--> --> Abstract: Seismic Evidence of Strike-Slip Tectonostratigraphy in the Hawtah Field, by Abdullah A. Al-Yahya; #90105 (2010)
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AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

Seismic Evidence of Strike-Slip Tectonostratigraphy in the Hawtah Field

Abdullah A. Al-Yahya1

(1) Reservoir Characterization, Saudi ARAMCO, Dhahran, Saudi Arabia.

Hawtah field is located in Central Saudi Arabia and constitutes a major structure within the Hawtah trend. The main objective here is to study the paleo-structures which existed during the deposition of the Lower Permian Unayzah formation and how they affected both its depositional thickness and stratigraphy. Seismic impedance as well as seismic amplitude has been utilized to map the Unayzah two-way time (TWT) structure of this complex field. The obtained TWT structure was then used to compute different seismic attributes to gain insight about the internal reservoir fabric. The TWT Previous HitcoherencyNext Hit map of the base Qusaibah hot shale indicates a clear presence of a dominating strike-slip tectonic regime characterized by steep faults that penetrates the Unayzah formation at various levels depending on the location of the fault within the field structure. Visual comparison between the base Qusaibah Previous HitcoherencyTop map and that of the reservoir suggests a possible link between the clearly observed strike-slip faulting at the Qusaibah level and the thickness and lithology changes observed at the reservoir level. The direct link between the two using seismic cross sections is a subtle issue, due first to the complex reflectivity within the Qusaibah formation, and second, to the steep angle of the existing faults, even though it is possible to carry it out successfully at many locations.

The reservoir impedance map, using seismic inversion, is consistent with the available FMI data at a number of wells within the area providing additional evidence of the link between the observed Qusaibah faults and the observed heterogeneity within the reservoir. The study concludes that the entire Hawtah field is a large pop-up structure characterized by a strong strike-slip tectonic control on both the sedimentology and the stratigraphy of the Unyzah reservoir. This is suggested by the geometry of the bounding faults of the structure, and also the presence of intra-structure mixed faulting modes (i.e., both normal and reverse). Careful mapping of the observed faults leads to a better understanding of the reservoir heterogeneity and lithology, and therefore more robust flow simulation models and the ability to plan more accurately future drilling operations.