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Eighth EAGE Arabian Plate Core Workshop
- Conference date: November 28-30, 2022
- Location: Dhahran, Saudi Arabia
- Published: 28 November 2022
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Stratigraphy of the Valanginian Buwaib Formation and recognition of the Weissert Event on the Arabian Plate.
Authors M. Deville de Periere, P. Brenac, I. Alhilali and F. LuSummaryThis study aims to reconstructs the stratigraphic framework of the Valanginian/Hauterivian carbonate deposits of the Buwaib Formation in Saudi Arabia by integrating detailed sedimentology and biostratigraphy along with carbon isotope variations. The main observations suggest that most of the Valanginian encompasses a 3rd order sequence initiated by the karstified early Valanginian exposure, likely dated from the top of the pertransiens ammonite zone. The early/late Valanginian transition has been identified by changes in dynocyst assemblages correlated with carbon isotope variations. The main result of this study particularly highlights that proliferation of the Lithocodium/Bacinella facies in the southern Tethys during the late Valanginian is strongly associated with the general drowning of the platform, associated with major climatic changes during the Weissert Event and would therefore correspond to a 3rd order maximum flooding interval at the vicinity of the verrucosum ammonite biozone.
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Outcrop-Based Reservoir Model of the Late-Jurassic Arabian Stromatoporoid/Coral Facies: Static Connectivity and Flow Implications During Waterflood
Authors A. Ramdani, A. Omar, P. Khanna, G. Gairola, H. Hoteit and V. VahrenkampSummaryThe high porosity-high permeability Late-Jurassic stromatoporoid/coral facies of the Hanifa Formation is one of Arabia’s most complex and laterally heterogeneous reservoir strata. The reservoir implication of this facies’ heterogeneity is poorly understood or completely ignored in most studies. Using an outcrop analog, this study numerically investigates the influence of stromatoporoid/coral facies heterogeneity on reservoir static connectivity and fluid flow during waterflood. This study performs a full three-dimensional outcrop investigation of the Hanifa reservoir analog over a 4 km2 area in Wadi Birk, Saudi Arabia. Geologically realistic static reservoir models were built using process-based facies modeling and subsurface analogous reservoir properties. The model employs a custom-made algorithm that mimics the scaling hierarchy and morphology of the stromatoporoid/coral buildup observed in the outcrop. Initial connectivity assessment suggests that a vertical 5-spot pattern with a 1 km spacing can, in the best case, only access 20% of the Gross Rock Volume. Twenty years of flow simulation during water flooding using a similar well pattern suggest different sweep efficiency at different stratigraphic levels. The lateral connectivity and heterogeneities in sweep efficiency are controlled mainly by the interconnected buildup clusters. These results underline the reservoir implication of the extreme heterogeneity of the late-Jurassic Stromatoporoid/Coral Facies.
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Hydrodynamic Simulation of The Late Jurassic Arabian Intra-shelf Basin: Insight on Marine Organic Productivity and Distribution
Authors A.N. Wicaksono, G.S. Gairola, P. Zhan, I. Hoteit and V. VahrenkampSummaryThis study is an attempt to assess the impact of hydrodynamic circulation in shallow intra-shelf basins on the distribution of organic matter and source rock richness. It provides insights into the paleo-current patterns and their potential relationship to organic matter generation and transport within the Late Jurassic Hanifa basin. The hydrodynamic simulation was carried out using the MIT general circulation model (MITgcm) - an open-source simulator - run on KAUST’s supercomputer Shaheen II. Results indicate that both surface and bottom currents are sufficient to cause significant lateral heterogeneity in organic matter richness and distribution. A closer look at basinal rock sequences confirms the presence of current features providing further support for the importance of considering hydrodynamic settings. Hydrodynamic simulations of paleo-basins are likely key to better understand the distribution and accumulation of source rock and generate more realistic subsurface models for exploration and production.
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N-S trending shallow water currents on Late Jurassic Arabian shelf: Evidence from paleo-hydrodynamic modelling and outcrops
Authors G.S. Gairola, A.N. Wicaksono, A. Ramdani, P. Zhan, P. Khanna, I. Hoteit and V. VahrenkampSummaryThis study presents a first attempt to assess hydrodynamic circulation in the shallow water environment of the paleo-ocean that covered Saudi Arabia some 180 million years ago. It provides insights into the paleo-current patterns that may have occurred and their relationship with sediment transport, as well as sediment distribution on the carbonate shelf.
Using MITgcm model we were able to simulate the current patterns in the Late Jurassic Arabian shelf which indicates strong currents in the shallow regions. Detailed outcrop investigation of exposed late Jurassic (Hanifa Fm) stromatoporoids/coral reefs provides ground truthing for paleo-hydrodynamic simulation exercise. The close agreement between the modelled current patterns and the orientation of stromatoporoid/coral reefs supports the outcome of the hydrodynamic modeling and underlines the usefulness of employing such models to understand and characterize sedimentary architecture in ancient sequences. An improved understanding of paleo-hydrodynamics could be used as a constraint to model realistic distribution of reservoir facies (patterns/trends) in subsurface models of carbonate sequences and reservoirs. This is crucial for generating optimized reservoir development plans.
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SEQUENCE STRATIGRAPHIC ARCHITECTURE OF THE MIDDLE AND UPPER JURASSIC OF THE ARABIAN PLATE - A SYNTHESIS
Authors F. Van Buchem, C. Gravestock, M. Simmons and R. DaviesSummaryBased on extensive outcrop and subsurface data a regional sequence stratigraphic model has been constructed for the Middle and Upper Jurassic strata of the eastern Arabian Plate. This model documents the evolution from mixed siliciclastic-carbonate ramps to the creation and partial asymmetrical infill of large intrashelf basins along a master-transect of 2000 km from Northern Iraq to the ocean margin in Oman. This type of regional synthesis allows to address fundamental sedimentological and stratigraphic questions such as: what were the tectonic controls? what are the drivers behind the creation of intrashelf basins? what was the composition and timing of their infill? and how did the carbonate factories evolve? In addition, since the Arabian Plate was tectonically stable for most of this time interval, these rock successions provide a good proxy for eustatic sea level fluctuations.
