Evaluation of Nubia sandstone reservoir as inferred from well logging data interpretation for Rabeh East-25 well, Southwest Gulf of suez, Egypt

Abstract

The present study interprets well log responses obtained from the Nubia sandstone in the Rabeh East-25 Well, Southwest Gulf of Suez in Egypt. The reservoir characterization of the Nubia sandstone reservoir demonstrates that it has excellent potential for hydrocarbon production. Based on the qualitative interpretation of available well log data, the examined well through the Nubia sandstone succession has been subdivided into four zones. The hydrocarbon-bearing zones include zone II, a shaly reservoir occurs between depths of 5610 and 5631 ft, and zone IV, characterized by a clean sandstone reservoir is located between depths of 5656 and 5685 ft. When both zones are combined, the net pay thickness of the Nubia sandstone reservoir in the studied well reaches 60 ft. The petrophysical parameters of the oil-bearing zones were calculated to determine their reservoir properties, including their fluid saturation, shale volume, porosity, bulk volume of water and permeability values. The shaly sandstones in zone II have low water saturation (17–47%), low shale volume (0–50%), high total porosity (18–23%) and high effective porosity (8–23%) values. However, the clean sandstones in zone IV display lower water saturation (8–38%), high total porosity (17–22%) and high effective porosity (14–22%) values. Both zones exhibit high permeability values (usually above 50 MD), and their values of the Movable Oil Index are lower than 0.7reflecting the movability of the preserved oil. The constructed Buckles plots for the two zones indicate that the points which follow 0.04 and 0.05 BVW hyperbolas in zone II and points track 0.02, 0.03 and 0.035 BVW hyperbolas in zone IV will produce oil without water. The relative permeability to oil is usually less than 1.0, and the relative permeability to water is less than 0.01. Additionally, the water contents accompanying production are relatively low, i.e., they vary between 0 and 20%, thus reflecting the good reservoir quality of both zones.