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To address the challenges associated with difficult casing running, limited annular space, and poor cementing quality in the completion of ultra-deep wells, the extreme line casing offers an effective solution over conventional casings. However, due to its smaller size, the joint strength of extreme line casing is reduced, which may cause failure when running in the hole. To address this issue, this study focuses on the CST-ZT F139.7 mm x 7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint, taking into account the influence of geometric and material nonlinearities. A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse load. The model investigates the stress distribution of each thread tooth subjected to various tensile forces and external pressures. Additionally, the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental approaches. The findings reveal that, under axial tensile load, the bearing surface of each thread tooth experiences uneven stress, with relatively high equivalent stress at the root of each thread tooth. The end thread teeth are valuable spots for failure. It is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth sequence. Under external pressure, the circumferential stress is highest at the small end of the external thread, leading to yield deformation. The tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7% compared to the analytical and experimental values, proving the reliability of the finite element model. The tensile strength of the joint is 3091.9 kN. Moreover, in terms of anti-collapse capability, the joints demonstrate higher resistance to collapse compared to the casing body, which is consistent with the test results where the pipe body experiences collapse and failure while the joints remain intact during the experiment. The failure load of the casing body under external collapse pressure is 87.4 MPa. The present study provides a basic understanding of the mechanical strengths of extreme line casing joint. [ABSTRACT FROM AUTHOR]

Abstract During hydraulic fracturing, there has been little research on casing tensile stress distribution from the tilting area to the horizontal area in the whole string. In order to study the casing tensile stress distribution in the bending sections during hydraulic fracturing, a three-dimensional finite element mechanical analysis model of casing–cement–formation in the bending sections was established. The analysis showed that: When the cement of tilting area was missing, the casing tensile stress decreased with in situ stress difference increasing, and the casing tensile stress increased when the middle area or the target area was missing. When the internal pressure of casing increased continuously, the casing tensile stress decreased first and then increased, and the casing internal pressure was 20 MPa, which was the minimum point. When the casing internal pressure was lower than 20 MPa, the casing tensile stress decreased with Poisson’s ratio of cement increasing. When the casing internal pressure was higher than 20 MPa, the casing tensile stress increased with Poisson’s ratio of cement increasing. Compared with the case where the temperature difference was ignored, the temperature difference below 5 ℃ had little influence on casing temperature stress; however, the temperature difference above 5 ℃ had significant influence on casing temperature stress. Fracturing in the formation where Young’s modulus of elasticity of rock was higher than 15 GPa could reduce the stress failure of casing tensile. The research results had a certain guiding significance for the prevention of casing tensile failure in the bending sections.

During hydraulic fracturing, there has been little research on casing tensile stress distribution from the tilting area to the horizontal area in the whole string. In order to study the casing tensile stress distribution in the bending sections during hydraulic fracturing, a three-dimensional finite element mechanical analysis model of casing–cement–formation in the bending sections was established. The analysis showed that: When the cement of tilting area was missing, the casing tensile stress decreased with in situ stress difference increasing, and the casing tensile stress increased when the middle area or the target area was missing. When the internal pressure of casing increased continuously, the casing tensile stress decreased first and then increased, and the casing internal pressure was 20 MPa, which was the minimum point. When the casing internal pressure was lower than 20 MPa, the casing tensile stress decreased with Poisson's ratio of cement increasing. When the casing internal pressure was higher than 20 MPa, the casing tensile stress increased with Poisson's ratio of cement increasing. Compared with the case where the temperature difference was ignored, the temperature difference below 5 ℃ had little influence on casing temperature stress; however, the temperature difference above 5 ℃ had significant influence on casing temperature stress. Fracturing in the formation where Young's modulus of elasticity of rock was higher than 15 GPa could reduce the stress failure of casing tensile. The research results had a certain guiding significance for the prevention of casing tensile failure in the bending sections. [ABSTRACT FROM AUTHOR]

Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Collapse failure under external pressure is one of the common failure forms of casing. Much research has been performed on the casing body, but few on the threaded connection, in view of the general belief that the threaded connection has a thicker wall and larger collapse strength than the casing body. However, under external pressure, the sealing capacity of a worn casing connection will decrease due to deformation of the sealing structure, so the influence of sealing ability should be considered to determine the collapse strength of casing. In this paper, we established a three-dimensional finite element model of a 7" crescent-worn casing connection and calculated the collapse strength of the connection under different wear depths. Meanwhile, the stress distribution characteristics on the sealing surface were obtained and the influence of wear on the sealing performance of the casing connection under external pressure was analyzed. The results showed that when the wear rate exceeds a certain value, the collapse strength of the connection based on sealing integrity was lower than that of the casing body. Based on these, a collapse strength model for a 7" crescent-worn casing connection considering sealing integrity was developed and a safety evaluation method of the collapse strength of the worn casing string was proposed. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents an approach for probabilistic design and safety assessment of sandwich pipelines under external pressure. The methodology consists of the categorisation of sandwich pipeline collapse strength models based on interlayer adhesion conditions. The models are validated by comparing their predictions against collapse test data of sandwich pipelines. The accuracy of the strength models and their prediction uncertainty are used to select the best model in each category. Regarding interlayer adhesion categories, uncertainty propagation of models' predictions over a wide range is assessed by the Monte Carlo simulation method. The proposed methodology is demonstrated using a case study of a sandwich pipeline with adequate probabilistic modelling of the basic random variables. Different limit states are defined for three categories of sandwich pipelines, based on which structural reliability indices are estimated. In employing the First Order Reliability Method for sensitivity analysis, the importance of basic variables of the limit states is evaluated. Later, a parametric analysis is conducted, presenting reliability variations for several design and operational scenarios of sandwich pipelines. Finally, to achieve a uniform level of structural reliability of sandwich pipelines, a few suggestions are provided, and practical partial safety factors are calculated. The results of the present analysis can provide guidance on the probabilistic design and operational safety assessment of sandwich pipelines. [ABSTRACT FROM AUTHOR]

This paper assesses the uncertainty in the collapse strength of sandwich pipelines (SPs) under external pressure predicted by various strength models in three categories based on interlayer adhesion conditions. First, the validity of the strength models is verified by comparing their predictions with sandwich pipeline collapse test data and the corresponding model uncertainty factors are derived. Then, a parametric analysis of deterministic collapse strength predictions by models is conducted, illustrating insights of models' behavior for a wide range of design configurations. Furthermore, the uncertainty among different model predictions is perceived at different configurations of outer and inner pipes and core thicknesses. A case study of a realistic sandwich pipeline is developed, and probabilistic models are defined to basic design parameters. Uncertainty propagation of models' predictions is assessed by the Monte Carlo simulation method. Finally, the strength model predictions of sandwich pipelines are compared with that of an equivalent single-walled pipe. [ABSTRACT FROM AUTHOR]

Submarine hulls are pressure vessels for which excellent structural integrity under underwater pressure loads is essential. The use of light-weight materials contributes to reduced fuel consumption, improved speed, and increased payload while strength properties are retained. The focus of this paper is on the collapse behavior of a filament-wound cylindrical structure that serves as the main hull of a submarine subject to hydrostatic pressure loads. This paper presents a computational modelling approach for the prediction of the collapse behavior mechanism using a commercial finite element (FE) solver. The collapse strength obtained from the numerical model corresponded closely to available experimental data. The composite and aluminum material models were compared and the effects of stacking angle and thickness portion in the ply sequence on collapse strength were investigated. The advantages and disadvantages of available design codes (i.e., American Society of Mechanical Engineers (ASME) BPVC-X and National Aeronautics and Space Administration (NASA) SP-8007) were reviewed by direct comparison with numerical results. It is concluded that the application of effective engineering constants for the prediction of the collapse pressure of submarine hulls may be feasible. [ABSTRACT FROM AUTHOR]

