Characteristics Of Multiple Seams Of The Upper Permian Longtan Formation In Zhijin Area Of Guizhou

On the basis of previous studies,this article analyzes coal bed formation sedimentary background and sedimentary facies features in terms of coal bed sedimentary environment and tectonic background in Zhijin area,which combines drilling core,logging and coal rock experimental.Coal accumulation pattern of the Permian Longtan Formation is concluded in the longitudinal direction,and studies the coal-bearing syncline coal reserves features of this coal bed formation,coal rock and coal quality,coal-bearing syncline tectonic deformation,fracture features,metamorphic degree,coal seam gas content horizontal distribution and affecting factors.The research shows that the major coal bed in the research area belongs to the Permian Longtan Formation,it can be divided bottom up into 3coal groups containing 34 coal seams,there are 7 major bedsamoungthem.The analysis of drilling core and log curve indicates that the Longtan Formation in Zhijin area is a deltaic-tidal flat sedimentary system,which is controlled by sea transgression and regression in the sedimentary stage of Longtan Formation,showing overlapping of tidal flat,delta and tidal flat vertically.The tidal flat facies benefits the sustained development of peat sediment,the developed coal seam is relatively good;and the number of coal beds,the number of recoverable seams and seam thicknesses decrease gradually from west to east.The metamorphism degree of the coals in Zhijin area is relatively high with high hydrocarbon production volume and strong coal rock adsorption ability,which is also the basic geological conditions for high coal seam gas content.By the comprehensive analysis gas bearing characteristicsand preservation condition of coal bed methane,the research clears Longtan formation coal bed methaneaccumulation control factors: the roof and floor lithology is basic condition for coal bed methane preservation;the tectonic action leads to many times gas production in coal seam and reservoir physical properties improvement.The depth of single coal bearing structure is main control factor for coal bed methane enrichment.Hydrogeological conditions in favor of preservation of coal bed methane.