Abstract
The extreme operational environmental conditions and aging conditions of subsea structures pose a risk to their structural integrity and is critical to their safety. Nondestructive testing is essential to identify defects developing within the structure, allowing repair in a timely manner to mitigate against failures that cause damage to the environment and pose a hazard to human operators. However, to be cost effective, inspections must be carried out without taking the risers out of service. This poses significant safety risks if undertaken manually. This paper presents the development of an automated inspection system for flexible risers that are used to connect wellheads on the seafloor to the offshore production and storage facility. Due to the complex structure of risers, radiography is considered as the best technique to inspect multiple layers of the risers. However, radiography inspection, in turn, requires a robotic system for in-situ inspection with higher payload capacity, precise movement of source and detector which is able to withstand an extreme operational environment. The deployment of a radiography inspection system has been achieved by developing a customized subsea robotic system called RiserSure that can provide precise scanning motion of a gamma ray source and digital detector moving in alignment. The prototype has been tested on a flexible riser during shallow water sea trials with the system placed around a riser by a remotely operated vehicle. The results from the trials show that the internal inner and outer tensile armor layer and defects in the riser can be successfully imaged in real operational conditions.
Highlights
During the 1970s, the flexible pipeline technology began to be used initially in benign, shallow water conditions such as the Mediterranean
This paper presents the development of an automated inspection system for flexible risers that are used to connect wellheads on the seafloor to the offshore production and storage facility
The developed robotic system for RiserSure is subjected to several laboratory based trials before taking it for sea trials to test and demonstrate that the system has the capability to transition to seawater operation
Summary
During the 1970s, the flexible pipeline technology began to be used initially in benign, shallow water conditions such as the Mediterranean. In 1984, it revolutionized the oil and gas industry when the flexible pipelines began to be used as risers in North Sea. Since the flexible pipes have been widely adopted for connecting floating equipment such as floating production, storage, and offloading to the seabed. The wide adoptability of flexible pipes was because of their inherent flexibility that enabled to overcome the challenges posed by dynamic environments [1] These flexible pipes used as risers are to connect offshore platforms to subsea equipment for production and drilling purposes. These are capable of carrying a wide range of fluids such as hydrocarbons, gas lift, and injection and control fluids.
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