Permeable high temperature reservoirs with high salinity formation water
Reservoirs with high salinity formation water creates a challenging environment for most Type I Polymers, as they are not able to maintain a linear chain structure, which is needed for viscosity build and retention if it is to propagate effectively through the formation. High salinity also impacts the dissolution of HPAM, as in such environments it will take much longer to reach a full dissolution state, which would result in higher facility CAPEX requirements, and increased risk of injectivity issues over time.
High reservoir temperatures creates additional challenges for Type I Polymers, as polymer stability in-situ is impacted. Higher temperatures drives chemical reactions between polymers and divalent and/or multi-valent ions present in the formation water. High temperatures drives the hydrolyzes of such polymers which will change its viscosity behavior with the changing degree of hydrolysis.
Polymers need to be carefully selected for this type of reservoir to ensure technical success of a polymer flooding project. Polymers that are suitable for this type of reservoirs, ZLPAM Type II and III should have the following characteristics:
1) Linear structure
2) Low surface viscosity
3) Gradual viscosity build and retention in presence of formation water and higher temperatures
4) Good long term stability over time
5) Good dissolution with injection brine targeted for use
6) Minimal adsorption on reservoir rock
7) Good polymer displacement efficiency in the reservoir
8) Minimal emulsion tendencies with formation fluid
ZLPAM
Type II and III Polymers