In the process of thermal recovery of heavy oil, the casing in oil production wells is subjected to complex stress conditions, which may cause potential damage and affect the lifecycle of the casing. The factors influencing the casing instability and the mechanism of the process in thermal production wells need to be comprehensively researched, particularly in the case where oil extraction is accompanied by sand production. In this paper, the authors have applied the three-dimensional finite element method to simulate the casing instability characteristics in the sand production section of a thermal recovery well. We have also analyzed the effect of sand production, perforation parameters, and the casing strength parameters on the axial and circumferential instability of the casing. The results show that sand production can cause a significant decrease in the lateral support of the casing and greatly reduce the buckling resistance of the casing in a thermal horizontal well. With increase in perforation diameter and perforation density, the critical buckling load of the casing decreases. On the other hand, the buckling load is less affected by the perforation phase. When the combination of the perforation density and perforation phase angle results in a bigger number of perforation holes in the row, it can significantly reduce the casing collapse strength and increase the risk of circumferential instability. The research results provide a theoretical basis in the design of casing in horizontal sections of thermal production wells. [ABSTRACT FROM AUTHOR]

This paper presents an approach for probabilistic design and safety assessment of sandwich pipelines under external pressure. The methodology consists of the categorisation of sandwich pipeline collapse strength models based on interlayer adhesion conditions. The models are validated by comparing their predictions against collapse test data of sandwich pipelines. The accuracy of the strength models and their prediction uncertainty are used to select the best model in each category. Regarding interlayer adhesion categories, uncertainty propagation of models’ predictions over a wide range is assessed by the Monte Carlo simulation method. The proposed methodology is demonstrated using a case study of a sandwich pipeline with adequate probabilistic modelling of the basic random variables. Different limit states are defined for three categories of sandwich pipelines, based on which structural reliability indices are estimated. In employing the First Order Reliability Method for sensitivity analysis, the importance of basic variables of the limit states is evaluated. Later, a parametric analysis is conducted, presenting reliability variations for several design and operational scenarios of sandwich pipelines. Finally, to achieve a uniform level of structural reliability of sandwich pipelines, a few suggestions are provided, and practical partial safety factors are calculated. The results of the present analysis can provide guidance on the probabilistic design and operational safety assessment of sandwich pipelines.

The stiffened panel under longitudinal compressive load is simulated in finite element (FE), where the two-span/bay model with periodic boundary condition is applied to consider the effect of the adjacent members. To obtain reliable numerical results, the FE modeling technology is calibrated by experimental results. The effect of the stiffener type on the collapse mode and ultimate capacity is discussed based on numerical results. Using the numerical results, closed-form expressions are developed by the regression method to estimate the load-carrying capacity of the stiffened panel. To cover most of the geometrical range of the members, the adopted dimensions of the specimens are based on statistical data of actual ships. The variables in the developed formula include the plate slenderness and column slenderness, which can consider the effect of the stiffener types by using a separate group of design samples for different types of stiffeners. To verify the approximating precision of predictions, the collapse strength of the stiffened panels assessed by the developed formula is compared with that obtained by the existing methods, FE analyses, International Association of Classification Societies-Common Structural Rules (IACS-CSR) requirement, and experiments. [ABSTRACT FROM AUTHOR]

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Submarine hulls are pressure vessels for which excellent structural integrity under underwater pressure loads is essential. The use of light-weight materials contributes to reduced fuel consumption, improved speed, and increased payload while strength properties are retained. The focus of this paper is on the collapse behavior of a filament-wound cylindrical structure that serves as the main hull of a submarine subject to hydrostatic pressure loads. This paper presents a computational modelling approach for the prediction of the collapse behavior mechanism using a commercial finite element (FE) solver. The collapse strength obtained from the numerical model corresponded closely to available experimental data. The composite and aluminum material models were compared and the effects of stacking angle and thickness portion in the ply sequence on collapse strength were investigated. The advantages and disadvantages of available design codes (i.e., American Society of Mechanical Engineers (ASME) BPVC-X and National Aeronautics and Space Administration (NASA) SP-8007) were reviewed by direct comparison with numerical results. It is concluded that the application of effective engineering constants for the prediction of the collapse pressure of submarine hulls may be feasible.

