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Mechanical Degradation of Polymers at the Field Scale - A Simulation Study
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IOR 2017 - 19th European Symposium on Improved Oil Recovery, Apr 2017, Volume 2017, p.1 - 21
Abstract
Polymer flooding is a chemical EOR method which aims to improve the oil recovery by making the water phase more viscous, and hence to increase the macroscopic sweep efficiency of a waterflood. However, the polymers considered for EOR applications are very susceptible to mechanical degradation in regions of high shear, such as in the injection facilities and in near well regions. If the applied flow rate is too high, an injected polymer solution may lose more or less all its viscosifying ability before properly entering the formation. This can be especially difficult to avoid if polymer is injected directly into a heterogeneous reservoir region where high molecular weight polymer species will have to travel through successive contractions and expansions inside small pores.
At EAGE-ECMOR XV we presented a new simulation model that is capable of modeling all the commonly observed flow regimes in porous media, such as Newtonian, shear thinning and shear thickening flow, as well as polymer mechanical degradation. Based on simple pore scale models, we derived expressions for the in-situ polymer rheology that can account for spatial variations in important reservoir parameters such as permeability, temperature, and salinity. This allowed us to match the different experiments with most of the input parameters kept fixed. The model captured very well how HPAM polymers of different molecular weights were mechanically degraded when injected into cores and series of cores with an order of magnitude variation in permeability.
In this paper we use the model with parameters that was history matched to lab data to study the polymer behaviour in a typical field operation. We investigate how the model scales from the lab to the field. In particular, we simulate flow of polymer near an injector in order to estimate the amount and extent of mechanical degradation as a function of injection rate and reservoir heterogeneity near the injection well. Preliminary results indicate that there will always be some degradation, but that this can to some extent be minimized using reasonable injection rates. In cases of open fractures near the injection well, the risk of degrading the polymer will be greatly reduced.