Optimizing Simulation Models by Upscaling from Integrated Reservoirs Models: A Case History

Abstract

This paper presents a case study of using integrated models in improving upscale accuracy that increases the model speed. This has a great impact on CPU time and therefore the cost of the study. A unique process that integrates data from all possible sources (open hole logs, RFT and production data, seismic and geologic interpretations) was used in a geologic model. This static geologic model was then used to build a DYNAMIC simulation model. We superimposed water encroachment movement over the geologic model that in turn was recycled back in developing the simulation (engineering) model. Up-scaling the resultant model was done using a multi step technique that captured all the varying details of the complex reservoir such as;A tilt in the free water level coupled with the effect of capillary forces on reservoir fluid distribution;Reservoir stratification which has the effect of limiting bottom water support and causing the injected water to move rapidly through the high permeability layers;While the effects of stratification and faulting are apparent, communication is observed across these features. The study was done on a sector model extracted from the full field geological model as a pilot testing of the method. The same procedure was then applied to the full field model. As a result of using this technique, pressure and water saturation match was obtained and prediction cases were submitted to predict reservoir performance for designing operational and production strategies for the field. Introduction Characterization of complex reservoirs, by nature requires more data for better description and management of hydrocarbon reservoirs. Coupled with reliable characterization model, faster delivery of simulation output is needed for better business decisions. Data integration did play a role in speeding the simulation model runs and shortened history match period. The technique used to integrate the data used RFT, gamma ray, FM logs as well as build up data to define lithofacies and reservoir flow units. The use of water encroachment in correlating lithofacies and the extent of sand bodies together with the incorporation of faults from 3D seismic in water encroachment study produced a smooth simulation model. This allowed us to track the water movement in the high permeability streaks as seen on production logs. Accordingly we built several simulation models with different properties to match this water encroachment model. As a result, history match changes were done on lithofacies of the full scale model which in turned speeded up simulation time of the model and reduced the history match period.