A Novel Subsea On-line Multiphase Fluid Sampling and Analysis System

1. Baker1,3, C. Bjelland1,2,3, J. Spilde1,3, K-E. Frøysa1,3, M. B. Holstad1,3, G. A. Johansen2,3,1,

2. T. Hjertaker2,3, B. Berntsen2 and S. H. Stavland2

1Christian Michelsen Research AS, Fantoftvegen 38, P.O. Box 6031, NO-5892 Bergen, Norway

2University of Bergen, Department of Physics and Technology, légaten 55, NO-5007 Bergen, Norway

3Michelsen Centre for Industrial Measurement Science and Technology

Email: marie.holstad@cmr.no

ABSTRACT

The trend in subsea petroleum production systems in offshore field developments points toward integrated production and processing facilities at the seabed along with more extensive use of multiphase transportation technology. The SOFA (Subsea On-line multiphase Fluid sampling and Analysis) system designed by Christian Michelsen Research is an autonomous metering station for permanent installation subsea where transfer of fluid samples to the surface by a remotely operated vehicle is avoided.

A prototype for capturing multiphase fluid samples in a dedicated measurement chamber/sample container has been built. This is equipped with ultrasound sensors and a dual modality (DMD) gamma- ray system, which together with pressure and temperature measurements will be used as a multi- modality system for fluid characterisation. This system brings about several challenges. Firstly, to design a mechanism that ensures representative sampling of the gas/oil/water fluid into the measurement chamber and secondly, to perform the actual measurement after the fluid is separated and stabilized in the chamber. The first issue is being studied by CFD-modelling and experimental tests.

The focus in this presentation will be on the first experimental results for fluid characterization with ultrasound and gamma-ray technology.

Keywords Gamma-ray measurement, ultrasound measurement, multiphase flow analysis