| Popis: |
A chemical EOR project has been implemented in the fluvial succession of the Rayoso Formation since 2014. In the aim to understand polymer flooding processes, geological 3D modelling and numerical simulation are powerful tools to interpret field data and help to mitigate uncertainties of an early polymer injection at field scale. The Rayoso Formation was modeled following a multi-scale rationale: a multi-field scale model (>50km), a field-scale model (>10km) and a pilot-scale model (>1km). The results of numerical simulations were compared with the observed field? data. These runs included polymer injection vs. water injection, multiple adsorption values and polymer degradation. The key results of that work are summarized as following: For polymer injection the simulation reproduces the increasing oil cut in the observed data, whereas the waterflooding cases show an oil cut drop. Polymer simulation also matches the observed bottom hole pressure drops in producers better than water simulation. Based on these results, it has been possible to determine the polymer response.Analytical calculations, based on tracer arrival time, give a polymer adsorption greater than 300 µg/g. Using different values of adsorption, the simulation shows that the actual value is one magnitude order less than the calculated one. Therefore, extremely high values of adsorption are excluded.Significant degradation is ruled out by running a simulation with a polymer viscosity 4 times smaller than the non-degraded one at the same concentration. The simulation shows an early arrival of the degraded (less viscous) polymer at the producer wells. This has never been observed in the wells showing that the degredation has a negligible effect. Numerical simulation is thus used to interpret the polymer pilot results and consequently, allows to mitigate risks and make early decisions. |
