Characterization and metering of multiphase mixtures from deep subsea wells

Deep, subsea production of oil and gas will necessitate the transport of two or more phases simultaneously through pipelines from remote multiple wells to a common subsea facility and platform. For such systems, there is a need to remotely meter these multiphase mixtures with a method that is reliable and non-intrusive. Previous work suggests that ultrasonic imaging and Doppler velocimetry can be used for this metering purpose. For the metering of multiphase mixtures in pipelines with ultrasonic imaging and Doppler velocimetry, it is very important to know the flow regime behavior of multiphase mixtures inside the pipeline.; The behavior of multiphase mixtures in horizontal pipelines, in particular, the behavior of multiphase mixtures in the entrance sections was studied by conducting gas/liquid two-phase flow experiments through a flow loop which consists of two pipelines, one with an ID of 2.5" and one with an ID of 7.25". From the results of the experiments, it was found that the pipe diameter had significant effects on the flow regime behavior in the horizontal pipe. We also investigated how the behavior of multiphase mixtures in the horizontal pipeline are affected by the flow in the vertical pipeline that feeds the horizontal line by conducting the fluids through a 500 foot-deep vertical well before they enter the horizontal flow loop. It was found that the flow regime behaved quite differently in the horizontal pipes with and without the prior vertical flow. A theoretical model was also developed to simulate the process that the liquid slugs formed in the vertical pipe were carried over into the horizontal pipe and the theoretical predictions matched the experimental observations.; The application of the ultrasonic imaging and Doppler velocimetry to the metering of horizontal, multiphase flows by placing the ultrasound transducer in the entrance section was also investigated. It was found that the ultrasonic imaging techniques provide a means of accurately measuring the distribution of the phases in horizontal gas/liquid flow. A clear picture of the water-air interface and many of the wave characteristics, such as wave amplitude and wave frequency, can be easily obtained from the ultrasound signals.