Page 382 - Numerical Analysis and Modelling in Geomechanics

RESERVOIR COMPACTION, SUBSIDENCE AND WELL DAMAGE 363

Figure 11.15 Deformed casing from a shearing simulation.
and failures were pervasive, the model was successful. However, in areas where
damage or failure was sparse, the model was not as successful. These
comparisons showed that the two-dimensional model may have lacked the detail
to capture variations in field operation, that the pore pressure field may not be
accurate in some areas of the flow model, or that important three-dimensional
effects on field-scale deformations occur that the two-dimensional model could
not capture. A similar history comparison for a three-dimensional model of
Section 33 is discussed in Refs. 39 and 40.

Tool length

Wireline tools are instruments or equipment lowered into the wellbore from a
steel wire for investigatory or maintenance purposes. If the casing is sufficiently
deformed, then such tools may not be able to pass through the deformed section
of casing, or worse yet, the tool may become stuck in the casing, thus requiring
further efforts to recover them. In the operation of the Belridge field, if tools
could not pass through the casing, then the well was noted as damaged on a
workover ticket. However, there were several instances when one tool could not
pass through the casing, but a second attempt with a smaller OD tool was