Motivation
The idea of SBT is to to measure the volumes of oil, gas and water production.
Objectives
Assess formation pressure in perforated formation units. oil, gaa and water production.
Data Acquisition Procedure
Design surveyAssess the duration of required shut-in period
Assess the expected static fluid level based on the minimal expected formation pressure around the well
Assess additional depth extension in order to capture the pressure gradient in static fluid column
Shut-down the well for a pre-calculated period of time
Pull down the memory gauge at pre-calculated depth
Retrieve the tool at surface and download the data
Pull down the memory gauge at pre-calculated depth
Data Interpretation
| Fig. 1. SGS SBT in oil producer |
Assumptions and Limitations
The survey assumes that
the achieved shut-in conditions are representative of the formation pressurethe fluid column across the surveyed interval stays the same all the way down to the formation datum
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.