Advanced Seismic Processing Reveals the Structures Hidden beneath Salt Diapirs on Legacy Data from the Onshore Netherlands

By means of two recent sub-salt imaging projects, using rather old short-cable narrow-azimuth and low-fold seismic surveys acquired two decades plus ago, some new/emerging model-building and imaging technologies will be discussed: - shallow subsurface model-building by 5D data regularization, before migration and by a joint tomographic inversion of deep reflection data and first-break picks; - enhanced structural interpretation of complex salt structures by intermediate RTM’s. The two projects enabled an extensive geophysical comparison between various depth imaging tools: standard and extended Kirchhoff, 1-way WEM and Reverse Time Migration. For one of the projects examining multiple salt-diapir scenarios, depth-imaging using RTM, led to reduced subsurface uncertainties especially regarding the risk of depletion of the target block (towards already producing neighbouring fields to the North and to the East); the imaging project consequently aided plans for a development well planned to spud Q2 2013. In the other project a large reduction in the subsurface uncertainty led to a confident decision not to drill the prospect.