--> Abstract: Facies and Core-Based Sequence Stratigraphic Framework for Shu’aiba Reservoir, Shaybah Field, by Nasser M. Al-Ghamdi and J.F. Read; #90077 (2008)

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Facies and Core-Based Sequence Stratigraphic Framework for Shu’aiba Reservoir, Shaybah Field

Nasser M. Al-Ghamdi1* and J.F. Read2
1Saudi Aramco
2Virginia Tech, USA
*[email protected]

The objective of this study was to construct a detailed facies-based sequence stratigraphic framework using cores, logs and available isotope data for reservoir characterization and development. This framework, when integrated with petrophysical data, should lead to bet-ter reservoir and simulation models. This study will also help refine our understanding of global climate and sea-level history in the Early Cretaceous. The succession consists of a composite sequence of seven high-frequency sequences and is dominated by 400,000 years (Ky), fourth-order sequences and 100 Ky parasequences. Sequence 1 and part of sequence 2 formed the transgressive systems tract (TST) of the composite sequence with a deeper open-platform of Palorbitolina-Lithocodium wackestone.

The remaining subsequences developed a platform rimmed by rudist rudstone and backed by rudist floatstone back-bank and lagoonal fine skeletal peloidal packstone; slope facies are fine skeletal fragmented packstone. Aggradational subsequences 3 to 5 make up the early highstand systems tract (HST). Progradational subsequences 6 and 7 are within the late HST marking the deterioration of the Offneria rudist barrier and deposition of wide-spread lagoonal deposits. Shu’aiba deposition on the platform was terminated by long-term sea-level fall, followed by exposure and karsting. The presence of 400-Ky fourth-order se-quences and 100-Ky parasequences, which were driven by long- and short-term eccentric-ity, respectively, suggests that early Cretaceous climate may have been cooler than gener-ally believed and was not an ice-free greenhouse world. This is pertinent to the debate con-cerning whether the Aptian was a time of green-house climate typified by small precession-ally-driven sea-level fluctuations, or whether there were small ice sheets at the poles that generated moderate-amplitude, fourth order fluctuations, driven by eccentricity.

 

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain