Abstract

During a typical field life of 30–50 years, significant changes occur in standard operating procedures, engineering, technology, standards, regulations, etc. Wells which met industry good practice and the relevant regulatory requirements when constructed can deteriorate over time so that they no longer meet the original requirements. Also as accepted good practice evolves and regulation improves, then wells which met the original requirements fail to meet today's improved requirements.

This is good as it demonstrates that as an industry, we are learning and improving.

The subject field produced since the 1960s, but was shut-in in early 2005 to conserve the driving energy of the reservoir.

However the operator carried out a review of the shut-in wells to evaluate their compliance with current industry well integrity practices and updated regulatory requirements. A major issue was that when originally drilled and completed it was not normal or required to have downhole safety valves.

A field survey was conducted to evaluate the integrity of the wells and the condition of safety barriers. At the same time the reservoir and surface shut-in pressures & fluid level were determined in each of the wellbores. This data formed the basis of a risk assessment, which concluded that a total 25 wells should be worked-over.

The asset team imposed a further requirement that, although the field was currently shut-in, the worked over wells should be available for future field re-development and capable of being produced if required. Consequently the well interventions were programmed and customized for each individual well. The individual well programs was reviewed in conjunction with the location of the wells on the jackets and the location of the jackets in the field. A plan was developed for both rig and rigless interventions. The workover schedule was optimized to carry out batch operations and minimize rig and vessel movements in the field.

The project has been implemented. A total of endangered 25 wells were intervened and integrity restored, in line with current industry practices. The operations were completed with no Loss Time Accidents (LTA) and 84 days ahead of the budgeted time. This case-history paper presents the development background and details of the optimized procedures which were developed and followed to set plugs in wells in an aging field to comply with upgraded safety requirements in the Gulf of Saudi Arabia. The planning and best practices that contributed to the success are detailed and explained.

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