--> --> Application of Seismic Attributes and Facies Modeling to Analyze The Reservoir Characterization In Intisar “103A” Field, Sirt Basin, Libya.

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Application of Seismic Attributes and Facies Modeling to Analyze The Reservoir Characterization In Intisar “103A” Field, Sirt Basin, Libya.

Abstract

Concession 103 located on the Agedabia Trough in the Eastern Sirt Basin contains an estimated 4.1 billion barrels of original oil in place (OOIP), and has produced 2.2 billion barrels of oil to date. There are 5 reefal fields in Concession 103, approximately 80% of the oil discovered in 103A and 103D fields. For the whole 103A Field fifty eight wells have been drilled. Most of the wells were drilled in the late 1960's to early 1970's. Detailed Reservoir characterization of this field was concentrated on the reef core only and not outside of reef and due to depletion of oil in the reef which make a challenge to find new discovery to compensate oil reduction in this area, which have complete surface facility. The use of High Frequency Imaging (HFI) seismic data played an important role capturing and delineating the detailed stratigraphy of the reservoir width. All wells were drilled in Concession 103 upon the new and re-processed 3D seismic data and the seismic attribute analysis methods led to the identification of an undrilled potential. To date, eight wells have been drilled in the east side of 103A field, and A48, A51, A52, A53, A54, A55, A56, A57 and A58–103A wells were drilled in field to test the Upper Sabil reservoir quality outside of reef core, termed the “Shoal” by previous studies. The reservoir sections of most wells were logged with dual induction later log, micro log, formation density log and sonic logs and/or neutron logs. Most wells have gamma ray and SP logs across the reservoir section. Seven wells penetrate the entire Upper Sabil section and reached to the Sheterat Formation (A48, A51, A53, A54, A55, A56 and A57). All of these wells were originally completed as oil producer except A57 as dump flood well. Approximately 200 ft. of core was taken from the Upper Sabil Shoal Unit from 4 wells (A48, A51, A52, and A55). Visual description of core material with respect to rock fabric, lithofacies and fossil content by Zueitina Geolab and additional detailed study of core from the A48 well was described as the shoal facies. The Shoal reservoir in the eastern area of 103A field was first recognized based on the inversion and seismic attribute studies. This study presents our approach to understand the Shoal reservoir in 103A field after integrating a detailed seismic interpretation, seismic inversion and multi-attribute analysis with lithofacies analysis of the cored wells and other available well data. The Shoal reservoir is new oil discovery outside of 103A reef and all indication shows the lateral distribution of the facies outside and inside the reef and formed the lower unit of Upper Sabil Formation. This facies is oil Bering zone; possibly open new discovery for whole Concession 103and that increase the original oil in place.