention is not implemented, the SRC will suffer Figure 4Scenario b, 5, and 6. Fluid present in the SRC seeps through non-evaporable rock layers (present in the SRC) until it reaches a geological fault, through which it seeps to the ground, causing fluid exudation (not shown). Additionally, if an aquifer (not shown) is present at that location, it will contaminate the aquifer. Alternatively, it could cause the top of the SRC to collapse, leading to ground subsidence and the formation of a sinkhole (surface subsidence, forming a sinkhole).

[0132] Therefore, the method of the present invention also aims to prevent ground subsidence above the SRC (due to excessive closure of the SRC) and the formation of sinkholes (due to the collapse of the top of the SRC and the strata above the SRC). Figure 6 (a and 6b).

[0133] The preferred embodiments of the present invention (Example 1), some embodiments of the present invention (Example 2), and comparative embodiments of the present invention with the prior art (Example 3) are described in detail below. These are merely descriptive and not restrictive. In any case, by reading this specification, those skilled in the art will understand that possible additional embodiments of the present invention still include the necessary and optional features described below.

[0134] Example 1 – Preferred Embodiment of the Invention

[0135] Figure 7 a-7g shows an SRC (03) constructed in a heterogeneous salt layer according to one application scenario of the present invention, wherein the SRC comprises a porous / permeable rock (non-evaporable rock) layer (02) and a geological fault / fracture (08).

[0136] First, the SRC (03) is filled with 60-90% of the goaf geometric volume (GVC) using treated or industrialized crushed stone from Class A C&D waste, which is fluidized with brine present in the SRC. The filling of the SRC (03) begins with crushed stone 3 (14a) (30-40% GVC) with a maximum characteristic dimension (MCD) of 25-50 mm; followed by crushed stone 2 (14b) (15-25% GVC) with an MCD of 19-25 mm; then crushed stone 1 (14c) (10-15% GVC) with an MCD of 9.5-19 mm; and then crushed stone 0 (14d) (pilomorphous gravel) (5-10% GVC) with an MCD of 4.8-9.5 mm.

[0137] In the next step, the SRC (03) is filled with sand that has been ground or industrialized (from Category A C&D waste), fluidized with brine present in the SRC, and filled with 40-10% GVC. The filling begins with coarse sand (15a) (5-25% GVC) with an MCD of 2.0-4.8 mm; followed by medium sand (15b) (3-10% GVC) with an MCD of 0.42-2.00 mm; and finally fine sand (15c) (2-5% GVC) with an MCD of 0.07-0.42 mm.

[0138] This process forms a framework within the SRC, enabling greater structural load-bearing capacity, greater infill capacity, and better conditions, thereby (i) sealing the flow in the SRC or in the porous / permeable rock strata (02) present on its collapsed or uncollapsed top, and (ii) sealing the flow in the fault (08).

[0139] After filling the SRC (03) with gravel and sand, the SRC (03) must be pressurized within 24-72 h by 50-90% of the previously calculated burial gradient or fracture gradient to facilitate the flow of smaller particles and fill the void volume (17), seal (18,19) the flow in the pores and faults (08) of the porous / permeable layer (02), and monitor the pressure, temperature and liquid level in the SRC (using pressure sensors, temperature sensors and sonar in the SRC channel well).

[0140] After pressurization, fine sand (20) must be added to the SRC to complete the replacement volume (16). At the end of this stage, the SRC channel well must be filled with cement grout (21) to end the permanent abandonment of the SRC (22).

[0141] The granular solid materials (crushed stone and sand) used to fill SRC can be natural crushed stone and sand (washed or extracted from a mine), but preferably are granular solidified materials that have been processed or industrialized from Class A structural demolition waste (C&D waste), which originates from the civil engineering project itself or not (from other areas subject to forced demolition), obtained by crushing (grinding and grinding) and then granulating using fixed or mobile recycling equipment. The processed or industrialized crushed stone and sand have the same physical properties and granularity as natural crushed stone and sand (washed or extracted from a mine), the only difference being that they may contain cement particles.

