Page 229 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

198 Reservoir Engineering

1 TOTAL TRAVEL TINE

Figure 5-121. CBL-VDL log run in casing eccentered in borehole making
contact with the formation [220].

to high. These indicate free pipe with no cement or cement-casing-formation
coupling. A high amplitude curve reading indicates low attenuation, hence no
cement in the annulus .
Strong casing and formation arrivals are shown in Figure 5-121. This pattern
has both the clean, pronounced casing signature as well as a strong, wavy-
formation signature. The lack of cement is indicated by the high cement bond
log-amplitude (Le., no cement attenuation). The combination of these signals
is inter reted as eccentered casing in contact with the wall of the well-bore. In
this sit 5 tion, proper cementation may be impossible.
Weak-casing and strong-formation arrivals are shown in Figure 5-122. This
pattern shows no apparent casing or very weak casing patterns and very strong
formation-patterns nearly filling the VDL in track 3. This indicates good casing-
cement formation bonding, confirmed by the low cement bond log amplitude
(high attenuation). Rayleigh and mud wave arrivals are also apparent along the
right side of track 3.
Weak-casing and weak-formation arrivals are shown in Figure 5-123. This
pattern shows what appears to be a slightly attenuated casing pattern but the
cement bond log amplitude suggests otherwise. The curve indicates strong to