Measuring and testing – Volume or rate of flow – Of selected fluid mixture component
Patent
1995-10-10
1997-12-02
Chilcot, Richard
Measuring and testing
Volume or rate of flow
Of selected fluid mixture component
7386163, G01F 144
Patent
active
056938918
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a flowmeter for use in measuring the flow rate of a two phase fluid in a pipe, such as an oil production pipe.
The invention has been developed primarily in connection with the measurement of the flow rate of fluids extracted from underground reservoirs of hydrocarbons, which can comprise liquid/liquid mixtures and gaseous/liquid mixtures, such as water/oil mixtures and natural gas/hydrocarbon mixtures.
It is known e.g. from GB2186981 (Schlumberger Limited) to provide a flowmeter for measuring the flow rate of a two phase fluid and which comprises a gradiomanometer and a venturi meter in series and which are formed by a first section of pipe with a first diameter, a second section of pipe with a second diameter less than the first diameter, a third intermediate section of pipe connecting the first and second pipe sections and having a diameter changing smoothly and gradually from the first diameter to the second diameter, and an arrangement of pressure sensors placed at selected positions in the pipe sections to monitor pressure differentials and from which the flow rate of the two phase fluid can be derived.
The arrangement of pressure sensors comprises a first pressure sensor positioned in the neighbourhood of the start of the change of diameter of the third section of pipe from the first diameter to the second diameter, a second pressure sensor in the first section of pipe spaced upstream from the first pressure sensor, and a third pressure sensor spaced in the pipe downstream from the first pressure sensor. Means is provided to make a first differential pressure measurement between the first and second pressure sensors which is indicative of the density of the fluid flowing through the pipe, and means is also provided for making a second differential pressure measurement between the first and third pressure sensors, and from this there can be derived the flow rate of the fluid flowing through the pipe from the density value obtained from the first differential pressure measurement and also from the second differential pressure measurement which is obtained.
The Schlumberger reference also describes in detail the calculations involved in determining the flow rate of the two phase fluid.
The present invention is concerned with an improved arrangement of pressure sensors in a pipe through which a two phase fluid is flowing and is to be monitored, and improved means of deriving pressure differential measurements from which the flow rate of the fluid can be derived.
According to the invention there is provided a flowmeter for measuring the flow rate of a two phase fluid in a pipe and which comprises a first pipe section having a first diameter, a second pipe section of a smaller diameter, an internally tapering third pipe section forming a smooth transition between the first and second pipe sections, and three pressure tapping points comprising upstream, downstream and intermediate tapping points, in which a first differential pressure monitoring arrangement is provided to measure the pressure differential between the upstream and the downstream tapping points and from which fluid density can be derived, and a second differential pressure monitoring arrangement is provided to monitor the pressure differential between the intermediate tapping point and one of the upstream or downstream tapping points, whereby flow rate can be calculated from the derived density value and the second differential pressure measurement.
The invention therefore applies a fundamentally different method of monitoring the pressure differentials between the upstream, downstream and the intermediate tapping points, which has a number of technical advantages over the known flow meter arrangement. In particular, the flow meter will usually be provided in a dedicated tubular section to be incorporated in an oil production well, and the novel arrangement of the first and second differential pressure monitoring arrangements enable the overall length of the dedicated tubular section to be reduced compared to existi
REFERENCES:
patent: 790888 (1905-05-01), Ferris
patent: 2984105 (1961-05-01), Nagel et al.
patent: 4231262 (1980-11-01), Boll et al.
patent: 4856344 (1989-08-01), Hunt
The Venturi Meter by Builders Iron Foundry, Bulletin 75, p. 4, Fig. 1.
Allen Joseph
Brown Andrew
Chilcot Richard
Patel Harshad
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