English abstract
The Sahmah field in Oman has been a significant hydrocarbon producer since its
inception in 1980, utilizing the prolific Gharif formation. This study evaluates and
locating the remaining oil within the Gharif formation reservoirs of the Sahmah field.
The Gharif Formation in the Sahmah field consists of four distinct reservoir units:
the Upper Haushi Sand (UHS), Dolomite Drain (DD), Sandstone Drain (SD), and
Lower Haushi Sand (LHS). To assess these reservoir units, wireline logs collected
from 24 wells were analyzed comprehensively. These logs provided insight into
lithology, shale volume, porosity, fluid saturation, fluid contacts, and permeability.
Porosity and permeability values were derived from porosity logs and matrix
density, cross-validated with core data to ensure accuracy and reliability. This
study proposes using a water saturation height function to estimate the initial water
saturation within the reservoirs. The estimated volume of hydrocarbon in place was
determined to be approximately 263 million barrels, emphasizing the significant
remaining potential within the Sahmah field. To better understand the distribution
of the remaining oil, a reservoir simulation was conducted. The simulation results
revealed promising indications that some oil may still be present in the upper
sections of the reservoir structures or in areas characterized by low-quality
reservoir conditions. Specifically, the UHS reservoir exhibited low oil recovery rates
due to its inherently low-quality reservoir characteristics. However, in the DD
reservoir, high oil recovery rates were observed, with the identification of two
domes containing substantial remaining oil that could potentially be extracted
through the implementation of new production wells. The SD reservoir displayed
good reservoir quality in its northwestern region, while its southeastern part
exhibited relatively lower reservoir quality. Nonetheless, oil extraction from all wells
within the SD reservoir proved effective. The LHS reservoir, noted as the highest
quality reservoir in the Sahmah field, showcased exceptional porosity and
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permeability characteristics. However, premature water breakthroughs resulted in
the abandonment of some wells before extracting all recoverable oil. The simulation
results strongly suggest that the LHS reservoir remains incompletely depleted,
presenting a compelling opportunity for further oil extraction by drilling new wells.
The methodology and findings of this research provide invaluable insights and
knowledge for future exploration and production endeavors in the Sahmah field. By
comprehending the remaining oil distribution and understanding the reservoir
characteristics, operators can optimize their extraction strategies, potentially
leading to increased oil recovery and enhanced operational efficiency within the
field.
