Sandstones blowout risk in the South-Western region of Lviv-Volyn coal basin
Abstract
The aim of the research. Investigation of coal-containing sandstones of the Tyagliv and Lyubelya fields of the Lviv-Volyn Coal Basin (LVB) has shown their potential ability for rapid blowout of rocks and gas. Methodology. Studies of structural-textural peculiarities of sandstones, determination of complex indication of blowout risk “B”, construction of lithological-stratigraphic sections, focus on the situa-tion of blow-out risk. Results. In the Tyagliv and Lyubelya fields the rocks of Buzhanka Suite of the Lower Carbonif-erous and the rocks of the Morozovychi Suite of the Bashkirian stage of the Middle Carboniferous have been studied. On the basis of the structural-textural peculiarities of sandstones, studies of their reservoir properties and gas presence it has been possible to prove the probability of the existing rock blowouts at depths more than 700 m for the South-Western coal-bearing region of the LVB. By struc-tural-textural indexes, transformation stages of certain minerals indicators, presence of secondary con-tacts between grains and values of the metamorphism coefficient “C”, it has been established that sandstones R, PVR and PМ of South-Western coal-bearing region belong to the stages of initial and deep catagenesis. Occurrence of sudden blowouts of rocks is possible for the sandstones of deep cat-agenesis stage under certain determined conditions. Layers and lenses of sandstones, potentially capable for sudden blowouts, are distinguished by the complex index of blowout danger “B” in the coal-bearing sequence of Tyahliv and Lyubela fields in deep horizons.For the rocks of Tyahliv field, which is more gas-bearing within the basin, the potential danger of blowouts is greater. Especially this refers to the local anticline highs, which complicate sections of the Tyahliv syncline. Lenses of potentially blowout dangerous sandstones have been distinguished also in unevenly de-gassed sequence of the Lyubela field. By their structural-textural features they are dense with great amount of rigid secondary incorporation and suture contacts between grains. Combination of in-creased stress of tectonic nature with significant brittleness of the sandstone is a sufficient condition for sudden release of highly stressful conditions in rocks.Scientific novelty. Application of the complex approach to the study of rock layers together with structural-textural peculiarities, determination of stages of catagenetic transformation is an important factor for establishment of reasons, factors of blowout risk phenomenon in coal-bearing rocks on the whole.Practical significance. Investigation of occurrence and spread of the gas-dynamic phenomena (blowouts of coal, rocks and gas, mountain shocks) are an integral part of gas-coal fields study. Investigation of the sandstones in South-Western coal-bearing region of LVB, allocation of the layers and lenses of sandstones, potentially capable for sudden blowouts, are relevant from the point of view of increasing the mineral-resource base of the basin by developing new deep horizons.The aim of the research. Investigation of coal-containing sandstones of the Tyagliv and Lyubelya fields of the Lviv-Volyn Coal Basin (LVB) has shown their potential ability for rapid blowout of rocks and gas.
Methodology. Studies of structural-textural peculiarities of sandstones, determination of complex indication of blowout risk “B”, construction of lithological-stratigraphic sections, focus on the situation of blow-out risk.
Results.In the Tyagliv and Lyubelya fields the rocks of Buzhanka Suite of the Lower Carboniferous and the rocks of the Morozovychi Suite of the Bashkirian stage of the Middle Carboniferous have been studied. On the basis of the structural-textural peculiarities of sandstones, studies of their reservoir properties and gas presence it has been possible to prove the probability of the existing rock blowouts at depths more than 700 m for the South-Western coal-bearing region of the LVB. By structural-textural indexes, transformation stages of certain minerals indicators, presence of secondary contacts between grains and values of the metamorphism coefficient “C”, it has been established that sandstones R, PVR and PМ of South-Western coal-bearing region belong to the stages of initial and deep catagenesis. Occurrence of sudden blowouts of rocks is possible for the sandstones of deep catagenesis stage under certain determined conditions.
Layers and lenses of sandstones, potentially capable for sudden blowouts, are distinguished by the complex index of blowout danger “B” in the coal-bearing sequence of Tyahliv and Lyubela fields in deep horizons.
For the rocks of Tyahliv field, which is more gas-bearing within the basin, the potential danger of blowouts is greater. Especially this refers to the local anticline highs, which complicate sections of the Tyahliv syncline.
Lenses of potentially blowout dangerous sandstones have been distinguished also in unevenly degassed sequence of the Lyubela field. By their structural-textural features they are dense with great amount of rigid secondary incorporation and suture contacts between grains. Combination of increased stress of tectonic nature with significant brittleness of the sandstone is a sufficient condition for sudden release of highly stressful conditions in rocks.
Scientific novelty. Application of the complex approach to the study of rock layers together with structural-textural peculiarities, determination of stages of catagenetic transformation is an important factor for establishment of reasons, factors of blowout risk phenomenon in coal-bearing rocks on the whole.Practical significance. Investigation of occurrence and spread of the gas-dynamic phenomena (blowouts of coal, rocks and gas, mountain shocks) are an integral part of gas-coal fields study. Investigation of the sandstones in South-Western coal-bearing region of LVB, allocation of the layers and lenses of sandstones, potentially capable for sudden blowouts, are relevant from the point of view of increasing the mineral-resource base of the basin by developing new deep horizons.Downloads
References
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