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5 <br />rcen developed. The <br />cd in well-cemented <br />ms arc used for: <br />are processed on the <br />Ieasured in a dieital <br />ivity of the surface <br />checked before each <br />rements at 20 kHz <br />equency sonic beam <br />I wave benveen the <br />:d 090 m 13 ft) from <br />CBL indicates the <br />Incemented and free <br />cement at 1351 m. <br />:r than 50 mV in the <br />;pondine to the first <br />in,. When the signal <br />.using a "stretch". I( <br />.er and, in this case, a <br />5 <br />ACOUSTIC ll'F.LL LOCGI~G <br />C9L <br /> <br />Ea 6 <br />Fie. 5.6. - E:c:tmplt of CBL. <br />(Srhlmnbcrgrr ducumentl <br />193 <br />The centering of the tool inside the casing mwt be done properly or else the arrivals of <br />the different sides of the borehole are not in phase and the signal becomes distorted. The <br />amplitude of the firs[ arrival is no longer sienificant. <br />The presence of a slieht unbondine o(the cement as the result of a hish pressure applied <br />inside the casin=can cause a response resembling a poorbond. This is a "microannulus" <br />phenomenon which is usually not harmful to the seal behind the casino column. <br />7flAN51r <br />~- AMPtIru OE <br />