Modelling a multi-layer coal mine deposit: A case study of avdan lignite site in Denizli, Turkey

Coal is one of the most important sources for energy production in all over the world. Sustainability of energy production from a thermal power plant should be correlated with reserve quality and quantity of coal deposit. Reserve quantity and quality must be determined from innovative approaches to decrease risk arising from ore body modelling. Geological formation of the coal deposit can be assumed as the initial stage for coal deposit research. Coal deposit can be found as vein, lake, or delta types based on the location, geological background and evolution. Understanding the geological background of coal deposit is useful for estimating possible development of coal deposit based on the location. Vein type coal deposits are the easiest to model due to the continuity while delta types are the most complex structures. Interburden defined as the material separating coal seams within strata is also continuous for vein type coals while several interburdens can be found randomly in coal band alternation for delta type deposit. Different veins in a single coal deposit can be correlated based on whole coal dating however it is hard to correlate the several different coal bands in a single delta type coal deposit. Avdan lignite mine deposit is located in the western part of Turkey. This deposit is important to supply coal for a 150 MWe capacity thermal power plant located close to the mine site nearly for 25 years. The lignite mine will be operated by open pit mining based on the feasibility project carried out for thermal power plant. The deposit is delta type that was a challenging study for modelling ore body. A database was formed from 103 drill logs in the study area for modelling the coal deposit. Maximum distance between the drill logs is prevented to exceed more than 250 m to obtain coal deposit reserve classification as per measured coal resource. Border of the coal deposit was defined from the database based on the geological structure. Cut-off values for minimum coal thickness and lowest calorific value are selected as 40 cm and 950 kcal/kg during the coal deposit modelling. These values were selected as per production method as well as thermal power plant technology. Afterwards, database was used to model the coal structures in the lignite zones. Two main coal structures that are named as Sekkoy and Yenidere Coal Zones were derived from the investigations. Due to the impossibility of correlations among the coal bands, coal zones were defined for these two main coal structures. Coal zone definitions that are the most innovative aspect of this research would be useful to determine the quantity of the coal reserve for the different coal zones in the study area. Hence, although it was not possible to correlate coal bands from one drill log to the other, it is possible to design the coal zones as well as the coal thickness that must be required for reserve estimation. On the other hand, the quality of the deposit based on calorific value, humidity, ash, and sulphur was also determined for each coal zone from geostatistical research. Thereby, quality distribution maps as well as calorific value and reserve estimation graph were also designed for the study area. Micromine software were used to model delta type coal deposit as well as geostatistical applications to obtain quality distribution maps.