Determination of plunger location and well performance parameters in a borehole plunger lift system

Abstract

Plunger lift operations are difficult to optimize due to lack of knowledge of tubing pressure, casing pressure, bottom-hole pressure, liquid accumulation in the tubing and location of the plunger. Monitoring the plunger position in the tubing helps the operator (or controller) to optimize the removal of liquids and gas from the well. The plunger position can be tracked from the surface by monitoring acoustic signals generated as the plunger falls down the tubing. When the plunger passes by a tubing collar recess, an acoustic pulse is generated that travels up the gas within the tubing. The acoustic pulses are monitored at the surface, and are converted to an electrical signal by a microphone. The signal is digitized, and the digitized data is stored in a computer. Software processes this data along with the tubing and casing pressure data to display plunger depth, plunger velocity and well pressures vs. time. Plunger arrival at the liquid level in the tubing and plunger arrival at the bottom of the tubing are identified on the time plots. Inflow performance is calculated. Software displays the data and analysis in several formats including a graphical representation of the well showing the tubing and casing pressures, plunger location, gas and liquid volumes and flow rates in the tubing and annulus, and inflow performance relationship at operator selected periodic intervals throughout the cycle. Several field cases are presented to show how this information is applied to optimization of plunger lift operations.