Imaging and characterization of a shale reservoir onshore Poland, using full-azimuth seismic depth imaging

Abstract

The exploration and development of shale plays in Europe show that the ‘statistical drilling’ approach used in some basins in recent years cannot be extend­ed to areas where local stress in rocks or fracture distribution varies both laterally and in depth. Moreover, drilling and fracturing practices confirm the presence of local geobodies resistant to hydraulic fracturing. This paper discusses the application of a new seismic data imaging method full-azimuth angle domain depth imaging, which is particularly useful when working with rich-azimuth seismic data. This innovative technology was applied to meet the challenges of imaging in a complex geological environ­ment, and is a pioneering solution in Polish shale gas geology. Results obtained in the study from the analysis of seismic data were in line with results of the geologic and geophysical analysis of the borehole data, as well as with information from microseismic monitoring of fracturing treatment. The technology delivered high-quality images of the reservoir and geomechanical characterization of rocks with the precision needed to steer horizontal drilling, detect sweet spots, and locate geobodies resistant to fracturing. The seismic imaging workflow is based on software spe­cifically developed to meet the challenges of shale gas seismic (Koren and Ravve, 2011, Koren et al., 2013, Canning and Malkin, 2013). One of the main advantages of this approach is that it works directly in the local angle domain (LAD) instead of the surface offset/azimuth domain. The use of in situ azimuth in LAD, visualized together with dedicated seis­mic attributes, provides information about the intensity and orientation of geological stress/fracture systems. Geothermal prospecting and seismic imaging of conventional hydrocar­bon plays can also profit from this method. This technique is particularly suitable for Poland, where conventional seismic migration of reflections from geology covered by a complex overburden has frequently resulted in improper imaging.