Near Well‐scale Heterogeneities in a Khuff Outcrop Equivalent (Saiq Plateau, Al Jabal Al Akhdar, Sultanate of Oman)

Abstract

The Middle Permian to Lower Triassic Khuff Formation is one of the world's most prolific hydrocarbon reservoirs. This study is part of a research project on Khuff outcrop equivalents whose overall aim is to investigate the reservoir architecture on different scales. The present paper focuses on heterogeneities in Khuff-equivalent grainstones at the near well scale.An outcrop in the Oman Mountains, where the Khuff-equivalent Saiq and Mahil Formations are exposed in an area 1800 m long by 100 m high, was studied to map lateral and vertical depositional heterogeneities. The investigated section represents parts of three third-order sequences: the upper part of Khuff sequence (KS)3 (grain-dominated), the whole of KS2 (muddominated), and the lower part of KS1 (grain-dominated). Real-Time Kinematic GPS, satellite imagery, outcrop gamma-ray and digitized sedimentary logs were used for outcrop description and were integrated into a three-dimensional digital outcrop model.The resulting 3D facies model indicates that the apparently simple, layer-cake geometry of the grainstone reservoir facies shows pinching and swelling with a standard deviation of 12.75% of bed thickness. These thickness variations may influence volume calculations during reservoir assessments. The heterogeneities of grainstone bodies are represented by compositional (ooid, peloid or intraclast-dominated) and grain-size variations.Muddy event beds at the cm-scale were mapped out in detail in a 200 x 40 m outcrop window and together form a dense network of potential baffles to fluid flow. The thickness of these beds varies significantly due to syndepositional erosion.An important conclusion of this near well-scale study is that the perceived simple, layer-cake Khuff-equivalent succession in the study area is in fact heterogeneous in mud-rich deposits, while grain-rich deposits extend over a wide area with some thickness variations. These findings can be directly applied in Khuff subsurface correlation and modelling attempts.

Flow Unit Characterisation in the Permian‐triassic Carbonate Reservoir Succession at South Pars Gasfield, Offshore Iran

“…In the northern Arabian Plate, the Permian-Triassic succession is dominated by a thick shallow-marine carbonate-evaporite succession developed on the northern passive margin of Gondwana (Edgell, 1996;Pillevuit, 1993;Sharland et al, 2001) which in general shows a stratiform or "layer-cake" geometry (Insalaco et al, 2006;Alsharhan et al, 2006;Ehrenberg et al, 2007;Koehrer et al, 2010Koehrer et al, , 2012Zeller et al, 2011). Powers et al, 1966;Sharland et al, 2001;Khalifa, 2005) In Iran, this succession is referred to as the Dalan and Kangan Formations (Fig.…”

Permian–Triassic Transition and the Saiq/Mahil Boundary in the Oman Mountains: Proposed correction for lithostratigraphic nomenclature

“…massive bedding". Recently, this lower position for the SMB was adopted in several papers and abstracts (Koehrer et al, 2010(Koehrer et al, , 2011(Koehrer et al, , 2012Zeller et al, 2011;Aigner and Pöppelreiter, 2012;Forke et al, 2012;Obermaier et al, 2012) (Figure 2 and Table 1).…”

“…Correlation chart modified and completed from Al-Husseini (2006). Data from: (1) Insalaco et al (2006); (2-4) Al Husseini ( 2006); ( 5) Aigner and Pöppelreiter, (2012), Forke et al (2012), Koehrer et al (2010Koehrer et al ( , 2012, , Zeller et al (2011); ( 6) Béchennec et al (1992), Rabu (1987), Coy (1997), Atudorei, (1999, Richoz (2001, 2005), Baud et al (2001), Richoz et al (2005), Richoz (2006) Richoz et al (2010), Baud et al (2010); (7a) Aqabat Amdah: Le Métour (1987), (7b) Wadi Aday: Bernecker (2010, 2011) with major modification (Richoz et al, in prep. ).…”

Inter-Well Scale Sedimentological Heterogeneities And Facies Architecture Of Upper Jurassic Carbonate Reservoir And Anhydrite Seals: Lessons Learned Using Outcrop Analogues

“…The geometric data obtained in these previous outcrop studies can be contradictory, sometimes showing a 'layer-cake' type architecture where pinch out and facies heterogeneities are rare (e.g. Borkhataria et al, 2005;Zeller et al, 2011;Pratt et al, 2012;Bendias et al, 2013), but other times displaying facies heterogeneity (e. g. French and Kerans, 2004;Sattler et al, 2005;Bádenas et al, 2010;Amour et al, 2011;Christ et al, 2011;Alnazghah et al, 2013;Sena and John, 2013;Brandano andLoche, 2014, Hönig andJohn, 2015).…”

“…For example, modern sabkhas along mainland coastal regions are very complex (Kinsman & Park 1976), and meter-scale evaporites and carbonates sequences, with contrasting petrophysical properties, frequently occur together and show lateral facies inter-fingering (Alsharhan & Kendall 2003). Small-scale quantitative data on geobodies dimensions in carbonate analogues are rare (Aigner et al, 2007), although recent constraints starts to emerge for the Jurassic of Morocco Christ et al, 2011), from Spain (Alnazghah et al, 2013), the Permian and Triassic of Oman and the United Arab Emirates (Zeller et al, 2011;Ahmadzamri et al, 2014, Hönig andJohn, 2015) and from Cretaceous outcrops in Oman (Immenhauser et al, 2004;Vaughan et al, 2004;Sattler et al, 2005;Grélaud et al, 2006;2010;Rameil et al 2010;Adams et al, 2011;John, 2013, Sena et al, 2014). The geometric data obtained in these previous outcrop studies can be contradictory, sometimes showing a 'layer-cake' type architecture where pinch out and facies heterogeneities are rare (e.g.…”