Experimental study on the effect of the internal design on the performance of down -- hole gas separators

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Ananaba, Ochiagha Victor

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The re-design of the internal geometry of static down – hole gas separators directly affects the gas – liquid separation performance. This thesis describes experimental results obtained after changing the dip tube design from the conventional straight design to a helical design. Typically, a static down – hole gas separator with a conventional straight dip tube design depends on gravity to induce density difference in the flowing wellbore fluid which causes gas – liquid separation to occur. Thus, the device is known as a gravity driven down – hole gas separator. This research compared the experimental results and visual observations from gravity driven down – hole gas separators to that of static down – hole gas separators with helical dip tube designs known as static centrifugal down – hole gas separators. The visual observations showed that not only did the driving mechanisms for gas – liquid separation inside static centrifugal down – hole separators include gravity it also incorporated other means such as induced centrifugal forces that greatly improved overall gas – liquid separation. The 6 inch/second threshold downward superficial liquid velocity generally regarded as the industry rule – of – thumb for down – hole gas separators was increased to 10 inch/second. In field units this is a 200 BPD increase in liquid production. This research also studied the effect of increasing outer diameter of gravity driven down – hole gas separators from 3inches (2.75" ID) to 4inches (3.75" ID). The results should that liquid handling capacity increased by over 90% due to favorable flow regimes observed inside the separator. However, critical examination of gas – liquid separation performances of both 3 inch OD and 4 inch OD separators in terms of downward liquid superficial velocity reveal that gas – liquid separation results are similar. It was concluded therefore that downward superficial liquid velocity is a reliable parameter in the design of down – hole gas separators and that all gravity driven separators regardless of separator outer diameter will operate in similar fashion except at different liquid flow rates. Bubble rise experiment performed in this research project gave a range of 1 – 100 cp as region of applicability for the results discussed in this thesis.


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