gas turbine performance test|Depth Control Issues for Drill Stem Testing

A Drill Stem Test is a temporary completion of a potential zone in an open drill hole, normally with the drilling rig on location and taking place after the well has been drilled to total depth and logged. Typically two packers are used to isolate a zone, one below and one above. The packers are inflated against the well bore and form a seal. The test string is then manipulated to open and close valves that allow the zone to flow into the wellbore, into the test tool and up the drill pipe to surface.read for more gas turbine performance test

There are a number of issues that arise with regards to setting the packers in the right place in the well bore: The first one comes from the fact that the zone to be tested is picked off the logs. The corresponding depth depends on the measuring wheel for the wireline working properly - no mud or ice build-ups. The counter was zeroed at the rotary table at the correct position of the logging tool stack. That the other secondary systems of depth control are working, such as the magnetic markers on the electric line, etc. The logging crew has had some sleep in the previous 30 hours and is paying attention to their present operation.This is a totally different method than how the depth of the zone was determined from the logs!

Quite often there are really three critical depths for a DST (Drill Stem Test). You want to straddle the zone and you want good in gauge (not oval) hole for the two packers to expand against and form a seal. The packers are one meter in length where they contact the well bore so if you have a wash out, water contact or oval section that you are trying to avoid, depth control becomes very important. read for more gas turbine performance test

Everyone who has called out DST's will have several wells, which stick in their minds, doubting whether they were on depth. Of course everyone will swear that they counted stands prior to testing and that the pipe tally and stick up calculations were done absolutely correct. Even if the rig crew double straps coming out of the hole and the pipe tally matches this doesn't address the possibility that the loggers depth could be off.

The trend now is for the rig crews to ask the Drill Stem Testing Rep on location if they can use the numbers straight from their system and just copy them over to a pipe tally sheet. from the possibility of errors this still does not address the separate issue of the logger's depth being off!The only way to ensure that the DST test tool is placed on the formation you want to evaluate is to do a correlation log. read for more gas turbine performance test