Reservoir Properties and Facies Distribution of Mishrif Formation in Ratawi Oilfield, Southern Iraq

Abstract

The M. Cenomanian-E. Turonian Mishrif Formation is considered as the most extended reservoir of south Iraq. The present paper reveals the facies of this formation in Ratawi oilfield by the analysis of seven wireline logs. According to reservoir properties, i.e. effective porosity, permeability, and water saturation, the Mishrif Formation is divided into two main units, the upper (mA) and the lower (mB), separated by a shale member. These reservoir units are almost capped by two shale intervals located in the lower and upper contacts with Rumaila and Khasib formations, respectively. The reservoir properties, in terms of porosity and permeability, decrease (porosity less than 5%, permeability less than 0.001 md) to the south of Ratawi structure due to the dominance of deep marine facies, whereas the formation predicted to have good reservoir properties (porosity more than 10%, permeability more than 5 md) to other directions especially to the east, contrary to what was previously expected.