Characterization of the dynamic heterogeneity during polymer flooding in reservoirs with stratified non-communicating layers

Yongge Liu, Jian Hou, Jingyao Liu, Qing Wang, Kai Dong

Abstract


Heterogeneity affects the development performance greatly and, therefore, is an important
property of the reservoir. The conventional method mainly takes permeability, which often does not
change during the production process as the characterization parameter of heterogeneity. However,
in polymer flooding, the injected polymer is more likely to enter the high-permeability zone with
low resistance, which leads to the decrease of the resistance difference between the high and lowpermeability
zones. This non-uniform resistance due to the unbalanced distribution of polymer
solution changes the heterogeneity of the reservoir dynamically, and it cannot be reflected by the
current representation method. In this paper, a new parameter called “motivation coefficient” (IP )
is proposed, in which not only is the static permeability included, but also the dynamic parameters
related with polymer property are taken into consideration, and the Gini coefficient of IP (GCIP ) is
selected to represent the dynamic heterogeneity during polymer flooding. Then physical experiment
and numerical simulations are done to study the variation law of dynamic heterogeneity during
the polymer flooding. The results show that the dynamic heterogeneity is greatly improved after
polymer injection. However, at the subsequent water flooding stage, the dynamic heterogeneity is
more intensified when the whole polymer flooding process is over. Comprehensively considering
the dynamic heterogeneity and development performance, the most favorable value of Gini
coefficient of permeability is 0.6, and the best range of polymer concentration is from 0.1% to
0.15%. As for the slug size, large sizes are preferred if they are economically viable.


Keywords


dynamic heterogeneity; quantitative characterization; polymer flooding; Lorenz curve.

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