Sequence Stratigraphic-Based Reservoir Architecture in Late Jurassic Outer-Ramp Carbonates, Hanifa Formation, Saudi Arabia

J. R. Markello, M. McGuire, M. L. Stockton, M. J. Al'Shammery, and M. O. Al'Amoudi

The Hanifa Formation (135-160 m tk; Kimmeridgian age), in our study area, comprises one 3rd-order, coarsening-upward, type 2 stratigraphic sequence. Sediments formed in outer ramp, ramp-margin and basinal environments defining a transition between the Rimthan Arch carbonate platform and adjacent Arabian intrashelf basin. Quantification of Hanifa reservoir architecture for simulation involved development of field-scale geologic models based on sequence stratigraphic principles. No seismic and biostratigraphic data were available. Sequence interpretations were based on regional facies and parasequence analysis from 32 cores and 142 gamma-ray/porosity logs.

In the study area, the Hanifa Formation has basinward-thinning tabular geometry, and contains (1) a lower member of organic-rich muddy carbonates and (2) an upper reservoir member of thick, medium- to coarse-grained skeletal packstones, skeletal peloidal grainstones, skeletal intraclast conglomerates, and stromatoporoid boundstones. The Hanifa reservoir consists of, from oldest to youngest: (1) a highstand systems tract: aggrading and prograding, sigmoidal-shaped parasequences and parasequence sets of grainstones, conglomerates and boundstones, capped by a subaqueous, type 2 sequence boundary; (2) a shelf margin wedge: prograding to aggrading, sigmoidal to tabular-shaped parasequences and parasequence sets of skeletal packstones, grainstones and local boundstones showing maximum basinward progradation; and (3) a transgressive systems tract: backstepping tabular-shaped parasequences of grainstones capped by a drowning surface. All facies are interpreted to have formed in subtidal settings of water depths from 5 to 150 m. No evidence was found for shoal-water bank, lagoonal or peritidal deposition or f r subaerial exposure in any facies.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California