{'fraction_non_alphanumeric': 0.0170316301703163, 'fraction_numerical': 0.0, 'mean_word_length': 4.792253521126761, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
A Laboratory Study of the Effect of Casing Pipe Roughness to Cement Plug Integrity


 Cement holds the most critical role for providing long-term zonal isolation for permanent abandonment phase. The loss of cement integrity is undesirable as it may threaten the surrounding environment and safety on the surface. The quality of cured cement is commonly associated with the properties of cement material and cement placement in the wellbore. However, there are still limited investigations that link these factors specifically to the sealing ability of cement plug, especially with the lack of proper equipment in the past.
 In the present work, a small-scale laboratory setup has been constructed to test the sealing performance of a cement plug. The cement plug is contained inside a test cell, connected to a pressurizing system and placed inside a heating cabinet. Consequently, the test can be simulated at downhole conditions in a controlled manner. By using this setup, it is possible to monitor the minimum pressure required for the plug to fail and the gas leak rate.
 Two different cement systems, neat- and silica-cement, were prepared as plugging materials. Both cement systems are placed inside pipes with three different levels of surface roughness and then tested. Results show that the inner surface roughness of the pipes affects cement plug sealing significantly, and the effect is independent of the type of cement systems. Plugs placed inside a very-rough pipe significantly reduce the gas leak rate. Our results also show that an immediate gas leak occurs in all samples from leak paths formed at the cement/steel interface.