[0142] Specifically, according to CONAMA Resolution No. 307 / 02, which sets out guidelines, standards and procedures for the management of structural demolition waste (as amended by the National Environment Committee (CONAMA) Resolution No. 348 of 16 August 2004 and Resolution No. 431 of 24 May 2011), when recycled solid materials of different particle sizes generated by crushing structural demolition waste (C&D waste) are used to fill SRC, it must be Category A.

[0143] Category A C&D waste can preferably originate from the civil engineering structure project itself within the SRC used for rock salt production (on-site), from storage within the SRC (which is decommissioned along with the SRC), or from other locations. This would significantly reduce both decommissioning costs and greenhouse gas (GHG) emissions.

[0144] According to CONAMA, Category A C&D waste corresponds to C&D waste as defined in the European Waste Inventory (EWL), namely: concrete, bricks, tiles, roofing tiles and ceramic materials.

[0145] Example 2 - Partial Scheme of the Invention

[0146] In one partial embodiment of the invention, it is used for dismantling ( Figure 9 a) Civil engineering infrastructure installed in the SRC project (27) or other nearby structures (27) affected by the SRC and subject to demolition.

[0147] After demolition ( Figure 9 (b) Demolition materials are added to, for example, a mobile recycling unit for structural demolition waste using an excavator (29), which consists of a roll-on / roll-off truck (28), a mobile crusher (impact or jaw) connected to the truck, and a mobile rotary screen. The waste is crushed or ground (to fragment the waste, crushing (coarse fragmentation) and grinding (fine fragmentation)), then granulated (screened and sorted), producing gravel (30-blue circle) and sand (31-yellow circle), and / or ferromagnetic materials are separated by electromagnetic separation.

[0148] Alternatively, the processed gravel and sand can be sourced from a stationary C&D recycling unit (not shown) and transported to the SRC disposal site.

[0149] Alternatively, gravel and sand can be removed from civil structures in other areas (outside the rock salt treatment facility) and / or disposed of or industrialized in a Category A C&D waste landfill.

[0150] Next, the processed gravel or sand is loaded onto the conveyor belt. Figure 9c) In a mixing vessel, crushed stone or sand is mixed with water (from the SRC itself, i.e., brine), and the fluidized crushed stone and / or sand is finally injected into the goaf access well at a flow rate lower than the fracture gradient of the SRC or the permeable porous top casing shoe.

[0151] Example 3- Comparative embodiments of the present invention and existing technologies in truck transportation

[0152] Depend on Figure 10 a-10c shows the transport distance profile of the prior art (32) and (33) and the present invention (34) in the absence of SRC (03) in heterogeneous salt layer (02) and near fault (08).

[0153] In existing technologies, for example, when filling SRC with sand from a licensed mine, trucks (up to 15 m³) are used. 3 Transporting sand mined from licensed mining areas to the abandoned / discarded SRC location involves thousands of transports over tens of kilometers (32). For reference, the average SRC volume is approximately 300,000 m³. 3 It would require 20,000 round trips, which would directly lead to increased traffic and greenhouse gas (GHG) emissions, as well as increased costs for truck rentals, drivers and diesel, and risks due to increased exposure.

[0154] Furthermore, with existing technology, for rock salt production or SRC storage, the disposal of waste from project facilities ( On the spot Infrastructure demolition waste (C&D waste), transported by truck (up to 15 m). 3 Transporting dismantling waste from the SRC facility to a licensed landfill (33) involves thousands of trips over tens of kilometers. This will also result in thousands of round trips, directly leading to increased traffic and greenhouse gas (GHG) emissions, as well as increased costs for truck rentals, drivers and diesel, and risks associated with increased exposure.

