A Core Flood Test-Program Performed with a Pilot-Skid to Quantify the Permeability Decline Induced by Real Treated Produced Waters Also Containing Degraded Polymer or Not

A water treatment pilot skid called WaOω has been developed by TotalEnergies to test the efficiency of the centrifugation technology in treating the produced water containing back produced polymer. In case of success, this technology would be implemented on field and the water quality targeted by the technology must allow re-injecting the treated produced water in matrix flow regime for pressure maintain and sweep efficiency. The same interest was expressed by OMV and a partnership project has been built. It was also agreed that OMV builds a second pilot skid called PRT that allows carrying out core flood tests onsite to assess the formation damage and related permeability decline that could be induced by the treated produced water. Both pilot skids have been implemented, connected to each other, and tested during more than one year on the OMV's Matzen oil field nearby Vienna where degraded polymer is already back produced by wells and present in the produced water. More than seventy core flooding tests have been performed in different centrifugation conditions in terms of speed and water qualities, some of them on high permeable sand packs representing the field targeted by TotalEnergies and some others on consolidated sandstone samples of lower permeability representing OMV reservoirs. The effect of adding fresh polymer to the treated produced water for EOR purposes has also been investigated. Some complementary core flood tests have also been performed in TotalEnergies labs using reconstituted sand packs and produced waters with and without polymer to understand the contribution of the degraded polymer alone, the produced water quality alone and both to understand the formation damage and some uncommon results observed with the PRT pilot skid. Core flood tests data often obtained on long injection periods revealed of a high quality, reliable and reproducible. They also showed that even if centrifugation seems to be a good technology, the very clean and transparent water that it delivered induced surprisingly some core permeability declines the origin of which would be discussed in this paper. However, it was clearly established that the presence of degraded polymer has a cleaning effect and limits the formation damage induced by the produced water injected on cores if the Total Suspended Solids in the treated water remains at an acceptable level. Adding fresh polymers limited even more the formation damage because their cleaning effect is more pronounced than with degraded polymer.