Integration of latest oil-base mud borehole images with lower resolution tools, Thunder Horse North field, GOM

Abstract

Summary Recent borehole imaging technology significantly improved the resolution within oil-base mud environments. The integration of such high-resolution borehole images (BHI) with data from vintage tools as well as core and seismic allows for an advanced interpretation of structural dip and depositional environment, being valuable particularly in challenging areas such as the Mississippi Canyon, Gulf of Mexico. The latest BHI data is used to verify previous hypotheses for the interpretation of the structural dip within the Thunder Horse field. The Thunder Horse reservoir interval is characterized by mass transport deposits, where the majority of mud-prone beds represent slump units and slide blocks of variable orientation. Therefore these mudstones cannot be used as paleo-horizontal indicator. Conversely, intercalated turbiditic sands with parallel layering are sought as reference for paleo-horizontal. As a consequence, the halokinetic tilting near the Thunder Horse North salt wall is analyzed from stereographic projections of these sand units instead. After restoring the pre-halokinetic bedding dip a S to SSE directed sediment transport is interpreted for these Middle Miocene reservoirs, hence excluding a salt barrier or deflection of the turbiditic currents.