[0155] In the method of this invention, SRC (particulate solid material) is filled with SRC (particulate solid material). Figure 7 First, fill with crushed stone (14a-14d), then fill with sand (15a-15c), preferably from [source missing]. On-site installation and operation SRC's civil engineering structure (27) was implemented using recycled demolition waste. Figure 9 a-9c-10a-10c). Considering that the distance between the raw materials (27) and the SRC (03) is shorter (34), this will result in a significant reduction in disposal costs, minimize greenhouse gas (GHG) emissions, avoid increased vehicle traffic, reduce the risk of traffic accidents, and further minimize the amount of C&D waste to be disposed of (non-Class A).

[0156] Alternatively, depending on the size and quantity of the C&D waste to be disposed of, gravel and sand can be recycled from other areas outside of rock salt treatment facilities and even from the recycling of structural demolition waste (C&D waste) from civil engineering waste landfills (not shown).

[0157] In addition, well drilling waste (compliant with national standards) can be disposed of between injected gravel and sand during the SRC filling process (not shown).

[0158] During the filling of the SRC (03) with crushed stone (14a-14d) or sand (15a-15c), the brine present in the goaf is drained from the SRC, where it can be treated (tanks, filters) to become drinking water, and the rock salt extracted from the brine can be used (not shown), such as Figure 11 As shown. Additionally, in cases where the SRC is near the sea (23), brine from the SRC can be discharged into the sea within environmental regulations (concentration and temperature) via hoses or brine pipes (24). Furthermore, in cases of shallow brine aquifers, brine can be discharged into a shallow well (26) constructed for this purpose near the (25) SRC (03) channel well, and then abandoned. These concepts are not mentioned in the prior art; only the release of brine from the SRC is mentioned.

[0159] Therefore, when the SRC is located in a heterogeneous salt structure or near a geological fault or top collapse, this invention prevents fluid leakage through the SRC and non-evaporable rock layers present in the geological fault. This avoids stability problems, seismic activity, ground subsidence, and sinkhole formation in the SRC.

[0160] Therefore, after filling, sealing, and disposing of the SRC, settlement and tilt measuring instruments should be installed on the ground around the SRC for monitoring and measurement for 2 years, or as required by relevant legislation.

[0161] Using the process described in Examples 1-3, the voids are filled more significantly, and as the SRC is closed, the filling material in the SRC compacts more quickly (almost immediately), resulting in negligible ground settlement.

[0162] Furthermore, using the method of this invention, the filling of the SRC ensures a larger filling volume (lower void ratio), sealing the flow of faults and porous / permeable layers, preventing the opening / expansion of faults, and minimizing ground subsidence. In this way, the volume of disposed C&D waste is maximized, the isolation of the SRC is ensured in the long term, and the safety of the environment, civil engineering, and property around the SRC is guaranteed.

[0163] Furthermore, by using Class A C&D waste instead of crushed stone or washed sand (mined from mines or riverbeds, transported by thousands of trucks for tens of kilometers, emitting greenhouse gases and causing traffic congestion), this invention is environmentally friendly and sustainable; it emits fewer greenhouse gases (GHG), i.e., has a smaller carbon footprint; it has less environmental impact; and it has a lower overall cost.

[0164] It is worth emphasizing that the methods described in this article fully comply with Article 9 of Law No. 12.305 / 2010, which stipulates that "in the management and treatment of solid waste, the following priorities must be followed: not to generate, reduce, reuse, recycle, treat solid waste, and ultimately dispose of waste in an environmentally sound manner." (National Solid Waste Policy - PNRS).

[0165] This invention also provides a system capable of filling, sealing, and abandoning salt reservoirs (SRCs) constructed in salt rock, the SRCs being located in heterogeneous salt structures (with porous / permeable layers within the SRC) and / or near geological faults and / or where the top of the SRC has collapsed, the system comprising:

[0166] (i) Equipment used to dismantle installed infrastructure or other structures;

[0167] (ii) Excavator;

[0168] (iii) A mobile recycling unit for construction waste, comprising a roll-on / roll-off truck, a mobile shredder connected to the truck, and a mobile rotary screen;

[0169] (iv) Conveyor belts for loading gravel or sand;

[0170] (v) A mixer used to mix gravel or sand with water;

[0171] (vi) Pressure, flow, temperature and filling volume instruments (sonar) in goaf areas;

[0172] (vii) A pump that pressurizes the SRC; and

[0173] (viii) Prepare and inject cement grout to fill the SRC channel well to complete the system for permanent SRC disposal.

