Well Control; Hot Tapping S135 Drillpipe with 12,000PSI Trapped Pressure


2 days


During a plug milling campaign, a washout occurred in a drillstring. Bridge plugs were placed above the washout with wireline and cement dump bailed on the top plug. Surface pressure was 42 MPa with a column of produced water in well. The trapped pressure between the plugs was expected to be between 11000-12000psi


Piston well control personnel were mobilized with a balanced 15k hot tap unit. Once the joint with the plugs was at surface, the decision was made on the tapping location. The joint exterior was cleaned with emery cloth and inspected for imperfections. Saddle clamps were installed and the valve was tested against the pipe to 15,000psi. The balanced hot tap unit was installed with the use of a crane and held in place. The hot tap unit was then pressure tested to 15000psi. The drill was advanced and pressure of 12,000psi was held as the 5/8 hole was drilled in 10 min. The drill was retracted and pressure was bled to zero. After a 10 min negative test, the gun was removed and the string hoisted above the suspected washout, and the procedure was repeated, ensuring there was no trapped pressure in the remaining 1,800m of drillpipe.