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Fault Mapping for Deeper Plays in Western Kuwait: Constraints and Way Forward

Prakash, Anand *1; Husain, Riyasat 1; Amar, Nada M.1
(1) Exploration, Kuwait Oil Company, Ahmadi, Kuwait.

The Permian, Triassic and Jurassic plays in western part of Kuwait are emerging exploration objectives in view of their established potential in the region. Consequently exploration activities starting from seismic data acquisition to drilling are in focus for these objectives. Seismic signal attenuation and presence of multiples arising from complex geological setting and multiple salt layers contribute to subjectivity in horizon interpretation in general and fault mapping and fracture characterization in particular at target horizons at greater depths. Fault and fracture mapping assumes greater exploration significance in view of their role in enhancing the reservoir properties of tight gas plays. The paper focuses on the approach employed in detection and mapping of sub-seismic faults using core data, image log and seismic attributes. The changes in seismic attribute corresponding to discontinuities could not be seen in vertical sections but the time slices or horizon slices yielded noticeable patterns that could be easily recognized and interpreted as faults. Coherency, Dip-Azimuth and Curvature attributes made it possible to attempt precise interpretation of faults. Identifying and retaining the appropriate signal band that enhances the feature of interest is key to extract meaningful information from 3D data. The Spectral Decomposition was used for this purpose and the attributes extracted from the band limited data brought out the discontinuities well. This integrated approach of combining more than one attribute was found to be very useful in fault interpretation. The major fault trends in the area are represented by NW-SE aligned structure bounding faults and ENE-WSW and NNE-SSW trending cross faults. The cross faults are very subtle and are visible only on seismic attributes. The fractures are likely to be better developed in the vicinity of faults therefore the position of faults guides in determining the fracture density and its orientation that can be expected in the sub surface. The fault maps generated form an important input for fracture modeling, a requisite for finalizing exploratory locations and reservoir characterization. Acquisition of High density 3D data, seismic data conditioning before attribute extraction and integration with fracture data sets observed are recommended as an integral part of the work flow.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California