International Research Journal of Engineering and Technology (IRJET)
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Volume: 11 Issue: 12 | Dec 2024
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Sedimentological Analysis and Reservoir Quality Assessment of the Hawaz Formation in the O2 Well NC-115 Concession Murzuq Basin, SW LIBYA Hafid Nanis1, Abdussalam Aziz2 1College of Engineering Technology, Zuwara, Libya 2Zallaf Libyan Oil & Gas, Tripoli, Libya
------------------------------------------------------------------------***------------------------------------------------------------------------in several other wells; (2) the second phase from 1980 to Abstract - Murzuq Basin is one of the major Libyan basins,
1992 with several companies had some discoveries in the basin, and the most attractive discovery was made by Rompetrol within the study area, where the results of drill on twelve structures with six new commercial discoveries; also LASMO and BOCO oil companies had Ambiguous discoveries; (3) the third phase is Development Exploration Repsol which was restricted to the central part of the original block, within an area about 5,000 km², which started in 1993, and has been characterized by the development of the three main fields discovered (A, B and H field) (Aziz, 2000).
and it occupies the southwestern part of the country and covering an area of about 350,000 km². It contains a sedimentary fill up to 4,000 m thick, containing mainly a marine Paleozoic unit and a continental Mesozoic unit. The Upper Ordovician Mamuniyat Formation can be considered as a primary reservoir target in the basin. 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 capped by Lower Silurian Tanezzuft Shale. The present study focuses on the sedimentological study of the Hawaz formation, which is based on the slabbed core, wireline log data, and thin sections from core samples for the Hawaz Formation within the exploration well O2 NC-115 in Murzuq Basin. The core analysis and petrographic study show the sandstones are fine to mediumgrained, moderately to well-sorted, and sub-angular to subrounded grains. Facies analysis shows that the Hawaz Formation was deposited along a marine shoreline in shallow marine shoreface and distal shelf. The average porosity of the Hawaz Formation ranges between 7 - 17%. The reservoir quality of the Hawaz Formation varies from poor to good, represented by the middle part of the core section, to good quality, represented by the lower and the upper parts.
The Hawaz formation, the focus of this paper, presents an exciting opportunity for hydrocarbon exploration. As a potential second reservoir rock in the petroleum system of Murzuq Basin, the Hawaz Formation Middle Ordovician age (Llanviru-Llandeilo) is a significant interest. It is conformable with the underlying Achebyat Formation and unconformable with the overlying Melez Shuqran Formation (Hallett, 2002). The Hawaz Formation is the second major unit of Burollet's Qarqaf Group named by Massa and Collomb (1960) after Jabal Hawaz from the type section on the western part of the Qarqaf Arch. Collomb divided the formation into three subdivisions, an upper 'Tigillites superieurs', a middle 'Gres intermediaires' and a lower 'Tigilliites inferieurs' (Massa and Collomb, 1960). The Hawaz Formation on the Qarqaf Arch comprises 120 m of alternating siltstone and thinly bedded, cross-bedded sandstones with abundant Tigillites. Vos 1981 interpreted this sequence as a coarsening-upwards delta front/delta top high-stand deposit. The type section of the Hawaz Formation on the Qarqaf Arch consists of fine to medium-grained sandstone, with subordinate siltstone and shale. This section has been described by Vos (1981), who suggested that the sediments were deposited in a fan delta complex which progreded across the Qarqaf Uplift towards the north. The formation is present in the Dur al Qussah Trough and around the Qarqaf Arch and in the subsurface of the Ghadamis Basin and at least into the northwestern part of the Sirt Basin (Hallett, 2002).
Key Words: Hawaz, Sedimentology, Core, Tine section, Facies, Reservoir Quality.
1. INTRODUCTION Murzuq Basin is one of the several intracratonic basins on the North African platform with a predominantly marine Palaeozoic clastic infill (Sola and Worsley, 2000). Murzuq Basin covers a massive area of about 350,000 km² in the southwestern part of Libya. The stratigraphic column of Murzuq Basin consists mainly of clastic deposits. To assess its reservoir characteristic and petroleum potential, the Upper Ordovician Mamuniyat sandstone represents the primary reservoir rock in the Basin. In contrast, the Hawaz Formation is represents the second reservoir target, and the main reservoirs sourced and capped by Lower Silurian Tanezzuft Shale. Potential younger traps, mainly in the Upper Silurian-Devonian, is considered in the basin (Aziz, 2000). The hydrocarbon exploration activities in Murzuq Basin have passed through three stages: (1) in the first exploration phase from 1956 to 1980, 17 wells were drilled, with oil discovery in B2-1 (Atshan) and hydrocarbon shows
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The uppermost Ordovician Mamuniyat Formation is usually considered to be the primary reservoir interval in NC-115. However, this formation is not preserved in the eastern part of the H-field, where the Hawaz Formation directly underlies the lowermost Silurian Tanezzuft shale
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