Entropy based multiphase flow detection

1. A method for characterizing multiphase fluid flow (MPF) to enhance measuring and monitoring of a flow regime in a segment of pipe for hydrocarbon-production operations, the method comprising the steps of:

sensing an acoustic emission from a MPF, the segment of pipe operable to support the MPF in hydrocarbon-production operations including at least two physical phases;

converting the acoustic emission to an electrical signal;

segmenting the electrical signal into short term, medium term, and long term time series;

assigning positive real numbers to the time series, the positive real numbers including larger values and smaller values, the larger values corresponding to process randomness, and the smaller values corresponding to instances of recognizable patterns in the electrical signal;

categorizing certain positive real numbers as outlier values;

calculating short term, medium term, and long term approximate entropy values for the MPF responsive to the short term, medium term, and long term time series from the electrical signal by performing the following steps:

assigning each of the short term, medium term, and long term time series of data to variables each representing raw data values measured at equally spaced time intervals,

forming a sequence of vectors using the variables each representing raw data values,

using the sequence of vectors to construct scalar components representing the distance between each respective vector sequence given by the maximum difference in their respective scalar components,

calculating each of the short term, medium term, and long term time series approximate entropy values using the scalar components,

comparing the short term, medium term, and long term approximate entropy values for the MPF to pre-determined short term, medium term, and long term approximate entropy values; and

determining characteristics of the MPF responsive to similarities between the short term, medium term, and long term approximate entropy values for the MPF and the pre-determined short term, medium term, and long term approximate entropy values.

2. The method of claim 1 , further comprising the step of displaying the characteristics of the MPF on a user interface, where the user interface is operable to graphically represent at least one flow regime.

3. The method of claim 1 , further comprising the step of preamplifying the electrical signal before the step of segmenting the electrical signal.

4. The method of claim 3 further comprising the step of filtering the electrical signal, before segmenting the electrical signal, responsive to programmed cutoff frequencies in a band-pass signal filter derived from an operating frequency and bandwidth of an acoustic emission sensor.

5. The method of claim 4 further comprising the step of converting the electrical signal to a digital signal, before segmenting the electrical signal.

6. The method of claim 1 , where the step of sensing an acoustic emission comprises the step of sensing a first acoustic emission, and further comprises the step of sensing a second acoustic emission from the MPF, the second acoustic emission being sensed simultaneously with and at a distance D from the first acoustic emission.

7. The method of claim 6 , further comprising the step of calculating an accurate measurement of flow velocity of the MPF in response to the distance D and sensing the first acoustic emission and sensing the second acoustic emission.

8. The method of claim 1 , further comprising the step of conducting a principal component analysis, where the principal component analysis comprises the steps of:

gathering acoustic emission data under a variety of flow parameters in situations in which an appropriate Reynolds number is known for the MPF for which data is being gathered;

forming time series of acoustic waveforms;

performing a Fourier Transformation on the data, the data being converted into measurements of acoustic power as a function of frequency;

executing a suite of measurements using a test matrix including different conditions of the MPF including at least one variable selected from the group consisting of: stepped values of watercut, stepped values of total liquid flow, and multiphase flow patterns; and

post-processing the data by applying principal component analysis to the data to determine measurable frequencies relevant to determining the characteristics of the MPF.

9. The method of claim 8 further comprising the step of optimizing the step of sensing an acoustic emission from the MPF to receive the frequencies determined by the principal component analysis to be relevant to determining the characteristics of the MPF.

10. The method of claim 1 , further comprising the step of conducting a principal component analysis, where the principal component analysis comprises the steps of:

gathering acoustic emission data under a variety of flow parameters in situations in which an appropriate Reynolds number is known for the MPF for which data is being gathered;

forming time series of acoustic waveforms;

performing a Fourier Transformation on the data, the data being converted into measurements of acoustic power as a function of frequency;

executing a suite of measurements using a test matrix including different conditions of the MPF including at least one variable selected from the group consisting of: stepped values of watercut, stepped values of total liquid flow, and multiphase flow patterns; and

post-processing the data by applying principal component analysis to the data to determine measurable frequencies relevant to determining the characteristics of the MPF.

11. The method of claim 10 further comprising the step of optimizing the step of sensing an acoustic emission from the MPF to receive the frequencies determined by the principal component analysis to be relevant to determining the characteristics of the MPF.