The idea of SGS is to pull a memory gauge down hole below, deep enough to capture a pressure gradient in wellbore fluid column and then use the same gradient to extrapolate the wellbore pressure to formation datum.
Assess formation pressure in perforated formation units.
Fig. 1. SGS in oil producer |
The survey assumes that
The survey is applicable for wells with one perforated unit with no integrity issues (behind casing communications, active leaks or leaky bottom-hole)
The survey is applicable for wells with multiple perforations providing that all perforated units have the same formation pressure so that well doe snot develop a cross-flow between perfoations during the survey.
In most practical cases the above conditions are not met and SGS maybe highly misleading.