Abstract
3D geological model for each reservoir unit comprising the Yamama Formation revealed to that the formation is composed of alternating reservoirs and barriers. In Subba and Luhais fields the formation began with barrier YB-1 and four more barriers (YB-2, YB-3, YB-4, YB-5), separated five reservoirs (YR-A, YR-B, YR-C, YR-D, YR-E) ranging in thickness from 70 to 80 m for each of them deposited by five sedimentary cycles. In the Ratawi field the formation was divided into three reservoir units (YR-A, YR-B, and YR-C) separated by two barrier units (YB-2 and YB-3), the first cycle is missing in Ratawi field. 
 The study involves 1 well in Luhais field (Lu-12), 3 wells in Subba field (Su-7, Su-8, and Su-9), and 5 wells in Ratawi field (Rt-3, Rt-4, Rt-5, Rt-6 and Rt-7), the Luhais, Subba, and Ratawi fields located in the Mesopotamia zone (Zubair subzone).
 The reservoir units (YR-C and YR-D) in Subba oil field, and YR-B in Ratawi oil field represent the major reservoir units that characterized by the best Petrophysical properties (the highest porosity, the lowest water saturation, and the best Net Pay Thickness), Luhais oil field has poor to moderate Petrophysical properties and low oil bearing in YR-A, YR-B and YR-C units, and produce heavy oil and salt water from YR-D and YR-E as indicated by low resistivity log reading, and according to the Drill Steam Test (DST) with the description of cutting in final geological reports.
Highlights
The Yamama formation represents one of the most promising carbonate reservoir, because of its wide geographic distribution over most parts of southern Iraq and the neighboring area, and carries a special economic importance, since it's consider one of the well-known oil traps in southern Iraq
This study aims to evaluate the formation in the southwest area of Basrah government, comparisons of the petrophysical properties of the three studied fields to estimate the amount of hydrocarbon and the differences in productivity between them
1- Digitized the structural contour maps for top of the Yamama formation at (Subba and Ratawi oil fields) by (Didger) program and loaded into petrel software. 2- Finding the petrophysical properties of the Yamama reservoir units in the study area using the Equations below: The secondary porosity index (SPI) may be computed as the difference between total porosity as determined from Neutron and/or Density logs, and primary porosity obtained from sonic log
Summary
The Yamama formation represents one of the most promising carbonate reservoir, because of its wide geographic distribution over most parts of southern Iraq and the neighboring area, and carries a special economic importance, since it's consider one of the well-known oil traps in southern Iraq. The Lower Cretaceous Yamama formation reported containing hydrocarbons at more than 26 structures in southern Iraq including West Qurna, North Rumaila, Majnoon [3], in addition to Siba, Sindibad, Nasirya and the three studied fields (Luhais, Subba, and Ratawi).
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