Online Journal for E&P Geoscientists

Hu, Yijun ^*1
(1) Area Exploration, Saudi Aramco, Dhahran, Saudi Arabia.

An Integrated Approach to Exploration of Eolian Stratigraphic Traps

in Central Saudi Arabia

Herbert Hu, Saudi Aramco, P.O. Box 5864, Dhahran 31311, Saudi Arabia

Mohammed Saeed Al-Zahrani, Saudi Aramco, P.O. Box 2612, Dhahran 31311, Saudi Arabia

Abstract

The purpose of this presentation is to demonstrate an integrated approach to exploration of Permo-Carboniferous eolian stratigraphic traps in central Saudi Arabia. To explore for potential eolian traps, we have integrated regional geological studies, rock property analyses of target intervals, and tied these to the seismic response.

Permo-Carboniferous eolian reservoirs are the primary objective for oil and gas exploration in central Saudi Arabia. Due to the nature of the non-marine eolian setting, this is a very challenging target, especially for stratigraphic traps. The eolian setting comprises a complex mix of depositional systems, including eolian ergs, ephemeral streams, and ephemeral (playa) lakes. Eolian dune sands and sand sheet deposits are the two major reservoirs, while lateral facies changes to tight playa deposits result in the primary up dip seals.

We carried out detailed well-to-seismic ties at the reservoir level, and found that the following seismic attributes were useful in interpreting the petroleum systems for eolian reservoirs:

1. Reservoir thickness and quality: (1) sum of positive amplitude over the target interval, (2) isochron from early Triassic to early Permian, and (3) isochron from top to base of the target interval

2. Up dip seal: Sum of the negative amplitude over target interval

3. Early charge: Isochron from Middle Triassic to early Permian (to image the paleo- structure and possible early hydrocarbon charge)

4. Trap: Present structure

Exploration results in the study area indicate that the above-mentioned seismic attributes correlate very well to the geological setting and to existing well control. In conclusion, an integrated approach using geology and geophysics has proven effective in exploring for eolian stratigraphic traps in central Saudi Arabia.