Publications

Plug and abandonment (P&A) project is conducted on the wells that are no longer able to produce profitable oil and gas, and poses a hazard to safety and the environment. Management of a P&A project is necessary to implement ongoing work effectively and efficiently. An offshore field located in South China Sea has been operated for more than sixteen years. This field is produced its oil from two reservoir formations. Three subsea wells from this field were proposed to be abandoned following the recommendations from the risk assessment results in 2014. The P&A project of these wells is divided into two sequences: pre-work and main work. Pre-work utilize remotely operated underwater vehicle (ROV) and diving operation, while the main work utilize a multi-purpose drilling vessel. An ROV survey job and diver work was conducted to identify the condition and cleaning the wellheads of the fishing net to allow intervention in the main work job. The P&A main work job was performed in two batches: primary isolation and additional isolation. The utilization of multi-purpose drilling vessel allows primary isolation operation performed in subsequent wells pending the settling of the cement in the previous wells. The need to modify the Blow Out Preventer (BOP) unit in order to adapt to the wellhead connection, resulted the ship was positioned out of the rental area before continuing to the second batch, which this was not feasible when using the jack up rig or similar. The P&A project was accomplished in total 72 days and spending US$9 million per well. This paper describes the management of the P&A project to be performed at standard compliance in effective and efficient way, and concluded by recommending the utilization of the multi-purpose drilling vessel for future subsea wells P&A project.