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~~~r. UNITED STS ENVIRONMENTAL PROTECT AGENCY <br />~,,,,,,,.~~ REGION VIII <br />999 18th STREET -SUITE 500 <br />DENVER, COLORADO 80202.2466 <br />111, u <br />APR 1 ° 19°~ <br />SUBJECT: GROUND WATER SECTION GUIDANeE NO. 34 <br />Cement bond logging techn' and interpretation <br />FROM: Tom Pike, Chief ~J <br />UIC Direct Implementatio Section <br />T0: All Section Staff <br />Montana Operations Office <br />These procedures are to be followed when running and <br />interpreting cement bond logs for injection and production (area <br />of review) wells. . <br />PART I - PREPARE THE WELL <br />Allox cement to cure for a sufficient time to develop full <br />compressive strength. A safe bet is to let the cement cure <br />for 72 hours. If you run the bond log before the cement <br />achieves its maximum compressive strength, the log may show <br />poor bonding. Check cement handbooks for curing times. <br />Circulate the hole with a fluid (either rater or mud) of <br />uniform consistency. Travel times are influenced by the <br />type of fluid in the hole. If the fluid changes between two <br />points, the travel times may "drift," causing difficulty in <br />interpretation and quality control. <br />He prepared to run the cement bond log under pressure to <br />reduce the effects of micro-annulus. Micro-annulus may be <br />caused by several reasons, but the existence of a micro- <br />annulus does not necessarily destroy the cement's ability to <br />form a hydraulic seal. If the log shows poor bonding, rerun <br />the log with the slightly more pressure on the casing as was <br />present when the cement cured. This will cause the casing <br />to expand against the cement and close the micro-annulus. <br />PART II - PARAMETERS TO LOG <br />Amplitude (mV) - This curve shows how much acoustic signal <br />reaches a receiver and is an important indicator of cement <br />bond. Record the amplitude on the 3 foot spaced receiver.. <br />Travel time (µs) - This curve shows the amount of time it <br />takes an acoustic signal to travel between the source and a <br />receiver. For free pipe of a given size and weight, the <br />travel time between points is very predictable, although <br />variable among different company's tools. Service companies <br />should be able to provide accurate estimates of travel times <br />for free pipe of a given size and weight. Travel time is <br />required as a quality control measurement. Record the <br />travel time on the 3 foot spaced receiver. <br />Printed on Rae yclW Paper <br />