Steam Communication of Well Pad System under Steam Assisted Gravity Drainage in a Heterogeneous Oil-sands Reservoir

This paper analyzed the steam communication among steam chambers made by the well pad system for steam assisted gravity drainage. The typical well pad system consisted of several well pairs so that steam communication between well pairs would be inevitable. This study introduced two comparative models to demonstrate the steam movement with respect to spatial distribution of reservoir permeability: one was homogeneous and the other showed an asymmetric distribution. Three well pairs, i.e. six horizontal wells, were installed. Notwithstanding the reservoir was homogeneous, the horizontal movement between steam chambers was occurred. The chamber shapes illustrated by temperature map were symmetric but one chamber growth was slightly limited so that their production profiles were not equal to each other. In the asymmetric distribution, the chamber enlarged more at the more permeable region and the steam moved from the larger chamber to the smaller one. Cumulative steam to oil ratio of the well-developed chamber was reduced after the steam chamber crossed over. At an experimental work mimicking a real heterogeneous oil-sands deposit, the local channeling was observed. Each production performance allocated to each well pair was so different and thereby the individual recovery rate was different. These results showed that the reservoir heterogeneity affected the steam communication and made the unequal steam enlargement, local unrecovered zone, and an energetic inefficiency.