Problem of unexpected water production with water saturation less than 40%: A case study from Alam El Bueib Formation, Safir Oil Field, Shushan Basin, Western Desert, Egypt

Abstract

Safir Oil Field which locates within Shushan Basin is considered one of the well-known oil fields in northern Western Desert of Egypt. Alam El Bueib 3A Member is the main oil producer in this field. This member in Safir-N07 well has water saturation (Sw) values less than 40% with 17% porosity. However, the available data of Drill Stem Test (DST) indicate that 999 barrels water per day (BWPD) and only one barrel oil per day (BOPD) of total 1000 barrels fluid per day (BFPD) were produced. This represents a challenging problem facing any petrophysicist. The presented article treats this situation by comparing water saturation with other two extremely important petrophysical parameters. These are the critical water saturation (Scw) and minimum bulk volume water (BVWmin). The critical water saturation (Scw) of the tested interval is 34%, which is less than the calculated Sw (i.e., Sw > Scw) that reflects the existence of water rather than oil. In addition, BVWmin has been calculated to be 0.05. The calculated BVW for AEB-3A Member (Φ × Sw) is 0.07 which is higher than the BVWmin value confirming the water productivity and matching the DST data. The presented technique was also applied to the same member in Safir-03 well in the same field. The calculated Sw and BVW are 12% and 0.03, respectively, which are lower than Scw (31%) and BVWmin (0.05) indicating that the reservoir is at irreducible state (no water will produced). During DST, this member recovered 1350 (BOPD) and zero (BWPD) confirming the importance and validation for the applied techniques. The constructed structure contour map shows a distinctive three-way closure in the southern part of the study representing a suitable place for hydrocarbon accumulation in Safir-03 well. On the other side of this map displays Safir-N07 well located in downthrown which proves oil-free production as residual oil saturation.