Depositional model for the distal Ordovician glaciated margin of Jordan; implications for the reservoir potential of the Risha Formation
Published:January 01, 2019
J. Philip P. Hirst, Maher Khatatneh, 2019. "Depositional model for the distal Ordovician glaciated margin of Jordan; implications for the reservoir potential of the Risha Formation", Glaciated Margins: The Sedimentary and Geophysical Archive, D.P. Le Heron, K.A. Hogan, E.R. Phillips, M. Huuse, M.E. Busfield, A.G.C. Graham
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Latest Ordovician glacial sediments crop out in southern Jordan and adjacent areas of Saudi Arabia, where they consist of mainly coarse clastics. These sediments were in part deposited within steep-sided tunnel valleys with palaeotransport towards the north to NE. In NE Jordan, the distal equivalents of some of these valley-confined clastics are encountered in the subsurface, where they form the reservoir units within the Risha gas field. Here, the succession consists of stacked sandstone units ranging from a few metres to >20 m thick alternating with thinner mudstone horizons. Some of the sandstone intervals show cleaning-upwards profiles and they can be correlated over tens of kilometres between the wells. Their lateral extents are much greater than the tunnel valleys and they are interpreted as stacked proglacial outwash sheets deposited subaqueously in front of the ice sheet. The reservoir quality of the sandstones has been compromised by extensive quartz cementation, although better porosities and permeabilities are preserved in the upper parts of some of the cleaning-upwards profiles, resulting in correlatable intervals from which gas is produced without stimulation.
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Glaciated Margins: The Sedimentary and Geophysical Archive
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Understanding the sedimentary and geophysical archive of glaciated margins is a complex task that requires integration and analysis of disparate sedimentological and geophysical data. Their analysis is vital for understanding the dynamics of past ice sheets and how they interact with their neighbouring marine basins, on timescales that cannot be captured by observations of the cryosphere today. As resources, sediments deposited on the inner margins of glaciated shelves also exhibit resource potential where more sand-dominated systems occur, acting as reservoirs for both hydrocarbons and water. This book surveys the full gamut of glaciated margins, from deep time (Neoproterozoic, Ordovician and Carboniferous–Permian) to modern high-latitude margins in Canada and Antarctica. This collection of papers is the first attempt to deliberately do this, allowing not only the similarities and differences between modern and ancient glaciated margins to be explored, but also the wide spectrum of their mechanisms of investigation to be probed. Together, these papers offer a high-resolution, spatially and temporally diverse blueprint of the depositional processes, ice sheet dynamics, and basin architectures of the world’s former glaciated margins; a vital resource in advancing understanding of our present and future marine-terminating ice sheet margins.