Errors in Production Measurement of Crude Oil & Condensate
There are several issues that can adversely affect crude oil and condensate measurement. One of the most common of these is the presence of gas bubbles in the liquid stream (i.e., flashing). Produced hydrocarbon liquid is in equilibrium with natural gas in the separator (at or near its bubble point). Under these conditions, any loss of pressure or increase in temperature may cause a portion of the liquid to flash. When this occurs, liquid meters cannot accurately measure the two-phase flow that results. The presence of vapor or “gas-void fraction” in liquid meters results in overstated volumes.
Some of the station design considerations that can minimize or even prevent this problem include installing the dump valve downstream of the meter, insulating the flow pipe upstream of the meter, and minimizing pressure drop before measurement. To minimize the pressure drop before the meter, it is common to install a choke downstream of the dump valve or a smaller dump valve seat.
“Everything that can be counted does not necessarily count;
everything that counts cannot necessarily be counted” ~ Albert Einstein