Abstracts by Mining Department

Symposium on Oil Shale

 

Table of Contents

Table of Contents. 1

ORAL PRESENTATIONS November 18, 2002 - 14.30-15.00, Estonian oil shale mining. 2

Estonian oil shale resources calculated by GIS-method. 4

Mining block stability analysis for room-and-pillar mining with continuous miner in Estonian oil shale mines  6

Sulphate Balance of Lakes and Shallow Groundwater in the Vasavere Valley, Northeast Estonia. 8

POSTER PRESENTATIONS – SECTION 1 - OIL SHALE RESOURCES, GEOLOGY AND MINING   8

No 1, Estonian oil shale mining map. 9

No 2, Estonian oil shale resources calculated by GIS-method. 9

No 3, Geotechnical processes of closed oil shale mines. 10

No 4, Mining block stability analysis for room-and-pillar mining with continuous miner in Estonian oil shale mines  10

No 5, Design of new oil shale surface mine. 11

No 6, Analyse of overburden rock jointing for optimisation of drill and plasting pattern. 11

No 13, Working mining block stability prediction methods in Estonian oil shale mines. 11

 


ORAL PRESENTATIONS November 18, 2002 - 14.30-15.00, Estonian oil shale mining

Alo Adamson, PhD (a), Mati Jostov (b)

(a) Department of Mining, Tallinn Technical University
(b) Estonian Oil Shale Company

The reserves of the operating mines and open casts of Estonian oil shale deposits approximate 0.6 bill. tonnes plus the reserves of exploration fields. According to the criteria determined by us, the active reserves of exploration fields exceed 2 bill. tonnes of oil shale rock over 17 EJ of energy and passive resources account for over 4 bill. tonnes of oil shale rock or over 30 EJ of energy.

Oil-shale resources of Estonia are state-owned and lie in the Estonian deposit which is of national importance.

AS Eesti Põlevkivi group consists of the parent company and 6 subsidiaries. In addition to 2 open casts and 2 underground mines, Põlevkivi Raudtee Ltd. (a railway enetrprise) and Mäetehnika Ltd. (mining machinery enterprise) also belong to the group. The parent company's competence is: general management, accounting, financial operations, sales, IT-services, mine surveyor's services, PR, etc.

All in all the group have 4,800 employees.

Approximately 80 percent of the extracted oil shale are used for the generation of electricity and thermal energy, and 20 percent is used for shale oil production. The shares of the company are held by Narva EJ (51 percent) and the Republic of Estonia (49 percent).

Volume of sales of oil shale mined by Eesti Põlevkivi is 12.36 million ton in the current business year.

Eesti Põlevkivi turnover forecast is 1,525 billion krone. Enterprise plans to get 102-million krone profit.

AS Eesti Põlevkivi invests 300 million krone including 242 million krone into production engineering and equipment.

Thanks to systematic cost cutting, the price of oil shale sold to Power Plants together with transportation costs is being reduced from 133.08 krone/ton last year to 127.94 krone/ton current year.

In 2001/2002, Eesti Põlevkivi began implementing an ISO14001-compliant environment management system and an ISO 9002-compliant quality management system.

 

 

Section 1 - OIL SHALE RESOURCES, GEOLOGY, AND MINING
November 18, 2002 - 17.40-18.00

Estonian oil shale resources calculated by GIS-method

Ingo Valgma, Dr. Eng.

Mining Department of Tallinn Technical University,
Kopli 82, Tallinn, 10412, Estonia,

http:/www.ttu.ee/maeinst/

Phone: +372 620 38 50, Fax: + 372 620 36 96,
E-mail: ingoval@cc.ttu.ee

A digital map of Estonian oil shale mining was created for joining data of technological, environmental, and social limitations in the deposit. For evaluating potential resource of oil shale, based on borehole database, its amount, tonnage and energy were calculated. Then the quantity of economical oil shale for power plants and shale oil resource were calculated. Energy rating is the most important factor for determining oil shale reserve in the case of using it for electricity generation. In the case of oil production, figures of oil yield and resource in oil shale are the most important for determining the value of the deposit. Basing on the models, oil resource has been calculated. Resource data can be used for composing master plans both for the deposit in purpose of power generation and for processing. The data can be also used for composing development plans of the mines and for logistics calculations.

