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Browsing by Author "Hodgetts, David"

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    A geocellular modelling workflow for partially dolomitized remobilized carbonates: an example from the Hammam Faraun Fault block, Gulf of Suez, Egypt
    (2021) Corlett, Hilary; Hodgetts, David; Hirani, Jesal; Rotevatn, Atle; Taylor, Rochelle; Hollis, Cathy
    Constructing geocellular models of carbonate rocks using standard software is challenging since most of modelling packages are designed, first and foremost, to represent siliciclastic depositional systems, where rock properties are strongly facies-controlled. The distribution and components of carbonate depositional facies vary drastically across the geological timescale as a result of paleoclimate and its effects on carbonate-producing biota. Furthermore, reservoir architecture is less strongly controlled by depositional environment than in clastic settings, and rock physical properties, including fracture networks, are controlled by both primary components and their subsequent diagenetic alteration. This means that rock property distribution is less predictable than in siliciclastic systems, and less well represented by geocellular models that are designed to represent sedimentary architecture. In other words, in carbonate systems, the depositional and diagenetic history needs to be reconstructed in order to successfully model reservoir properties. In this study a geocellular model was created by using a well-characterised outcrop analogue obtained from the Hammam Faraun Fault (HFF) Block, located on the eastern coast of the Gulf of Suez in Sinai, Egypt. This model integrates sedimentological, petrophysical, diagenetic, and structural information into a single database. The workflow utilizes the regional tectonic history, upscaled lithological logs, and two-stage facies modelling (reflecting in and ex situ depositional facies) and resulted in the creation a realistic model of remobilized carbonates that were deposited on the slope of a carbonate platform during a period of tectonic instability. Diagenetic overprinting was achieved using probability functions to reflect the history of burial, rifting, and the spatial relationship of stratabound and non-stratabound dolostone bodies. The study demonstrates a workflow for modelling mass-transport carbonate facies and multistage fault-related diagenesis so that flow controlling facies and diagenetically altered poroperm and fracture networks are accurately represented using commercially available modelling software, and in particular demonstrates how diagenetically controlled geobodies can be captured using simple algorithms.
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    Origin, dimensions, and distribution of remobilized carbonate deposits in a tectonically active zone, Eocene Thebes Formation, Sinai, Egypt
    (2018) Corlett, Hilary; Bastesen, Eivind; Gawthorpe, Rob; Hirani, Jesal; Hodgetts, David; Hollis, Cathy; Rotevatn, Atle
    Determination of the distribution and mechanism for carbonate-dominated mass transport sediments is often compromised by the scale and access to exposures. Consequently, many studies lack the resolution to capture the heterogeneity and dimensions of mass transport deposits. This study documents the size, shape, and stratal assemblage of remobilized carbonates in the Eocene Thebes Formation in the Hammam Faraun Fault Block (HFFB) of western Sinai, revealing the complexities of carbonate mass transport deposits at sub-seismic scale. Present day pseudo three-dimensional exposure of the Thebes Formation in a large fault block, formed during the opening of the Gulf of Suez, allowed for lateral and down-dip measurement of slope and basinal facies in the field and from photos. Remobilized facies were digitized in the photos and evaluated using image analysis software, a technique with a wide range of applications to outcrop studies of sedimentary architecture. Debris flow deposits in the lower section of the Thebes Formation comprises clasts with differing fossil assemblages. A relative sea level rise at the start of upper Thebes Formation deposition resulted in basinal sediments comprising periodic incursions of high-density turbidite grainstones encased within a background of planktonic foraminiferal wackestones. Foraminiferal assemblages of remobilized facies imply multiple sources on the carbonate platform, demonstrating the effect of short-lived tectonism on slope instability and deposition of mass transport deposits. The results of the study confirm that tectonism associated with the Syrian Arc Fold Belt, which altered the style of basin sedimentation between Egypt and Syria, persisted into the Eocene at least as far south as Wadi Araba in the western desert and Hammam Faraun in Sinai. In addition, the shape, size, and extent of the two dominant remobilized facies, debris flows and grainstone turbidites are influenced by their mud-rich versus grainy compositions.
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    Quantification of depositional and diagenetic geobody geometries for reservoir modelling, Hammam Fauran Fault Block, Sinai Peninsula, Egypt
    (2013) Hollis, Cathy; Corlett, Hilary; Hirani, Jesal; Hodgetts, David; Gawthorpe, Rob; Rotevatn, Atle; Bastesen, Eivind
    Outcrop data has traditionally been used to constrain conceptual models during subsurface reservoir characterisation and geocellular modeling, but published data of depositional and diagenetic geobodies in carbonate systems is lacking. Furthermore, few studies address how these diagenetic bodies, which often cross-cut sedimentary bedding, can be captured in reservoir models, even though diagenetic modification is likely to impart a significant influence on flow behaviour. This paper presents a case study from the differentially dolomitised pre-rift Eocene Thebes Formation on the Sinai Peninsula. It documents the size of depositional and diagenetic geobodies and demonstrates how these data have been incorporated into a 3D geocellular model. The results can be used as input parameters or templates for reservoirs in which fault/fracture controlled dolomite bodies have been described, whilst the workflow could have broader applications to other carbonate reservoirs.