Transition Zone Concept and its Application for Seismic Interpretation of Shale Deposits

The concept of transition zone (Wolf ramp) was incorporated for seismic interpretation for two shale gas surveys in Poland. The results of interpretation from the Lublin Basin, eastern Poland will be presented. For interpretation well data, 2 and 3D seismic, and VSP data were used. The integrated studies enabled to find the link between Wolf ramp and to interpret such a structure in the potential shale gas horizon of the Silurian age. The conclusions from the investigation can help in future seismic project design, especially by defining the frequency bandwidth of a seismic signal and its frequency characteristics.

The main idea behind Wolf ramp states that it is a layer of a defined thickness that manifests a linear change of velocity with depth The reflection coefficient that is produced at such a boundary is frequency-dependent.

These properties of reflection coefficient are preliminary characteristics for identifying transition zones. The Silurian strata from the Polish Basin, which is a potential shale gas may be understood as a velocity transition zone, hence the reflection coefficient that is produced at its boundary should be frequency-dependent.