Premium Connections Fatigue Assessment Methodology Fit for Multi-stage Hydraulic Fracturing Operations
Published: 15 September 2021
Abstract: Objectives/Scope During casing installation and drilling operations, Oil Country Tubular Goods (OCTG) strings are often rotated inside deviated wellbores, generating cyclic bending loading that could lead to fatigue damage. This phenomenon has been previously studied and understood. The completion of multistage fractured horizontal wells (MFHW) involves tens of fracture operations (an ever growing number) as part of the stimulation program in order to maximize production. These fracture operations involve a combination of cyclic pressures and tension loading in the production casing, through which they are conducted, with maximum loads often repeatedly reaching the upper limit of the pipe body performance ratings. This process of cyclic pressure and tension loading near the upper limit of the pipe body performance is the subject of this work. In unconventional plays, where MFHW are the standard approach, both cyclic bending due to rotation and cyclic burst and tension due to multiple fracturing operations are applied on OCTG strings. This combination may lead to a failure mode in which a crack opens due to material fatigue during rotation or fracturing cycles, and subsequently propagates (to failure) during the demanding fracturing stages. Methods, Procedures, Process As it would be expected during any technological evolution, the industry has seen an increase in casing failures during hydraulic fracturing, often not explainable by the current understanding of loads scenarios present in wellbores. Some of these events could be associated to the failure mode described above. Despite the potential risk introduced by this failure mode, to date, there is no standardized testing methodology available to evaluate the resistance of pipes and connections to this loading sequence. Results, Observations, Conclusions In order to cover this gap, a testing sequence aimed at replicating actual operating conditions was developed and deployed by the authors. This includes evaluating the resistance of a premium connection to rotation through a curved hole, and subsequent burst and tension cycles. The methodology and results are presented in this paper. Novel/Additive Information Through this testing approach, operators, manufacturers, and laboratories alike, can ensure the performance and reliability of OCTG, which are key elements in the well construction process. As main observations, all tested specimens successfully passed this very demanding testing sequence, aimed to replicate operative conditions during installation and subsequent stimulation operation.
Keywords: upstream oil & gas / rotation / petroleum engineer / premium connection / multistage fracturing / multi-stage hydraulic fracturing operation / loading / axial load / hydraulic fracturing / connection fatigue assessment methodology fit
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