巴西国家石油公司

Uncontrolled drill-string vibrations can lead to loss of productivity, with fatigue failure being a major factor that can lead to the rupture of these structures. The main contribution of this paper is to propose a probabilistic model to take into account uncertainties associated with the bit-rock interaction parameters, system parameters, and fatigue properties and evaluate its impact in multiaxial fatigue factors. To test the proposed methodology, stress signals are obtained from a coupled axial-torsional drill-string model, which is calibrated with experimental data. Two multiaxial fatigue models are considered, and, for the configurations analyzed, the model proposed by Findley is more conservative than the one proposed by Papadopoulos. Regarding uncertainties, system parameters have more influence in regions with a greater tendency for occurrence of stick–slip oscillations, and fatigue properties uncertainties are more important in regions with lower oscillations.

This work presents an atmospheric-pressure protocol for generating and characterizing cyclopentane hydrate slurries. Water-in-oil emulsions containing 30 and 40

Steam reformer furnaces for large-scale hydrogen production in the petrochemical industry consist of a set of catalyst tubes made from state-of-the-art centrifugally cast heat-resistant modified HP-Nb or HP-NbTi stainless steel. These tubes are designed for a typical lifespan exceeding 100,000 hours, usually limited by creep damage. Currently, continuous service times can exceed 200,000 hours due to improvements in manufacturing methods, alloying additions, and confidence in nondestructive testing. Long-term in-service exposure to temperatures up to 1000 °C and internal pressures of 1-5 MPa presents severe operating conditions that lead to microstructural evolution. The relationship between creep and aging is indirect, but periodic assessment of microstructural evolution during operation provides important information for residual creep life assessment. This study proposes a general microstructural classification criterion for Nb-modified and Nb-Ti micro-alloyed HP alloys based on six characteristic aging states derived from systematic microstructural observations of tubes from different furnaces, manufacturers, and service histories, with aging times ranging from 70,000 to 135,000 h. Aging states are closely related to service temperatures, with limited dependence on operating time. After approximately 5000 hours of operation, the aging states are defined and remain in that configuration until the end of the tube’s service life. During scheduled shutdowns, the proposed criterion can be used as a basis for a comprehensive industrial procedure for nondestructive examination of extraction replica by optical microscopy. Complementary characterization of interdendritic phases and secondary precipitates was carried out using scanning and transmission electron microscopy, respectively. Long-term creep data obtained under different stress levels at 900 °C, 950 °C, and 980 °C further demonstrate a strong correlation between creep behavior and aging state, reinforcing the applicability of the proposed classification for life cycle assessment methodologies.

Abstract This paper presents a real-time methodology for recognizing operational events in oil wells by integrating multivariate time-series segmentation with hybrid classification and novelty detection techniques. A 1D U-Net architecture is used to segment sensor data streams and isolate candidate event windows, which are then analyzed by an ensemble of binary classifiers trained to identify known production behaviors such as valve operations, spurious closures, severe slugging, and hydrate formation. To address the limitations of deep learning models, particularly their tendency to become overconfident on unseen events, and the noise sensitivity of statistical distance measures, the strategy incorporates Mahalanobis distance scoring computed in both the raw feature space and the low-dimensional latent space from an autoencoder. The resulting hybrid decision function increases robustness and generalization across a wide range of operating conditions. Experimental validation using the publicly available 3W dataset along with proprietary field data shows that latent-space Mahalanobis scoring improves novelty detection by an average of 17%, achieving more than 96% detection for critical events and raising the detection of challenging patterns such as Rapid Productivity Loss from near-zero accuracy with classifiers to 67.5%. The methodology also preserves strong performance on known-event classification, with binary classifiers exceeding 90% accuracy in most categories and U-Net segmentation delivering consistent event boundaries with 94% mean Intersection Over Union (IOU). These results demonstrate the suitability of the proposed approach for real-time operational monitoring, providing early warnings, reliable recognition of both known and novel events, and practical deployment potential in production environments.

Carbonate scaling in the Brazilian pre-salt oil production systems represents a challenging flow assurance issue driven by the release of CO 2 caused by head loss. This reduction in pressure causes CO 2 degassing, increases the pH and thereby promotes the CaCO 3 precipitation. Recent studies indicate that scaling rates intensify with the inherent flowing fluid turbulence. However, this phenomenon has not been comprehensively studied at elevated temperatures, pressures, and high CO 2 content, typical of presalt subsurface environments. This study uses a batch reactor equipped with a rotating cage system (according to the ASTM G184 standard) to investigate the effect of fluid dynamics on CaCO 3 scaling at up to 80 degrees C, 70 barg, different levels of turbulence and shear stress, being subjected to the effects of CO 2 degassing. Analyses were conducted using 3D profilometry, gravimetry, photomicroscopy, SEM, XRD, and Rockwell C scratch tests. The results reveal that, under oil well conditions, the turbulence distinctly influences the scaling rates compared to bench experiments (room temperature, atmospheric pressure, and without dissolved CO 2 ). What distinguishes the results of this study from other works is the appearance of a reversal point at sufficiently high turbulence-that is, the scaling rates begin to decrease with increased turbulence-still within the pre-salt oilwell operation range. The material adhered to the rotating cage coupons was investigated to understand this phenomenon, identifying that the calcium carbonate polymorphs contribute to this reversal. (c) 2025 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).