Improving Middle East Carbonate Reservoir Models with Digital Outcrop Modeling

Adams, Erwin W.¹, Anita E. Csoma¹, Carine Grélaud², Loïc Bazalgette¹, Cathy Hollis¹ (1) Shell International E&P, Rijswijk, Netherlands (2) University of Bordeaux 3, Pessac Cedex, France

Commonly, the interiors of Middle East carbonate platforms are modeled in a homogeneous layer cake fashion. Nevertheless, high-resolution 3D seismic data of epeiric platform carbonates reveals a complicated internal stratigraphic architecture, comprising depositional geometries such as platform incisions and clinoforms. These depositional geometries are also recognized in several kilometer-scale outcrops where direct interwell-scale observations can be made in 3D. In order to ground-truth and quantify the internal spatial complexity and heterogeneities of these outcrop geometries digital outcrop modeling was used. In essence, this allows outcrop-based geologic features to be spatially positioned and recorded with GPS, lidar, digital elevation models, and satellite imagery. The large-amount of collected data can be assimilated, visualized, and modeled to create a digital outcrop model (DOM). A DOM can serve as quantitative reservoir analog and as such improve reservoir characterization. For Middle East carbonate systems, the digital approach allows detailed quantification of facies partitioning within platform interior clinoforms and incisions. Grainstone shoal complexes with decameter-scale clinoforms were observed, characterized by complex internal architectures and lithological and diagenetic changes. For example, silicified layers mark the boundaries of clinoform bundles. Furthermore, the platform incision fill comprises dolomitized mudstone indicating that diagenesis plays a role in defining the reservoir properties of the incision. In parallel, a strong influence of subtle sedimentary/diagenetic discontinuities on fracture distributions has been identified, whereas the role of large-scale fracture corridors on the development of dolomitized areas is anticipated. Consequently, integrating sedimentological, diagenetic, and structural digital outcrop studies is essential for predicting interwell-scale subsurface heterogeneities.