Integrated Interpretation of North Sea Turbidite Play Combining Elastic Inversion, Sedimentology and Seismic Geomodelling Technology

Schmidt, Ingelise ¹; Stanbrook, David A.¹; Hansen, Hans P.²; Kiely, James M.¹
(1)Exploration, Maersk Oil, Copenhagen, Denmark. (2) Cooperate Petroleum Engineering, Maersk Oil, Copenhagen, Denmark.

In mature areas such as the North Sea, identification of new plays is challenging but essential as readily identified prospects and plays have already been drilled. Thorough integration of geophysical, geological data and the use of new methods become increasingly important to identify new plays and prospects. This study demonstrates how new tools combined with traditional analysis can provide detailed information supporting a geological model in a new play.

A potentially large turbidite system was identified from seismic using conventional interpretation methods and attribute extractions showed this to be seismically anomalous. Firm evidence supporting reservoir potential was lacking however and a key concern was that the system could be mud dominated. Various geological and geophysical approaches were utilized and new seismic geomodelling technology proved a powerful aid to investigate attributes derived from seismic elastic inversion, extract maps of subtle geometries indicating channelization and for interpretation of environments of deposition. The outputs were thus used for volumetric calculations and to support the interpretation of basin filling and seal hypothesis.

The elastic inversion was performed integrating local well control to establish a shale rock-physics model, combined with data from a nearby analogue well for sand attributes. Relative impedance, relative Vp/Vs, and transforms of these volumes were produced. The seismic geomodelling tool allowed these attribute volumes together with seismic envelope attributes to be extracted along a great number of surfaces/horizons throughout the seismic volume - far more than feasible with conventional seismic interpretation. The surfaces, also called 'surface stacks' were derived using seismic geomodelling technology and the “scanning” using these surfaces revealed details of the depositional system supporting a sand dominated turbidite system.

A thickness attribute derived from the seimic geomodel was also “scanned” and used to identify channelized geometries. Importantly, this particular attribute also revealed information on basin filling history and seal risk. Sedimentological interpretation of core data from wells that were drilled proximal and distal to the areas of interest provided evidence for an active turbidite environment, supporting the interpretation of the seismic anomalies. The paleo-environmental and geographical interpretation of these wells also supported the proposed model.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.