Page 18 - Acoustic Fluid Level Measurements

Fluid Level Measurement Applications for Plunger Lift Wells 11-1

Petroleum Extension-The University of Texas at Austin
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Fluid Level Measurement Applications for Plunger Lift Wells

In this chapter:
• Detailed analysis of plunger cycle performance
• Basics of plunger lift to produce liquid and gas
• Acoustic survey and monitoring
• Plunger fall characteristics
• Problem detection and analysis
• Benefits of plunger tracking

Plunger lift is a low-cost method for lifting liquids is repeated throughout the day to produce liquids and
(water, condensate, and/or oil) from gas and oil wells. gas from the well.
In general, the objective is to remove as much of the In plunger lift wells, acoustic fluid level instruments
liquid accumulating in the well as possible and to are used to monitor and analyze the progress of the cy-
increase gas production by minimizing back-pressure clical plunger operation in real time and determine the:
on the formation. The plunger lift system reduces the • Position and depth of the plunger as a function
cost of operating a well compared to other artificial lift of time
methods because the formation pressure supplies most • Fall velocity of the plunger
of the energy required to lift the liquids. • Rise velocity of the plunger
During plunger lift operations, a motor-controlled • Plunger travel time to the liquid and to the bot-
valve is opened and closed at specified intervals to cycle tom of the tubing
a gas-driven plunger from the bottom to the top of the • Tubing and casing pressure as a function of time
tubing and remove any liquid that accumulated at the • Volumes of gas and liquid flowing into and out
bottom of the well. When the surface valve to the flow of the well
line is closed, the produced gas and liquid accumulate
inside the well’s casing and tubing. When the flow is The objective is to visualize in detail the performance
stopped at the surface, the plunger falls down to the of the plunger lift system to determine the appropriate
bottom of the tubing. After a predetermined amount cycle time for optimum operation. Acquisition and
of time, the surface flow valve opens, and the tubing analysis of acoustic and pressure data is generally per-
head pressure drops to the flow-line pressure. The dif- formed automatically, using a portable computer with
ferential force across the plunger—due to the drop in appropriate software. Thus, the operator can quickly
pressure in the tubing above the liquid column and the and efficiently determine the adjustments necessary to
high well pressure below the plunger—lifts the plunger optimize the plunger lift operation .
1,2
and a portion of the liquid above the plunger to the The following sections present a brief overview of
surface. Gas and some liquid continue to flow out to plunger lift operation and describe in detail the equip-
the flow line until the motor valve is closed. The open ment and procedure used to acquire and interpret the
and shut-in operational cycle of the plunger lift system acoustic data for plunger lift analysis.

For distribution by Petroleum Extension-The University of Texas at Austin
11-1