Page 9 - Acoustic Fluid Level Measurements

Examples of Fluid Level Survey in Producing and Static Wells 2-1

records acquired in wells with similar characteristics. University of Texas at Austin
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Examples of Fluid Level Surveys in

Producing and Static Wells

In this chapter:
• Acoustic data analysis and quality control
• Recommendations for optimizing acoustic signal records
• Examples of different well types, acoustic fluid level records, and analyses
• Summary reports and comparisons of multiple records
• Testing for safety valve position and casing integrity, and determining gas composition using acoustic records

This chapter presents a series of examples of acoustic reference distance is the average length of pipe joints
records that illustrate some of the most likely cases (in feet per joint) or the distance to a known wellbore
encountered in practice. The objective is to provide cross-sectional area anomaly that creates a detectable
guidance to the reader for interpretation of the acoustic echo in the acoustic record. It is important that these
Petroleum Extension-The
reference lengths be as accurate as possible, or else the
The assumption is that the reader has access to acoustic distances computed from acoustic signal travel times
analysis software that is similar to that used to process can have very significant errors.
these records , provides graphical representation of the The distances to specific points in the wellbore may
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acoustic signal, and includes tools to determine the travel have been measured either relative to the wellhead or
time to specific echoes. relative to the rotary table of the completion or workover
rig. The difference in distance between these values cor-

GUIDELINES FOR ACOUSTIC RECORD responds to what is defined as the KB correction (kelly
ANALYSIS bushing correction) and can be a significant quantity,
especially when dealing with wells on offshore platforms.
The acoustic record analyst should have a clear un- It is important to verify which reference point is used
derstanding of the wellbore configuration with all its when depth information is provided for input into the
geometric details. This will allow the analyst to visual- acoustic analysis software.
ize all features that may generate echoes of the acoustic
pulse transmitted from the surface. In wells that have a
complicated wellbore (multiple casing or tubing sizes, GUIDELINES FOR QUALITY CONTROL
liner, multiple perforations, and so on), it is advantageous OF ACOUSTIC DATA
to overlay the wellbore diagram onto the acoustic record To determine the position of the liquid level, it is important
using a distance scale based on the average acoustic to obtain a clear indication of the corresponding echo and
velocity in the wellbore. an accurate measurement of the round trip travel time
The conversion of round trip travel time (RTTT) to (RTTT) of the acoustic pulse. This also assumes that the
a distance implies that an accurate reference distance can moment of generation of the transmitted pulse is identified
be used as the basis of the conversion. Generally, this correctly and is used as time zero for the record.

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