[0174] The description of the methods and systems of the present invention and their embodiments to date should be understood as not limiting the invention, which is limited to the scope of the following claims.

Claims

1. A method for filling, sealing, and abandoning (discarding) goafs, characterized in that it is used for goafs (SRCs) constructed in salt rock, particularly those located in heterogeneous salt structures, near geological faults, or where the top of the goaf has collapsed, said method preferably comprising the following steps: a) Demolition of civil engineering infrastructure installed in the SRC project (27) or other nearby structures affected by the SRC and forcibly demolished (27); b) Using an excavator (29) to add demolition materials to a mobile recycling unit (28) for structural demolition waste (C&D waste) to crush Class A structural demolition waste (C&D waste) to obtain treated or industrialized crushed stone (30) or sand (31) of different particle sizes. c) Load crushed stone (30) or sand (31) onto a conveyor belt, mix with water in a mixing container, and inject the fluidized crushed stone or sand into the goaf passage well respectively; d) The goaf is filled sequentially with granular solid materials, that is, first with larger particle size materials (crushed stone 3, crushed stone 2, crushed stone 1, crushed stone 0), and then with smaller particle size materials (coarse sand, medium sand, fine sand) to form a structural frame within the SRC. e) Pressurize the goaf area and monitor variables (temperature, volume, pressure) within 24-72 hours; f) The replacement volume (16) in the goaf is replenished by adding fine sand (20) to the SRC to replenish the replacement volume to the non-salt rock and faults; and g) Fill the SRC channel well with cement grout (21) to complete the permanent abandonment of SRC (22).

2. The method of claim 1, characterized in that the mobile C&D waste recycling device is powered by electricity or a diesel engine; it consists of a roll-on / roll-off truck (28), a mobile crusher (impact or jaw) and a mobile rotary screen, both of which are connected to the truck.

3. The method of claim 1, characterized in that the filling of SRC(03) is: a) Starting with crushed stone 3 (14a), its maximum characteristic size (MCD) is 25-50 mm (30-40% of the geometric volume of the goaf - GVC); then crushed stone 2 (14b), its MCD is 19-25 mm (15-25% GVC); then crushed stone 1 (14c), its MCD is 9.5-19 mm (10-15% GVC); and crushed stone 0 (14d) (pea gravel), its MCD is 4.8-9.5 mm (5-10% GVC); b) Start with coarse sand (15a) with an MCD of 2.0-4.8 mm (5-25% GVC); then use medium sand (15b) with an MCD of 0.42-2.00 mm (3-10% GVC); and fine sand (15c) with an MCD of 0.07-0.42 mm (2-5% GVC); c) Pressurize SRC (03) to 50-90% of the previously calculated burial gradient or fracture gradient to assist the flow of smaller particles and fill voids (17), and seal (18,19) the flow in the pores of the porous / permeable layer (02) and the fault (08). d) Monitor the pressure, temperature and liquid level in the SRC within 24-72 hours (using pressure sensors, temperature sensors and sonar in the SRC channel well); e) The replacement volume in the goaf is replenished to non-salt rock and faults by adding fine sand (20) to the SRC.

4. The method of claim 1, characterized in that the gravel and sand can be alternatively demolished by civil engineering structures in other areas (other than rock salt treatment facilities) and / or processed or industrialized by a Class A C&D waste landfill.

5. The method of claim 3, characterized in that the crushed stone used in filling the SRC (03) is processed or industrialized from Class A civil engineering demolition waste (C&D waste), fluidized with brine present in the SRC, and filled with 60-90% GVC.

