The conservation and liquidation of wells of mining enterprises is carried out under conditions incompatible with the circumstances of the cessation of work of production sites of organizations of other national economic sectors. The difference is that if appropriate measures are not taken, there will be a risk of adverse environmental consequences. Over time, this threat will only increase.
Adverse effects
Well conservation and abandonment performed in violation of the requirements may lead to:
- Deformations of the earth's surface, structures, buildings located in the mining area. Such consequences are caused by geomechanical processes occurring in the rock mass.
- Water pollution. This is due to the mixing of surface and quarry (mine) waters.
- Air pollution. The negative impact on the atmosphere is caused by the release of mine gases and erosive processes occurring on the surface of sides and ledges, dumps.
- Deterioration of geological conditions due to the continuation of geophysical, geomechanical processes in the bowels.
Given the danger of the consequences, work on the liquidation of wells should be accompanied by measures to prevent negative impact on the environment.
Regulatory requirements
In the Russian Federation, special regulations apply for entities that have decided to cease mining. In particular, the Instruction on the procedure for liquidation / conservation of wells is in force. It was adopted in accordance with Article 26 of the Federal Law "On Subsoil". According to the general provisions:
- The elimination of wells and other production sites of mining enterprises is carried out at the end of the validity period of the permit document (license) or in case of early termination of the use of subsoil.
- Until the completion of the process, operating entities bear the responsibility assigned to them by law.
- Activities should ensure the safety of public health, the protection of nature, structures / buildings.
- During the forced termination of the operation of the sections, surveying, geological, other documentation and an act of well liquidation are executed at the time the activities are completed. Papers are deposited in the prescribed manner.
- Activities are considered completed after the certification of the act by the bodies that issued the license and exercising mining supervision.
- All procedures are performed at the expense of user enterprises or at the expense of the fund created by the investor.
Instruction on the procedure for liquidation of wells
This document defines the rules for the termination of the functioning of production sites laid for the search, exploration, exploitation of hydrocarbon pools, deposits of geological structures for the formation of storage facilities for raw materials, the burial of harmful industrial wastes, industrial wastes. According to the established requirements, liquidation of oil wells drilled to eliminate fountains and griffins is also carried out. Activities are monitored by Rostekhnadzor. The authorized body carries out activities in accordance with the Regulation on the implementation of state policy in the field of supervision of compliance with industrial safety requirements.
Well Elimination Project
It reflects:
- Geological and hydrological characteristics of the subsoil.
- The status of off-balance sheet and book reserves of minerals. This information is provided at the date of termination of mining activities. At the same time, they separately describe the reserves located in areas not affected by the work, and the remaining resources at previously redeemed and existing horizons, including industrial ones, with the division into ready-made, prepared and opened.
- The prospect of growth in PI volume.
- Plots of penetration of harmful and toxic compounds into the enclosing massif, the burial and storage of which was carried out in an underground structure that ceased to function.
- The status of workings, safety and barrier pillars, as well as hydraulic installations. It also provides an assessment of their stability, preventing the likelihood of a breakthrough of water, pulp, gas to neighboring areas and mines.
- The state of sanitary and production facilities, structures, buildings, ventilation and drainage plants and other stationary equipment.
- Assessment of the state of the environment.
- Probable formation of cracks, dips, flooding, waterlogging of the surface, other negative phenomena after conservation / liquidation of the well and their impact on nature.
- Penetration zones of mine / mine aggressive waters into aquifers and the host rock mass.
Planning
The instruction for the liquidation of wells also prescribes the inclusion in the document of time, sequence, methods of implementing the necessary procedures. In particular, we are talking about activities for:
- Ensuring the stability of the workings or their artificial collapse. This is necessary to prevent unacceptable deformations and dips of the earth's surface.
- Prevention of pollution of water bodies and bowels.
- Prevention of penetration of harmful gases into the atmosphere and surface structures.
- Elimination of cracks, dips, fencing of all hazardous areas.
- Land reclamation.
- Prevention of waterlogging, surface flooding, violation of hydrogeological conditions.
- Prevention of falling into failures and development of animals and people.
- Prevention of damage to structures, buildings, communications (ground and underground) located in the negative impact zone of mothballed / liquidated facilities.
- Preservation of the reference surveying and geodetic network.
- Elimination of foci of underground fire (if any).
- Prevention of activation of threatening geomechanical processes (landslides, landslides, etc.).
- Safety measures. In particular, the rules are envisaged in accordance with which the prevention / elimination of accidents in the well is carried out.
Nuances
The procedure for the conservation / liquidation of wells located under built-up areas requires users to lay down workings above safe depths or to take constructive protective measures to ensure safety during the operation of structures / buildings. When the facility ceases to function on the initiative of the mining enterprise due to the unprofitability of the subsoil, the relevant technical and economic calculation is included in the documentation. The elimination of wells with undeveloped mineral reserves within the allotment is carried out after analysis of the feasibility of their subsequent accounting or write-off from the state balance.
Additional features
The liquidation project should include measures to use:
- The remaining balance and economically viable resources for the extraction of off-balance bowels (including those that are in the pillars).
- Stockpiled fossils. They include substandard reserves.
- Wastes from the extraction / processing of raw materials containing components useful or suitable for the production of building materials.
