scholarly journals Facies and stratigraphic framework of a Khuff outcrop equivalent: Saiq and Mahil formations, Al Jabal al-Akhdar, Sultanate of Oman

GeoArabia ◽  
2010 ◽  
Vol 15 (2) ◽  
pp. 91-156 ◽  
Author(s):  
Bastian Koehrer ◽  
Michael Zeller ◽  
Thomas Aigner ◽  
Michael Poeppelreiter ◽  
Paul Milroy ◽  
...  
Keyword(s):  
Middle East ◽  
Lower Triassic ◽  
Distal Portion ◽  
Marine Fauna ◽  
Sequence Stratigraphic ◽  
Stratigraphic Analysis ◽  
Oman Mountains ◽  
Stratigraphic Framework ◽  
Al Jabal Al Akhdar ◽  
Fifth Order

ABSTRACT The Middle Permian to Lower Triassic Khuff Formation is one of the most important reservoir intervals in the Middle East. This study presents a sequence stratigraphic analysis of the Khuff Formation of a well-exposed outcrop in the Oman Mountains, which may provide a reference section for correlations across the entire Middle East. On the Saiq Plateau of the Al Jabal al-Akhdar, the Permian Upper Saiq Formation is time-equivalent to the Lower and Middle Khuff Formation (K5–K3 reservoir units in Oman). The Permian section is dominated by graded skeletal and peloidal packstones and cross-bedded grainstones with a diverse marine fauna. The Lower Mahil Member (Induan Stage), time-equivalent to the Upper Khuff Formation (K2–K1 reservoir units in Oman), is dominated by grainstones composed of microbially-coated intra-clasts and ooids. In general, the studied outcrop is characterized by a very high percentage of grain-dominated textures representing storm-dominated shoal to foreshoal deposits of a paleogeographically more distal portion of the Khuff carbonate ramp. A sequence-stratigraphic analysis was carried out by integrating lithostratigraphic marker beds, facies cycles, bio- and chemostratigraphy. The investigated outcrop section was subdivided into six third-order sequences, named KS 6 to KS 1. KS 6–KS 5 are interpreted to correspond to the Murgabian to Midian (ca. Wordian to Capitanian) stages. KS 4-Lower KS 2 correspond to the Dzhulfian (Wuchiapingian) to Dorashamian (Changhsingian) stages. Upper KS 2–KS 1 represent the Triassic Induan stage. Each of the six sequences was further subdivided into fourth-order cycle sets and fifth-order cycles. The documentation of this outcrop may contribute to a better regional understanding of the Khuff Formation on the Arabian Platform.

scholarly journals High-resolution anatomy of a grainstone package in Khuff Sequence KS4, Oman Mountains, Sultanate of Oman

GeoArabia ◽  
2013 ◽  
Vol 18 (4) ◽  
pp. 17-44 ◽  
Author(s):  
Marlene Maria-Louise Haase ◽  
Thomas Aigner
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Lower Triassic ◽  
Depositional Environments ◽  
Sultanate Of Oman ◽  
Heterogeneous Architecture ◽  
Sequence Stratigraphic ◽  
Oman Mountains ◽  
Facies Associations ◽  
Outcrop Analog

