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drilling 05-15-2009 07:23 PM

Case Study: Chevron Jack Well Subsea Test Tree Challenge
 
CHFR resistivity tool helps locate potential production in Altmark gas field in Germany



Challenge

Obtain good-quality resistivity data behind well casing despite extensive casing corrosion.


Solution

Run CHFR Cased Hole Formation Resistivity tool in cased well to obtain reliable resistivity measurements and identify potential production.


Results

CHFR measurements indicate two gas-bearing zones and one water-bearing zone below 3,400 m.


Identify potential production in plugged well

EEG, a subsidiary of Gaz de France, needed good-quality resistivity data to determine potential production in a plugged well in the Altmark gas field in Germany. Previous resistivity data for the well consisted of an openhole laterolog plus uncompensated neutron data. The openhole logs showed a shale-sand sequence with five gas-bearing layers.


Obtain reliable resistivity measurements

This cased well was originally drilled in 1986 and had produced more than 480 million cubic meters of gas prior to being plugged in 1992. In January 2001, EEG drilled out the plug and ran the CHFR tool to measure resistivity behind the existing casing.

The PS Platform multifinger imaging tool was also run and showed casing corrosion problems throughout the well. Nevertheless, the CHFR tool was consistently able to make good contact and provided a valuable resistivity log.

Using the ToolPlanner job-planning application, Schlumberger determined that the CHFR tool would have a depth of investigation of 2 m, which is much greater than with other testing methods. More than 180 m of the well was logged in just 10 h, delivering real-time measurements. EEG was able to rapidly set about running drillstem tests to validate the data.


Identify previously bypassed pay

Despite the casing corrosion problems, the CHFR tool ran smoothly and provided a reliable resistivity log. Measurements positively identified two gas-bearing zones and one water-bearing zone below 3,400 m.


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