Electromagnetic Monitoring of the Propagation of an Injected Polymer for Enhanced Oil Recovery in Northern Germany

In an Enhanced Oil Recovery (EOR) pilot project Wintershall Holding GmbH, Kassel, is testing their newly developed biopolymer Schizophyllan in one of their oil fields. Mixture with the highly saline formation water results in a polymer solution with much lower electrical resistivity than the displaced oil within the reservoir. To advance and optimize EOR techniques it is essential to know the spatial propagation and distribution of the injected fluids in the subsurface. At GFZ Potsdam, we investigate the applicability of the CSEM method to monitor the distribution of the polymers solution. Based on a 26-site MT survey across the oil-field and calibration with resistivity well-logs, we constructed a 3D resistivity model of the reservoir region for 3D CSEM forward simulations; main focus of the study was to test the sensitivity of various source-receiver configurations. 3D modelling results suggest that CSEM is sensitive to resistivity changes at reservoir depths, but the effect is difficult to resolve with surface measurements only. Resolution potential increases significantly, however, if sensors/transmitters can be placed in observation wells closer to the reservoir. In particular, observation of vertical electric fields in shallow boreholes and/or use of novel source configurations consisting of vertical and horizontal dipoles appear promising.