ABSTRACT This study is part of a large-scale outcrop analog study on Middle Permian to Lower Triassic Khuff-equivalent strata in the Oman Mountains, Al Jabal al-Akhdar, Sultanate of Oman. The Khuff outcrop equivalent can be divided into six sequences (Khuff sequences KS6 to KS1, from base to top). The main focus of this study is the description of the internal anatomy of the shoal grainstone bodies in the lower part of Sequence KS4 (“lower KS4”). High-resolution sedimentological logging of three outcrop sections in wadis Sahtan, Bani Awf and Mistal yielded eight lithofacies types that were grouped into five facies associations. Lower KS4 strata were mainly deposited within a “shoal complex” of an epeiric carbonate ramp, resulting in a thick pile of up to 70 m of grainstones that, on first sight, appear relatively homogeneous. However, detailed facies and microfacies analysis revealed their heterogeneous architecture on various scales: (1) Minor changes in depositional environments directly affected the type of carbonate grains (ooids versus peloids/cortoids versus bioclasts), leading potentially to highly variable pore systems (moldic versus interparticle versus intraparticle). (2) Vertically, detailed sequence-stratigraphic analysis revealed a higher-order of cyclicity (“mini-cycles”) on a decimeter- to meter-scale. Four mini-cycle types were recognized. (3) Laterally, facies changes, the amalgamation of grainstone beds and mini-cycle pinch-outs were observed in 2-D correlations on a scale of a few kilometers. These different types of heterogeneities may contribute to varying production rates commonly observed in the subsurface KS4 reservoir.

scholarly journals Outcrop sedimentology of the Natih Formation, northern Oman: A field guide to selected outcrops in the Adam Foothills and Al Jabal al Akhdar areas

GeoArabia ◽  
2008 ◽  
Vol 13 (3) ◽  
pp. 39-120 ◽  
Author(s):  
Peter Homewood ◽  
Philippe Razin ◽  
Carine Grélaud ◽  
Henk Droste ◽  
Volker Vahrenkamp ◽  
...  
Keyword(s):  
Sequence Stratigraphy ◽  
Three Dimensional ◽  
Depositional Environments ◽  
Field Guide ◽  
Sequence Stratigraphic ◽  
Oman Mountains ◽  
Facies Associations ◽  
Al Jabal Al Akhdar ◽  
General Section ◽  
Petroleum Development

ABSTRACT This field guide describes eleven outcrops of the Natih Formation in the Al Jabal al Akhdar-Jabal Shams and Adam Foothills areas, not far from Nizwa, at the foot of the Oman Mountains. The outcrops have been chosen for their accessibility, as well as for the fairly complete picture of the Natih Formation, which they piece together. To visit all eleven outcrops requires several days and the use of 4-wheel-drive vehicles, but the locations offer no serious physical difficulty, nor long hiking, to gain access. The outcrop descriptions follow in stratigraphic order from the lower to the upper Natih members, roving back-and-forth across the outcrop area. Much of the detailed account of the sedimentology and stratigraphy of the Natih that has been used as the basis of this field guide, has been given previously by van Buchem et al. (1996, 2002), Grélaud (2005), Schwab et al. (2005) and Grélaud et al. (2006). The observations and interpretations given here come in part from those studies, but this paper is also largely the product of a subsequent project that was carried out for the Fahud Studies Team of Petroleum Development Oman (PDO), to provide detailed sedimentology and high-resolution sequence stratigraphy of the Natih Formation for further development of the Fahud field (Homewood et al. 2006). In this respect, this field guide is not so much intended to be an original contribution in terms of the science concerning the Natih Formation. The intent is to provide the ways-and-means for all to gain a first-hand personal understanding of the rocks we have enjoyed working on. Following the outcrop descriptions, a general section provides a discussion on facies and facies associations in terms of the constraints of sequence stratigraphy, sea-level change and clay influx on the carbonate factory. With the incorporation of limited subsurface seismic and well data, geobodies and depositional assemblages, the three-dimensional objects that form the stratigraphic packages at outcrop and seismic scales, respectively, are also discussed. Facies are thus interpreted not only in terms of depositional environments, but are also placed within both geometrical (geobody, depositional assemblage) and sequence-stratigraphic frameworks. In the conclusion, it is argued that a deeper understanding of the Natih Formation has been gained by comparison of outcrop data with subsurface data, and by contrast with modern analogs. The detail required to apply what was learned from outcrop to the nearby subsurface, in a practical manner (but also properly to reconstruct the successive Natih scenarios), requires building several facies models. This is in contrast to giving a single composite picture of Natih facies distribution in space and time, under one single facies model.

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