Online Monitoring for Measuring the Viscosity of the Injected Fluids Containing Polymer in Chemical Eor

Abstract

Viscosification of water with polymers is a mature technique used in different enhanced oil recovery processes (AP, ASP, SP and P flooding). The viscosity of the injected fluids is generally measured in the lab on solutions sampled manually at different locations of the polymer injection process. In order to increase the reliability of these measurements and to alleviate the quality control, there is a strong need for measuring online the viscosity. On a field, polymer solutions can be highly degraded if they are sheared during the sampling or contaminated by the oxygen when exposed to the atmosphere during the viscosity measurement. Different procedures have been proposed in the industry to prevent or minimize degradation. However, routine measurements through manual sampling mobilize operators, take time and are often questionable. In this paper, we present three types of online viscometers developed for avoiding degradation during the sampling and the viscosity measurement. A fourth one enables to do reliable viscosity measurements in the lab. A low pressure tank viscometer enables to measure continuously the viscosity of the polymer mother solution. This viscometer is particularly adapted to highly concentrated and viscous solutions since it is not sensitive to the presence of particles, gel debris and oil. Two high pressure viscometers can be connected at any point of the high pressure injection line (well head for example) to monitor continuously the viscosity of the injected polymer solution. Their low foot print make them easily transportable. Sensitivity and precision of these equipment were assessed through online measurements at the lab and pilot scale. They were found to perfectly match the viscosity measurements performed with lab rheometers even on pure water. A fourth lab viscometer was developed in order to improve the reliability and the robustness of classical viscometers used in operations. Measurement in anaerobic condition prevent any risk of oxidative degradation. All the viscometers are automated with a minimum need of human intervention. All the developed rheometers are at the prototype stage. Particular attention was paid to the robustness of each element and its adequacy with field constraints. Field tests are now needed to finalize their development and assess their durability on the long term. The use of robust online viscosity measurements during EOR operations would allow effective continuous remote monitoring, greatly improving pilot interpretability and operability during pilot and commercial stages.