Application of Novel Upscaling Approaches to the Magnus and Andrew Reservoirs

Abstract

TX 75083-3836, U. S. A., fax 01-972-952-9435. AbstractCases studies from three North Sea turbidite reservoirs will be presented, which together demonstrate our current understanding of permeability and relative permeability upscaling. The three formations, the Magnus, Magnus Sand Member (MSM), the Magnus, Lower Kimmeridge Clay Formation (LKCF), and the Andrew reservoir each provide distinct challenges for reservoir modelling, either because of reservoir complexity, the fluids in place, or the phase of field life. To meet these challenges, several novel upscaling approaches have been developed. Their use will be explored and current best practice delineated. This best practice differs significantly from previous definitions of "effective permeability" by placing more emphasis on extracting multiple properties from the fine scale geologic models. Distinct upscaling calculations are required to assess (i) the quality of sands, (ii) the quality of barriers, and (iii) the tortuosity of flow around these barriers. Similarly, when constructing upscaled relative permeabilities, the "e~ective" curves are distinguished from the "pseudo" curves. The former describe the physical displacement of fluids, while the latter include the additional numerical dispersion corrections required when implementing the relative permeability functions within a coarsely gridded full field simulator. Effective PermeabilityWhat is effective permeability? A cynic could describe it in terms of putting incorrect information into the wrong model. to get the r&& answer. The "wrong model" is that carried in a typical full field simulator: homogeneous blocks of numerical rock that extend for perhaps a hundred metres or m-ore laterally, and which may be ten's of metres thick. The "incorrect information" is the effective property. But, what the cynic would emphasise is that we can only define this property based on our expectation of the "right answer".Consider the simplified sketch of a simple sand/shale reservoir zone, in Figure 1a, and focus your attention onto the "coarse cell" in the centre of the figure. What is the vertical permeability of the cell? With the standard flow based computation of effective permeability [1], the upscaling region is treated as if it were a laboratory coreflood, Figure 1b. The sides of the system are sealed, a pressure drop is exerted vertically, and the pressures and flux are determined numerically.The volumetric flux defines the effective permeability, according to Darcy's Law.

The Effective Use of Effective Permeability

“…In this report we continue the themes introduced in a previous publication [1], in which we examined the application of novel upscaling approaches to the Lower Kimmeridge Clay Formation (LKCF) of the Magnus reservoir. The LKCF is a geologically complex generally low net-to-gross reservoir, consisting mainly of sequences of sandstones and mudstones inter-bedded on the centimeter to meter scale.…”

Multi-Disciplinary Reservoir Description to Characterize Connectivity in a Complex Minibasin Fill: an Integrated Approach at Holstein Field

“…A flow based upscaling was used for cell permeability estimation in all 3 directions i, j and k. In order to better preserve the baffle effects from the shales, the half-cell High Out/zero South approach (3) was used to compute transmissibility multipliers TM between cells in all 3 directions. A sealed boundary condition with a skin of 1 cell was applied in this calculation.…”

Integration of 4D Seismic Data into the Management of Oil Reservoirs with Horizontal Wells between Fluid Contacts

“…Andrew full-field model (FFM) was initially constructed using vertical permeability barriers to reflect the stacked sand structure 3 and with a few lateral fault barriers. It proved robust in representing the initial water breakthrough, but proved increasingly over-optimistic in its water and GOR predictions at later times.…”