 

Section 1 - OIL SHALE RESOURCES, GEOLOGY, AND MINING
November 19, 2002 - 10.20-10.40

Mining block stability analysis for room-and-pillar mining with continuous miner in Estonian oil shale mines

Oleg Nikitin, Researcher, M.Sc.

Tallinn Technical University, Department of Mining
82 Kopli St., Tallinn 10412, ESTONIA
Phone: (372)6203850
Fax: (372)6203696
E-mail: Ole.Nik@mail.ee
Homepage: http:/www.ttu.ee/maeinst/

The most important mineral resource in Estonia is a specific kind of oil shale. About 99% of electric and large share of thermal energy are being generated from oil shale. The importance of oil shale production can not be overestimated for development of Estonian economy. It is estimated that about 80-90% of the total underground oil shale production is obtained by room-and-pillar method with blasting. The method is cheap, highly productive and relatively simple to apply. Now, it appears some problems:

·               Decreasing of amount of oil shale production ( about 50%);

·               Old technology and fashioned mining machinery (low extraction factor);

·               Mining block stability (collapse and surface subsidence).

Elaborated new room-and-pillar mining method with continuous miner allows to give greatest extraction factor, high productivity and leave no-conditional rock mass in underground mined out areas. It is known that the deposit of oil shale is located in a densely populated and intensely farmed district. Consequently, the mining system must guarantee the long-term stability of the pillars and roof.

Determination of the pillars and roof optimum parameters for new mining technology is the main aim of the present work.

The conventional calculation formulas and conditional thickness methods were used. Used methods allow to determine the room-and-pillar mining system parameters, which guarantee the long-term stability. Used calculation methods give excellent results.

Section 1 - OIL SHALE RESOURCES, GEOLOGY, AND MINING
November 19, 2002 - 10.40-11.00  

Sulphate Balance of Lakes and Shallow Groundwater in the Vasavere Valley, Northeast Estonia

Katrin Erg, M.Sc

Tallinn Technical University, Department of Mining
82 Kopli St., Tallinn 10412, ESTONIA
Phone: (372)6203850, Fax: (372)6203696
E-mail: erg@staff.ttu.ee
Homepage: http:/www.ttu.ee/maeinst/

The Vasavere valley is situated in the centre of the Estonian oil shale deposit area. The valley is of north-south orientation, and surrounded from all sides by oil shale mines. The area (ca 30 km²) contains 39 lakes that are more or less influenced by oil shale mining, water consumption and industrial activities. The state of the lake ecosystems is, first of all, determined by the groundwater regime.

The data available on the state of the lakes before World War II is quite limited. It may be assumed that up to the 1950s natural conditions prevailed. The earliest published data, characterising the end of the 1930s support this assumption. Comparing these data with the present ones, it is possible to evaluate the extent of man-made changes in the lakes and shallow groundwater. Some of these effects are as follows:

·               introduction of airborne pollutants into groundwater,

·               increase in the concentration of sulphate in shallow groundwater and in lakes.

The content of sulphate in the groundwater indicates directly the influence of the mining waters. Oxidation of the pyrite contained in Ordovician deposits, serves as a source of this compound, and concentrations up to 500-mg l-1 have been found in mining waters. In 1937, when the lakes studied were mostly in natural conditions, the sulphate content was in the range of 1.0-6.7 mg l-1 in the lakes and, presumably, also in the groundwater. In resent years the content of sulphate has increased both in the closed lakes and in those influenced by mining waters. This rise has been especially high in the lakes affected directly (discharge) or indirectly (infiltration) by mining waters, having recently the sulphate values in the range of 160-259 mg l-1. When, for example, in 1937 the sulphate content in Lakes Nõmmjärv and Konsu were 5.8 and 1.0 mg l-1, then in 2001 it was 259 and 184 mg l-1, respectively; in the shallow groundwater the content of sulphate increased more than 70 times during 1970-2001.

