Online Journal for E&P Geoscientists

Poppelreiter, Michael C.^*1
(1) Shell Kuwait E&P, Shell, Kuwait City, Kuwait.

The Permo-Triassic Khuff platform is a classical epeiric sequence with limited seismic scale reservoir geometries. The thickest ‘pile of grainstones on earth’, as it is referred to by some, shows significant variations in productivity. To better understand these, grainstone dimensions and distributions were investigated in outcrops to:

- Establish a regional tie point for the Khuff stratigraphic framework.

- Describe grainstone architecture on different scales.

- Correlate reservoir bodies on sub-seismic scale (architecture of epeiric deposits).

The Study area is the Jebel Al Akhdar in the Sultanate of Oman. Six outcrop sections of Lower to Upper Khuff time-equivalent strata (each about 1000m thick) were investigated.

The study was designed:

- Multi-scale: from near-well bore to regional scale (‘Russian-doll’ approach).

- Multi-disciplinary: sedimentology-bio-chemo-sequence stratigraphypetrophysics.

- Multi-dimensional: from 1D sections to 3D digital models.

Results:

-Khuff analogues in the Oman Mts constitute the seaward margin of the Permo-Triassic platform.

- Study established the first complete Permo-Triassic outcrop section in the Middle East (bio.-chemo.-sequence stratigraphy).

- Two 2nd order super sequences were interpreted in the Khuff equivalent strata with maximum flooding in KS6 and KS2 respectively.

- Interpreted time-lines allowed a regional correlation of 6 Khuff sequences.

- The presence of several important regional biostratigraphic markers (benthic foraminifera) has been reported for the first time in the Jabal Al Akhdar region.

- Nested 3D models (‘Russian-doll’ approach) were created and predictive rules and trends established that describe grainstone architecture and geometries from 10s to >10,000s meters.

- Geological concepts suggest potential for stratigraphic traps in the KS6-5: (onlap and bypass channels) and potential source rock intervals around the KS6-2 mfs.

- Grainstone attributes (e.g., aspect ratio, grain types, texture) are controlled by stratigraphic and paleotectonic position.