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Regional Upscaling: a New Method to Upscale Heterogeneous Reservoirs for a Range of Force Regimes

  • Carolina Coll
  • Ann Muggeridge
  • X. D. Jing
Part of the Studies in Fuzziness and Soft Computing book series (STUDFUZZ, volume 80)

Abstract

Oil recovery and water breakthrough time for a waterflood are a function of the prevailing flow regime and the reservoir heterogeneity. However, small scale heterogeneities cannot be represented explicitly in field scale simulation models. Upscaling is used to represent the average effects of small scale heterogeneity on the large scale flow. The ‘upscaling’ method to use for a particular problem will depend upon the flow regime as different methods assume that different flow regimes are prevailing in the reservoir. For example, vertical equilibrium will apply for gravity or capillary-gravity dominated displacements. Steady state ‘pseudos’ can be used for capillary dominated flows whereas dynamic methods can be used for viscous dominated flows. In homogeneous reservoirs the dominant flow regime can be determined from examination of the relevant scaling groups. However, in heterogeneous reservoirs, the flow regime can vary with permeability so different flow regimes may be present in different reservoir regions. Hence different upscaling methods may be necessary in different parts of the reservoir. This paper presents the results of a new upscaling method called ‘Regional’ upscaling which takes into account the different flow regimes that can take place in the reservoir. The method calculates ‘Local’ Dimensionless Numbers on a grid block by grid block basis to determine the dominant flow regime in each fine grid cell. The coarse grid is dynamically selected by the user based upon the spatial locations of the different force regimes operating in the fine grid simulation model. User experience is mainly used in this process. The ‘pseudoisation’ method varies across the grid and is assigned according to the prevailing force regime by the user based on the so-called ‘Force Maps’. The method applies dynamic techniques to the viscous dominated regions whereas vertical equilibrium ‘pseudos’ are applied to the capillary or gravity dominated regions of the reservoir. Waterflood simulations of computer-generated heterogeneous reservoir models were performed to test the method. A comparison of its performance against other ‘pseudoisation’ methods is presented and its accuracy examined for breakthrough time and recovery prediction. It is demonstrated that the method can give more accurate estimates of hydrocarbon recovery and breakthrough times. A real reservoir case study is presented as a final test of the new methodology. The field data corresponds to a real heterogeneous Fluvial/Tidal reservoir in the Lake Maracaibo Basin in Western Venezuela. Simulations of one sedimentary unit with half of a million grid cells were performed on a parallel machine and compared with results from coarse grid simulations. The ‘Regional’ upscaling method proved to be 37% more accurate than traditional upscaling methods to predict water breakthrough time in the reservoir. It was also 11% more accurate in predicting hydrocarbon recovery. The method allows a considerable reduction in the number of grid blocks and hence significant speed-up of the simulations. The new methodology has the potential to facilitate applications of soft computing (e.g., neural nets, fuzzy logic or other clustering techniques) in reservoir characterization and modelling.

Keywords

Coarse Grid Grid Block Heterogeneous Reservoir Layered Sandstone Force Regime 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2002

Authors and Affiliations

  • Carolina Coll
    • 1
    • 2
  • Ann Muggeridge
    • 1
  • X. D. Jing
    • 1
  1. 1.Centre for Petroleum StudiesImperial College of Science, Technology and MedicineLondonUK
  2. 2.PDVSA E&PVenezuela

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