Method and apparatus to measure multiphase flow properties

Claim 1

A method for determining the liquid and gas flowrates and/or the watercut of multiphase mixtures of oil, water and gas flowing through a horizontal or inclined pipeline in an intermittent type of flow, comprising the steps of a) locating a pair of non-moving parallel plates inside the horizontal pipe in line with the flow, said plates being positioned substantially vertically and at least one of said plates comprising a plurality of segmented electrodes, the segments of an electrode being located one below another thus forming a nxm matrix of n columns and m rows of capacitor plates (n,m = 1,2,3....), and the other plate of said pair comprising at least one continuous electrode, arranged in such a manner that a segmented electrode on the first plate and the electrode on the second plate form a capacitive sensor that gives a signal related to the mixture of oil, water and gas that happens to be between the said electrodes; b) measuring by impedance the level of the liquid to gas interface in the pipeline and the gas fraction across the whole cross-section of the pipeline, said measuring being obtained from a single column of sensors; c) continuously measuring the flow pattern velocity by timing the passage of disturbances within the flow patterns between matrix segments located on a same row near the top of the pipeline; d) continuously measuring liquid phase velocity between matrix segments located on the same level or row by cross-correlating the variations in impedance between them; and e) deriving from the above measuring quantities the flowrates for both the liquid and the gas.

Claim 3

The method as claimed in claims 1 or 2 wherein the flowrates of gas and liquid and the watercut are derived from signals produced by the said matrix.

Claim 4

An apparatus for determining the liquid and gas flowrates and/or the watercut of multiphase mixtures of oil, water and gas flowing through a horizontal or inclined pipeline in an intermittant type of flow, comprising a pair of non-moving parallel plates inside the horizontal pipe in line with the flow, said plates being positioned substantially vertically and at least one of said plates comprising at least one segmented electrode, the segments of the electrode being located one below another, thus forming a nxm matrix of n columns and m rows of capacitor plates (n,m = 1,2,3,....), and the other plate of said pair comprising at least one continuous electrode, arranged in such a manner that a segmented electrode on the first plate and the electrode on the second plate form a capacitive sensor that gives a signal related to the mixture of oil, water and gas that happens to be between the said electrodes means for measuring by impedance the level of the liquid to gas interface in the pipeline and the gas fraction across the whole of the pipeline; means for continuously measuring the flow pattern velocity by timing the passage of disturbance within the flow patterns between matrix segments located on a same row near the top of the pipeline; means for continuously measuring liquid phase velocity between matrix segments located on a same level or row by correlating the variations in impedance between them; means for measuring the watercut in the liquid filled part of the pipeline by calculating the dielectric constant of the fluid between the plates from the impedance measurement; and means for deriving from the above measured quantities the flowrates for both the liquid and the gas.

Claim 6

The apparatus as claimed in claims 4 or 5 wherein said matrix forms a 2x8 matrix.

Claim 7

The apparatus as claimed in any one of claims 4-6 wherein said plates are arranged in a spool piece which is connectable to said pipeline.