Shallow Hazard Seismic Cube: A Decision Pathway For The Optimization Of The Processing Sequence

Abstract

Introduction Shallow geological hazards possibly affecting drilling, platforms anchoring, and subsurface installations are a major threat lurking in the shallow zone below the seabed. These hazards could appear in different forms such as fault scarps, gas hydrates, gas-charged sediments, pockmarks, buried channels, abnormally pressured sands, and reefs. The detection and interpretation of these shallow located multiform hazards requires high-resolution, fit for purpose 3D seismic data. Since Kerry Campbell in a 1999 TLE article stated that, "Clearly, the most reliable technical approach to minimize geo hazards risk would be to use 3D exploration seismic data for a preliminary geo hazard assessment...." the use of exploration and reservoir oriented 3D seismic have been accepted among the shallow hazards specialists. Nowadays their use appears completely mandatory as Nader C. Dutta & al. stated in their TLE special section article in 2010, " We think that the use of 3D seismic data could be and should be a standard practice….?? The production of shallow hazard dedicated seismic volumes (later called SHAZ cubes) by enhancement of classical exploration or reservoir 3D seismic raw data through specialized processing flows is now well controlled and accepted by the industry. These specific flows could greatly improve the added value that could be extracted from exploration and high resolution reservoir 3D volumes acquired with classical acquisition designs. We present a decision pathway for the optimization of the processing sequence for SHAZ cube production. Three different processing flows are proposed, relying on the full exploration processing sequence. Pro's and con's of each flow are discussed in terms of result quality, turnaround and cost. This embedded SHAZ cube production approach yields first of all to a better quality output products but also allows a regional scale interpretation, reducing " rush-hush?? situations frequently associated to localized so-called short offset cubes and to cost saving. Discussion: Exploration and reservoir oriented 3D surveys allows the production of 3D cubes (SHAZ) through specific Short-offset processing. Such dedicated SHAZ cubes are instrumental to shallow geological hazard interpretation and evaluation and they lead to a better assessment of related risk for E&P activities. SHAZ cubes are deemed a mandatory tool for assessing the sea bottom and subsurface conditions at large scale. Early availability of these specialized datasets are always welcome by interpreters in order to have a broader view of the potential hazards at a local and regional scale. An efficient way to produce efficiently regional SHAZ cubes will be implemented by systematically including the production of such cube in any given new processing or reprocessing project. Derogations to this rule will be granted if such validated fit for purpose recent dataset is already available for the designated area.