Inversion Of Coalfield Limestone Fissure Based On The Pre-stack Azimuthal AVO Technique

As the complicated hydrogeological conditions in coal mines, water inrush accident is the important factor influencing the safe mining. Geophysical exploration methods as an economic and effective means for detection, have been a great development.We detected limestone fracture by referencing seismic exploration in detecting carbonate fracture method. Based on the prestack and poststack data, in terms of theory and thenumerical simulation and azimuthal AVO inversion, we tried to predict carbonate fracture.The limestone model mostly accord with HTI medium model. By analyzing limestone parameter and logging curves, we realized the forward modeling of HTI medium, and studied the relationship between limestone reflection coefficient with incidence Angle and azimuth Angle. When the offset direction parallel to fracture,reflection coefficient is the largest. When the offset direction and fissure vertical,reflection coefficient is minimal. As the incidence Angle should be 15°~25°, with the increase of fracture density, azimuth anisotropy bigger, reflection coefficient decreases.In this paper, we improved the pre-stack data by establishing macro bin, and delimited the scope of incident angle based on the ray tracing, and extracted the sesmic data to six azimuth angle gathers. Improved the synthesis of record accuracy through drillings to guarantee the accuracy of the limestone layer. After extracting azimuth Angle gathers and maximum amplitude value, limestone fracture density and direction are inversed through the least square method.Post-stack attribute technology plays an important role in seismic exploration method. Through the relevant properties of post-stack data extraction, the information fusion limestone fracture zone are obtained. So we can validate the accuracy of the pre-stack Azimuthal AVO technology to improve the interpretation precision and accuracy.Through geophysical prospecting method, identifying the location of the rich water plays an important role in the safety of coal mining. For the work of grouting borehole layout plays an important role, also can improve the effectiveness and efficiency of grouting.