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

Abstract

Four main areas of uncertainty can be described in polymer-injection projects:1. Are we able to deliver the polymer solutions at the required quality to the wellhead? 2. Are we able to inject polymers at the required quantity and quality? 3. Are we producing sufficient incremental oil? 4. Are we able to separate and treat oil and water cost-effectively after polymer breakthrough? The monitoring program that was developed for the polymerinjection pilot aims to reduce the uncertainty and quickly identify operational difficulties, as described in the following:• Polymer quality at the wellhead: The polymer concentration and viscosity of the "source" solution and injected polymer solution were 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 wellheadand bottomhole-pressure measurements, repeated falloff tests, and visual observation of the polymer solutions in the well. The results showed the mobility reduction of the polymer solutions 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 fines and small oil droplets existing in the injection water with polymer-and biologicalgenerated mass that plugged the pores during injection.

Historical and recent observations in polymer floods: An update review

“…This strategy was considered for Matzen polymer flood pilot. Injection rates were kept constant above the frac gradient constrained by the wellhead pressure operating conditions tapering polymer concentrations (Clemens, T., Deckers, M., Kornberger, M., Gumpenberger, T., & Zechner, M., 2013;Lüftenegger et al, 2015).…”

“…• Polymer losses in unconfined pilot patterns such as Matzen Field (Laoroongroj et al, 2015;Lüftenegger et al, 2015), Tambaredjo Field (Manichand et al, 2013) and Yariguí-Cantagallo Field (Maya et al, 2015) to just mention a few. This can lead to lower polymer production reducing the probability of reaching a potential threshold limit (if any) to cause productivity losses.…”

“…FOT performed with surface shut-in makes difficult to infer induced fracture geometries (Haynes et al, 2013;Lüftenegger et al, 2015). FOT's implemented using downhole pressure gauges permanently installed in the injectors offers more detailed pressure readings over time reducing the effects of wellbore storage and liquid level drop in the wellbore due to reservoir depletion Van den Hoek et al, 2012).…”

“…However, it is not clear if this trend in well productivity losses is influenced by the decrease of pump efficiencies, injectivity reduction (i.e. reduced throughput volume) and/or polymer production (Chiotoroiu et al, 2016;Lüftenegger et al, 2015), among other possible variables.…”

Supramolecular Polymer-Surfactant System for Heavy Oil Recovery

“…According to Zaitoun et al [23] and Sheng et al [17], shearing occurs within several devices during the different phases of polymer handling and injection process in the high flow rate region close to the injection well such as in shearing devices during polymer dissolution, during recirculation of the polymer solution through centrifugal pumps, polymer flow through chokes and downhole valves under high differential pressure, and during the flow of polymers at high flow rates through the perforations of the reservoir rock and sand face [25]. The shear degradation of the polymer structure consists of the breakage of the macromolecule chain reducing its molecular weight, size, and viscosifying power.…”