Azimuthal Anisotropy Analysis to Determine Stress Regimes from a Reprocessed Full Azimuth 3D Seismic Survey

In 2000 a full azimuth 3D seismic survey was acquired over an undeveloped coal seam gas field in order to determine detailed structure, seam thicknesses and fracture regimes. In 2010 this survey was reprocessed to determine whether it was possible to get reliable ‘sweet spot’ and stress indicators from the seismic. In the intervening 10 years several wells have been drilled with varying levels of production and hydraulic fracturing success. A few even had casing collapse during drilling as a result of extreme stress with a resultant loss of drill stem. Consequently, if seismic could identify localised stress azimuth and magnitude through seismic anisotropy then it would have a significant impact on any future development; particularly with the need for horizontal drilling for both environmental and production purposes. Wells drilled on the field, subsequent to the 3D acquisition, had image logs recorded and processed, thus it was possible to calibrate azimuthal anisotropic seismic attributes with those logs and quantify the results. The presentation discusses the acquisition geometry and the approach taken in the processing and analysis. Various comparisons are made to assess which attributes are key indicators of stress. Finally the results are reviewed and quantified