The subsurface development and well intervention teams recently completed a campaign of five production logs (PLTs) in the extended reach and highly deviated production wells of the Piltun field. The challenges of running the PLT logs were considerable: 4,000 to 7,000 m long deviated wells, complex well trajectories, long tractoring intervals, risk of tool lift due to high oil and gas rates, high wellhead pressures of ~2000 psi, harsh winter conditions, the problem of hydrate formation on the wire and in the pressure control equipment when pulling out of hole. Despite these challenges, the logs were completed safely and revealed a number of surprises about production from these multi-reservoir commingled wells.

The logs revealed that major reservoir intervals, with excellent porosity and permeability development, were not flowing. Some lower completion intervals in these good quality reservoirs remained covered with completion brine and debris, while selective zones with high GOR development had dominated production from the wells. Prior to this learning, the team assumed production from the wells had followed a rate distribution profile matching permeability thickness (kh) distribution. The logs also revealed off-depth perforations in some cases, which may have contributed to productivity issues for those reservoirs.

The learning from the PLT logs has affected dynamic modeling history matching effort, influenced further field development plans, and has driven the need for workovers to install smart-well equipment in essentially all of the production wells drilled to date. Learning from the logs has also led the team to apply greater quality control and assurance to perforation operations, investigate the use of less damaging completion methods or perforation pills, and use smart-well equipment for newly planned development well completions.

This paper discusses the issues and challenges to further field development and how learning from the recent PLTs has affected this effort.

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