The Petrophysical Characteristics of the Sinjar Formation, Kirkuk Oil Field, Northeastern Iraq
Abstract
The current research presents a petrophysical evaluation of the carbonate reservoir rocks of Sinjar Formation units (Paleocene-Early Eocene) in well (K-319), Kirkuk Oilfield, northeastern Iraq. The thickness of the formation is about 55 m, and it is divided into two units, the lower unit (23 m), which includes successive limestone and dolomitic limestone, and the upper unit (32 m), which includes dolomitic limestone beds. Thin sections, wireline logs (density, neutron, and gamma-ray), and modern programs have been used to study the accumulation and productivity of hydrocarbons in this oilfield through the study of reservoir properties including volume of shale, lithology, calculating and classifying of porosity, and reservoir partitioning, which is determined based on interpreted and analyzed data from logs. According to the petrophysical properties of the reservoir rocks, Sinjar Formation is divided into four porosity zones, zone (A) that demonstrates very good porosity (25-35%), zones (B and D) of intermediate to good porosity (10-25%), and zone (C) that exhibits poor porosity (5-12%) because of the high shale content, which hinders the fluid flow and reduces porosity. Thin sections are examined for porosity classification. There are two main porosity types in Sinjar Formation. The first type is interparticle porosity in its three classes, class (a) of grainstone facies, class (b) of packstone facies, and class (c) of mudstone facies. The second type is vuggy porosity of both types: separate vug pores and touching vug pores. The interparticle porosity is considered one of the most critical features affecting the transport of liquids and gases inside rocks.