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Underground Injection Control Branch Guidance No.: w~wyg://35/hup://www.epa.gov/reg5oh2o/uidr5_OS.htm y intensity of detected noise within various frequency ranges. B. Advantages and Disadvantages of Noise Logs Informational Advantages Relative to Other Log Types: Relative to oxygen activation log, it is practical to increase vertical resolution by increasin€ spacing density Can identify flow of gas and differentiate it from liquid flow Informational Disadvantages Relative to Other Log Types: Can identify only turbulent flow Relative to temperature logs, cannot be used to demonstrate confinement Operational Advantages Relative to Other Log Types: ~ Relative to temperature logs, little or no shut-in time is required Operational Disadvantages Relative to Other Log Types: ~ Requires liquid in well bore through the interval [o be tested Injection pressure must be maintained to ensure identification of fluid flow near the injectit zone Actual logging time and cost are usually greater than for temperature logging C. Equipment and Forms Noise logging tools are wireline tools which are essentially sensitive microphones. Sampling is d in a stationary mode and the time required at each station is approximately 3-4 minutes. Any sour detected are transmitted to recorders which measure the amount (loudness) of sonic energy recei~ over a period of time. A cumulative measure of the sound energy which has been received is recorded. Sonic energy travels considerable distances through solids so sampling can be done in a reconnaissance mode, with additional stations run where increases in energy aze detected so that exact locations of conditions which cause sonic events can be found. Sonic logs aze similar to temperature logs in that they aze much more effective in liquid-filled holes because of improved coupling. The log is the only form which must be submitted. When the level of sound is low, a linear scale used, and when there are intervals with higher sound, a logarithmic form is used. Either is accept: The vertical scale should be small, one or two inches per 100 feet. In addition to the graphical lo€ tabulation of sound energy is normally included on the log Form and it should also be submitted. D. Procedure for Producing the Noise Log: Noise logging may be carried out while injection is occurring in many wells because flow restrict caused by the logging tool is often insufficient to cause turbulence. [t is especially desirable to lot while injecting when looking for flow resulting from pressure increase near the top of the injectic zone. If ambient noise while injecting is greater than ]0 mv, injection should be halted. Logging procedures should include the following steps: 1. Make noise measurements at intervals of 100 feet to create a log on a coarse grid; 22 or 34 5/28/99 1:09 PM