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effect of ovality length on imperfect sandwich pipes is investigated using the finite element method in the scenario of local buckling under external pressure. First, the finite element model of the imperfect sandwich pipelines is established in ANSYS and is validated by comparing the results from numerical simulation with those from experiments. Then, the effect of ovality features on the collapse strength of the sandwich pipes is studied. At last, based on the calculation results from 1200 cases, a prediction equation is proposed to represent the relationship between collapse strength and ovality length of imperfect sandwich pipes. Good agreement is achieved between the proposed equation and the calculation results, leading to the conclusion that the proposed simplified model can be an efficient tool in the evaluation of the local collapse strength of subsea sandwich pipes under external pressure.

Copyright of China Petroleum Machinery is the property of China Petroleum Machinery Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Petroleum Machinery is the property of China Petroleum Machinery Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Petroleum Machinery is the property of China Petroleum Machinery Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • A 'large unit cell' approach for multilayer BCC lattice structure is proposed. • Collapse stress and corresponding strain are analyzed for multilayer structures. • Array configuration has a great influence on multilayer structures. Abstract The body-centered cubic (BCC) lattice, as a type of cellular lattice structure, has been widely researched with the representative volume element (RVE) homogenization method. This ideal theoretical approach requires infinite unit cells in a structure, which is unrealistic and unfeasible with the current manufacturing technology. In this paper, a new theoretical approach considering the effect of array configuration is developed to predict the strength of a multilayer BCC lattice structure. First, the compression behavior of the multilayer BCC lattice structure is analyzed by finite element method (FEM) simulation. Then, an analytical model inspired by the combination of the derived stress-strain curve and the specific contour is built. Predictions of the compression strength are compared with the FEM results for multilayer structures with various spatial array configurations to validate the applicability of the proposed model. And, they are in very good agreement within acceptable errors. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

• The SETs made from high-strength steels have poor resistance to collapsing after expansion. • There is no correlation between the obvious degree of the Bauschinger effect and the post-expansion collapse strength. • The conclusions of the Bauschinger-effect influence drawn from various steels SETs differ from those of only one steel SETs. • The main influencing factor on the post-expansion collapse strength, residual stress, is identified. At present, there are different ideas about on the main factor influencing post-expansion collapse strength of solid expandable tubulars (SETs). In this study, three SETs with the same dimensions, which were made of 20 (Chinese grade), a twinning-induced plasticity (TWIP) and a transformation-induced plasticity (TRIP) steels, were expanded so the inner diameter increase by about 14%. The test results showed that the SETs made from high-strength steels (a TWIP and a TRIP) had poor resistance to collapsing after expansion. Through a combination of finite element method (FEM) simulations and experimental tests, the post-expansion collapse strength of three SETs were comparatively analyzed to find out the main influencing factor. After isolating the influences of geometric factors on the collapse strength, the influences of the Bauschinger effect and the residual stress on the collapse strength were studied. There was no correlation between the obvious degree of the Bauschinger effect of the three steels and the post-expansion collapse strength of the three SETs, which suggested that the Bauschinger effect was not the main factor influencing the post-expansion collapse strength. This is obviously different from the conclusion for SETs made from only one steel. The post-expansion collapse strength calculated by FEM simulations differed greatly from that of the actual measurement if the residual stress after expansion was ignored, though both were very close when the residual stress after expansion was considered. This clearly indicates that the residual stress after expansion has a significant effect on the post-expansion collapse strength and it is the main factor influencing the post-expansion collapse strength. [ABSTRACT FROM AUTHOR]

The cavitation is directly related to the safety of many large water conservancy projects. There are two types of cavitation bubbles, one is generated by the gas nucleus, called the non gas-bearing cavitation bubble, and another is generated by the gas bubble, called the gas-bearing cavitation bubble. They have significantly different collapsing characteristics. This paper studies the cavitation bubbles, generated by a high voltage pulse bubble generation system, and discusses the gas-bearing cavitation bubble's characteristics a from the aspects of the collapse process, the cycle, the size and the collapse strength. It is shown that: (1) the collapse of the gas-bearing cavitation bubbles can be divided into two types: the centripetal collapse and the bisected collapse, (2) the cycle period and the size of the gas-bearing cavitation bubble increase significantly, and the increase norm has a certain relationship with the bubble diameter ratio, (3) the collapse strength of the gas-bearing cavitation bubble decreases significantly. The larger the bubble diameter ratio, the greater the effect will be. [ABSTRACT FROM AUTHOR]

