| abstract |
The invention relates to a method and an apparatus for determining the cut (percentage) of one component of a multiphase fluid flowing in a pipeline, for example, oil or other hydrocarbon in a fluid flow that comprises oil, water, gas, and soil components, by use of NMR analysis. The fluid is flowed through an apparatus specifically designed to perform the analysis on the flowing fluid. Carefully sequenced 90° pulse series are used to take advantage of the different spin relaxation times of the selected atomic species when they are constituent parts of molecules having inherently different levels of random molecular motion. The timing between pulses in a series and between series of pulses is chosen so that NMR emissions from unwanted matter do not occur, and FID peaks from the desired matter are registered. The FID peak amplitude of the measured component of the flowing fluid is then compared to the FID peak amplitude of a 100% sample of the component, with the resulting ratio being directly related to the percentage of the component in the flowing fluid. In this way, a direct and highly accurate measure of the desired component, oil for example, is achieved on a real-time basis in the field, without the need to interrupt operations. Results of these measurements can be used with total flow meters to derive an accurate measure of flow rates of the desired component. |