Study of fluid / fluid interfaces existing in oil and gas reservoirs

The interfacial light scattering spectrometer used to study fluid/fluid interfaces.Study of interfaces between fluid phases existing in oil and gas reservoirs is performed by dynamic light scattering.
Both model systems and samples from actual gas and oil fields are studied under reservoir conditions (studies can be performed at pressure up to 700 bar and temperature up to 180°C). The studies are performed with the purpose of improving condensate and oil reservoir management and production.

With the spectrometer used for the studies described above, we measure light scattered from thermally excited waves (with amplitude of the order of 1 nm) on the fluid/fluid interface. Interfacial wave components of different wavelengths are probed by measuring scattered light at different scattering angles. Our spectrometer is designed to measure scattered light over a relatively large range of scattering angles, giving the opportunity to probe interfacial waves with wavelengths from 5 µm to 500 µm.

In recent years Microbial Improved Oil Recovery (MIOR) has seemed very promising. We therefore present an example of measurements performed (in cooperation with Statoil, UNIFOB and SINTEF Petroleum Research) to find out to what degree stimulating bacterial growth in an oil reservoir may result in an essential reduction of the interfacial tension (IFT) between oil and water. Such a reduction in IFT may cause mobilization of previously capillary trapped oil. A model system consisting of dodecane and nutrient water was studied at ambient conditions. The bacteria used (of the genus Dietzia) are naturally occurring in sea water. The measured IFT versus age of interface is shown for different flow rates of nutrient water. The IFT was reduced from 38 mN/m to about 0.01 mN/m, which value is to our knowledge, by far the lowest value obtained hitherto for a bacterial system. This large reduction in IFT is an indication of the possible great potential of MIOR.

Light scattering measurements of IFT between dodecane and nutrient water at 20.0°C before (·) and after ( ­) injection of bacteria versus age of interface. Data points are connected by straight lines. Uncertainty of individual points is typically smaller than the plotted points. Water flow rate regimes are indicated by coloured line segments.