Water resource development has often been based on the predominant use of either surface or groundwater; it must be emphasised that these two components of the total water resource are interdependent. Changes in one component can have far-reaching effects on the other.

Numerous models have already been developed to simulate the above – mentioned hydrochemical processes. Balancing the input and output of sulphate in the Vasavere valley enables to provide a provisional hypothesis about internal hydrochemical processes in the Quaternary aquifer. A chemical model can describe possible paths of reaction. A description of the influence of different kinds of land use on sulphate content in groundwater can be achieved by this method. In order to estimate the kinetics of reactions involved, it is necessary to obtain detailed information about groundwater flow in the aquifer.

Due to the combined effect of natural and technogenic factors, a persistent tendency for transformation of physico-chemical composition of the waters has developed (heightened content of sulphate). This tendency will not disappear after finishing the active production processes and closing the mine.

 

 

POSTER PRESENTATIONS – SECTION 1 - OIL SHALE RESOURCES, GEOLOGY AND MINING

November 18-19, 2002

No 1, Estonian oil shale mining map

Ingo Valgma, Dr. Eng.

Mining Department of Tallinn Technical University,
Kopli 82, Tallinn, 10412, Estonia,

http:/www.ttu.ee/maeinst/

Phone: +372 620 38 50, Fax: + 372 620 36 96,
E-mail: ingoval@cc.ttu.ee

Overview. Oil Shale is Estonia’s prime mineral resource. Oil shale is deposited in a single economic layer with thickness of 2,5 to 3 meters in depth of 7 to 100 meters in area of 2700 km². Its production makes 70 percent of world’s oil shale production and two thirds of Estonia’s total mineral production. Mining activity started in 1916, peaked in 1980 and is ending in next 30 years. Therefore it is important to save oil shale mining history in easily accessible database. The Mining Institute of Tallinn Technical University has created geographically referenced database of oil shale. MapInfo Professional is used for mapping geology and mining situation. The map includes research and mining fields, mineral and overburden properties, underground and surface workings. Additionally technological diagrams and data are saved. For analyzing underground mining influences, exact current mining situation and previous situation is compared with surface topology in mined out areas. Open cast mining results are compared with aerial photos and digital base maps.

Map. MapInfo Professional has been used for analyzing digital maps of oil shale mining area. All maps are created in Mining Department of Tallinn Technical University. Additional information could be found on Internet location http://mgis.gz.ee/. Following technologies are described on the map:

·               Advancing and retreating mining, depth in meters H = 8 - 30 m, mining duration in years = from 1916 to 1967

·               Open cast mining by handwork, Depth in meters H = 0 - 6 m, Duration in years =, from 1918 to 1941

·               Open cast mining, with first stripping equipment, Depth in meters H = 6 - 10 m, Duration in years =, from 1928 to 1944

·               Longwall mining with, partial backfilling, Depth in meters, H = 9 - 40 m, Mining duration in years = from 1952 to 1989

·               Room & Pillar mining with scraper conveyor, Depth in meters H = 10 - 75 m, Duration in years = from 1960 to 2005

·               Room & Pillar mining with LHD, Depth in meters H = 40 - 80 m, Duration in years = from 1970 to 2030

·               Longwall mining, Depth in meters H = 10 - 40 m, Mining duration in years =, from 1971 to 2000

Current open cast mining, Depth in meters H = 3 - 27 m, mining duration in years = from 1919 to 2030

The study was supported by EstSF GRANT G3403. Poster will be presented as detailed map of oil shale mining technology, including illustrative diagrams and photographs, overview could be found on http://mgis.gz.ee/

 

No 2, Estonian oil shale resources calculated by GIS-method

Ingo Valgma, Dr. Eng.

