Failure pressure calculation of fracturing well based on fluid-structure interaction

Oil and gas pipeline failure and leakage can seriously damage people's lives and the ecosystem. The prediction of failure pressure for pipelines with damage is one of the most important and challenging tasks faced by industry, which affects the assessment of pipeline safety. Previous studies widely used industrial models or the finite element (FE) method to predict the failure pressure. However, the industrial models may give limited information, and the FE method has much heavy computation burden. In this work, three machine learning models - artificial neural network (ANN), XGBoost (XGB) and CatBoost (CAT) are developed for forecasting the failure pressure of pipelines with defects. Firstly, the simulation results of the FE method are validated by real failure pressure and compared with the calculation results of industrial models (ASME-B31G and DNV). Then 180 pipeline samples including pipeline attributes and defect sizes collected from real in-line inspection data in a pipeline company and the corresponding FE simulation results of failure pressure of these 180 defective pipelines are used for the training and testing of the machine learning models. The results show that the simulation accuracy of the FE method is higher than the calculation accuracy of the industrial models, and the FE simulation results are suitable to be the outputs of machine learning models. The three machine learning methods all provide satisfactory prediction accuracy in failure pressure. Specifically, CAT is the best machine learning method in this study for its lowest relative error (3.11% on average), mean absolute error (0.53), root mean square error (0.78) and highest coefficient of determination (R2) up to 98% in testing. Moreover, the machine learning models present better performance on average relative errors compared to the industrial models. CAT shows higher accuracy than the industrial models and FE simulation on minimum and average relative errors. Finally, the prediction result of CAT is used to discuss the effect of input features on failure pressure of pipelines, which demonstrates that the importance of features follows the order of pipeline thickness > pipeline outside diameter > defect depth > defect length > defect width. Once the above machine learning methods are used in industry, more and more real data will be collected to train a model and make it more accurate. In this way, these methods will provide an efficient way to evaluate the safety of defective pipelines. In addition, the failure pressure of pipeline could be estimated to help operators figure out a pipeline condition and further prioritize the pipelines for maintenance.

An investigation of pore water pressure and consolidation phenomenon in the unfrozen zone during soil freezing

Effects of effective stress changes on permeability of latrobe valley brown coal

One significant factor affecting pore pressure prediction is choosing a method of calculation. If we choose the inappropriate method, the result may not refl ect not only pore pressure condition in an area, but also geological processes operating in the whole basin. In this research, two methods are applied to wireline-based pore pressure calculation in the Peciko Field: the Eaton Method and the Soil Mechanics Method. The results of the calculation show a signifi cant difference between these methods. The Eaton Method resulted in reservoir-shale pressure discrepancy (by over-predicting the reservoir pressure) at shallower depth, and reservoir-shale pressure equilibrium at depth. On the contrary, the Soil Mechanics Method resulted in reservoir-shale pressure equilibrium at shallower depth and an under-predicting at depth. It seems that, in terms of processes operating in this fi eld which affect pore pressure regimes, i.e. lateral reservoir drainage and rapid mud-dominated deltaic sedimentation, the result of the Eaton Method is more plausible than that of the Soil Mechanics Method. This research also reveals an important inference: if there is a pressure discrepancy, then it is likely that a hydrodynamic condition is present.

The Sidoarjo mud volcano is a geological disaster which still erupting after 16 years located in a densely populated. The eruption of Sidoarjo mud volcano is the longest continous disaster that Indonesia has ever experienced. It is known that there is overpressure in subsurface that propagated to the surface throught faults. However, the overpressure generation leads to the increase of pore water pressure, so the effective soil stress decreases. This study aims to estimate the change of pore water pressure and effective stress on the subgrade of Sidoarjo mud volcano due to the subsurface pressure. Furthermore, this study considers the existing embankment and excess pore water pressure due to the consolidation process using Finite Element Method. The results show high active pore water pressure in these area is around -580 kPa, due to the consolidation process is -372 kPa and the contribution of subsurface pressure is -208 kPa. The anomaly of effective stress occur from a depth of -13 m to -30 m. Thus, the reduction of effective stress is around 6%-56% from the ideal conditions with the largest reduction occurred at a depth of -30 m.

