| Gas outburst and mine water inrush are two major disasters in the process of mine production.The development of tectonically deformed coal(TDC)is a pre-condition for the occurrence of gas outburst,and the abundant water content is a pre-condition for the occurrence of mine water inrush.In this paper,we combine well logs analysis with petrophysics and seismic inversion methods to identify and predict tectonically deformed coal and water-content for coalbed and roof aquifer.The prediction results can provide important geological information for the safety production of coal mines.For the method research of TDC prediction,we use the 8th coal seam of Luling coalmine as the study target.First of all,we use the response characteristics of well logs from different coal structure types to identify coal structure.In order to improve the recognition accuracy,we use multi-scale wavelet analysis to extract the components of low frequency and intermediate frequency from original well logs,and use the extracted components of low frequency and intermediate frequency as the inputs to classify the types of coal structure using cluster analysis.Through the practical identification,we have identified the primary coal,the cataclastic coal,the granulated coal and the mylonitized coal from the study target,as well as the coal gangue.Then,based on the identified coal types of all wells,we plot a ternary phase diagram of coal structures and use the distribution of wells to classify coal seam into I,II,III and IV regions where the coal seam is combined with different types of coal.After that,based on the ultrasonic testing results of different structural types of coal,we obtain P-wave velocity and P-wave impedance inversion slices of the 8 coal seam through impedance inversion,and classify the coal seam quantitatively into the four types regions where the coal seam is combined with different types of coal through crossplot analysis.In the region of III and IV,the coal seam is composed of the most developed tectonically-deformed coal,and is the key area to prevent and cure coal and gas outburst.Finally,we find that the burial depth of coalbed and the tectonic movement are the main factors affecting the development of TDC in the study area.For the method research of water content prediction of roof sandstone,we use the 30101 goaf and 30102 goaf of Hanglaiwan coalmine as the study target.First of all,we identify the aquifers of #1-6 sandstone,the separation structure 1 and the separation structure 2 based on various well logs comparison.Through P-wave velocity and P-wave impedance inversion as well as Gassmann equation,we obtain slices of #1-6 sandstone.Through crossplot analysis,we can qualitatively divide the water saturation of roof sandstone into three types: saturated gas,semi saturated water and saturated water.Then,we obtain inversed porosity slices of #1-6 sandstone based on PNN inversion.Through comparison and analysis,we can find that the porosity of the sandstone in the gooaf area is obviously larger than that in the unmined area because the influence of mining will damage roof sandstone and develop fracture structure.After that,we qualitatively divide the watercontents of #1-6 sandstone into three types: dry,weak water enrichment and strong water enrichment using water saturation and porosity as inputs.Through comparison with the analyzed results of well logs,they show high consistency.Through comparison and analysis,we find the water content of roof sandstone in the goaf area is obviously larger than the content in unmined area.Finally,we identify and predict the coal pillar,separation structure and "three zones" of the goaf through comparing various inversion sections in the study area.In summary,this paper research on the lithology prediction methods of TDC and water content of roof sandstone through combining well logs analysis with petrophysics and seismic inversion.The research results serves as reference for preventing coal mine disaster. |
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