Abstract
This paper reports on a new model which upgrades earlier history matches of Shell’s Peace River in-situ bitumen sands recovery process. The new model uses a four component oil phase description which includes high and low molecular weight components, carbon dioxide and methane. A mild thermal cracking reaction based on laboratory tests reduces bitumen viscosity to match produced fluid viscosity. A water-rock reaction which generates carbon dioxide is also used in the model.
Two Cartesian and one radial simulation prototypes of the reservoir are described. A 1/12th element of symmetry model of inner and outer wells of seven 7-spot patterns uses 59 ft [18 m] grid blocks and is adequate for modeling the steam drive. Another 1/6th element of symmetry model of a single 7-spot pattern using 29 ft [8.8 m] grid blocks is adequate for modeling soak processes. Both models require connection to a pseudo-aquifer beyond the patterns to represent historical performance. Details of the models and history match results are presented.
A radial model history matched to the extensive field data gathered from a high rate injectivity/productivity single well test and subsequent multiple soak cycles formed the initial basis for all models. Subsequent matching of average performance of seven 7-spot patterns (PRISP) with the 1/12th element of symmetry model indicated that reduced bitumen mobility was required. By adjusting Kv/Kh and the activation energy of the mild thermal cracking a good match with PRISP field data was obtained, while yielding and overall reasonable but a poor oil production match to the single well test.
History matching of the early production response of the Peace River Expansion Project (PREP) on a cluster by cluster basis has resulted in an improved understanding of significant process mechanisms at work during the soak cycles and subsequent pressure cycle steam drive. The numerical model was used to evaluate current operations at PREP. This evaluation showed that a low pressure continuous steamdrive was a viable alternative to the pressure cycling process. As a consequence of this work and additional operational benefits recognized, the project was converted to a continuous steam drive in October, 1990 after the completion of the first pressure cycle.
