Subsalt exploration risk in deep water

The high rewards of finding hydrocarbon in subsalt plays make them very attractive for exploration. However, it is a challenging mission. Subsurface pressure uncertainty causes recurrent failure to reach the drilling targets. After the discovery of Mahogany Field in the GOM 15 years ago, special attention was directed to subsalt plays. That attention gradually shifted from the shelf to deep water (>1000-ft water depth), Fig. 1. Deepwater yearly production increased from 21 million bbl of oil and 33 Bcfg in 1985 to 339 million bbl of oil and 1.1 Tcfg in 2006, according to the US Minerals Management Service. Consequently, the cost of acquiring and testing prospects has increased due to the prospects’ location in deepwater salt mini-basins. The prospect’s risk results from intricate geopressure compartmentalization in a salt environment accompanied by a deep mud line, deep target depth and shallow sediment hazards.