08.05.2014|Bockstedt: Quantifying the remaining amount of crude oil in a reservoir and assessing the efficacy of production techniques – these are the main objectives of joint research initiated by scientists from GFZ and Wintershall. Availability of such resources is important as for the majority of reservoirs more than half of the oil cannot be produced. Whether the amount of oil in a reservoir can be determined is now investigated with a field test using geophysical electromagnetic methods.

With Controlled-Source Electromagnetics (CSEM) an alternating electric current with low frequency is injected into the ground.  The current generates electromagnetic fields in the subsurface, which can be measured with passive receiver stations at surface. This method is used to decipher the electrical conductivity structure of the subsurface. A reservoir contains oil and salt water, which have different electrical conductivities. Salt water is very conductive, oil is much less conductive. The higher the overall measured conductivity, the less oil is in the subsurface.  If oil production works as expected, over time, more and more of the oil in the pores of the rocks is replaced with the salty formation water. This would mean the measured electrical conductivity is expected to increase with continuing production of oil. This change could in turn be detected with repeated CSEM surveying.

To find out if electrical conductivity measurements are really suitable, the research partners are conducting a first field experiment in the Bockstedt oil field near Barnsdorf in Lower Saxony/Northern Germany. The experiment started in early May on an 18 square kilometer large area and will continue for approximately three weeks.

The experiment does not harm the environment, animals and plants remain unaffected. Should the tests be successful, the method would provide an environmentally friendly instrument to control and asses oil production techniques.