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Seismic Attributes Analysis to Detect Small Faults and Potential Fractures in Mauddud Reservoir of Raudhatain Field, Kuwait

Syed, Mohammed Ismail 1; Hussain, Thekriat 1; Al-Ajmi, Bader 1
1 Exploration Group, Kuwait Oil Company, Ahmadi, Kuwait.

Recent advances in visualization technology and seismic attribute analysis has revolutionize scope of 3D seismic interpretation in resolving structural and stratigraphic uncertainties. A large number of seismic attributes are known to highlight seismic discontinuities which are directly related to reservoir fractures. This presentation focuses on the interpretative use of post-stack seismic attributes for mapping of subtle faults and associated fractures to fine tune reservoir compartmentalization of the target reservoir, The Early Cretaceous Mauddud Formation of Raudhatain Field of North Kuwait.

Raudhatain Field is one of the major fields of North Kuwait discovered in 1955. It is a faulted anticlinal dome dissected by two major sets of faults, NW-SE and NE-SW in addition to minor E-W trending strike-slip faults having very little or no throw. Mauddud Carbonate Formation is deposited in low angle ramp setting. Primary rock fabric controls the best flow characteristics in high-energy inner ramp grainstone. Reservoir quality deteriorates in mid ramp to inner ramp wackestones and mudstones due to diagenetic carbonate concretions. The challenge was to identify and map the areas of high fracture density in the flanks of the field where we have very little or no well control.

To achieve the desire objective we targeted the problem in two steps. The first was to improve the signal-to-noise ratio of available 3-D seismic data using appropriate processing steps and then to highlight the specific structural features by analyzing various post-stack attributes. Seismic data re-processing was helpful in overall S/N improvement leading to improved continuity of reservoir top and better resolution of structural features. The traditional horizon based interpretation approach ,ie, auto picking followed by time derived geometric attribute extraction: amplitude, dip, azimuth and shaded relief was able to accurately delineate and map subtle faults and associated fractures. The interpretation was refined by using non-geometric attributes: Spectral decomposition, coherency and semblance. Integration with the hard sub-surface data (core and image log data) has improved the understanding of distribution of fractures which leads to delineation of several potential fracture corridors. The study lead to improved and more robust structural model of the reservoir which was successfully used for development planning.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009