Reservoir flow unit identification of the Mishrif formation in North Rumaila Field

Abstract

North Rumaila Oil Field is located about 54 km to the west of the Basra in southern Iraq. The Mishrif Formation in North Rumaila is one of the most important reservoirs in southern Iraq. Identifying and characterizing petrophysical flow units are the key to understanding and improving reservoir description, exploitation, and production and predicting the performance of carbonate reservoirs to represent them as combinations of different flow units, each with uniform pore throat size distribution and similar performance. The present work is a reservoir unit identification of the Mishrif Formation in North Rumaila Field. It is based on 14 wells, nine of which are from North Rumaila Field, three wells from West Qurna Field, and two wells form South Rumaila Field. In this study, the main reservoir units of Mishrif Formation are subdivided into subunits depending on the similarity of the log curves, water saturation–porosity–depth relationship, capillary pressure data, porosity–permeability cross plots (R35), flow zone indictor approach, and computer-processed interpretation. Unit MI, which is equal to unit MA, was subdivided into two secondary reservoir units (MI.1 and MI.2), and unit MII, which is equal to unit MB1, was subdivided into four secondary reservoir units (MII.1, MII.2, MII.3, and MII.4), while unit MIII, equal to unit MB2, was considered as one flow unit. As a result, we conclude that of the subunits, MII.4 is considered the most important reservoir in the field, subunits MI.1 and MII.2 may be classified as good reservoirs, whereas subunits MI.2 and MII.1 are of moderate reservoir characteristics. On the other hand, subunit MII.3 and unit MIII may be classified as intermediate–poor reservoir characteristics.