Well Integrity, Plugging and Abandonment: Abrasive Cutting Applications for Well Severance

Upon cessation of production the cost of well abandonment is absorbed as a liability within the oil and gas industry under increasing financial pressure in the current climate. One of the key opportunities when undertaking a well abandonment campaign is identifying new and innovative technology available and adopting it to reduce operating time, project risk and ultimately cost. The final phase of the plugging and abandonment (P&A) is the well severance and conductor removal operation that is traditionally performed using mechanical knives for rig-based campaigns. This involves operating online, deploying on drill pipe and multiple deployments into the well to cut and recover the multi-string casing. An alternative approach to the traditional mechanical cutting method is the use of water-abrasive cutting technology that uses a high-pressure water and abrasive mixture to sever through the well's multiple casings and conductor below mudline. Abrasive Water Jet (AWJ) cutting technology is used to cut through multi-string casing and conductors from 7″ to 36″ in a single deployment, regardless of the number of casing strings, casing weight or cement presence in the well annuli. The cutting time is between five and eight hours depending on well construction. The water-abrasive cutting technology can be utilised during rig-based P&A campaigns where the cutting tool can be deployed offline using a standalone deployment system to sever the well below the sea-bed whilst online operations continue with the rig and well services teams, hence providing P&A SIMOPS. By operating offline, the overall rig time per platform is reduced. The water-abrasive cutting tool also provides the solution for the removal of subsea tie-back and dual bore wells which can't routinely be cut with mechanical knives due to the knives range limitations and the risk of getting ‘stuck in hole’ and the subsequent recovery operation. The non-intrusive water-abrasive method not only provides a solution to the problematic subsea tieback wells and dual bore wells but also removes the cutting operation from the critical path of the rig. Similarly, the water-abrasive cutting technology can be operated from a vessel or barge rather than the rig. This allows the well severance and removal phase of the P&A process to be removed from the rig's scope and the high cost asset to be off-hired as early as possible. This approach is applicable for surface wells and subsea wells alike and also allows the asset owner to combine the well severance with the platform removal phase.