Formation Evaluation Through Casing - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 176

If the carbon content of the formation due to carbonates is 10 % then the TOC
would be given by:

TOC = 0 135 01 0 035 35 . - . = . or . %

Cased-Hole Wireline Formation Tester

Wireline formation testers are routinely used in open hole before casing is set in
order to evaluate the formation pressure, permeability, and fluid content. The tech-
nology developed for such testing is also applicable to cased holes with some modi-
fications. Essentially a standard tool is adapted to include the means to make a hole
through the casing and cement and a way to seal such a hole when the test is com-
plete. One embodiment of such a testing tool is shown in Fig. 11.35 .

Fig. 11.35 Cased-hole
wireline formation tester

The hole making part can be accomplished by either a motorized drill or by an
explosive shaped charge. Once communication is established between the tool's
plumbing and the formation beyond the casing and cement the actual testing is
analogous to that performed in an open-hole test. Sealing of the hole is accom-
plished by injection of an appropriate epoxy sealer or similar substance. Application
for these kinds of tools can be found in work-over situations where there is a lack of
data in the well files and there is uncertainty regarding the current formation fluid
content and pressure.