Tool Configuration 15 20 k HZ Transmitter Piezoelectric

Tool Configuration 15 -20 k. HZ Transmitter Piezoelectric CBL amplitude Transducers 103” t 3” Receiver (gives CBL) 5” Receiver VDL (gives VDL) 0 100 CBL amp

CBL/VDL TOOLS

Casing Mud Cement Formation Sonic Wave Paths T Mud Casing R R Cement Formation The signal observed at the receiver is a composite of these signals.

Signal There are two measurements made: 1 - Amplitude (AMP) 2 - Transmit time (TT) l the amplitude reflects the amount of cement. This curve shows how much signal record by the receiver? l the transmit time is constant for a given casing (size and weight) and well fluid. l it is an important log Quality Control.

Variable Density (VDL) Amplitude Casing Arr. (m. V) Transmitter Formation Arrivals Mud Arrivals Poor Bond Good Bond VDL is logged on the 5 foot spaced receiver. VDL reveals qualitative information on both the pipe and formation bond.

Cement contact with casing and formation 1) Free pipe(no cement) 2)Cement bound to casing but poor bound to formation 3)Cement bound to formation but poor bound to casing 4)Cement Good bound to both casing and formation 5)Partial cement 6)Exist of micro annulus(micro gap between cement and casing) – Channeled cement – Poor bond to pipe but good bond to formation? – Good bond to pipe and poor bond to formation – Poor bond to both pipe and formation – Compromised cement (i. e. gas cut cement) 35

Good cement “Amplitude” low. “VDL” formation signals are strong. “VDL” casing signals are poor. 36

No cement “Amplitude” High. “VDL” straight. No formation signals. 37

Partial cement “Amplitude” is low and moderate. “VDL” can shows both wiggly formation signals and straight casing signals. 38

Micro annulus (micro gap between cement and casing) “Amplitude” is moderate. . “VDL” can shows both wiggly formation signals and straight casing signals In case of doubt, repeat the log under 1000 psi pressure to the well. The gap will be closed and log will change to "Good Cement“. Micro-separation (yellow) between pipe and cement (< 1 mm) caused by a drop in temperature or pressure. 39

Cement without bound to formation “Amplitude” low. “VDL” doesn't show casing and formation signals. Thin mud and cement signals are visible. 40

Cement bound in hard formation “Amplitude changes between low and high Formation signals cover casing signals. Cement is good. 42

Well cemented and poor cemented casing 43

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