Mining Department of Tallinn Technical University,
Kopli 82, Tallinn, 10412, Estonia,

http:/www.ttu.ee/maeinst/

Phone: +372 620 38 50, Fax: + 372 620 36 96,
E-mail: ingoval@cc.ttu.ee

A digital map of Estonian oil shale mining was created for joining data of technological, environmental, and social limitations in the deposit. For evaluating potential resource of oil shale, based on borehole database, its amount, tonnage and energy were calculated. Then the quantity of economical oil shale for power plants and shale oil resource were calculated. Energy rating is the most important factor for determining oil shale reserve in the case of using it for electricity generation. In the case of oil production, figures of oil yield and resource in oil shale are the most important for determining the value of the deposit. Basing on the models, oil resource has been calculated. Resource data can be used for composing master plans both for the deposit in purpose of power generation and for processing. The data can be also used for composing development plans of the mines and for logistics calculations.

 

No 3, Geotechnical processes of closed oil shale mines

Enno Reinsalu, PhD, Ingo Valgma, Dr. Eng.

Department of Mining Tallinn Technical University

Mining Department of Tallinn Technical University,
Kopli 82, Tallinn, 10412, Estonia,

http:/www.ttu.ee/maeinst/

Phone: +372 620 38 50, Fax: + 372 620 36 96,
E-mail: maeinst@cc.ttu.ee

 

During years 1998…2001 geotechnical processes of closed underground oil shale mines and opencasts were investigated. In addition to kukersite oil shale deposit closed Sillamäe uranium mine (dictyonema oil shale) was prospected. The main tools and methods for studying were mine plans, aerial photographs and GIS. The study object was area of 290 km² underground and 130 km² strip mined area. The maps of underground mines of Estonia and oil shale surface mining maps were created during this study. The main objective was the stability of underground mined area, which has been mined by room and pillar method. The stability was studied with help of aerial photographs, mine drawings, maps of quaternary sediments and mathematical modelling of rock failure. The main results are: 20% of subsidences remain undiscovered; 42% of the subsidence occurrences do not have remarkable influence to the land cover; the probability of subsidence remain and increase in case of mine drowning. Because of several mines are being closed during next few years the problems of drowned waste (which were not subjects of this study) are going to be more actual than before: increase of underground water level, underground water pollution, technogenic water sources and over flooding of reclaimed areas.

 

No 4, Mining block stability analysis for room-and-pillar mining with continuous miner in Estonian oil shale mines

Oleg Nikitin, M.Sc.

Tallinn Technical University, Department of Mining
82 Kopli St., Tallinn 10412, ESTONIA
Phone: (372)6203850, Fax: (372)6203696
E-mail: Ole.Nik@mail.ee
Homepage: http:/www.ttu.ee/maeinst/

The most important mineral resource in Estonia is a specific kind of oil shale. About 99% of electric and large share of thermal energy are being generated from oil shale. The importance of oil shale production can not be overestimated for development of Estonian economy. It is estimated that about 80-90% of the total underground oil shale production is obtained by room-and-pillar method with blasting. The method is cheap, highly productive and relatively simple to apply. Now, it appears some problems:

·               Decreasing of amount of oil shale production ( about 50%);

·               Old technology and fashioned mining machinery (low extraction factor);

·               Mining block stability (collapse and surface subsidence).

Elaborated new room-and-pillar mining method with continuous miner allows to give greatest extraction factor, high productivity and leave no-conditional rock mass in underground mined out areas. It is known that the deposit of oil shale is located in a densely populated and intensely farmed district. Consequently, the mining system must guarantee the long-term stability of the pillars and roof.

Determination of the pillars and roof optimum parameters for new mining technology is the main aim of the present work.

The conventional calculation formulas and conditional thickness methods were used. Used methods allow to determine the room-and-pillar mining system parameters, which guarantee the long-term stability. Used calculation methods give excellent results.

