RU2363848C1 - Method of anthropogenic epigenesis of backfilling water permeable areas or zones in salt rock - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: invention refers to mining industry and can be implemented for reducing water permeability of salt rock and flush danger. Known technologies of backfilling zones of heightened water permeability in pay thickness of salts are based on application of solutions of various cements, clay, synthetic resins, salt powders and other compositions characterised with higher values of viscosity, and small radii of rock densification, which negatively effects quality of mineral. The method of anthropogenic epigenesis of backfilling of water permeable areas or zones in salt rock consists in exposing zones of heightened water permeability with backfilling boreholes, in preparing salt solutions on surface, in their heating, if necessary, and in pumping them into the zone of backfilling. Saturated true salt solutions or natural brines are used as backfilling solutions; under conditions of temperature drop these solutions isolate excess of salt into sediment and backfill water conducting fissures.

EFFECT: invention facilitates safety of underground mining operations, conservation of favourable ecological environment and maintaining quality of mineral on salt mines.

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Description

The invention relates to the mining industry and can be used to reduce water permeability of rocks, water cut of mine workings and breakthrough hazard.

The purpose of the invention is to ensure the safety of underground mining while maintaining a favorable environmental situation and the quality of minerals in salt mines developing minerals that are highly soluble in water (sylvin, halite, carnalite, etc.), as well as reducing the cost of grouting.

Both in the past and at present, the development of salt deposits is often accompanied by the emergence of zones of increased water permeability with different intensities of water manifestations - from casing at the initial stage to catastrophic breakthroughs, often ending in flooding of mine workings and loss of the mining site (chamber).

The causes of such zones may be:

- tectonic processes, seismic impact;

- deformation of the rocks of the ceilings of the mine under the influence of the extraction of minerals;

- blasting operations;

- destruction of pillars, etc.

It is known that at the present time during the grouting of water manifestation sites, a wide arsenal of grouting compositions is used to reduce the permeability of rocks and prevent the further development of karst phenomena in salt mines. These include solutions based on: Portland cement, alumina and magnesia cements, clays, clay-cement mixtures (N. G. Trupak “Cementation of fractured rocks in mining.” M., “Metallurgizdat”, 1956). For these purposes, synthetic resins KM-3 diluted with a saturated solution of potassium chloride are also used (B. A. Rzhanitsyn, “Some results of work in the field of chemical fixation of soils.” Materials of the VIII All-Union Conference, Kiev, Buddelnik Publishing House 1971), carbamide- lignin compounds, melamine-formaldehyde resins (Yu.G. Startsev “Waterproofing of mine workings of potash and salt mines with synthetic resins.” In the collection “Technology of underground development of potash deposits”, Perm, 1988), as well as solutions (suspensions similar to clay coagulant) that are prepared from powders of NaCl or KCl (GDR Patent №252029 "injection method fissured and porous plugging salt-breed" 1987).

The specified method is selected as a prototype.

Significant disadvantages of the known methods of reducing the permeability of salt rocks 1 and protecting underground mine workings 2 from groundwater are:

- increased viscosity used in the grouting of compositions;

- small radii of fixing aquifers;

- clogging of productive formations with fixing compounds, reduction in the quality of the mineral;

- environmental degradation in the fields due to the use of synthetic solutions;

- susceptibility of grouting compositions to aggressive environmental influences;

- the high cost of the compositions used for grouting and their delivery.

The noted disadvantages are especially negatively manifested in the development of deposits of various salts, which are characterized by good solubility. Under such conditions, the appearance in the mine workings of even a slight cape is a harbinger of a groundwater breakthrough.

In order to eliminate the above drawbacks, a method is proposed based on the property of many salts to reduce their solubility in water with a decrease in its temperature and the property of supersaturated solutions upon contact with the solid phase of the dissolved salt to precipitate excess salt.

