Integrated Reservoir Characterization and Depositional Model of Zubair Formation in Exploration Phase, in Bahrah Area, Kuwait

Abstract

Barremian to Early Aptian Zubair Formation in Northern Kuwait constitutes the significant oil reserve in Sabriyah, Raudhatain, Abdali and Ratqa area. In Bharah area which is situated to the south of Sabriyah field, Zubair Formation has not yet been explored in a systematic way. Five deep wells which were drilled to explore Jurassic section, have shown strong hydrocarbon presence during drilling. The open hole log evaluation (16″ hole size) has also substantiated the hydrocarbon presence from Zubair section. The challenge of this work has been the evaluation of hydrocarbon potential based on robust depositional model to characterize and to define the geometry of Zubair reservoir. Integrated core and petrographic analysis brought out that Zubair Formation was deposited under tidal influenced deltaic setting that episodically displayed an estuarine character. This indicates that the architecture and reservoir quality of Zubair reservoir sand bodies are representing the deltaic, estuarine channel fill, mouth bar and sandsheet facies association. The gross sequence stratigraphy of Zubair Formation in Bahrah can be described in terms of low frequency sequence sets which contain superimposed higher frequency system tracts. The lower Zubair TST is characterized by back stepping or retro-gradational character suggesting limited lateral extension of sand bodies. The middle Zubair HST shows isolated and stacked channel with very good reservoir potential. The upper Zubair LST is bounded by the sequence boundary at the base and flooding surface at the top that mark the distinct change of depositional style. These channel sand bodies show NW-SE orientation with widespread lateral extent with very good to excellent reservoir quality. Horizon based geo-body extraction of RMS amplitude from PSDM seismic data established the geometry of delta, channel fill and sandsheet facies association. A band pass inversion of seismic guided integrated reservoir model shows very good to excellent reservoir quality with wide spatial distribution of upper Zubair LST sand and comparatively fair to good reservoir quality with limited extent in Lower Zubair TST sand. Integration of above information, analog of nearby producing fields and seismic attributes indicates Zubair Formation has a significant untapped oil production potential in Bahrah. This work will be highly beneficial for efficient selection of locations to prove hydrocarbon potential of Zubair Formation in Bahrah area.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015