A Discussion on Premium Connection Qualification for CCS/CCUS Well

Abstrak

This work aims to depict the different aspects that need to be considered for the evaluation of threaded OCTG connections used in CCS (Carbon Capture and Storage) projects. The paper also shows the different stages followed by the authors to develop a methodology that could be used to conduct such evaluation.

Considering that the evaluation of threaded connections used in wells should take into loads, pressures and temperatures expected during injection and a less likely survival case, the authors have found two methods to physically evaluate the specimens and a numerical analysis to investigate extreme load cases.

Numerical methods allow a quick simulation of the exposure to the survival loads by imposing sudden changes in temperatures and combined loads and pressures. In such a way, it is possible to understand the mechanical behavior within a define perimeter and be prepared for the physical testing.

The physical evaluation, also known as Full Scale Testing, consider the two above-mentioned scenarios: injection in steady conditions and survival loads. For the steady conditions the evaluation of a connection following a test load envelope at sub-zero temperatures in the range of -25°C to -35°C covers most of the known scenarios. For the survival loads, it is necessary to demonstrate with a sudden exposure to freezing temperatures around -70°C that the connections can both maintain structural integrity and, subsequently, a sealing response under normal operation.

The methodology described by the authors combining numerical analysis and full scale testing was applied in real cases. It demonstrated its suitability for the evaluation of OCTG threaded connections under the extreme low temperatures that could be seen during the operation of the well in Carbon Capture and Storage projects. Different materials were also evaluated during the preliminary stages as well as with the final procedure demonstrating its applicability to different types of materials from carbon steels to martensitic alloys.

Considering that there is no standard in the industry capable of covering all the potential scenarios of the carbon storage well, the methodology presented herein can be used a starting point for future projects.