Some wells are drilled primarily to retrieve cores. This puts a lot of pressure on the drilling engineers to find methods that moves the recovery factor beyond that of good luck. This coring case is presented because it gave full core recovery AND also provided for documentation of the vibration challenges from MWD recordings.
The AST saved at least on day on each section drilled compared to previous wells having the same sea conditions.
Drilling hard carbonates is often a costly affair with slow ROP and equipment damage. At the international IADC/SPE Drilling Conference in London 2015, Norwegian operator Det norske together with a joint team of suppliers including Tomax presented a paper on how to drill these hard carbonates with fast ROP:
Deepwater exploration from large drillships is on the rise. These vessels offer great benefits in terms of mobility and capacity but, from a drilling perspective, they may sometimes present challenging motion characteristics that are transmitted all the way to the bottom of the hole.
Torque arrestors and other features are added to reduce vibrations and to keep PDC drill bits safe. ROP however suffers. The AST allows for the fast, aggressive bits to be used again.
Drilling, shale, play, unconventional, lateral, Permian, Eagle Ford
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.
Severe drilling vibrations in top-hole section created unacceptable noise and risk. An AST was implemented to solve the problem.
The AST principle provides a stabilized load on the bit in lateral and extended reach wells to prevent erratic reactive torque that would otherwise reduce drilling efficiency.
Use of very aggressive PDC cutters, a RSS system with a mud motor and an AST produced a steady cut through hard limestone and repeatedly drilled sections to TD in one run.
Drilling a slim hole from a semi-submersible in rough seas was almost impossible due to inadequate load on the heave compensator system. AST was called out to solve the problem.
Offeset data stated a minimum of two bit run was needed to reach TD in a Central North Sea well. By deploying an AST and aggressive cutters, the section was drilled in one fast run with minimal wear.
Bad weather on floating drilling facilities can make the heave compensator struggle and the WOB becomes unstable. An AST can be used to improve on this.
A production packer was set in the wrong place and needed milling out from inside a new, high grade tubing. In order to safely mill the packer with minimal risk to the tubing, an AST was used.
The maximum drilling torque supplied from the Top Drive is defined by the highest peaks produced downhole. An AST can be used to reduce such downhole peaks.
Milling collapsed pipe is difficult and in this case it was done deep down in an extended reach well. To be able to land and engage the mill, two AST tools were run in tandem.
Use of composite plugs makes milling faster, but in this case a plug set in a 7” liner had to be milled by a 2 7/8” motor on coiled tubing with limited power reserves.