Basin and depositional control on the initiation and development of fluid-escape pipes in the Canterbury Basin, New Zealand.

Abstract

The influence of basin and depositional context on the formation and growth of fluid escape pipes in sedimentary basins is not fully understood. While seismic reflection data is commonly used to study these structures, direct observation and sampling of field analogues of pipes and their related structures are rare. In this study, we investigate the evolution of meter-tall fluid escape pipes (100-800 m) in the Canterbury Basin, New Zealand, using open source seismic and borehole data. Our analysis includes seismic interpretation of 19 unconformities within the Neogene-Quaternary successions, characterization of pipes and fluid-related anomalies in the subsurface, modelling of the shale volume (Vsh), lithology characterization, 3D static modelling, and seismic inversion. We identify thirty-one vertical to sub-vertical pipes with three parts consisting of top, main conduit/stem, and root zone on seismic profiles. Our results suggest that lithology plays a crucial role in the initiation and modulation of pipe structures in the Canterbury Basin, with pipes mostly formed post Tarantian (0.113 Ma) and truncated at the U19 unconformity. Furthermore, vertical fluid migration from overpressured units, such as the tops of contourite mounds, was observed in the pipes. Our findings provide new insights into the subsurface fluid flow and sedimentary architecture of the Canterbury Basin and have wider implications for other passive continental margins with similar characteristics.