Casing Wear Evaluation from Small-Scale Test
Authors: Moura E. I. F. , Rosa L. R. , Moraes J. O. , Riente A. F. , Percy J. G. , Franco S. D. 
Published: October 2023

During drilling operations, there is contact between the tool joints (TJs) of the drilling string and the well casing. This interaction, which occurs in the presence of drilling fluid and abrasive particles detached from the well walls, can lead to excessive wear of these components. In the case of the casing, this wear is known as casing wear (CW), a phenomenon that has been a continuous concern in the development of oil and gas fields. This is because CW is related to implementation costs and has the potential to lead to catastrophic outcomes if it results in ruptures or well collapse (Thomas, 2001). To reduce casing wear and prolong the lifespan of TJs, hardbandings are deposited on the latter. However, hardbandings are typically made of ferrous alloys, containing hard phases in their microstructure (carbides and/or borides) (Cernocky and Paslay, 1990), and it is crucial in the material selection to balance between the protection offered to the TJ (which should be high) and the wear generated on the casing by the hardbandings (which should be low).

Furthermore, challenges lie in controlling field variables and the time needed to assess wear conditions. These factors may result in longer decision-making processes crucial for the industry. Given these factors, there is a possibility to develop, in a laboratory environment, a full-scale test condition that can experimentally study material wear, based on controlling variables and utilizing accelerated testing parameters. However, such a full-scale setup requires greater financial investments, primarily due to equipment development, specialized labor, physical space, and in some cases, the use of full-sized test pieces. Therefore, despite its validity, this experimental study condition may not always be attractive. A second option often employed in laboratory studies involves conducting tests at a reduced scale, which significantly narrows down and controls the parameters influencing wear, making this test condition valid and practical for obtaining faster and more accurate results.

Therefore, the study of CW, especially through experimental testing, is relevant to the industry as predicting casing wear is crucial to ensure well integrity. In this context, this work will present the steps for the development and qualitative validation of the reduced-scale test based on the full-scale API 7CW test. The qualitative test comparison aims to compare the wear factor (WF) curve behavior over time in a way that develops an accessible, fast testing methodology capable of ranking materials and severe abrasive wear conditions. The aim of this work is not to develop a test that replaces the one proposed by the API 7CW standard, considering the importance of obtaining quantitative parameters closer to field conditions inherent to the full-scale test conditions. Thus, this work proposes the development of an accelerated testing methodology for conditions proposed by the API 7CW standard that allows, in a practical way, the selection of materials and the evaluation of different severe wear testing conditions.