Facies Characteristics of Aptian Formation within the Regional Stratigraphic Framework of a Giant Carbonate Field in the Middle East

Abstract

AbstractFacies and their distribution in space are key building blocks to determine the depositional architecture of hydrocarbon reservoirs. For this reason, the unified high resolution facies and sequence stratigraphy boundaries are needed to constrain facies architecture and their properties distribution for constructing the 3D static and dynamic model. A comprehensive facies analysis and modeling within the established stratigraphic framework, was conducted to reduce the uncertainty in correlating and building-up the architecture between wells.Over 30,000ft of core data from 155 wells and their log data are used in integration with the seismic interpretation. Knowledge of the facies results in a better correlation, used then to generate a total of 47 spatial facies maps. Some facies are combined to facies associations (FA) maps, representing the FA at each sequence boundary in its sequence package. For each selected interval, the dominant FA observed in individual wells has been correlated; preserving the general evolution of the depositional environment and the sequence stratigraphy framework. These maps are used to constrain the variograms for the petrophysical properties distribution in terms of orientation and ranges.A conceptual facies model was created based on facies distribution following an evolving platform to basin topography during transgressive (Apt1&Apt2), early-highstand (Apt3), late-highstand (Apt4a&Apt4b), and composite lowstand (Apt5) phases of carbonate platform development during the Aptian. The best reservoir quality is dominated by dissolution related mouldic and vuggy macropores. The grain supported textures demonstrate better overall reservoir quality as a result of more abundant interparticle and intraparticle pores and enhanced macro-vuggy porosity created by leaching process. Some poor reservoir quality is observed in grainy facies due to cementation.A detailed understanding of the core-based facies description/analysis is required for identifying the reservoir properties and its relation to rock-texture; leading consequently to the rock-flow-units in the dynamic model.