The aim of the project is to develop new non-intrusive acoustic methods for two phase flow determination in long distance transportation systems. This will include a new tool for the development of a wide range of products including multi-phase metering, leak detection, acoustic fatigue detection, control of slug catchers and other multi-phase systems and SPICE applications. The development of suitable instrumentation technology for monitoring will be a key success factor for cost-effective multi-phase production and safe efficient delivery of offshore oil and gas.
The tests carried out at BHR Group and SOLAIZE have proved that the use of acoustic methods for detection and measurement of slug characteristics is a viable technique. Use of accelerometers is recommended as the preferred choice for detection and recording of signals.
Comparison of Fast Fourier Transform (FFT) technique and Fast Wavelet Transform (FWT) technique has shown that FWT is the superior and recommended method for filtering and analysis of signals. Development of a fast and reliable on-line microprocessor has proved to be achievable for efficient analysis of signals FWT technique.
Further tests on Sidi El Itayem field in Tunisia and subsequent analysis of signals has shown that slugs can be detected with the use of appropriate filtering technique without the need for real time FWT analysis. This means that the instrumentation may be limited to a number of accelerometers, a filtering system and a simple microprocessor for detection of slugs and computation of their characteristics ie. velocity and length. The system has also been identified for other applications namely; leak detection, solids detection (sand etc), as part of a multi-phase metering system and for use by intelligent pigs.
The work includes a review of available information on the signal processing techniques which are regarded as potentially suitable for the project. A report has been produced at the end of the first two stages which identified the advantages and disadvantages of the various options available for the analysis of acoustic signals.
The report also included a comparison of the Fast Fourier Transform techniques (FFT) and the newer Fast Wavelet Transform Techniques (FWT). FWT technique has been used successfully in signal processing and shows potential for multi-phase flow characterisation applications. Also included are results of the preliminary tests using a simplified system together with the evaluation of possible noise sources that can influence the analysis of the recorded signals. The results have been related to the flow patterns encountered during the preliminary tests in order to enable recognition of flow patterns characterisation.
The stage II of the project has involved long term testing using the test facilities at BHR Group (Cranfield) and SOLAISE (France). The results are used for the development of noise abatement and FWT techniques for recognition and measurement of slug characteristics. Further work in stage III includes long term field tests to obtain 100% representative signals for the development and verification of real time FWT algorithm.
Stage IV, the final stage of the project, involves bringing together the findings from all previous tests and commenting on the application or limitations for the system and identifying requirements for the development of a full instrumentation for field application. This also includes identifying future commercial applications in the oil and gas industry.