Coal Measure Gas Accumulation Potential And Evaluation Of Favorable Areas In The Kele Syncline,northwestern Guizhou

The research object of this thesis is the Kele syncline in northwestern Guizhou,and the research horizon is the Late Permian Changxing Formation-Longtan Formation/Xuanwei Formation coal measure strata.On the whole,the degree of coal-measure gas(CMG)geology research in the study area is relatively low.Therefore,based on a large number of CMG evaluation wells and test laboratory data,the CMG stratigraphic deposition,reservoir physical properties,and rich accumulation characteristics have been analyzed and studied.The results of favorable sections of CMG in the study area are obtained.Get the following conclusions.First,The sedimentary characteristics of coal-measure strata in the study area are clarified,and a three-level sequence is divided.According to the lithology markers of the sequence interface and the largest flooding surface,geophysical logging response,and wavelet analysis,the study area is divided into 3 third-order sequences and 9system tracts in the Late Permian coal-bearing rock series.Through field outcrop observation,core description,and drilling data analysis,sedimentary facies such as fluvial facies,deltas,tidal flats and lagoons are identified.The SQ3 sequence is the main coal-bearing sequence in the study area.The western and central parts of the SQ3 sequence developed delta plain facies,the central and western parts developed riverbed subfacies,and the eastern part was dominated by lagoon-tidal flat facies.In some areas,carbonate platforms and barrier sand bar facies developed,and medium-thick coal seams appeared(M11),it is the main mineable coal seam in the study area,and the top of the M11 coal seam is the largest flooding surface.The study area contains 5 main mineable coal seams(M3,M11,M15,M16,M18).The thickness of sandstone gradually decreases from west to east,and the thickness of mudstone gradually increases from west to east.Second,The physical properties of coal-measure reservoirs were evaluated,the law of CMG enrichment was revealed,and the superimposed gas-bearing system was divided.The coal seams in the study area are mainly lean coal-anthracite coal,belonging to low-medium permeability reservoirs.The vertical gas content varies greatly,and the average gas saturation is undersaturated.The gas saturation in the east is better than that in the west,and the reservoir is underpressure-The overpressure states are all distributed,mainly underpressure,and the central coal body has a better structure.Vertically,the content of clay minerals in coal-measure reservoirs gradually increases.For continental coal-bearing strata,the coal seam section is mainly in a gas-bearing system.For sea-continent coal-bearing strata,the coal seam section is mainly in a large gas-bearing system,which can be subdivided into two small gas-bearing systems,with M11 the coal seam is the boundary.Affected by the sedimentary environment,from west to east,the degree of development of the superimposed coalbed methane(CBM)system gradually increases.The CMG accumulation model of "sedimentation controlling source and storage,hydrological structure controlling reservoir" is proposed.Third,Third: The evaluation index for favorable sections of CBM and tight gas has been established,the optimization of favorable sections of CBM and tight gas has been completed,and the favorable co-extraction areas of coal-measure methane and their resource potential have been preliminarily evaluated.Based on the actual CBM geological conditions and development effects in the study area,the CBM content,coal body structure,and combined production coefficient are selected as key indicators for the optimization of favorable areas for multi-layer combined mining of CBM,and quantitative evaluation indicators have been formulated,using multiple levels The fuzzy mathematics evaluation method is used to optimize the favorable areas of CBM.In addition,evaluation indicators for favorable areas of coal-measure tight gas have been formulated.For coal-measure tight gas,the idea of “field” is introduced,and the SQ3 sequence is selected as a favorable interval for CMG development in the study area.The multi-source information superposition method is used to complete the optimization of the favorable tight gas area.Favorable areas of CBM type I are mainly distributed in most of the central and western regions,and less in the east.Favorable areas of tight gas type I are mainly distributed in the central and western regions of the study area.At the same time,the method of plane superposition is used to optimize the advantages of CBM/tight gas co-production The favorable areas for common mining are mainly distributed in the central and western part of the study area.This paper has 102 figures,52 tables and more than 140 references.