Sedimentological and rock-typing definition of the Khuff Formation of an offshore Abu Dhabi field

Azzam, Ibrahim N. (1) and Arnaud Meyer (2)

A reservoir facies (lithotypes) classification and Core Rock Typing (CRT) study was carried out on the Khuff Formation of an offshore Abu Dhabi field. This study was a part of the full-field simulation model, and aimed at improving the 3-D geological model of this gas field. The CRT approach was conducted on: (1) a sedimentological description of 2,482 ft of cores from six wells and mainly representative of the Upper Khuff Formation (K1 to K4 reservoir units; K5 reservoir unit was also investigated); (2) the observation of 1,330 thin sections of rocks; and (3) the analysis of 2,480 CCAL and 87 MICP measurements. The first part of the study consisted of the definition of the depositional facies based on lithology, texture, and sedimentological features, deduced from both macroscopic and microscopic descriptions of cores and thin sections. This resulted in proposed sedimentary lithofacies, reservoir layering (based on sequence stratigraphy analysis), and reservoir lithofacies property description. The second part of the study defined: (1) rock types with observed differences of porosity networks; (2) diagenetic evolution of sediments; and (3) qualitative interpretation of petrophysical data. Core-to-log matching and the CRT recognition and identification on wireline logs was difficult and sometimes biased, especially in the dolomite intervals. The application of the CRT approach to the uncored zones remains uncertain, particularly in K4 and K5 reservoir units. Lithofacies and CRT descriptions for the six wells were used to build the 3-D geological model. The 3-D grid also incorporated the sedimentological layering based on facies description, and the sequence stratigraphy analysis. Maps of lateral variations of core type were used in the 3-D model to provide constraints for depositional orientation, facies changes, etc. This study contains a full analysis and integration of all sedimentological and petrophysical available data.

Azzam, I.N., and Meyer, A., 2004, Sedimentological and rock-typing definition of the Khuff Formation of an offshore Abu Dhabi field: Bahrain, Gulf Petrolink. GeoArabia.