<sec>Fluid-structure interaction pipeline systems are extensively adopted to transfer matter, energy and momentum, which are widely used in various fields. Due to the fluid-structure interaction effect, the pipe wall proves to produce strong vibration and noise under fluid action, which has a serious influence on the safety and concealment of the equipment, even leading to serious damages. Therefore, it is of great significance to study the vibration characteristics of fluid-structure interaction pipeline and methods to reduce the vibration of pipeline both in theory and in practice. </sec><sec>Phononic crystal can suppress the propagation of elastic waves in a specific frequency range by their special band-gap characteristics, which have wide application prospects in the field of vibration and noise reduction. Especially, the band gap characteristics of phononic crystal pipeline used to design fluid-structure interaction pipeline system have been widely studied, thus providing a new technical approach to reducing the vibration and noise of the pipeline. </sec><sec>In this paper, based on the theory of phononic crystal, the vibration transfer characteristics of the Bragg phononic crystal pipeline under fluid-structure interaction are studied. Combining the transfer matrix method and the finite element method, the band structure and band gap characteristics are calculated. Using the finite element method, the vibration characteristics of the phononic crystal pipeline under fluid-structure interaction effect, the shock excitation of pipe wall and the shock excitation of the fluid are considered. The influence of the fluid-structure interaction on the vibration transmission characteristics of the phononic crystal pipeline is also analyzed. </sec><sec>The research results indicate that when the fluid velocity in the fluid-structure interaction pipeline system is small the Bragg phononic crystal pipeline has a good attenuation effect on the shock excitation of pipe wall in the band gap range, and that when the fluid velocity increases the fluid-structure interaction effect becomes significant, the attenuation effect becoming weaker. Bragg phononic crystal pipeline has a certain attenuation effect on the pipe wall vibration caused by the fluid shock excitation near the band gap. The research results are expected to be able to provide a technical reference for the vibration control of pipeline systems under fluid-structure interaction conditions. </sec>

We propose a non-intrusive numerical coupling method for transient fluid-structure interaction (FSI) problems simulated by means of different discretization methods: smoothed particle hydrodynamics (SPH) and finite element (FE) methods for the fluid and the solid sub-domains, respectively. As a partitioned coupling method, the present algorithm can ensure a zero interface energy during the whole period of numerical simulation, even in the presence of large interface motion. In other words, the time integrations of the two sub-domains (second order Runge---Kutta scheme for fluid and Newmark integrator for solid) are synchronized. Thanks to this energy-conserving feature, one can preserve the minimal order of accuracy in time and the numerical stability of the FSI simulations, which are validated with a 1D and a 2D trivial numerical test cases. Additionally, some other 2D FSI simulations involving large interface motion have also been carried out with the proposed SPH---FE coupling method. Finally, an example of aquaplaning problem is given in order to show the feasibility of such coupling method in multi-dimensional applications with complicated structural geometries.

Modeling 3D finite element analysis of a semi-elliptical crack on stress corrosion cracking of API X52 pipeline

Partitioned solution strategies for coupled BEM–FEM acoustic fluid–structure interaction problems

This work shows the effect of artificial aging on the mechanical properties of an API 5L Gr. B steel that undergoes different artificial aging times (0, 500, 1250, and 1500 h). Among the mechanical properties studied are the stress–strain curve, yield stress, and ultimate tensile stress. In addition, the parameters from the Ludwik–Hollomon equation, which are the parameter (K) and the work-hardening coefficient (n), are obtained for the true stress–strain curve. Once the true stress–strain curve is plotted, a 3D model of a transverse crack in a pipeline is proposed. The crack defects are straight, and the finite element method (FEM) is used to determine its behavior at different sizes in order to estimate the failure pressure. It can be said that the mechanical properties (stress–strain curve) increase for an aging time of 500 h compared to the air condition because of the over-aging process, something that is well recognized in the literature. In general, past the over-aging condition, with an increase in the aging time, the mechanical properties tend to decrease. This behavior is similar for the failure pressure. The FEM is sensitive to the decrease in mechanical properties along with the true stress–strain curve.

The purpose of this paper is to understand the dynamic response of rubble-mound breakwater with seawater-breakwater-foundation interaction after a real earthquake shock. This study employs the Arbitrary Lagrangian Eulerian approach and dynamic finite element method, in which the seawater and the foundation of rubble-mound breakwater are considered;then the dynamic response of rubble-mound breakwater during earthquake is simulated. It is found that the seawater-breakwater-foundation interaction does have considerable effect on residual displacements of the rubble-mound breakwater. The difference in horizontal residual displacement due to the effect of seawater-breakwater interaction is greater than that of vertical residual displacement. The vertical component of earthquake has a considerable effect on the hydrodynamic pressure on breakwater face. According to the results presented in this study, it is necessary to consider the effect of interaction for rubble-mound breakwaters seismic safety evaluation. The present research provides some guidance for the seismic design of rubble-mound breakwater. ©2016, Engineering Mechanics Press. All right reserved.

