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Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Rule-Based Static Modeling of Shoal-Dominated Carbonate Reservoirs
(1) Shell International E&P, Rijswijk, Netherlands.
(2) Department of Earth Sciences, University of Geneva, Geneva, Switzerland.
Several important carbonate reservoirs in the Arabian Platform, such as the Khuff Formation, are comprised of carbonate shoal geobodies. While it has been demonstrated that individual carbonate sand geobodies are correlatable over large distances (more than 10 km) and can have uniform stratigraphic thicknesses, the internal sedimentologic partitioning of texture and fabric is intricate. In addition, diagenetic processes, which can either follow or cross cut the depositional architecture, introduce another level of complexity by altering primary porosity and permeability. To better predict the significant lateral reservoir property variations associated with carbonate shoal deposition and early diagenetic overprints, a forward modeling approach is adopted. We choose to use cell-based forward modelling aiming to reproduce both sedimentary and early diagenetic processes, since these processes feedback and interlink through time during the development of the initial porosity and permeability architecture. The cell-based rules that have been postulated are efficient in simplifying the interaction of complex processes while creating emergent carbonate geometries. The model grid of the approach can be defined at the scale of the relevant heterogeneities within a subsurface reservoir. The cell-based forward modeling approach is supported with process-oriented input data from analogs to constrain modeling parameters and by geometry-oriented studies to constrain fundamental geometries associated with shoal deposition and early diagenesis. The analogs used are modern-day carbonate banks, which display diverse external landscape geometries as well internal partitioning of sedimentological properties. In addition, digital outcrop modelling is used to quantitatively validate the emergent geometries produced by the cell-based forward models. The outcrop we studied is the Permian Saiq Formation of the Akhdar Group exposed on the Saiq Plateau in Oman. This outcrop provides an ideal opportunity to investigate and quantify relevant geometries such as height and spacing of shoal crests and grain size distributions. Preliminary results are promising as model geometries are mimicking observations made on these modern-day and outcrop analogs. The combined forward modeling and quantitative analog approach tries to achieve a significant reduction in the present uncertainties of spatial prediction of properties in shoal-dominated carbonate reservoirs.