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Electric Expansion Machine

The objective of this project was to develop a low power process for sealing perforations in production oil well casings. The concept involved expanding a smaller diameter pipe, previously placed loosely inside the casing, until it squeezed against the casing’s bore. Continuous high pressure contact between the two pipes was intended to ensure that multiple small radial perforations in the casing would be covered and hence sealed. The chosen method had to be capable of performing the expansion on 10m lengths of pipe and at positions several thousand meters from the topside entry point into the well casing.
 

The prototype was only required to operate within a laboratory environment rather than down an actual well. This decision provided the client with a cost effective evaluation on which to base a commitment to develop a production tool capable of operation within a real well environment. XL assumed complete responsibility for this three phase project, undertaking all design, assembly, testing and reporting. The project finished with the successful hand over of a fully automated machine capable of expanding full scale test pieces. Speed, torque and force monitoring also demonstrated that the process was operable within allowable power limits.

Phase 1 involved a paper study of existing pipe expansion technologies and ended with the construction of a hand powered test rig and the evaluation of a tool that had already been developed for the expansion of heat exchanger tube ends. The rig was instrumented with several strain gauges and a torque sensor to monitor operating loads (via a National Instruments PC based data acquisition system running Labview software). The tests demonstrated the physical capability of the existing tooling and provided data better prediction of full scale loadings and power consumption.

Phase 2 involved building a second unpowered expansion tool. Whilst the first one had an inadequate expansion ratio, the second one incorporated several novel features to the original basic design. These were to allow theoretical expansion ratios in excess of 20% compared to just 2% from the original tool. After it’s manufacture, a second round of testing confirmed that the new features did indeed yield the necessary functional improvements. Once gain, data logging allowed a reappraisal of power requirements from the new process and demonstrated the start-up load factors that would be essential in the sizing process for the drive system of the fully automated machine that was to follow.

Finally, in Phase 3, a fully automated and instrumented three axis machine was built and tested. The linking of a Parker AC servo-control drive system with a Siemens inverter allowed both fully automatic and manual machine operation and the generation of complex expansion profiles. It could produce a series of axially spaced short sealing patches or just one continuous and fully expanded patch. The transition distance between the unstretched and stretched pipe could also be controlled to minimise stress concentrations. On this rig the test pieces were constrained by custom-made load and torque sensors which maximised data acquisition at minimum cost.