Characterization of the Late Aptian Top‐dariyan Disconformity Surface Offshore Sw Iran: A Multi‐proxy Approach

Abstract

The late Aptian disconformity at the top of the carbonate‐dominated Dariyan Formation is a regional‐scale surface recognised throughout SW Iran and adjacent areas to the south. This study investigates the disconformity using wireline logs, petrographic analyses, SEM observations, and CL and stable isotope data from an oilfield offshore SW Iran. The top‐Dariyan surface in the studied field is characterised by erosional incisions and clastic‐filled fissures which, together with secondary porosity in the underlying carbonates, uranium enrichment and meteoric infill cements, are interpreted as subaerial exposure‐related features. The clastic‐filled fissures were identified from gamma‐ray logs in horizontal wells, and infill material is composed of argillaceous carbonates, clays, quartz and iron‐bearing minerals. The correlation of GR logs in 19 vertical wells resulted in the recognition of erosional incisions (up to about 16 m deep) on the top‐Dariyan surface, together with thickening of siliciclastic sediments in the overlying basal part of the Kazhdumi Formation. Back‐filled sediments in erosional incisions may form potential exploration targets. Secondary porosity in the uppermost 20 m of the Dariyan Formation was created by meteoric processes during subaerial exposure. Cathodoluminescence microscopy of diagenetic cements, carbon and oxygen isotope data and elemental analyses were used to reconstruct the diagenetic history of the carbonates in the Upper Dariyan interval.

Evidence for Isolated Platform Development in the Cenomanian on the Passive Margin of Neotethys, Southwest Iran

“…The second one (the Late Cenomanian) occurred due to local palaeoheight, as indicated by faulting, basement block uplift, and halokinetic movements [60]. These unconformities are readily traced and correlated on a regional scale in the Arabian Plate and Zagros region [61][62][63][64][65][66]. However, they gradually disappear towards the N.W.…”

Heterogeneity evaluation of pore types based on dipole shear sonic imager logs by means of statistical parameters, the central Persian Gulf

“…The upper Dalan and Kangan formations with Late Permian to Early Triassic ages are located in the central part of the Persian Gulf basin. The geological structure of the study area has gentle limbs that forms one of the several structural highs of the Qatar-Fars bulge on the carbonate platform of the region (Konert et al, 2001;Naderi-Khujin et al, 2016a, 2016bZeigler, 2001). Qatar arc with an area of about 466 km 2 and northeast-southwest trend is one of the most important tectonic structures on the Arabian Plate.…”

Petrophysical and Sedimentological Characterization of the Aptian Shu'aiba (Lower Qamchuqa) Formation Reservoir at the Khabbaz Oilfield, Northern Iraq

“…The Shu'aiba-equivalent Dariyan Formation is a major carbonate reservoir at oilfields in SW Iran and the adjacent offshore, including fields such as Salman, Alpha, Reshadat, Resalat and Soroush (e.g. Alsharhan and Nairn, 1997;Naderi-Khujin et al, 2016).…”