الملخص الإنجليزي
This project aims to study and characterize the fluvial sequence of the Middle and Upper
Gharif Formation in the Asfoor field of Central Oman. The Gharif Formation is one of
the most prolific hydrocarbon reservoirs in the Sultanate of Oman and is the target for
extensive exploration and production campaigns. The study seeks to understand the
reservoir architecture, depositional environments, and reservoir quality of the upper and
middle members of the Gharif Formation. In particular, Middle Gharif 2 (MG2), Middle
Gharif 1 (MG1), Upper Gharif 4 (UG4), and Upper Gharif 3 (UG3) in the Asfoor field.
Well correlation was conducted on 53 wells in the Asfoor field using the Petrel (2020)
software for all Gharif units. Paleogeographic (channel fairway) maps of Gharif subunits
were created with the aid of log signature analysis, petrophysical facies logs, and
paleocurrent analysis. Integrated reservoir descriptions “plumbing diagrams” scenarios
were created and linked to the paleogeographic maps. A conceptual depositional model
of Middle and Upper Gharif was created based on this analysis. The reservoir quality of
Middle Gharif was assessed using core and petrophysical data and associated with the
previous findings of the study.
Well-correlation results indicate that MG3 was deposited in a shoreface environment. In
contrast, MG2 and MG1 were deposited in a fluvial environment dominated by ephemeral
channels and sheetflood deposits (arid to semi-arid climate). UG4 was deposited above
an erosional surface, resulting in compensational stacking in a meandering fluvial
environment, while UG3 was deposited in a classical high-sinuosity meandering fluvial
system (humid/tropical climate). MG2 and MG1 paleogeographic maps indicate two
channel belt orientations trending NW-SE and NE-SW, with relatively wide channel
belts. UG4 and UG3 show an overall channel belt orientation of NE-SW, matching the
regional channel belt orientations.
MG1 in the Asfoor field is Arkose to subarkose in composition, while MG2 is dominantly
litharenitic to sublitharenitic. The reservoir quality of MG1 is highly impacted by clay
mineral infiltration directly below an erosional surface. Conversely, the reservoir quality
of MG2 is controlled by the rock fabric and compaction. The distribution of the reservoir
properties in the Asfoor field was found to closely resemble the paleogeographic maps of
this unit.
