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m UNITED STATES ENVIRONMENTAL PROTECTION AGENCY <br />~~~~ r~ REGION VIII <br />\r\Y~f•~rl Y 999 18th STREET -SUITE 500 <br />DENVER. COlORA00 80202.2466 <br />uu ... <br />APR 1 ° 1994 <br />SUBJECT: GROUND WATER SECTION GUIDANCE 270. 34 <br />Cement bond logging/~techn es and interpretation <br />FROM: TOm Pike, Chief ~ /Lv.~~~~ <br />UIC Direct Implementation Section <br />TO: 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 - FREPARE THE WELT. <br />Alloy cement to cure Cor a sutticient time to develop full <br />compreaaiva strength. A safe bet is to let the cement cure <br />foz 72 hours. If /ou run the bond log before the cement <br />achieves its maximsm compressive strength, the log may show <br />poor bonding. Check cement handbooks for curing times. <br />Circnlats the hole with a fluid (either eater or mud) o! <br />unitorm consistency. Travel times are influenced by the <br />type o! Eluid in the hole. If the fluid changes between two <br />points, the travel times may "drift," causing difficulty is <br />interpretation and quality control. <br />ee prepared to run the cement bond log under pressure to <br />reduce the eltect9 of micro-annulus. Micro-annulus may be <br />caused by several reasons, but the existence of a micro- <br />annuius does not necessarily destroy the cement's ability to <br />form a hydraulic seal. if the 1oq 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 ZI - 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 ~n the 3 Loot spaced receiver. <br />Travel time (µa1 - 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 companira <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 />rehired as a quality control measurement. Reeord the <br />travel time on the 7 foot spaced receiver. <br />Airnl ~w RN~ebI AOr <br />