Acoustic well sounders (#AWS) are sonar or sonic instruments. A small gas impulse at surface generates a sound wave, which travels down the wellbore. A microphone picks up the amplitude of reflected sound waves. The signal is recorded on an analogue paper strip chart, or on to a computer hard drive. Sound waves are reflected to surface by variations in the path, either: constrictions such as tubing collars or anchors, or expansions such as perforations or the end-of-tubing (EOT). Reflection of the entire sound wave occurs when it hits a liquid (fluid) level or PBTD.
AWS surveys are often referred to as simply ‘liquid levels’ because of the common application for detecting producing liquid levels in oil wellbores. This knowledge is necessary for completion and production operations, pump optimization and for determining sandface or bottom hole pressures from surface measurements (#PTA). AWS surveys are also effective in a gas (#LNG) #welltest.
Sonic surveys are also used to find wellbore anomalies such as holes in the casing or tubing, something plugging the wellbore (bitumen, wax, salt, or sulfite deposits), casing patches, or a fish (lost tool).