--> Basal Khuff Incised Channel-Fill Sandstones and Their Significance within a Sequence-Stratigraphic Framework, in Central Saudi Arabia, by M. Senalp, A. Ai-Duaiji, and J. Vander Eem; #90986 (1994).

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Abstract: Basal Khuff Incised Channel-Fill Sandstones and Their Significance within a Sequence-Stratigraphic Framework, in Central Saudi Arabia

Muhittin Senalp, A. Ai-Duaiji, J. Vander Eem

The Khuff Formation (Tatarian in age) unconformably overlies the Unayzah Formation (Kazanian in age) which composed of poorly sorted conglomerate, sandstone, siltstone, and mudstone which were deposited in an alluvial fan-playa environment under arid-semiarid climatic conditions.

The Khuff Formation consists primarily of marine shale and fine-to very coarse-grained sandstones in the lower parts and shale, limestone and anhydrite in the upper parts. The Unayzah reservoir occur both in the Unayzah Formation and the basal Khuff sandstones. However, they show significantly different geometry, continuity, and reservoir quality. The Khuff sandstones occur as long narrow sinuous trending incised channels or valleys. They are best developed in Hazmiyah, Nuayyim, and Hawtah fields. They generally cut directly into the Unayzah Formation, but in some wells about 10 ft of marine shale indicating marine transgression was preserved between the Khuff sandstone and the Unayzah Formation. Lag sandstone and mudstone pebbles of the Unayzah Formation covers the channel base which represents an erosional surface unconformity during relative sea level low stand. Paleosols were formed on the exposed marine shale. However during relative sea level rise, generally up to 58 ft thick good reservoir sandstone and some interbedded sandstone and shale were deposited by aggradation within the incised channels (estuaries). Marine shale and limestone section above the sandstones represents maximum sea level highstand.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994