A strong-coupled method combined finite element method and lattice Boltzmann method via an implicit immersed boundary scheme for fluid structure interaction

The dynamic characteristics of a structure are modified considerably when it is immersed in a dense fluid. Dynamic interaction between fluid and structure includes the phenomenon of Fluid Structure Interaction (FSI). In the present study, transmission of vibration between two parallel plates partially immersed in a fluid is investigated considering FSI. It is assumed that the plates are clamped along their edges and the fluid is bounded between the two parallel plates to form a rigid rectangular container. Excitation of one plate by an impact load results in the response of the opposite plate. An experiment was conducted and the results were compared with the three-dimensional Finite Element Method (FEM) analysis using CAST3M. Wet dynamic displacement, the frequency of vibration of the two parallel plates with variation in the fluid level are the parameters considered in the present study. Effect of liquid free surface and viscous damping are considered. A benchmark validation from literature has been presented for the free vibration of immersed cantilever plate using CAST3M. It is observed that the damping ratio decreases with an increase in the fluid level and the displacement of the response plate increases. This study especially has been carried out towards the investigation of vibration transmission between structures partially immersed in the liquid sodium in Fast reactors. The objective of the present work is the numerical verification and experimental validation of the FEM model which would make it convenient while analyzing the vibration of immersed structures with FSI.

Flutter is one of the most known instability phenomena. This condition occurs when a given structure exhibits sustained, harmonic oscillations, sometimes leading to catastrophic events. The prediction of flutter represents a crucial point for a correct and safe design. When fluid structure interactions produce dynamic instability, flutter analyses require accurate descriptions of body deformations and aerodynamic loads. To this end, aerodynamic theories have been coupled with structural models to develop aeroelastic analysis tools, whose reliability is the results of a trade-off between the accuracy and the computational efficiency. From a computational point of view, the most efficient formulation is based on the 1D assumption, where the problem is reduced to a set of variables that only depends on the beam-axis coordinate. Besides the well-known classical beam theories, several refined kinematic models have been proposed, to study the stability of rotating blades and shafts. However, when these structures are highly deformable or the material distribution involves non-classical structural couplings, 2D and 3D solutions are still required. Within this work, we propose an advanced 1D formulation to analyse the stability of rotating structures. The higher-order beam theories are obtained using the Carrera Unified Formulation (CUF), which allows to derive, at least theoretically, an infinite number of kinematic models. The Equations of Motion (EoM) for shafts and blades include the Coriolis term and the centrifugal effects (spin softening and geometrical stiffening). For the subsonic flow regime, aerodynamic loads are defined following the unsteady strip theories proposed by Theodorsen and Loewy. For the supersonic regime, the linear Piston theory is extended to structures rotating in compressed air flow. The Finite Element Method (FEM) is used to solve the weak form of the EoM. Firstly, to evaluate the accuracy of 1D CUF elements, static and free-vibration analysis are carried out on compact and thin-walled structures of isotropic, orthotropic and functionally graded materials. Then, higher-order elements are used to study the dynamics of laminated shafts, thin cylinders, discs and blades, which rotate about the longitudinal and transverse axis. Results show the improved performance of the 1D CUF theories compared to 2D and 3D solutions. In order to evaluate the proposed aeroelastic formulation, we test different wing configurations, including thin-walled box beams. The effects of the sweep angle and the lamination scheme on flutter conditions are evaluated, and results are compared with plate solutions, experimental tests and aeroelastic analysis carried out with the Doublet Lattice Method (DLM). Moreover, comparisons between Theodorsen and Loewy aerodynamic theories are presented for a realistic rotary-wing model. In the last numerical examples, the linear Piston Theory is used to describe the dynamics of thin plates with different aspect-ratio surrounded by compressed air. For this cases, results are compared with an existing solution based on a non-linear plate theory

The integration and application of a new multi-objective tabu search optimization algorithm for Fluid Structure Interaction (FSI) problems are presented. The aim is to enhance the computational design process for real world applications and to achieve higher performance of the whole system for the four considered objectives. The described system combines the optimizer with a well established FSI solver which is based on the fully implicit, monolithic formuFlation of the problem in the Arbitrary Lagrangian-Eulerian FEM approach. The proposed solver resolves the proposed uid-structure interaction benchmark which describes the self-induced elastic deformation of a beam attached to a cylinder in laminar channel ow. The optimized ow characteristics of the aforementioned geometrical arrangement illustrate the performance of the system in two dimensions. Special emphasis is given to the analysis of the simulation package, which is of high accuracy and is the core of application. The design process identifies the best combination of ow features for optimal system behavior and the most important objectives. In addition, the presented methodology has the potential to run in parallel, which will significantly speed-up the elapsed time. Finite Element Method (FEM), Fluid-Structure Interaction (FSI), Multi-Ojective Tabu search (MOTS2). Copyright © 2013 Tech Science Press.