Paper on polymer selection guidelines

A. Thomas, N. Gaillard and C. Favero

Among Chemical Enhanced Oil Recovery (CEOR) methods, polymer flooding is a straightforward technique with a long commercial history and proven results. It consists in injecting polymer-augmented water into a subterranean formation in order to improve, thanks to the viscosity increase, the sweep efficiency in the reservoir and provide a mobility control between water and the hydrocarbons. However, implementing successfully a polymer flood in the field requires specific know-how to avoid polymer degradation and associated viscosity loss.

The first stage begins with the selection of the right polymer for the reservoir, depending on the water quality, temperature, permeability and presence of contaminants such as iron, hydrogen sulfide and oxygen. Several laboratory tests have to be performed to ensure the long-term stability of the product as well as core flooding experiments to check parameters such as injectivity and propagation through the porous medium.

The next step is the design and selection of equipment for the dissolution and the injection of the polymer solution into the reservoir. Surface facilities are paramount for the quality of the injected solution: the goal is to allow a good hydration, maturation and transport of the solution while avoiding any type of degradation that can occur either chemically (oxygen ingress) or mechanically (chokes, centrifugal pumps).

Another aspect that can be assessed is the degradation of the back-produced polymer. Several studies have shown that there is no influence of the polymer on the separation of crude and water; the polymer being water-soluble. However, when the viscosity of the produced water is above 4 mPa.s, a treatment may be operated before the water treatment process to avoid any difficulty in the surface facilities and an optimum efficiency.

To see the full article, see Oil&Gas Science and Technology Journal “Challenges and New Technologies in EOR”

 

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