Application of varied datum in time-to-depth conversion for high resolution coal seam micromorphology characterization

Coal seam burial depth is a key factor evaluating coal seam sweet spots, and research on coalbed methane (CBM) exploration and development, particularly the deployment of horizontal CBM wells, requires high-precision characterization of coal seam morphology. However, conventional time-to-depth conversion methods for three-dimensional (3D) seismic data exhibit limited accuracy under complex surface conditions. In this study, the floating datum in the depth domain was accurately defined within the depth domain based on static correction values, and that a high-resolution spliced velocity model was successfully constructed by splicing inversion and migration velocities. On this basis, a novel time-to-depth conversion method using the floating datum was proposed, improving the prediction accuracy of coal seam burial depth. The results demonstrate that the proposed method reduced the depth prediction error for the No. 3 coal seam from 2% to 0.87% within the study area, providing a novel methodological framework support for the development of CBM horizontal wells. Furthermore, the obtained burial depth of the No. 3 coal seam exhibited a strong correlation with its physical properties and gas content, demonstrating that accurate characterization of coal seam burial depth effectively guides evaluation of CBM sweet spots.