CRITICALITY OF CONDUCTOR / CASING INTEGRITY FOR AGEING OFFSHORE WELL LIFE EXTENSION

The increase in ageing offshore wells and the continued requirement to maintain operations beyond their original design life is beginning to be a major challenge faced by operators worldwide. This problem is further compounded by the limited availability of well construction records, unknown operational conditions and inadequate through life maintenance. In many cases the large number of wells which may be required to be evaluated can also make the process of developing acceptable integrity procedures challenging. Defining an accurate understanding of the present condition of these assets is essential to ensure that the structural integrity of the well can be confirmed, and the acceptability of extending the life of the asset can be evaluated. This papers focuses on the criticality of the well integrity specifically of the conductor and surface casing corrosion and the deterioration of the annular cement due to ageing on shallow water injector wells. Several structural assessments techniques are proposed for evaluating the in-place strength of the corroded well structures under operational and environmental loads, including the detailed analysis on the annular cement deterioration and its ability to mitigate well loads, whilst providing sufficient barriers for the environment. The initial results of these assessments show allowable stress exceedance by more than 20% in some instances, indicating the requirement for immediate plugging and repair/rehabilitation work. Further refinementsare proposed in this paper to reduce the over-conservatisms built in the assessments including the development of non-destructive material hardness based well construction preload measurement tool. The combined use of this tool with integrity assessments listed in this paper will prove to be a streamlined approach to tackling ageing well integrity issues in this region, with lean resource consumption and effective life extension of ageing wells for continued operations.