Study On The Formation Of Coal Measures Superimposed Gas-bearing System Under The Constraints Of Structure-sedimentary Evolution In Jixi Basin

The Jixi Basin is one of the key coal-bearing basins in northeast China,and the exploration practice has proved to have good geological conditions and prospect of exploration and development of coal-gas.In this paper,in view of the particularity of the cretaceous coal formation situ in the Jixi Basin,the new theory of tectonic geology,sedimentology,stratospheric stratigraphy,unconventional natural gas geology and new theories of unconventional natural gas exploration,new technologies and new methods,combined with regional geological background,comprehensive use of geological data such as drilling,logging,two-dimensional earthquake,etc.,to identify the geological conditions of coal gas formation in the Jixi Basin,and to reveal the coal gas combination,storage and cover combination of coal gas configuration.On this basis,it is revealed that the structure and sedimentation evolution have a control effect on the formation of overlapping coal gas systems.The spatial distribution law of sedimentary phase in coal system is clarified by means of the identification of sedimentary phase signs,the identification of sedimentary phase marks,the determination of sedimentary phase combination,and the spatial distribution of sedimentary phase in coal system.In the early Cretaceous coal line formations of the Jixi Basin,river phase(curved river,braided river),lake phase,delta phase(curvature river delta,braided river delta),alluvial fan phase 4 deposition phase,12 subphases,31 kinds of microphases,analysis and summary of various types of sedimentary phase characteristics.Through the key interface of the sequence and the formation comparison,the early Cretaceous coal line formation in the Jixi Basin is divided into two three-stage sequences,and the coal line layer sequence frame is established,and the ancient geographical pattern and evolution of the coal formation under the sequence frame are analyzed.The process and characteristics of paleogeographic evolution of coal system sedimentation are analyzed by using "single-factor analysis and multi-factor comprehensive mapping".It is based on the subsequent analysis of the characteristics of coal formation spread and the division of gas-bearing systems in coal line gas stacking.Taking gas measurement anomaly as a clue,combining the sedimentary environment and the stratospheric frame,identifying and dividing the gas-bearing system of coal system in the city-to-river group,analyzing the spatial configuration relationship of the gas-bearing system,and revealing the influence of the structure and sedimentary evolution on the gas-bearing system configuration of the coal system.The thick layer of mud rock or limestone developed near the maximum water inlet surface is divided into three gas-bearing systems.The symbiotic combination relationship of coal-based gas into Tibet is determined to have three types: single-source double storage,double-source double storage and double-source multi-storage.On this basis,the control effect of tectonic-desondonic evolution on coal gas system is discussed.