oa Identifying Hydrocarbon Accumulation with Sea Bed Logging

Shell’s deepwater portfolio in North West Borneo (NWB) is dominated by Miocene toe thrust anticlines. Although the prospects are broadly supported by direct hydrocarbon indicators (DHI) Quantitative Analysis does not discriminate low from full saturation hydrocarbon. In addition, seismic imaging is poor over some crestal areas, largely due to shallow gas and complex crestal faulting. Electromagnetic Seabed Logging (SBL) is a new technology that utilizes the Controlled Source Electro-Magnetic (CSEM) technique to detect and characterize HC-bearing layers within the subsurface. Modeling suggests that the method is insensitive to low saturated hydrocarbon and has the potential as a tool to de-risk or high-grade prospects in an exploration portfolio. In 2002, a global deployment and implementation plan was exercised for the technology in exploration. In 2004, Shell acquired the region’s first SBL data over 7 prospects in the North-West Borneo Block G and J. Over 350km of EM data was acquired over the prospects within the agreed 30 days of operation. Operational learnings were in abundance, with sliding receivers on the seafloor and potential source-entanglement with submarine cables being included as some of the operational challenges. SBL data was also acquired over the then Malikai-A well. With a processing turn-around time of about a week, the SBL data has positively identified the HC accumulation in the structure, which was proven later with the well and the oil discovery. This result has driven Shell to further utilize this new<br>exploration technique in the region to accelerate exploration and improve drilling success.