Study On Predicting Coal Seam Fissure By Seismic Method

The coal methane is usually present in the fissure zone of coal seam,and the fissure are closely related to the distribution characteristics of subsurface structures.With the development of the coal methane exploration,the requirements for identifying and describing the fissure inside the coal seam are becoming more and more fine.In the seismic data body,it contains many information which is closely related to the internal structure of the coal seam and the tectonic distribution.It is very good to identify the fissure in the coal seam by accurately extracting the information.In this thesis,Yan Chuan South 2# coal seam as the object of study,synthesize prediction the distribution of coal seam fissure and fissure zones,mainly the following research results:(1)Aiming at the geological characteristics of the working area,set up a variety of geological models,and perform numerical simulations to obtain the seismic response characteristics of each mode,then analysis the relationship between seismic response characteristics and coal seam porosity.(2)Use the principal component analysis to integrate the dynamics parameters attributes of 2# coal seam,like the amplitude,complex seismic and spectral properties,and the principal component of the maximum eigenvalue contains most characteristics of the original seismic attributes,then get the fusion attribute layer slice of the study zone.(3)From the seismic data of 2# coal seam,the curvature can extract the spatial orientation information about the underground structure,to reflect the deformation of underground structures,to identify subtle structural features.On the basis of the existing segregation of coal seams,faults and slight flexure can produce more fissure,so the curvature can reflect the development of fissure in coal seam from the aspects of tectonic deformation.(4)The coherent can detect the lateral variation of the stratum,but the variation of the coal seam is not enough to cause obvious lateral changes to the seismic waveforms.Therefore,the coherent do not have good recognition effect on the coal seam fissure.In order to improve the ability to identify the slight change of coal seam lateral,the generalized S-transform is used to decompose the seismic signals to make up for the lack of the coherence.Combined the curvature and frequency-dependent coherence based on generalized S-transform,predict the distribution characteristics of the pore,fissure and fracture zone of the coal seam,and improve the accuracy of identifying the development degree of the fissure.The coal seam fissure has a certain correspondence with the coal methane enrichment area,so the coal seam fissure prediction provides an effective way for the exploration and development of the coal methane.