Abstract
Flexible riser is a class of flexible pipes which is used to connect subsea pipelines to floating offshore installations, such as FPSOs (floating production/storage/off-loading unit) and SS (semisubmersible) platforms, in oil and gas production. Flexible risers are multilayered pipes typically comprising an inner flexible metal carcass surrounded by polymer layers and spiral wound steel ligaments, also referred to as armor wires. Since these armor wires are made of steel, their magnetic properties are sensitive to the stress they are subjected to. By measuring their magnetic properties in a nonintrusive manner, it is possible to compare the stress in the armor wires, thus allowing the identification of damaged ones. However, one encounters several sources of noise when measuring electromagnetic properties contactlessly, such as movement between specimen and probe, and magnetic noise. This paper describes the development of a new technique for automatic monitoring of armor layers of flexible risers. The proposed approach aims to minimize these current uncertainties by combining electromagnetic measurements with optical strain gage data through a recursive least squares (RLSs) adaptive filter.
Highlights
Flexible risers are an important component of offshore production systems of oil and gas
This paper describes the development of a new technique for automatic monitoring of armor layers of flexible risers
This paper focuses on the integrity monitoring of the outer layer of tensile armor, which supports axial load and the riser weight
Summary
Flexible risers are an important component of offshore production systems of oil and gas. They are used to link subsea pipelines to floating installations, such as FPSOs (floating production/storage/off-loading unit). Flexible risers have been one of the preferred deepwater riser solutions in many regions of the world due to their good dynamic behavior and reliability [1]. Petrobras is a Brazilian multinational petroleum company whose businesses include oil and gas exploration, production, transportation, refining, and distribution. Since most Brazilian oil reserves are located offshore and often under deepwater, Petrobras oil production is highly dependent on platforms and offshore equipments such as flexible risers. Integrity management of flexible risers is essential to ensure the safe operation of a production unit
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