Three-Dimensional Numerical Modelling of Clinoforms and Their Impact on Fluid Flow and Hydrocarbon Recovery within Deltaic and Shoreface Reservoirs

Key factors influencing fluid flow and reservoir behavior include facies architecture and heterogeneity distribution conditioned to stratal surfaces. Within shallow-marine reservoirs, clinoforms are one common type of stratal surface. Clinoforms are paleoseaward-dipping surfaces whose geometry preserves the depositional morphology of the delta-front or shoreface slope and whose position reflects shoreline progradation history. Clinoform surfaces control aspects of facies architecture within parasequences and can also act as barriers or baffles to flow when there are permeability contrasts (e.g. carbonate cementation or mudstone deposition) along them. Therefore it is important to include clinoforms in reservoir models under certain displacement conditions. However, standard reservoir modelling techniques are not well suited to capturing clinoform surfaces, particularly if they are numerous, below seismic resolution and/or difficult to correlate between wells. We present a numerical algorithm that generates multiple clinoform surfaces within a volume defined by two bounding surfaces, for example a delta-lobe deposit or shoreface parasequence. A geometrical approach is taken to describe the shape of a clinoform surface, by combining the relative height between any top and base bounding surfaces with a function such as a power law. The method is flexible and allows the user to define the progradation direction of the clinoform surfaces as well as the parameters which control the geometry, spacing and permeability of individual clinoform surfaces.

We use this algorithm to build a range of three-dimensional surface-based reservoir models, using outcrop data from the fluvial-dominated delta-lobe deposits in the Cretaceous Ferron Sandstone, Utah, USA, incorporating surfaces that represent boundaries between facies associations and surfaces that represent clinoforms. An experimental design is created to assess the impact on fluid flow and hydrocarbon recovery of a range of parameters including production strategies, permeability contrasts between different facies associations, geometries and distributions of clinoforms and the degree of mudstone barriers associated with clinoforms and trends used to model them. Finally, we illustrate the application of the algorithm to a subsurface reservoir model, using the Sognefjord Formation of the Troll Field, Norwegian North Sea.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California