Abstract This paper derives an empirical formula for predicting the collapse strength of composite cylindrical-shell structures under external hydrostatic pressure loads as a function of geometric dimensions and layered angles, where the effects of initial manufacturing imperfections are implicitly taken into account. A series of experiments are undertaken on [ ± θ / 90 ] FW filament-wound-type composite cylindrical-shell models subjected to collapse pressure loads. A total of 20 composite cylindrical-shell models are tested to derive the empirical formula, which is validated by comparison with experimental data, existing design formulas of ASME 2007 and NASA SP-8700, and solutions of the nonlinear finite element method. It is concluded that the proposed formula accurately predicts the collapse pressure loads of filament-wound composite cylinders and will thus aid the safety design of composite cylindrical shell-structures under external pressure loads. Highlights • Derivation of an empirical formula based on the database of testing and FEA. • Collapse strength of composite cylindrical-shells. • Under external hydrostatic pressure loads. • A function of geometric dimensions and layered angles. • Effects of initial manufacturing imperfections. [ABSTRACT FROM AUTHOR]

Copyright of China Petroleum Machinery is the property of China Petroleum Machinery Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Petroleum Machinery is the property of China Petroleum Machinery Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Screen/slotted liners can be used in geothermal well completions. However, the thermally-induced stress caused by elevated temperature could substantially deteriorate the collapse strength. This paper presents an integrated workflow which complementarily utilizes analytical and numerical methods to design screen/slotted liners in geothermal wells. The collapse rating of a screen/slotted liner is obtained by a modified analytical approach. The thermally-induced stress is estimated through the Finite Element Method Subsequently, the collapse strength assessment for a screen/slotted liner when subjected to high-temperature is made by combining these two approaches. Finally, a selection guide for the schematic of holes/slots configuration is provided. The result depicts that high-temperature could substantially impair the collapse strength of a screen/slotted liner. It also suggests that prediction of the critical temperature for plastic deformation is important in the safe design of the screen/slotted liners in geothermal wells. The method is simple and versatile, without complicated mechanical-thermo-coupling process. It can provide a guidance for completion engineers to modify the design of screen/slotted liners prior to the actual treatment in geothermal wells. [ABSTRACT FROM AUTHOR]

This paper presents an integrated framework for the reliability-based design of deep-water vertical subsea separators using a novel collapse strength model. An analytical model for collapse strength prediction of a vertical subsea separator subjected to external pressure is proposed based on numerical simulations covering different geometries and imperfections. The proposed strength model is verified against experimental collapse pressure and other analytical models. The application of the presented methodology is demonstrated in a case study where uncertainties are systematically considered and the target reliability is used as a single design constraint. The First Order Reliability Method is adopted for the reliability-based design and probabilistic safety evaluation of the subsea separator and sensitivity and partial safety factors assessment. This framework is useful for the design of subsea processing systems as technology qualification and standardization of subsea separators are not fully available. • An integrated framework is presented for the reliability-based design of deep-water vertical subsea separators. • An analytical model for collapse strength prediction of a vertical subsea separator subjected to external pressure is proposed. • The proposed strength model is verified against experimental collapse pressure and other analytical models. • The application of the presented methodology is demonstrated in a case study. • FORM is adopted for the design and safety evaluation of the subsea separator and partial safety factors assessment. [ABSTRACT FROM AUTHOR]

