Compared to the traditional method of separation, in which all the wells have to work with same inlet separation pressure, a variable speed multiphase pump would allow a controlled reduction of well head pressure. Induced benefits may include reduced loss of production due to water breakthrough, postponed stimulation and maintenance of gravel-packed wells, and longer production periods for low pressure wells. However the power required by the pump for those two conditions is very different, as the mixture density would change by a factor of 100. If one would do so, the driver would be oversized and work most of the time at part load. Strategies General Depending on the production cases and operational requirements, various control strategies can be proposed.
Standard practice calls for the appropriate level of mechanical protection for the pump driver unit.
Typically, trigger values are used for alarm to prevent undue shut-downs and for trip to avoid damages to the equipment. The buffer tank is basically a static mixer of small dimensions that can be installed upstream of the pump suction nozzle in case of slug flow. Its main functions are to break the energy of liquid slug fronts, smooth out any fluctuations in the incoming flow and act as a sand trap. Obviously, when instantaneous production flows do not vary much from the average values of liquid and gas flowrates, there is no need to install a buffer tank. One particular example is the succession of liquid slugs and gas pockets with a frequency of less than a minute while the pump runs at constant speed.