Monitoring of High Pressure Separation of Real Hydrocarbon/Water Mixtures by Single Electrode Capacitance Probes

R B Schüller1, K Olsen2, M Halleraker3 and B Engebretsen3

1 Agricultural University of Norway, 1432 Ås, Norway, reidar.schuller@inf.nlh.no

2Norsk Hydro ASA, Research Park Porsgrunn, 3900 Porsgrunn, Norway, knut.olsen@hydro.com

3Sentech AS, 1411 Kolbotn, Norway, morten@sentech.no

ABSTRACT

A 500 bar test cell with a volume of 500 ml has been used to investigate the separation of North Sea oil and saline water. The test cell is made of Titanium and is fitted with 92 internal SeCaP electrodes (Single electrode Capacitance Probes) monitoring the content in the vessel. The high pressure rating of the cell is justified by the need to perform separation tests on actual down hole well samples. The cell is fitted with a channel through the Titanium body and is placed in a temperature-controlled environment, thus controlling the temperature during the test runs. Pressurized bottom-hole hydrocarbon samples can be transferred to the test cell without any contamination with oxygen or other unwanted compounds. The test cell is equipped with a centrifugal mixer.

The system is able to detect the transient variations inside the cell during filling or mixing operation and the subsequent separation of the phases. The system detects foam, emulsion phase, oil phase and water phase.

The presented results include a dynamic plot of filling the cell with an oil/water dispersion. Foam is produced during the filling operation as well as an oil/water emulsion zone. Similar plots are also shown for three different North Sea fluid systems, showing the separation process after an initial mixing time. The plot of vertical distribution of dielectric constant versus time shows a 2D plot where the interfaces (zones of large gradients) are clearly visualized.

Keywords Capacitance, Separation, Oil/Water, High-Pressure