Seismic imaging of fluid conduits and their lookalike artifacts

Remote assessment of seal integrity is a key component in exploring for oil and gas and assessing subsurface locations for gas storage and fluid and other waste sequestration in the subsurface. Reflection seismic imaging is the main technique utilized in subsurface's high-resolution characterization and the key technique for pre-drill assessments of seal integrity. In many basins, the seal efficacy is compromised or thought to be compromised by seal bypass systems such as diapirs, faults, fluid flow pipes and chimneys and intrusions (Cartwright et al. 2007). This project addresses some of the more controversial and enigmatic phenomena, including pipe-like anomalies. The issue is that not all vertically stacked anomalies in seismic data are what they appear to be in the seismic image, but these anomalies could arise from geological bodies that are located in the near seabed/land surface such as channels and gas hydrate formation. Using inaccurate velocity models obtained during conventional seismic processing could be one of the factors responsible for these anomalies in seismic sections because conventional seismic processing cannot deal with a high degree of complexity in the subsurface, especially lateral velocity contrast in the shallow subsurface. Thus, this research aims to contribute to the understanding of subsurface fluid flow that bypasses pore networks and faults and further the understanding of seismic reflection interpretation of such systems whether real or imagined. To achieve this goal, a 2D model was built with some geological features in near surface to generate synthetic data by using (FD) modeling and then obtaining an accurate velocity (using advanced processing techniques) and an inaccurate velocity models (using conventional processing technique) to use them as an input for prestack depth migration and to compare their results. This comparison provides a tool for interpreters to distinguish real pipes from the artifacts (pullup or pushdown). As a result, angle stacks allow the differentiation between seismic pipes caused by near surface velocity anomalies and actual pipe-like conduits as the wide angle images show a downward fanning' fish tail' split below the near surface anomalous geobody while the actual pipe-like conduits give rise to a persistent vertical pipe in all the angle stacks.