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Advanced Carbonate Rock Typing and Property Distribution in an Upper Jurassic Reservoir: Getting the Geology Right
Authors P. Mangane, J. Kenter, J. Borgomano and T. MecheriSummaryCarbonate rock typing methodologies are essentially an attempt to identify reliable statistical relationships between geological parameters, mostly from core when available, and the log domain and distribute the resulting categories in the reservoir using spatial trends and relationships embedded in the geological domain, mostly based on depositional and textural concepts. The reality, unfortunately, is that the log domain relationship with geological parameters from core is generally weak (below statistically acceptable thresholds) and therefore obscures petrophysical distributions in resulting models. On the one hand, diagenetic modification may explain part of this lack of correlation, but our knowledge of diagenetic body trends and juxtaposition are poor due to the absence of reliable analogs. On the other, we may question the reliability and grounding of depositional facies models used. Finally, the common carbonate rock typing approach is not tailored to test and handle such uncertainties. By focusing on the statistical predictability of petrophysical rock categories first and understanding kriged distributions in reservoir space we attempt to resolve this conundrum. This paper uses a Middle East example to highlight such pitfalls and, at the same time, to integrate sedimentary characteristics in rock typing practices and reservoir characterization.
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Remote Capture and Quantification of Diagenetic Products: An Outcrop Example from the Lower Jurassic in Morocco
Authors E. Dujoncquoy, J. Kenter, S. Thiele, R. Bourillot, J. Champagne, A. Ransinangu, J. Grellier, A. Bordenave and R. GloaguenSummaryDiagenetic modification of carbonate depositional systems is a dominant process changing their pore systems away from primary texture and responsible for their challenging multi-modal and multi-scale behavior. It is these pore system characteristics that control dynamic behavior across many scales from plug – to log – to reservoir scale. One common diagenetic product in many Middle East reservoirs is dolomite and is invoked to be associated with improved storage and excess permeability. Despite these observations, reliable spatial models of dolomite distribution are rare, especially at field or seismic scale. This paper documents how the dolomite distribution across an outcrop in Morocco was captured and validated using high resolution 3D photogrammetry combined with hyperspectral acquisition. It suggested that these, “remote” attributes can be combined and not only provide spatial rules but also point to scenarios for reconstruction of timing and process of dolomitization.
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Determining Geological Control on Multi-scale Reservoir Quality in Carbonates: Time to Change the Paradigm?
Authors J. Kenter, P. Mangane, E. Dujoncquoy, O. Mangane and J. BorgomanoSummaryChallenges in carbonate reservoir characterization (conventional marine, unconventional including continental) result from their often-heterogeneous nature, variable mineral composition, multi-modal and multi-scale pore systems, and presence of excess permeability conduits which jointly undermine our ability to predict reservoir quality, particularly at interwell scales. Traditionally, stratigraphic, and sedimentological attributes, with the emphasis on depositional facies and textures, have been used to explain reservoir quality at different scales. This paper reviews examples of where such approach fails to explain reservoir quality and why it is important to shift the focus to alternative methods. For example, why is it that geological (depositional facies partitioning) influence on property distributions in a sample of more than 370 reservoir zones is almost negligible? Why is it that the influence in porosity-permeability space of the Shuaiba Formation only shows a partitioning in grainy shallow-water – and deeper muddy facies? Why is it that dolomite in the Middle East is generally associated with better reservoir quality while limestone has clearly better porosity-permeability relationships? Resolving such paradigms is critical for well placement in field development and optimization of production while offering opportunities to saving cost.
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A Statistical Approach To Discern Lithological Heterogeneity And Connectivity Of Tidal Deposits In The Subsurface Based On Data From Modern And Ancient Analogs: Examples From The Middle Jurassic Dhruma Formation, Saudi Arabia’’.
Authors B. Al Shammeri, L. Colombera, N. Mountney and M. Al-MasrahySummarySand bars are notable depositional elements in many tide-dominated or -influenced environments such as estuaries, deltas and shelves. The sand bars that accumulate in estuaries, which are the focus of this study, typically accumulate in the middle and outer parts of tidal estuaries, and the inner parts of mixed energy estuaries. Estuaries have a long-term sediment preservation potential due to their sheltering morphology ( Biggs and Howell, 1984 ; Demarest and Kraft), which makes preservation of estuarine deposits, including tidal sand bars, extremely likely. Moreover, being systems that are developed in transgressive settings, estuaries with tidal sand bars have significant potential for burial by subsequent highstand, mud-prone deposits such as shelf mudstone or prodelta mudstone (e.g. Shanmugam et al., 2000 ; Chen et al., 2014 ). Therefore, tidal sand bars are encouraging reservoir bodies to target in the subsurface. However, their heterogeneity and connectivity in the subsurface is not well understood. To bridge the gap in knowledge and improve the understanding of the tidal sand bar morphology and their internal anatomy, a quantitative study was conducted. Specific objectives of the study are as follows: I) investigate the geometry and size of tidal bars known from modern systems and ancient successions; ii) illustrate their sedimentological characters, iii) investigate the nature of juxtaposition of tidal sand bars in association with other estuarine and shallow-marine elements; iv) highlight tidal-bar development and preservation; and vi) present implications of the results for reservoir prediction and characterization.
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