At the depth of the arising zones of increased water permeability 3 under conditions of lower temperatures (10 ° -15 °), saturated solutions become supersaturated and excess salt will crystallize and precipitate on the walls of cracks and pores, which are groundwater filtration paths, and reduce their water permeability. As a result, the filtering section of the reservoir will be plugged and waterproof.

Saturated solutions of the salts used to crack the cracks are prepared on the surface and do not require heating in the summer. In the prepared solutions to accelerate the crystallization processes of the proposed method provides for the addition of fine powder of dissolved salt.

At temperatures close to the conditions in which salt solutions are prepared on the surface (20 ° -25 °), sodium chloride additives should not exceed 5%. An increase in the amount of salt added to the solution slows down the processes of structure formation and crystallization (Bulatov A. I. “Grouting Materials and Cementing Technology for Wells”, section “Preparation of Saline Grouting Solutions” M., “Nedra”, 1977). In order to prevent a decrease in the penetration of a salt solution containing solid salt particles into thin cracks, the addition of salt must be limited to 1% -2% of the dissolved salt.

The additive (sometimes the term “seed” is used) is designed so that the powder particles become centers of crystallization of salt that precipitates when the temperature of the solution injected into the bowels decreases, and at the same time does not affect the viscosity or mobility of the salt solution.

In the zone of colmatization, a salt solution is supplied through injection injectors 4.

Since the viscosity of true salt solutions (~ 1.05-1.2 cP) does not differ significantly from the viscosity of water (1 cP), the distribution radii of the clogging compositions are quite large and reach 20-30 meters, which is the main advantage of the claimed method.

In practice, in the zone of increased filtration 3 with a temperature difference on the surface (20 ° -25 °) and at depths of the salt stratum (10 ° -15 °) with each cubic meter of the injected saturated salt solution, the following can actually be delivered: halite - 50 kg; sylvin - 60 kg, mirabilite 320 kg, epsomite - 100 kg.

To increase the solubility of salts, the following can be used: increasing the temperature (heating) of water, additives, magnetizing water, evaporating, changing pH, etc.

When using supersaturated solutions or natural brines, the amount of salts supplied to the plugging zone increases significantly, which allows you to complete the grouting work in a shorter time. In this case, natural brines, which are often found in salt deposits, can be used.

An important result of grouting is the restoration of a layer of brines over the filtering zone, which prevents the entry of fresh, weakly mineralized water into the zone and prevents the resumption of the process of dissolution of the salt layer.

The proposed method is especially effective at the initial stage of water development in mining, when the process of intensive karsting of the salt mass has not yet been developed.

The monolithization of the fractured massif with saline solutions is essentially a process of technogenic epigenesis, which is a secondary process of sedimentation of minerals in the fractures of the salt massif and their cementation.

The main technological operations of the developed method of plugging water-permeable sections of rocks consist of:

1) in the establishment and contouring of permeable zones 3;

2) in drilling and equipment for injection 4 and observation wells (not shown) in section 3 with increased permeability of the massif;

3) in the preparation of a saturated salt solution with the addition of 1% -2% dissolved salt powder;

4) in the injection of a salt solution into the zone of increased permeability;

5) in conducting hydrogeological observations of changes in the intensity of water occurrences in mine workings and the formation of a protective layer of brines in the contact zone (in the upper part of the salt stratum);

6) in carrying out liquidation grouting of injection wells after completion of grouting works.

Technical results that can be obtained using the invention:

- the ability to use for tamping salts produced in the field, that is, colmatants that do not require delivery;

- the exclusion of clogging of minerals and reducing the quality of products of the salt-producing enterprise;

- preservation of the ecological balance prevailing in the field;

- the absence of the need for subsequent grouting, since the salts falling in the cracks do not differ in composition and properties from the plugged rocks and do not exfoliate;

- used salts (colmatants) are not subject to aggressive effects of plugged rocks and brines;

- increase the radius of the grouting due to the low viscosity of the used salt solutions;

- reduction in the number of injection wells compared to technologies using slow-moving suspensions (cement mortars, etc.);

- the possibility of creating impervious curtains with a significant length of areas with increased permeability;

- ease of grouting of the proposed method.

