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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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