Practical Aspects of Scaleup of Simulation Models

Abstract

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized to be experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Abstract With the advent in the early 1990s of stochastic geologic models with increased structural and stratigraphic complexity, a need arose for improved technology to create dynamic simulation models that preserve the displacement behavior of the more finely gridded static geologic model. This process of constructing relatively coarsely gridded simulation models from fine-scale geologic models is referred to as scaleup. Introduction Scaleup technology was developed for two reasons.• With model sizes ranging from 1 million to 50 million cells, geologic models are too large to simulate directly.• Because the new techniques for geologic modeling produced complex spatial variations in permeability and porosity for complex structures, simple methods used in the past for averaging properties across the model were no longer accurate. This paper describes technology currently used to develop a simulation-model grid and scaleup grid properties, the underlying basis for the technology, and the practical process used to ensure that the simulation model preserves the behavior of the geologic model used as input. Most, if not all, of the individual components of this procedure have been implemented in commercial software. However, the process used to ensure creation of a useful model is as important as any of the individual algorithms. This paper describes such a scaleup process, which has been applied extensively at ExxonMobil over the last 10 years. It consists of six steps, as follows.Interrogate the geologic model.Construct the simulation grid.Generate static properties.Use flow-based scale averaging to determine permeability.Connect the wells.Verify quality of the model. An example application of this process will be described briefly at the end of the paper. The goal of this process is to create the simplest, coarsest simulation model that adequately preserves displacement-process physics and reservoir description.