Sequence Stratigraphy and Reservoir Architecture of Late Ordovician Glacially-Related Deposits, Murzuq Basin, Libya

The Upper Ordovician deposits comprise two main stratigraphic units: Melaz Shuqran, and Mamuniyat, of which Mamuniyat Sandstones represent the primary reservoir targets in Murzuq Basin. <br>Sequence stratigraphic analysis of these deposits using well and seismic data led to the subdivision of the Melaz Shuqran into two third order sequences: Pre-Melaz Shuqran Sandstone - and Melaz Shuqran Seq.#2, and the Mamuniyat into three sequences. The Pre-Melaz Shuqran Sandstone represents the initial massive deposits in the deepest parts of the troughs (Palaeovalleys). The MZseq.2 shale comprises stacked, fining-upward parasequences. The Pusgillian Melaz Shuqran is separated by a stratigraphic break from the Upper Ashgillian Mamuniyat. <br>The Mamuniyat sequences correspond to a periglacial sediments and exhibit a cut and fill geometry related to successive glacial events during Hirnantian times. The Mamuniyat Sequence#1, interpreted from seismic, incised Melaz Shuqran. Seismic character suggests that it comprises massive deposits, probably coarse grained. The Mamuniyat Sequence#2 started with retrogradational parasequences culminating in Maximum Marine Flooding Surface. This was followed by progradational parasequences of the Highstand System Tracts (HST). The Mamuniyat Sequence#3 initiated with Transgressive System Tracts either very thin or absent. The HST locally displays poor reservoir quality which reflects variations in the energy of the depositional systems. <br>