Analyzing Well Performance
Authors: McCoy James N. 
Published: December 2007

Introduction

Analyzing well performance is an important step toward increasing profits by improving production techniques. Generally the analysis is made by field observation and examination of well data. The acoustic liquid level instrument since downhole pressures can be determined from the depth to liquid measurement.

THE ACOUSTIC LIQUID LEVEL INSTRUMENT

The instrument works on an echo principle much like a person's echo in a mountainous area, except the original sound is made by discharging a blank shell and the echos are sound reflections from tubing collars and the liquid. A microphone is used to receive the initial sound and the reflected echos, and these signals are amplified and recorded on a moving strip of paper.

During actual operation, the instrument is connected to the casing annulus opening. The tubing in the well, and rods if present, are not disturbed in any manner. A blank shell is discharged into the casing annulus emitting a sound wave which travels down the annulus. Each tubing collar reflects a portion of this sound and the reflected sound energizes a microphone. This signal is amplified and recorded on a paper roll. The liquid level in the well reflects a very high percentage of the sound and is recorded as a relatively large pulse on the paper. The number of collar reflections to the top of the liquid and a tubing talley or estimate of the average joint length indicates the depth to the liquid. A sample chart from the Echometer is shown.

TECHNIQUE OF OPERATING THE INSTRUMENT

The fluid level instrument is a precision tool and the results obtained are very accurate where certain conditions are met. The instrument should be maintained in excellent condition, and all electrical connections should be kept clean. After the instrument is connected to the well and the casing valve is opened, the natural noise level in the well should be measured. If the natural noise level is excessive, judged from experience with the particular type of well, an attempt to reduce the natural noise level should be made. Often this noise is from microphone vibration, leaking check valves, or leaking valves. The most common cause of microphone vibration results from excessive pumping unit engine speed and can be reduced by slowing or stopping the engine. After these initial conditions are met, a fluid level and a rebound should be obtained on each well unless the well is pumped down sand the operator is familiar with the particular well. If several anomalies are recorded during the fluid level test from such obstructions as liners, tubing catchers, salt rings, and the fluid level, the last anomaly to repeat itself must be the fluid level if all of the anomalies are repeated. Another test should be made when any doubt exists about the fluid level interpretation. Where the well was producing fluid immediately before the first test, the liquid level will rise if the well is shut down between tests. The anomaly which raises must be liquid since it is the only sound reflector which can move to any extent.

The Acoustic Liquid Level Instrument

The instrument works on an echo principle much like a person's echo in a mountainous area, except the original sound is made by discharging a blank shell and the echos are sound reflections from tubing collars and the liquid. A microphone is used to receive the initial sound and the reflected echos, and these signals are amplified and recorded on a moving strip of paper.

During actual operation, the instrument is connected to the casing annulus opening. The tubing in the well, and rods if present, are not disturbed in any manner. A blank shell is discharged into the casing annulus emitting a sound wave which travels down the annulus. Each tubing collar reflects a portion of this sound and the reflected sound energizes a microphone. This signal is amplified and recorded on a paper roll. The liquid level in the well reflects a very high percentage of the sound and is recorded as a relatively large pulse on the paper. The number of collar reflections to the top of the liquid and a tubing talley or estimate of the average joint length indicates the depth to the liquid. A sample chart from the Echometer is shown.

TECHNIQUE OF OPERATING THE INSTRUMENT

The fluid level instrument is a precision tool and the results obtained are very accurate where certain conditions are met. The instrument should be maintained in excellent condition, and all electrical connections should be kept clean. After the instrument is connected to the well and the casing valve is opened, the natural noise level in the well should be measured. If the natural noise level is excessive, judged from experience with the particular type of well, an attempt to reduce the natural noise level should be made. Often this noise is from microphone vibration, leaking check valves, or leaking valves. The most common cause of microphone vibration results from excessive pumping unit engine speed and can be reduced by slowing or stopping the engine. After these initial conditions are met, a fluid level and a rebound should be obtained on each well unless the well is pumped down sand the operator is familiar with the particular well. If several anomalies are recorded during the fluid level test from such obstructions as liners, tubing catchers, salt rings, and the fluid level, the last anomaly to repeat itself must be the fluid level if all of the anomalies are repeated. Another test should be made when any doubt exists about the fluid level interpretation. Where the well was producing fluid immediately before the first test, the liquid level will rise if the well is shut down between tests. The anomaly which raises must be liquid since it is the only sound reflector which can move to any extent.

Technique Of Operating The Instrument

The fluid level instrument is a precision tool and the results obtained are very accurate where certain conditions are met. The instrument should be maintained in excellent condition, and all electrical connections should be kept clean. After the instrument is connected to the well and the casing valve is opened, the natural noise level in the well should be measured. If the natural noise level is excessive, judged from experience with the particular type of well, an attempt to reduce the natural noise level should be made. Often this noise is from microphone vibration, leaking check valves, or leaking valves. The most common cause of microphone vibration results from excessive pumping unit engine speed and can be reduced by slowing or stopping the engine. After these initial conditions are met, a fluid level and a rebound should be obtained on each well unless the well is pumped down sand the operator is familiar with the particular well. If several anomalies are recorded during the fluid level test from such obstructions as liners, tubing catchers, salt rings, and the fluid level, the last anomaly to repeat itself must be the fluid level if all of the anomalies are repeated. Another test should be made when any doubt exists about the fluid level interpretation. Where the well was producing fluid immediately before the first test, the liquid level will rise if the well is shut down between tests. The anomaly which raises must be liquid since it is the only sound reflector which can move to any extent.