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Advanced Automatic Seismic Detection of Structural Features in Carbonate Reservoirs: Technology Overview, Validation and Application on a Libyan Offshore Case Study

Tosoratti, Filippo 1; Corrao, Antonio 1; Fervari, Massimo 1; Magistroni, Corrado 1; Milluzzo, Vincenzo 1
(1)ENI E&P, San Donato Milanese, Italy.

Structurally complex carbonate reservoirs often challenge geophysicists with a difficult interpretation; “standard” approaches usually consist of manual interpretation and picking of faults and discontinuities: even if greatly assisted by advanced seismic attributes (continuity, curvatures, etc) it can still be very time-consuming and the result can be too subjective (based on the interpreter’s experience). Moreover - and hence the purpose of the proposed workflow - we always fail to effectively capture, represent and summarize the huge amount of information contained in the seismic data and its derived structural attributes.

This is particularly true for sub-seismic structural features, which might carry a lot of useful information and yet are hard to detect and properly describe. Therefore, they are very susceptible to interpreter’s subjectivity or to the risk of being simply discarded. In this frame, we present the experience built in several case studies from offshore Libya, pertaining to eocene bioclastic carbonate reservoirs in a structurally complex area.

Although of complex and challenging interpretation, the target reservoirs are generally well imaged, and seismic data has proven to be reliable in the area. These facts, together with extensive knowledge of the area, represent the premises of the present paper.

A new approach for automatic extraction of structure-related heterogeneities from seismic data has been developed, providing a simple, but robust and effective, volumetric representation of the huge amount of information spread in the standard geometric attributes.

The methodology was tested and benchmarked on a well-known Libyan field, where extensive studies had been carried out in the past using several seismic datasets and approaches to properly describe the structural complexity of the reservoir. In parallel to this, an advanced structural study, supported by manual interpretation, was carried out as a reference.

Comparison of results from the two approaches validated the robustness of the proposed workflow, which then was deemed ready for application to a new dataset.

A nearby field, with similar characteristics (eocene bioclastic carbonates) and complexities, was an ideal candidate for application; practical outcomes of the new approach (robust description of sub-seismic heterogeneities) contributed to the seismic reservoir characterization and, ultimately, improved the quantitative description used in the reservoir modelling study.

 

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