Geo-models for fine-scale flow simulation of chalk reservoirs

摘要

This report presents procedures for producing and analysing fine-scale geo-models. The geo-models are constructed in order to carry original measured data at the correct scale in the input stage. This is achieved by selecting cell size at the same scale as the core analysis data used for input. This report presents an example of fine-scale porosity-permeability models of a reservoir sequence, and selected methods to generate these models. The purpose of investigating these models is to analyse effective properties as a consequence of the layering and contrasts in the model. These effects are largely ignored in most large-scale geo-statistic reservoir models so far. Outcrop data has been used as analogue for the layered structure in the chalk geomodels, and the correlation structure is used to induce layering in the model, reflecting beds of approximately one meter thickness. The variability and range of porosity and permeability values are derived by comparison to actual well data. The contrasts in the sedimentary sequence are developed by a combination of sedimentary processes, compaction processes and effects from later diagenesis. The detailed geo-model has been subjected to single-phase flow simulation, and the average anisotropy factor Kv/kH can be derived for each type of model. The porosity/permeability relation for the effective properties reflects the upscaling that is carried out with this procedure. Preliminary results from analysing the effective properties of the detailed geostatistical model of size 80x80x1 m is illustrated. The detailed models have been subjected to single-phase flow simulation in order to get the effective permeabilities for the models. The procedure is applied in order to investigate the consequences of layering in the formation on the effective and directional permeabilities. (au) EFP-86. 11 refs.