conferences by Simon Zavsek
The TOPS project takes a radical and holistic approach to coupled UCG-CCS, and thus the site sele... more The TOPS project takes a radical and holistic approach to coupled UCG-CCS, and thus the site selection criteria for the coupled processes, considering both geological, reservoir and process engineering aspects and different end-uses of the produced synthetic gas in order to optimise the whole value chain. In particular, the experimental research carried out utilises a newly constructed high pressure gasification reactor investigating several prospective options of UCG technology implementations. Integrated research addresses field based technology knowledge gaps, such as cavity progression and geomechanics, potential groundwater contamination and subsidence impacts, together with research into process engineering solutions in order to assess the role/impact of site specific factors and selected reagents on the operability of given CO2 emission mitigation options. Ultimately, research aims to minimise the need for on-site CO2 storage capacity as well as maximising the economic yield of UCG through value added end products. © 2014 The Authors. Published by Elsevier Ltd.
Papers by Simon Zavsek
International Journal of Coal Geology, 2015
Uncontrolled and excessive gas emissions pose a serious threat to safety in underground coal mini... more Uncontrolled and excessive gas emissions pose a serious threat to safety in underground coal mining. In a recently completed research project, a suite of monitoring techniques were employed to assess the dynamic response of the coal seam being mined to longwall face advance at Coal Mine Velenje in Slovenia. Together with continuous monitoring of gas emissions, two seismic tomography measurement campaigns and a microseismic monitoring programme were implemented at one longwall top coal caving panel. Over 2000 microseismic events were recorded during a period of four months. Over the same period, there also was a recorded episode of relatively high gas emission in the same longwall district. In this paper, a detailed analysis of the processed microseismic data collected during the same monitoring period is presented. Specifically, the analysis includes the spatial distribution of the microseismic events with respect to the longwall face advance, the magnitude of the energy released per week and its temporal evolution. Examination of the spatial distribution of the recorded microseismic events has shown that most of the microseismic activity occurred ahead of the advancing face. Furthermore, the analysis of the gas emission and microseismic monitoring data has suggested that there is a direct correlation between microseismicity and gas emission rate, and that gas emission rate tends to reach a peak when seismic energy increases dramatically. It is believed that localised stress concentration over a relatively strong xyliterich zone and its eventual failure, which was also identified by the seismic tomography measurements, may have triggered the heightened microseismic activity and the excessive gas emission episode experienced at the longwall panel monitored.
International Journal of Coal Geology, 2014
International Journal of Coal Geology, 2015
The longwall top coal caving method, which enables the most productive exploitation of thick/ultr... more The longwall top coal caving method, which enables the most productive exploitation of thick/ultra-thick coal seams, may result in a distinct geomechanical response of strata and associated gas emission patterns around longwall layouts. A two-way sequential coupling of a geomechanical and a reservoir simulator for the modelling of gas emissions around a longwall top coal caving (LTCC) panels was developed building on the understanding established from the analysis of in-situ gas pressure and concentration measurements carried out at Coal Mine Velenje in Slovenia. Model findings have shown that the modelling method implemented can reproduce the dynamic changes of stresses and gas pressure around a LTCC face and predict the total gas emissions and mixed gas concentrations accurately. It was found that, in LTCC panels, although the rate of gas emission from mined coal depends highly on the coal face advance, floor coal and roof goaf act as a constant and steady gas source accounting for a considerable part of the overall gas emission. Research has shown that, at first and/or second mining levels of multi-level LTCC mining, a notable stress relief and pore pressure drop induced by fracturing of the mined and roof coal can be experienced within 40 m ahead of the face-line. In the floor coal, on the other hand, the pore pressure change was found to extend to 20 m below the mining horizon. Model results have clearly shown the permeability enhancement and gas mobilisation zones around the LTCC panel, which can be the target zones for gas drainage boreholes.
International Journal of Coal Geology, 2012
Stable isotopes of carbon were used to trace organic and inorganic carbon cycles and biogeochemic... more Stable isotopes of carbon were used to trace organic and inorganic carbon cycles and biogeochemical processes, especially methanogenesis within different geologic substrates of the Pliocene lignite-bearing Velenje Basin in northern Slovenia. Lithotypes of lignite, coalbed gases, calcified woods (xylites), carbonate-rich sediments, and groundwaters were investigated. Carbon isotope (δ 13 C) values of the different lignite lithotypes ranged from − 28.1 to − 23.0‰, with the variability likely a function of the original isotopic heterogeneity of the source plant materials and subsequent biogeochemical processes (i.e. gelification, fusinitization, mineralization of organic matter) during the early stage of biomass accumulation and diagenesis. In the lignite seam, CO 2 and CH 4 were the major gas components with small amounts of N 2 . The carbon isotope values of CO 2 (δ 13 C CO2 ) and CH 4 (δ 13 C CH4 ) were highly variable, ranging from − 9.7 to 0.6‰ and − 70.5 to − 34.2‰, respectively. Carbon dioxide is likely sourced from a mixture of in situ microbial activity and external CO 2 , while CH 4 is dominantly sourced from microbial methanogenesis, with possible addition of thermogenic gas from deeper formations, and the influence of microbial oxidation of methane. Calcified xylites enriched with 13 C (δ 13 C values up to 16.7‰) indicate that microbial methanogenesis was active during formation of the basin. The δ 13 C DIC values (from − 17.4 to − 3.2‰) of groundwaters recharging the basin from the Triassic aquifer are consistent with degradation of organic matter and dissolution of dolomite. Groundwaters from the Pliocene sandy and Lithotamnium carbonate aquifers have δ 13 C DIC values (from − 9.1 to 0.2‰) suggestive of degradation of organic matter and enrichment via microbial reduction of CO 2 .
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conferences by Simon Zavsek
Papers by Simon Zavsek