SEDIMENTOLOGICAL STUDY OF HAWAZ FORMATION, MIDDLE ORDOVICIAN, ''O'' FIELD, NC115 CONCESSION - MURZUQ BASIN, SW LIBYA

Murzuq Basin is one of the major Libyan basins, and it occupies the south-western part of Libya covers an area of about 350,000 km². The primary reservoir target in the basin is the Upper Ordovician Mamuniyat Formation. In some places, where the Mamuniyat Formation is missing, the Middle Ordovician Hawaz Formation is considered the primary target. The Ordovician reservoirs are sourced and caped by Lower Silurian Tanezzuft Shale. The average porosity of the Hawaz Formation is ranging between 2-20% and permeability 0.02-1500 mD. Clay mineral and diagenetic cement are mainly in the form of quartz overgrowths and trace of siderite, dolomite and pyrite have reduced the porosity and consequently the reservoir quality. The present study focused on the sedimentological study of Hawaz Formation based on slabbed core, log data, thin sections from the O2-NC115 exploration well. The core analysis and petrographic study show the sandstones are fine to medium-grained, moderately to well-sorted, subangular to subrounded grains. Facies analysis shows that the Hawaz Formation was deposited along of fluvial system to marine shoreline in shallow marine shoreface to distal shelf. The reservoir quality of this formation varies from poor to excellent; the Middle succession is characterized the best reservoir quality.