Flexible pipes are increasingly popular in the oil and gas industry for the development of deep-water fields – for example offshore Brazil – and small fields in mature regions such as the North Sea. Flexibles are complex structures, and the options for inspection to confirm integrity as they age are limited. At present, no technologies are available to provide a complete picture of the condition of a high-pressure unbonded flexible. This paper provides an overview of the initial development of engineering assessment approaches for unbonded flexible pipes using data collected through in-line inspection (ILI). The data collected during an ILI run allows for some engineering assessments to be performed, giving some valuable information regarding condition. However, as of yet, a complete picture is not possible. The experience gained in completing limited assessments can contribute to the further development of ILI tools specifically for the more complete inspection of flexible pipe. To get useful information regarding the condition of the flexible pipe and potential threats to the remaining service life, it is necessary to combine specialist knowledge in both ILI data assessment and the operation and failure modes of unbonded flexible pipes. Examples of issues that can be identified are end-fitting issues, denting, carcass buckling, overstress, metal loss, external fitting locations and curvature. Used appropriately, this data can enhance the integrity management of unbonded flexible pipes. Examples from laboratory tests and field-collected data are used to illustrate some of the possibilities of existing technologies. Future plans to enhance the capabilities of ILI tools with respect to the inspection of flexible pipes are also covered.
Engineering assessment of flexible pipes using ILI data
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