--> ABSTRACT: Core and Image Log Analysis of Paleowind Directions in the Lower Permian Unayzah-A Reservoir, Subsurface Central and Eastern Saudi Arabia, by Al-Masrahy, Mohammed A.; Melvin, John ; Abdulatif, Osman; Makkawi, Mohammed ; #90142 (2012)

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Core and Image Log Analysis of Paleowind Directions in the Lower Permian Unayzah-A Reservoir, Subsurface Central and Eastern Saudi Arabia

Al-Masrahy, Mohammed A.*1; Melvin, John 1; Abdulatif, Osman 2; Makkawi, Mohammed 2
(1) Reservoir Characterization, Saudi Aramco, Dhahran, Saudi Arabia.
(2) Earth Science, KFUPM University, Dhahran, Saudi Arabia.

The Lower Permian Unayzah A reservoir unit in the subsurface of central and eastern Saudi Arabia displays widespread evidence of deposition under arid to semi-arid conditions, very commonly in a wind-dominated, aeolian setting. In the area studied, a number of distinctive aeolian depositional facies are recognized from core and image logs including: dunes, interdunes, sand sheet and playa lakes. These facies occur with a high degree of vertical and areal repeatability throughout the Unayzah A. The study further investigated the distribution of azimuthal variability in Permian paleowind data across the Kingdom. These data were derived from image log patterns throughout the aeolian dune facies identified in the Unayzah A reservoir unit from within four fields selected for this study. The study involved sedimentological description of 1160 feet of core from six wells, and analysis of 4000 feet of image log data from twenty one wells, spanning an area from central to eastern Saudi Arabia. A hierarchical approach was employed to investigate the paleowind directions. The paleowind azimuth data were i) recorded appropriately for each identifiable bed, ii) averaged over each bedset within each well, iii) averaged over each well, iv) averaged over each field and, v) averaged over the four studied fields. This rigorous approach resulted in the identification of a dominant paleowind direction toward the east-northeast (present day), ranging between 40 and 100 degrees with a mean vector of 72 degrees. Identifying the dominant paleowind direction provides an understanding of dune distribution and shape throughout the reservoir. It also facilitates the optimum exploitation of porosity and permeability distributions during field development.

 

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