Underwater plasma arc cutting process of oil casing in shallow water environment

Numerous aging oil production facilities are currently being decommissioned. The removing and plugging of abandoned oil wellheads are important for ecological protection. Plasma-arc cutting is highly efficient for the removal of steel structures and is expected to play a significant role in oil casing removal. This study experimentally investigated the underwater plasma-arc cutting of oil casings. A workpiece composed of a steel plate and a cement block was used to simulate a segment of the oil casing during the cutting process. The working states of the plasma arc and slag emissions during cutting were analyzed using the plasma arc voltage, kerf depth, and slag distribution. The results showed that the vicious cycle of slag emission during the fixed-speed cutting of steel plate-cement structures caused severe slag bridging in the kerfs. The introduction of side-airflow optimized slag emissions during fixed-speed cutting, but reduced the kerf depth. The proposed breakpoint cutting avoids slag bridging and ensures the kerf depth. These findings are beneficial for advancing the application of underwater plasma arc cutting in oil casing removal.