Wells – Processes – With indicating – testing – measuring or locating
Patent
1987-01-16
1989-03-28
Suchfield, George A.
Wells
Processes
With indicating, testing, measuring or locating
166 53, 166 64, 166 66, 166369, 166372, 73 611R, E21B 4312, E21B 4706, G01N 936, G01N 3328
Patent
active
048155365
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND FIELD OF THE INVENTION
This invention relates generally to a method and apparatus for determining selected properties of a multi-phase mixture.
Whilst it will be appreciated by those persons skilled in the art that the method and apparatus of the invention are readily applicable to the analysis of a wide variety of multi-phase mixtures, one particularly advantageous application relates to the analysis of the oil mixture discharged from an oil well. It will be convenient therefore to hereinafter describe the invention with reference to that particular application.
It is often necessary to be able to monitor and/or determine the various properties of the oil/gas/water mixture being discharged from an oil well. The properties of the mixture which are particularly important are the volume rate and density of each phase. It is the current practice when analysing the mixture discharged from an oil well to feed a relatively large quantity of the mixture to a "test separator". The "test separator" separates the multi-phase mixture into discrete phases before flow measurement is effected.
Separators of this general type are known and it is not proposed to provide a detailed description here. The major disadvantages of separators of this type are that they are relatively bulky and take up considerable space particularly when used on off-shore platforms. As a result each offshore platform usually has only one test separator, and this test separator is employed to take measurements from one well at a time. A further disadvantage is that they are relatively expensive.
It is an object of the present invention to provide a relatively simple method and apparatus for analysing multi-phase mixtures and with reference to the specific application referred to above, it is an object to alleviate one or more of the aforementioned disadvantages.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a method of analysing multi-phase mixtures for determining selected properties of components in the mixture flowing along a flow path comprising the steps of directly measuring or calculating the density of the mixture at two or more points along the mixture flow path, directly measuring or calculating the mass flow rate of the mixture at at least one of the aforementioned points along said flow path and causing a change in the characteristics of the mixture flow between said one or more adjacent points and thereafter determining the selected properties on the basis of information collected.
The characteristic which is changed can be any one of a suitable group. For example the characteristic changed may be a pressure change or a temperature change or at least a partial separation of the phases in the mixture.
The characteristic change may also be effected by adding a substance to the mixture between the two points. This substance may be in the form of a chemical to cause a reaction or may be by the provision of a side stream of gas. In another arrangement, the characteristic change can be initiated by a change at some other point in the flow path which thereby causes the characteristic change. For example, a pressure differential upstream of the two points may be sufficient to cause a change between the points.
By using the above method, it is possible to determine the properties of the various phases of the mixture such as, for example, the volume and density of each particular phase. To determine these properties it may be necessary to carry out more than two density and/or mass flow measurements or calculations and where two or more measurements are carried out a corresponding flow characteristic changes are required between the adjacent measuring points. In some instances not all variables may be required to be determined purely from the mass flow measurement technique. For example, in mixtures such as the oil mixture from oil wells it may be convenient to assume that the density of the water phase and the oil phase remain constant along each pressure differential. From the
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Prendergast Gavan J. J.
Webb David A.
Carroll Noel
Suchfield George A.
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