Accurate Water-Cut Measurement for Thermal Operations

ABSTRACT

Measurement of the water-cut (the water fraction) of the produced emulsion is necessary for oil producers in determining their daily oil production. Typically water-cuts are routinely measured by manual sampling of the emulsion and then analyzed by methods which may include spinning the sample in a centrifuge onsite to separate the oil from water, or sending the samples to a commercial lab. Magnetic resonance (MR) technology has been applied to address this problem and it has advantages over other existing technologies. MR is a well-established technology in chemical and medical applications. When applied to analyze oil and emulsions with water, it has proven to be fast, reliable and accurate, compared to Dean-Stark analysis, for determining water-cut. MR has been incorporated into the design of an online instrument to measure water-cut in produced oil-water emulsion streams. This technology is insensitive to changes in salinity of the fluids, which is a problem for other technologies in measuring water-cuts. The instrument described in this paper operates on a slipstream, or by-pass, of flow of the produced emulsion that is taken off a main flow line. For a given MR measurement the flow in the by-pass loop is held stationary for the measurement which takes about 2 minutes. The heart of the instrument employs a non-intrusive electrical coil and a permanent magnet surrounding the instrument pipe. Magnetic Resonance technology detects electro-magnetic signals from both the water and the oil components in the fluid. The main advantages of the MR water-cut meter are: i) relatively fast (2 minutes to measure) and accurate water-cuts near the well head, ii) high frequency of measurement (every 5 minutes) on a continuous basis without the need for manual sample collection, iii) ability to monitor directly the water, oil and gas fractions in the production stream.

For more information go to DMG Online.