It should be emphasized that poorly soluble salts and salts whose solubility in water practically does not drop when the temperature of the solvent, for example, bischofite, gypsum, etc., cannot be used as colmatants.

When the temperature is equalized between the injected solutions and the plugged rocks in the bottom-hole zone of the injector, the process of cracking stops. Therefore, at the final stage of the work, a site of limited size of loose rocks is plugged with a suspension of salt powder in its saturated solution (GDR patent No. 252029).

The practical application of the claimed invention is illustrated by the following example.

The salt dome is developed underground. Over-salt deposits are represented by alluvial loams, sands and clays with a total thickness of 18–20 m. The sandy-clay stratum lies on the surface of the contact zone (“gypsum hat”), which includes clay-gypsum weathered rocks and the upper layer of karsted salts with an average total thickness of up to 10 m .

When mining the northern part of chamber No. 7, intense casing appeared in the ceiling, and brines with the smell of hydrogen sulfide were noted from the lower holes. The total flow rate of the brine did not exceed 3 m ³ / hour. Initially, it was assumed that “uterine brine” enters the mine, however, after three days the flow rate of the incoming brine increased to 4 m ³ / h and its density decreased markedly, which indicated the penetration of fresh water from the overlying sediments through the filtration zone. The brine came out with a pressure of ~ 70 m water. pillar. The dimensions of the water manifestation zone in the chamber approached 30 m in length. In order to eliminate the flow of water into the chamber, to prevent the development of the salt karst process and to break through the water into the zone of increased permeability, an injection well was drilled urgently from the surface with a depth of 72 m and a final diameter of 46 mm, in which a filter was installed on the entire permeable per-chamber thickness of salts. The borehole was rotationally flushed with brine. A saturated salt solution with the addition of the powder of the same salt was injected through the injector with a flow rate of ~ 0.5-1 m ³ / h under a pressure of about 10 atm.

A brine (brine from Lake Tuzluchnoye) with a density of 1.245 g / cm ³ and a temperature of 23-25 ° C was used as a solution. Salt was added to the brine until it was completely saturated. Given the polysalt composition of the productive stratum, the salt content in 1 m ^{3 of the} solution was able to reach 370 kg.

The salt solution was prepared in a conventional clay mixer, from which it merged into a settling tank. When the solution was injected into the clogged zone, up to 1% salt powder was added to it through the dispenser. Once in the plugged zone of the salt reservoir, the temperature of the solution decreased to 10-12 ° C, as a result of which the saturated solution turned into a supersaturated state, about 50 kg of salt precipitated from each m ^{3 of} injected solution, which crystallized on the walls of water-supply cracks, reducing them water permeability.

After three days, the intensity of the dropping began to noticeably decrease, and after 8 days the water output practically stopped.

The injection well was eliminated by creating a salt plug in the barrel, and from the clay-cement mixture in the upper part. In general, the work on the mudding of the zone of increased permeability was practically completed in 10 days.

Thus, the fractured zone of water development, which had dimensions in the plan of up to 30 m, was plugged through one injection well, that is, the radius of fixation of salt rock really exceeded 15 m. When using known compositions - cement, clay and salt “solutions” (suspensions, mixtures ) to solve the same problem would require drilling at least 10 injection wells.

Claims (1)

The method of technogenic epigenesis of plugging of water-permeable sections or zones in salt rocks, including opening zones of increased permeability of grouting wells, preparing salt solutions on the surface, heating them and pumping them into the plugging zone, characterized in that saturated saturated salt solutions are used as the grouting composition or natural brines, which under conditions of lowering temperature, precipitate an excess of salt, plugging water-conducting cracks.