The ideal compression process of multiphase flow varies from isothermal for pure liquid to isentropic for all gas. Between these two extremes, the gas heat of compression is partially absorbed by the liquid which can be represented by a polytropic process. The theoretical performance of multiphase pumps is investigated showing how a pump's effectiveness decreases from the all liquid performance as the amount of gas, inlet pressure, exit pressure, and thermodynamic process are varied. Comparisons are also made between an isentropic gas compressor and the multiphase pump's performance.
Multiphase pumps are used by the oil industry to boost production, to reduce installation costs, maintenance, and size, and to transport mixtures from production sites to gathering facilities. Production rate and lifetime well production is increased by decreasing the well bore pressure. This can be accomplished by using a down hole multiphase pump or a pump at the well head. The down hole pump will have a higher inlet pressure and lower GVF. The well head pump can be larger with easier installation and maintenance but will have lower inlet pressures and higher GVF. The selection of which application is best depends not only upon what type of pump may physically be installed, but how is the performance of the pump affected by the changes in GVF and inlet pressure. This performance variation will be investigated in this paper. Multiphase pumps are being used in ever increasing applications over wider ranges of gas volume fraction. A single pump can replace a flow separator, pump, and compressor resulting in lower installation costs, less maintenance and a smaller footprint. Part of the driving force is that gas well can have long periods of very low GVF as liquid that has collected at the bottom is finally forced to the surface.