Sequence Stratigraphy of the Middle Jurassic Dhruma Formation in the Oman Mountains (Sultanate of Oman)

Abstract

Summary This outcrop analog study focuses on a genetic understanding of the reservoir/seal potential and architecture of the Jurassic Dhruma Formation in Oman. As a joint project of the University of Tubingen (Germany) and Petroleum Development Oman (PDO) outcrop logging in nine sections in the Oman Mountains was carried out, supplemented by thin section analyses and spectral gamma-ray measurements. Observed facies types range from peritidal sandstones and microbial laminites to low-energy lagoonal deposits and high-energy, peloid and ooid dominated, shoal associated deposits. Cores and cuttings of the Dhruma, Tuwaiq Mountain and Hanifa/Jubaila Formations were logged over central and northern Oman. A sequence stratigraphic framework and 2D correlations were established based on litho-, chemo- and biostratigraphy. They reveal a clear decrease in thickness of the Dhruma Formation from west to east, which is due to (1) a small unconformity at the bottom and (2) a large Tithonian unconformity, which cuts down into Jurassic strata, eroding the whole Hanifa/Jubaila and Tuwaiq Mountain Formations as well as the top of the Dhruma Formation in outcrops. A 3D geo-cellular facies model was created with Petrel for the Dhruma, Tuwaiq Mountain and Hanifa/Jubaila Formations in central and northern Oman which has implications for the regional prospectivity.