 

No 5, Design of new oil shale surface mine

Tõnis Kattel, B.Sc

Mining Department of Tallinn Technical University,
Kopli 82, Tallinn, 10412, Estonia,
http://www.ttu.ee/maeinst/
E-mail: toniskat@staff.ttu.ee

Last open cast oil shale mine in Estonia was opened in 1974 (Aidu karjäär) and underground mine in 1972 (Estonia kaevandus). Today all oil shale mining enterprises belongs to the company Eesti Põlevkivi. During last years some of the oil shale users have been seeking opportunities to own themselves mines/open casts. The most sucsessful has been Kunda Nordic Tsement (cement indusry). There have been carried out a number of geological and environmental survies at Ubja site. Also several technical design plans have been made. Today is almost clear that new open cast mine at Ubja will be opened soon.

 

No 6, Analyse of overburden rock jointing for optimisation of drill and plasting pattern

Ülo Sõstra, D.Sc

Mining Department of the TTU

Data, received at mining, and special study of jointing and tectonic dislocations in Estonian oil shale basin (Heinsalu, Andra, 1975; Puura, 1986) show, that territory is divided into blocks by NE direction system of tectonic dislocations (middle scale set of two folds, anticline and syncline, with flexure or normal fault between, with amplitude 10-26 m) and system of long NW direction joints. Distances between biggest joints and jointed rock zones are usually 15-30 m. After the first blasting overburden limestone massif is divided into 20-50 m wide blocks with open joints, 20-30 cm between the walls. Future cracking process is possible only inside these blocks.

Known regularities of joint and dislocation orientation gives possibility to use it for more effective compiling of drill and plasting pattern. Department of Mining during last years began special study of Estonian bedrock jointing to find out regional rules of its forming and orientation. Some next years these works will be continued in NE Estonia, including territory of oil shale deposit. Co-operation with oil shale open pits helps to use regularities of joint density and orientation for making more effective works for removing the overburden and saves blasting materials.

 

 

No 13, Working mining block stability prediction methods in Estonian oil shale mines

Jüri-Rivaldo Pastarus, Dr.Eng

Tallinn Technical University
Department of Mining
82 Kopli St.,Tallinn, 10412
ESTONIA
Phone: (372)6203850, Fax: (372)6203696
e-mail: pastarus@cc.ttu.ee

The most important mineral resource in Estonia is a peculiar kind of oil shale. Deposit is located in a densely populated and intensely farmed district. It is estimated that about 80-90% of the total underground oil shale production is obtained by room-and-pillar method. It has become apparent that the processes in overburden rocks and pillars have caused unfavorable environmental side effects accompanied by significant subsidence of the ground surface.

Identification of the reasons of the mining block collapse, elucidation of the basic mechanism of this process and elaboration of the method of prognosis are the main aim of the present work.

In Estonian oil shale mines, the pillars and the roof are non-homogeneous and structurally complicated. The pillars are arranged in a singular grid. Consequently, the stability analysis demands the special methods and calculation schemes. The studies are based on the complex method, including: investigations of in situ conditions, theoretical investigations and modeling on PC.

The mining block stability depends on the real parameters of the roof and pillar. For the stability analysis the concept of critical width, methods of conditional thickness and sliding rectangle have been used. They suit for modeling on PC. Visual Basic for application in Excel and MapInfo was used for numerical modeling. The results are presented by conditional thickness contours, which allows determine the collapse parameters in a mining block. Error does not exceed 4%. Conditional thickness is related to the load on a pillar. If the load is too much for the pillar, a sudden failure is likely.

On the other hand the rheological parameters of the rocks determine the strength of a pillar. Exponent function describes adequate the rock weakening process in a pillar during time. The error is about 16%. The pillar load (conditional thickness) and strength (exponent function) determine the stability of a mining block. The utility of these methods was clearly demonstrated.

Above mentioned methods allow to determine the exact location, parameters and time of a potential collapse. Surface subsidence parameters will be determined by conventional calculation scheme. Proposed method suits for stability analysis, failure prognosis and monitoring.

 

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Abstracts by Mining Department

Symposium on Oil Shale