Abstract

Heterogeneities in the reservoir can result in poor sweep efficiency during water and chemical floods. In many cases the sweep efficiency is improved significantly when changing to polymer flood. However, in the presence of very high conductive features polymer by itself may not be sufficient and result in undesired polymer production. Diversion of the flow to oil saturated regions and minimization of polymer production is then desired. In the presence of cross-flow the best option is placing a (chemical) plug deep in the reservoir. Adding a second component to the injection polymer stream that can react with the polymer to form a cross-linked gel is then an effective solution. However controlled placement and triggering of the reaction is very challenging.

In this paper we will present the results of static bulk measurements and dynamic core flooding experiments that were performed to identify cross-linked polymer systems. The polymers in the system are the typical high molecular weight partially hydrolyzed polyacrylamide (HPAM) polymers used in polymer flooding projects. The experimental work is focused on understanding and controlling the gelation time to enable proper placement and triggering at any given distance from the injectors. Parameters of investigation included temperature, brine composition, polymer concentration and rock mineralogy. The main parameters affecting the gelation process and possible failure mechanisms were identified. For given conditions, retardation of gelation time varying from few days up to several months could be designed. The learning from the experimental results can be used for improved material selection and design for other chemical and water flooding.

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