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Advanced Selection of Polymers for EOR Considering Shear and Hardness Tolerance PropertiesNormal access

Authors: N. Gaillard, A. Thomas, S. Bataille, G. Dupuis, F. Daguerre and C. Favéro
Event name: IOR 2017 - 19th European Symposium on Improved Oil Recovery
Session: Polymer II
Publication date: 24 April 2017
DOI: 10.3997/2214-4609.201700333
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 2.71Mb )
Price: € 20

Polymer flooding has proven to be an effective technique to improve oil recovery from mature reservoirs. The selection of polymer, focusing mainly on its temperature tolerance properties and its ability to propagate in porous media, is key to achieve a successful EOR job. This selection also depends on brine injection compositions that covers a large range of salinities and hardness worldwide. A screening of viscosity behavior with different polymers in different brine conditions is obviously helpful in order to select the most cost effective chemistry. The impact of different acrylamide based polymer chemistries is evaluated through viscosity measurement over a wide range of salinities and hardness. A parameter called R+, corresponding to the molar ratio of divalent cations divided by the total mole number of cations in the brine is introduced. Salt tolerance and hardness tolerance of polymers in solutions are evaluated for brine considering either constant Total Dissolved Salt (TDS) with different R+ either the impact of different total salinities for constant R+. This parameter is as well considered to compare shear stability of the different polymers. At least, the impact of the type of divalent cations on viscosity is reported. Polymers from the study are all anionic and acrylamide based. The introduction of different amounts of sulfonated monomer (ATBS) was performed and its impact on hardness and shear tolerance was assessed. For all the polymers, a threshold beyond which viscosity remains constant is reached for R+ > 0,5. Interestingly, this threshold is obtained for lower value of R+ for polymers containing ATBS since they provide better calcium tolerance. Calcium provides a higher impact on viscosity compared to magnesium for all the polymers studied. Increasing the amount of ATBS leads to higher tolerance to divalent cations. It also provides better stability to shear degradation. A minimum amount of sulfonated monomer is required to improve stability. The objective of this paper is to complete guidelines in the selection of industrial polymers considering a wide range of salinities and hardness. The screening of brine and polymers selected for this study is wide enough to represent worldwide injection brine conditions and helps selecting the most appropriate chemistry for each reservoir condition.

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