Establishing an integrated geoscience workflow to optimize well plug and abandonments in the Gippsland Basin

Abstract

Well plug and abandonment (P&A) is the process of permanently sealing and abandoning a hydrocarbon reservoir, and any required shallow formations, prior to title surrender. As some of the Gippsland Basin assets have reached end-of-field life, platform decommissioning requirements have led to a significant increase in P&A activity. The scale of this P&A activity has provided the opportunity to establish a standardized workflow for geoscience support to the P&A design process. Utilizing this integrated geoscience workflow during early assessment screening can optimize individual well P&A designs, resulting in efficiencies to the well planning, regulatory approval, and execution stages. The three key pillars of geoscience assessment for P&A design are shallow hazards identification, cap rock definition and mechanical rock strength assessment. Working as an integrated team of geoscientists, wells engineers and reservoir engineers, these assessments have been successfully used in the Bass Strait to reduce complexity in P&A design and execution, while working within regulatory expectations for permanent abandonment. With over 150 well P&As already completed, and over 200 wells associated with the Campaign 1 decommissioning project, integrating the geoscience input early in the P&A design process is expected to drive better outcomes in overall execution efficiency. This can result in less complex and safer rig operations, with incremental savings on a well-by-well scale expected to deliver impactful cost savings in the overall decommissioning scope. The workflow also provides a consistent approach in engaging with the regulator and meeting evolving regulatory requirements.