Mothballing Initiative Ensuring Operations Efficiency for Inactive Facilities

摘要

In oil and gas production, certain cases require to shutdown Wellheads or surface facilities for extended period to anable preventive maintenance or reservoir monitoring. The major concern is how to preserve the equipment's from corrosion risk during the shutdown periods. The corrosion potential increases with the presence of sour gases (H2S and CO2) and exposure of piping facilities to sour gase media under high pressure is the main cause for metallic corrosion. Despite well flowing condition to production facilities is designed to have continuous corrosion inhibitor injection which forms a protection film layer as a corrosion control, the shutdown condition diminishes the role of the the protection layer, hence, mothballing was identified as an alternative resolution to ensure piping integrity and corrosion control in place while shutdown duration. In this paper, the sour gases corrosion effect is described by defining corrosion types. Mothballing process is identified based on the preservation concept, duration and different procedures for protection, noted the resources required and mitigation to perform the activities with assigned team members. Downhole tubing and surface facilities piping is also discussed for mothballing while inactive and offline duration of sour gas wells and associated surface piping facilities. Two types of mothballing media are listed based on target equipment for effective results, inhibited diesel was selected for well down hole mothballing, and dry inert nitrogen gas as media for X-mass tree and surface pipe line facilities. Additional improvement and opportunity for operation efficiency is to carry out the mothballing as campaign to optimize the resources for both time with cost saving initiative. Team members from different disciplines required to contribute for mothballing operations, task asssignement for each disciplines as per roles and responsabilities organize stream line all resources to achieve ultimat goal for facilities integrity.