The difference between conventional polymers and LPS is that the latter consists of a partially hydrolysed polyacrylamide at low concentration and a crosslinker, usually aluminium citrate.
IOR mechanisms for LPS are believed to be complex. However, it presumably boosts recovery through pore blocking or the “log-jamming” effect. This diverts the water flow and improves both microscopic and macroscopic sweep.
Statoil is evaluating the IOR potential of LPS on the Norwegian continental shelf.
Preliminary results based on core floods are very encouraging.
Recovery profile from core flooding before and after injecting LPS.
In addition to evaluating the potential of this method, current research aims to explain some unanswered questions about LPS.
These include:
- the behaviour of particle sizes at higher salinity
- recovery mechanisms
- long-term stability of the polymer at reservoir temperature
- applicability to improve waterflooding of North Sea oil reservoirs.