Operational Challenges and Monitoring of a Polymer Pilot, Matzen Field, Austria

AbstractFour main areas of uncertainty can be described in polymer injection projects: Are we able to deliver the polymer solutions at the required quality to the wellhead?Are we able to inject polymers at the required quantity and quality?Are we producing sufficient incremental oil?Are we able to cost-effectively separate, and treat oil and water after polymer breakthrough?The monitoring program which was developed for the polymer injection pilot aims at reducing the uncertainty and at fast identification of operational difficulties - details are described below:Polymer quality at the wellhead: the polymer concentration and viscosity of the “mother” solution and injected polymer solution was measured at various locations in the surface facilities. A quality check of the delivered polymer, including a filter ratio test of the dissolved polymer was performed, the biological activity monitored, iron content measured and polymer solution investigated for “fish-eyes”. The monitoring program enabled us to identify challenges related to shearing the polymers after changing the operating envelope, to identify problems related to biological activity and to ensure data quality for interpretation of the pilot. Injectivity and Degradation: monitoring involved wellhead and bottom-hole-pressure measurements and repeated fall-off tests as well as visual monitoring of the polymer solutions in the well. The results showed the mobility reduction of the polymer solutions versus water mobility and an indication of induced fractures. Combining the various measurements led to identification of an operational issue: the injectivity decreased more than expected from polymer rheology and prepilot water quality assessment. The reason was the combination of polymers and biological activity in combination with fines and oil (despite being small). This challenge is currently tackled by reducing the biological activity. Incremental oil: accurate measurement of the water cut of the producing wells is key; in particular of the wells producing at water cuts above 90%. In addition, water salinity at the producing wells was measured and a repeated tracer program was set up. The results have been used to assess the reservoir architecture and incremental oil related to polymer injection. The challenges in the interpretation of the pilot related to conformance of the pilot could be resolved using this data. Polymer, oil, water treatment: the surface facilities are constantly monitored for separation efficiency and plugging owing to back produced polymers. Operating challenges are seen in all treatment steps for full field polymer injection implementation due to separation but also handling of the polymers in water treatment facilities.