Diagnosis of the Upper Cretaceous palaeokarst and turbidite systems from the Iranian Persian Gulf using volume-based multiple seismic attribute analysis and pattern recognition

Abstract

Depositional facies variability with a secondary overprint of Turonian palaeokarst controls the quality of the Cenomanian Mishrif reservoir, the main oil producer in the southeastern Persian Gulf. Subsequent drowning of the prominent area and successive deepening of the basin during the Coniacian and Santonian enabled the deposition of pelagic marls of the Coniacian Laffan Formation and the development of a carbonate turbidite system within the overlying Santonian Ilam Formation. The Ilam Formation occurs within slope and pelagic carbonates and consists of oil-bearing channel-reworked limestone facies.Although high-quality 3D seismic data exist over the Sirri C/D oil fields studied in this paper, it is a real challenge to map the palaeokarst and turbidite deposits in 3D space using conventional seismic interpretation procedures.This work describes a procedure using Paradigm's Seisfacies software for seismic facies classification and uses this to develop a volume-based interpretation of palaeokarst geobodies and sedimentary patterns of the carbonate turbidite. A hierarchical facies classification technique combined with principal component analysis (PCA) is used to analyse a set of seismic attribute volumes that capture the seismic stratigraphic patterns inherent in the data. PCA as a data reduction algorithm greatly optimized the analysis of the attribute volumes while preserving the essential features of seismic character. A hierarchical facies classifier recognized enough variability within the seismic data to reveal details of the associated geological features. This classification method uses multiple 3D volume attributes as input and generates a single 3D seismic facies volume (a synthesis of different attributes). Using this method, interpretative work can focus directly on geological features in 3D space. This study gives new insights into the internal variability of palaeokarst and carbonate turbidite systems in the Sirri C/D oil fields (SE Persian Gulf) that are essential for the estimation of reservoir volume, connectivity and variability.

Controls on depositional facies in Upper Cretaceous carbonate reservoirs in the Zagros area and the Persian Gulf, Iran

“…10a, b, d). The presence of palaeohighs is also recorded on seismic profiles in SW Iran and the Persian Gulf (e.g., van Buchem et al 2001;Farzadi and Hesthmer 2007). One of the most important palaeohighs is detected below the reservoir anticline of the Gachsaran Oilfield and the others are located in the Rag-e-Safid and Abteymour fields, in the Dezful Embayment (van Buchem et al 2001).…”

“…Paleohighs and intrashelf basins are recorded in both onshore and offshore of south and southwestern Iran, including the Dezful Embayment, Fars region and the Persian Gulf (e.g., van Buchem et al 2001;Sepehr and Cosgrove 2005;Alavi 2007;Farzadi and Hesthmer 2007;Rahimpour-Bonab et al 2013). Palaeoclimatic proxies suggest that the Cretaceous was one of the warmest Phanerozoic periods (Barron 1983).…”

“…c Schematic cross sections across the SW Iran illustrating tectonic setting of the study area during the Upper Cretaceous (adapted with some modifications from Ziegler 2001; Letouzey and Sherkati 2004) Buchem et al 2001;Sepehr and Cosgrove 2005;Grelaud et al 2006;Ahmadhadi et al 2007;Farzadi and Hesthmer 2007). Diagenetic history and reservoir properties of the Upper Cretaceous deposits were investigated in the context of tectonic setting and palaeoclimatic condition (Taghavi et al 2006;Hajikazemi et al 2010;Rahimpour-Bonab et al 2012a, b, 2013Mehrabi and Rahimpour-Bonab 2014;Mehrabi et al 2014Mehrabi et al , 2015.…”

A framework for assessing the role of karst conduit morphology, hydrology, and evolution in the transport and storage of carbon and associated sediments

“…Notable examples include the Cretaceous Mishrif Formation in the Persian Gulf region (Farzadi & Hesthammer 2007) and the Ordovician Ellenburger Limestone (Kerans, 1989) and Permian San Andres Dolomite (Craig, 1988) in the Permian Basin of west Texas, USA. However, published global values on hydrocarbons stored in paleokarst seem rare.…”

Characterizing and Modelling Fractures and Karst in Carbonate Units - The Porocarste Project

“…Third, scale problems may affect the investigation of karst systems. Although these systems can be observed at a scale from 10 m to 10 km, conduits less than 10 m long can hardly be mapped in sedimentary basins, even with the advent of 3D seismic data (Farzadi and Hestharnmer, 2007). Conversely, conduit architecture is difficult to detect in borehole data (Major and Holtz, 1997), which provide non-systematic and incomplete samples of karst systems.…”