The parameters that need to be measured on a cement pumping job include, pump rate, pump total, pressure, and sometimes cement slurry density.
Pumping rate and total pumped volume on an oilfield pumping unit is usually measured by means of a stroke counter that faces a rotating flange on the transmission shaft. The flange has a number of bolt heads or protrusions that pass in front of the stroke counter. Every time a bolt head passes in front of the stroke counter a signal is generated and the data acquisition system records this.
Normally it is important to know both the pumping rate and the total volume pumped by a pumping unit. In order to do this the data acquisition system needs to record the frequency of the pump stroke signal pulses and also keep track of the total number of signal pulses. The displacement of the pump and the number of bolts installed on the rotating flange needs to be known in order to be able to determine the pump rate and total volume pumped.
This method of pump stroke measurement applies to all types of pumps where a rotary shaft has been instrumented for pump rate measurement. This includes nitrogen pumps, gravel packing pumps, acid pumps and general fluid pumps.
The measurement of pump pressure is done by means of a pressure sensor that hammers in to a wing union on the discharge end of the pump.
Most of the time the cement slurry is mixed with water in a mixing tank and the density is calculated by knowing the amount of cement mixed with the number of barrels of water. However some of the time this is not possible or sufficient, in these cases a densitometer is used.
The measurement of density can be done by means of a radioactive densitometer or a coriolis densitometer.
