Contaminants such as mercury in offshore petroleum production are the common problems in Southeast Asia. In the near future, abundant subsea pipelines are to be decommissioned. Leaving pipelines in-situ option is preferable due to less environmental impact - but the question is "How clean is clean in the subsea pipeline?". The tool that can sampling contaminants has been therefore developed. The contaminant levels will determine whether further cleaning is required as part of decommissioning process.
The collection of samples from pipeline internal surface can be achieved by deploying a "Sampling Pig". The sampling pig is driven by pressure to various locations for sample gathering each point. The samples are then sent to laboratory analysis to determine the quantity of contaminants which may be harmful to the environment.
The pig utilizes a drilling mechanism to obtain the samples. It will also record various data including distance, time, pressure, orientation, photo, video and numbers of samples. The tool is self-learning and makes decisions by itself in various conditions based on continuous input references and measurement of motor load current.
The tool was developed to be mechatronic pig that was self-contained and could detect the pipeline surface based on the measurement of motor load current in the firmware. It was programmed to be self-learning and to autonomously make decisions in various conditions based on previous and continuous input references. The intelligent mechanisms and limit sensors could determine drilling depth and ensure the pipeline wall would not penetrated.
The developed sampling was tested in pilot facilities. It could pass 3D pipe bends and function as designed. The sampling was made at the determined locations. 12 samples were kept separately in water-proof containments inside the pig assembly. After sampling operation, samples were retrieved and collected separately. All the collected data were retrieved to a computer to analyze the function and compare to the retrieved samples.
The Intelligent Sampling Pig for 14″ pipeline was therefore successfully developed and tested in the pilot facilities. The way forward of this development is to conduct field trial in the Gulf of Thailand in 2019-2020.
The success of this work allows pipeline operators and/or regulators to evaluate the subsea pipelines that would otherwise require people e.g. saturation divers to access and take samples from the in-situ pipelines so as to make decision if further cleaning or decontamination is required. This sampling pig can then answer the question "How clean is clean in the subsea pipeline?" in the conditions that human cannot access practically and economically.