A troublesome formation known to lock-up the cutters and cause twist-offs was to be drilled with under-reamer. An AST was deployed to solve the problem.
A particular package of Oligocene sediments under the Snorre A TLP caused trips and delays when drilling the 16” section from the rig. Then the need for ECD management required the interval to be under-reamed up to 17 ½” while drilling.
Tool
9 1/2” XD-AST
Client
Statoil
Country
Norway
Field
Snorre
Rig
Snorre A
Section
16” x 17 ½”
BHA
16” bit, PowerDrive RSS, MWD, 17 ½” XR-Reamer, AST, DC, jars and 5 ½” DP
Objective
A new strategy for
vibration control
The established strategy for drilling the section was based on avoiding twist-off with a switch to roller-cone type bits when strong torsional vibrations occurred. Now with a PDC reamer, this strategy had to be abandoned and with input from Security DBS, Statoil changed to Anti Stick-slip Tool (AST) technology to mitigate risks.
Results
One run to TD
in half the time
The new BHA with AST and under-reamer drilled to section TD in one run using half the time of previous sections. Torsional vibrations were not an issue and the results were safely repeatable.
Value
$1 million saved
per well
The direct saving was around USD 1 million per well and the achievement was nominated the most significant process improvement for Snorre A in that year.
