The Application And Research Of Seismic Inversion In Coalbed Gas Rich Area

In recent years,environmental pollution is becoming more and more serious,and conventional oil and gas resources have entered the later stage of development,so finding unconventional clean energy has become the trend of energy development.Coalbed gas is an indispensable clean energy for human being at present.It is of great significance to safely exploit Coalbed gas and predict its reserves.Geophysical analysis of underground gas-bearing reservoirs is the basis of safe exploitation and accurate prediction of gas-bearing properties.Therefore,the seismic inversion method is needed to combine the seismic profile which reflects the characteristics of wave impedance boundary between rock layers laterally and the logging data that reflect the physical characteristics of rock strata in longitudinal way,so as to transform the interfacial seismic data into the interfacial seismic data.For the formation type information which is similar to the logging data,the geological structure interpretation is realized by directly contrasting with the geological or logging data.The purpose of this paper is to describe and analyze the reservoir characteristics in the study area by seismic inversion method,to realize the division of the distribution area of coalded gas resources and the prediction of gas content.It provides the basis for safe mining and accurate prediction of coalded gas.Through the research of this paper,the response model of coalded gas resources in the study area is established,and the reference model of coalded gas resources exploration in other regions is established at the same time.The main contents of this paper are as follows:firstly,from the existing logging data in the working area,we use the normalized log data of eight wells to carry out the intersection analysis.The sensitivity parameters of reservoir lithology and the threshold values of the corresponding sensitive parameters are obtained,and the post-stack inversion is used to analyze the sensitive parameters.The P-wave impedance information and pseudo acoustic impedance information of reservoir in the study area are obtained by pseudo acoustic wave inversion method.The S-wave impedance,density combination information and other elastic parameters are obtained by using prestack synchronous inversion method.Physical characteristics of reservoir from seismic interpretation and seismic inversion Accurate and comprehensive analysis to realize the prediction of coal seam gas content.Through the intersection analysis of logging curves,the information of P-wave impedance,pseudo-acoustic impedance with gamma value and velocity ratio of P-S wave are determined as sensitive parameters of reservoir in the study area.The classification of coal seam and its surrounding rock is realized by model-based inversion method,the geological structure of target horizon is determined,and the effective distinction of thin interbedded sand and mudstone is realized by post-stack inversion method of pseudo acoustic curve.Combined with the actual data in the working area,the information of the roof and floor slate and the coal thickness of the coal seam are obtained,and the P-wave velocity,the shear wave velocity,the density,the P-S wave velocity ratio,the incidence angle and other more complex data are obtained by using the prestack synchronous inversion method.The combined information of the elastic parameters is used to evaluate the gas bearing area and gas content of the reservoir.The division of gas bearing area and the prediction of gas content in coal seam are completed.