6. The method of claim 3, characterized in that the sand used in filling the SRC (03) is processed or industrialized from Class A civil structure demolition waste (C&D waste), fluidized with brine present in the SRC, and filled with 40-10% GVC.

7. The method of claim 1 or 3, characterized in that, in step (d), in addition to plugging or sealing faults, cracks or permeable materials with non-polluting and harmless C&D waste, a filling volume of more than 95% of SRC is obtained, the resulting settling funnel is minimized, and the pollution and seepage of surface water are avoided.

8. The method of claim 1 or 4-6, characterized in that the gravel or sand is produced as follows: - Preferably, through a crushing or grinding process (crushing, grinding, and granulation) of the local civil engineering and construction waste (C&D waste) at the site of the SRC project; and - Alternatively, it can be obtained through crushing or grinding processes (crushing, grinding and granulation) of civil engineering demolition waste (C&D waste) recovered from other areas outside of rock salt processing facilities and even from civil engineering waste landfills, or even from mining areas.

9. The method of claim 1 or 3, characterized in that, additionally, well drilling waste (compliant with national standards) can be disposed of between gravel and sand injection during the SRC filling process.

10. The method of claim 1 or 3, characterized in that the brine discharged from the SRC is treated in a tank or filter to become drinking water, or discharged into a shallow brine aquifer or sea area.

11. The method of claim 1, characterized in that the goaf passage well is sealed with a cement plug from the end casing shoe to the ground and is eventually abandoned (step g).

12. A system for filling, sealing, and abandoning (discarding) goafs, characterized in that it is used for goafs (SRCs) constructed in salt rock, particularly those located in heterogeneous salt structures, near geological faults, or where the top of the goaf has collapsed, said system comprising: (i) Equipment used for dismantling installed infrastructure or other structures (27); (ii) An excavator (29) for adding demolition materials to a mobile recycling unit (28) for civil engineering waste; (iii) A mobile recycling device for civil engineering waste (28), which consists of at least one roll-on / roll-off truck, a mobile crusher connected to the truck, and a mobile rotary screen; (iv) A conveyor belt for loading crushed stone (30) or sand (31); (v) A mixer for mixing gravel or sand with water; (vi) Instruments (sonar) used for pressure, flow rate, temperature and filling volume in goaf areas; (vii) A pump that pressurizes the SRC; (viii) Prepare and inject cement grout to fill the SRC channel well to complete the system for permanent SRC disposal.

13. The system of claim 12, characterized in that the recycling device is capable of obtaining waste, such as gravel and sand, having the following dimensions: a) Crushed stone 3 (14a), with a maximum characteristic size (MCD) of 25-50 mm (accounting for 30-40% of GVC); b) Crushed stone 2 (14b), with an MCD of 19-25 mm (accounting for 15-25% GVC); c) Crushed stone 1 (14c), with an MCD of 9.5-19 mm (accounting for 10-15% GVC); d) Crushed stone 0 (14d) (pea-shaped gravel), with an MCD of 4.8-9.5 mm (accounting for 5-10% GVC); e) Coarse sand (15a), with an MCD of 2.0-4.8 mm (accounting for 5-25% GVC); f) Medium sand (15b), with an MCD of 0.42-2.00 mm (accounting for 3-10% GVC); and g) Fine sand (15c) with an MCD of 0.07-0.42 mm (accounting for 2-5% GVC).

14. The system of claim 12 or 13, characterized in that larger-particle waste (crushed stone) is added at the bottom of the SRC, and smaller-particle waste (sand) is added at the end of the SRC filling to seal voids and faults.

15. The system according to any one of claims 12-14, characterized in that after the pressurization and monitoring period, the replacement volume in the goaf is replenished by adding fine sand (20) to the SRC and finally filling the SRC channel well (21) with cement slurry, thereby completing the permanent abandonment of the SRC (22).

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