- Mining, wells designed for purposes that are not related to production.
special instructions
Designing of conservation / liquidation of wells in cases when it is planned to prepare underground workings for further operation for purposes not related to the extraction of minerals is carried out in accordance with the terms of the license for the use of reserves. Technical measures in specific or complex areas are determined by special research and other competent organizations that carry out activities on the basis of permits issued by the State Technical Supervision Authority. With wet preservation, the project indicates the period of its permissible duration without loss of workings, the possible duration of drainage, restoration of ventilation, repair of roof supports, lifting and other equipment. The document also defines the rules of work, technical support, the frequency of monitoring the status of workings and their impact on nature.
Technical Activities
The liquidation of oil wells and other production areas may be carried out underground or open way. In the first case, the following activities are carried out:
- Filling the rock with gaps that occurred on the surface in connection with the collapse, fencing potentially hazardous areas.
- Backfill of vertical shaft and mine shafts, as well as inclined objects with an angle of more than 45 degrees. Filling with rock is carried out to the level of the earth's surface. At the same time, the trunks reliably overlap with two shelves of metal / reinforced concrete beams. One is installed at a depth of bedrock, but no less than 10 m from the surface, the other at ground level. Around the mouth of the trunk is a strong fence, the height of which should not be less than 2.5 m, as well as a drainage ditch. The distance at which these structures are arranged is determined by the project.
- Inclined trunks, other workings with an angle of less than 45 degrees, the mouths of which open on the surface, adits remote 4-6 m inland from the bedrock level are covered with a reinforced concrete or stone lintel. The rock is poured on top and rammed. On top of it, another reinforced concrete or stone lintel is installed.
- Pits with an angle of inclination greater than 45 degrees, regardless of their depth, should be filled up.
- The mouths of inclined and vertical openings that open in floodplains of rivers and ponds, in places of likely formation of flood waters, are bunded to prevent a breakthrough. They are overlapped and marked with long-term decals.
Failure Risk Assessment
Well abandonment procedures require a hazard analysis. Assessment of the risk of formation of dips is based on the volume of voids left in the array. When located above workings with depths of up to 20 m (m is the removable thickness of the fossil) of structures and buildings with a shallow bed of rocks or when these objects are in potentially dangerous zones when developing round and inclined formations, ore deposits, precautionary measures are taken. The boundaries of plots in which failures over inclined structures are likely to be established by the project. Calculations of the expected area of rock movement are taken into account. When the inclined working depth is more than 80 m, the projection of isohypses is accepted outside the zone of dips on the dip side. It passes through the axis of the plot. The elimination of gas-hazardous wells includes the determination of the boundaries of its release area and the level of risk in such areas. At the same time, special measures are envisaged to ensure control of emissions and to protect them from penetration into ground structures, including residential ones.
Open way
Liquidation of wells by this method includes the following measures. Fencing or embankment are arranged (shafts with a height of at least 2.5 m at a distance of at least 5 m behind the assumed prism of collapse of the upper ledges of sections / quarries). This measure is aimed at preventing the fall of animals and people. It is allowed to carry out other activities, for example, flattening the sides on the ledges. At the same time, their stability is estimated taking into account flooding. The elimination of wells and facilities associated with the extraction of water-soluble minerals, on the surface of which structures, buildings are located, is carried out according to plans drawn up in accordance with the specifics of the field, mining and other conditions by organizations licensed by the State Technical Supervision Authority.
Additionally
The liquidation of oil wells of an operational type provides, depending on the period of use, the possibility of exploring the restored areas. At adjacent facilities, safety must be ensured. Technical measures include:
- Checking the correctness of applying to the graphic documents the contours of the workings that are adjacent to the boundaries of the branch.
- Installation of insulating jumpers to prevent breakthroughs of gas, water or the spread of fires (underground).
During the conservation / liquidation of facilities that produce piezoelectric and quartz-gem raw materials, measures are taken to prevent outsiders from accessing valuable mineralogical components.
Checks
The safety of the workings, gas and oil wells, which are in a mothballed condition, is controlled by the methods and within the time limits established in the plan. Inspections are carried out at least 2 times a year and in case of natural disaster. Inspections of liquidated facilities are carried out at least 1 time per year. Verification is carried out by a specialized commission. Its composition is approved by the bodies of the State Technical Supervision Agency. For violation of the requirements established by law and the Instruction, the perpetrators may be held liable in the manner established by the norms.
Facilities including waste storage and hydraulic structures
When they are eliminated, the following activities are planned and carried out:
- Bringing the parameters of drives to values ensuring their long-term stability. In particular, the indicators of angles, slopes, etc. are adjusted.
- The structures are protected from wind and water erosion.
- Accumulators formed by radioactive and toxic waste are isolated from sediment infiltration.
- The bases are protected from erosion and flooding by atmospheric and flood waters.
- Accumulators from rocks prone to spontaneous combustion are isolated from sediment infiltration and air access to the massif.
Document approval
It is carried out in the bodies of the Gosgortekhnadzor. To obtain approval, the company sends a letter with the application:
- The list of structures and buildings planned for transfer.
- The layout plan of workings and wells.
- Geological maps and sections characterizing the structure of the site.
- Projects of measures to protect facilities from the negative impact of mining developments in the liquidated / conserved zone.
In the case of unfinished processes of moving the surface of the earth, a written consent of the receiving enterprise is also attached to carry out systematic monitoring of deformations and inform the control and supervisory authority about all cases of their occurrence.