Whipping/springing research started in the 50’ies. In the 60’ies inland water vessels design rules became stricter due to whipping/springing. The research during the 70-90’ies may be regarded as academic. In 2000 a large ore carrier was strengthened due to severe cracking from North Atlantic operation, and whipping/springing contributed to half of the fatigue damage. Measurement campaigns on blunt and slender vessels were initiated. A few blunt ships were designed to account for whipping/springing. Based on the measurements, the focus shifted from fatigue to extreme loading. In 2005 model tests of a 4,400 TEU container vessel included extreme whipping scenarios. In 2007 the 4400 TEU vessel MSC Napoli broke in two under similar conditions. In 2009 model tests of an 8,600 TEU container vessel container vessel included extreme whipping scenarios. In 2013 the 8,100 TEU vessel MOL COMFORT broke in two under similar conditions. Several classification societies have published voluntary guidelines, which have been used to include whipping/springing in the design of several container vessels. This paper covers results from model tests and full scale measurements used as background for the DNV Legacy guideline. Uncertainties are discussed and recommendations are given in order to obtain useful data. Whipping/springing is no longer academic.

Closed-cell aluminum foam is widely used as energy absorbing material. The cell regularity profoundly affects the mechanical behavior of this material. To investigate the influence of irregularity on elastic and plastic behavior of closed-cell foams, the compression behavior of Voronoi foams was simulated using the finite element method. The results show that with the increasing randomness of the foam, the elastic modules decrease a little while the collapse-strength decrease considerably. A theoretical analysis is conducted with the simple springs model. The results match well with simulation which shows theoretical analysis is reasonable. The Voronoi models were also compressed under different loading velocities and with different relative densities in simulation. The results reveal that foams with low regularity are more suitable for application in protective structures. [ABSTRACT FROM AUTHOR]

Aiming to address the difficulties in predicting the collapse strength of sand control screen pipes with internal corrosion defects under the external pressure in offshore unconsolidated sandstone oil and gas reservoirs development, a parametric analysis model of a screen pipe with corrosion defects was established based on secondary development of ABAQUS by Python script, and was verified by the published experimental data. Then, the effect of corrosion defect and hole parameters on the collapse strength of the screen pipes was analyzed. Furthermore, a novel data-driven model with the gradient boosting regression tree (GBRT) method was used to explore and characterize the laws contained in the numerical simulation data based on a large volume of numerical simulation data. The results demonstrated that the proposed data-driven prediction model for the collapse strength of screen pipes exhibited a stable prediction average difference of 3.97% in the test set. And a large number of generalization practices based on data-driven prediction model indicated that corresponding corrosion parameter warning interval existed when the screen pipe design structure was determined, and when the corrosion defect size was greater than the warning interval, the collapse capacity of the screen pipe was considerably weakened. Moreover, the collapse strength was the lowest when the corrosion defect was located at the center of the screen pipe. And the collapse strength of the screen pipe gradually decreased with an increase of corrosion defects parameter and hole arrangement parameter. This study can provide a reference for evaluating the strength and establishing a safety-related warning mechanism of sand control screen pipes with corrosion defects. • A novel GBRT data-driven model was proposed to characterize the collapse pressure of the screen pipe. • Generalization practice based on data-driven model predicted corrosion parameter warning intervals of the screen pipe. • A parametric analysis had been established to investigate the collapse behavior of screen pipes with corrosion defects. [ABSTRACT FROM AUTHOR]

With the increase of the ultra-deep well for oil and gas exploration and development, the conventional America Petroleum Institute (API) casing strength cannot meet the strength criteria of deep and ultra-deep wells. However, the high collapse casing (HCC) shows a higher resistance to collapse pressure so that it has obviously improved collapse properties in excess of API ratings. For limitation of the API model, the ISO collapse strength model with manufacturing imperfections has been proposed, which improves the casing strength calculation accuracy and increases the benefits for casing strength design, rather than just using API model. But the study on the ISO collapse model shows that it is inappropriate to predict the collapse strength of HCC of all sizes. Hence, a new high collapse model with manufacturing imperfections, strength differential (SD) effect, yield-to-tensile strength ratio, material hardening and intermediate principal stress effect, which can predict the collapse strength of HCC, has been presented based on unified strength theory. Numerical and experimental comparisons show that the calculation results of new high collapse model are much closer to the test data than that of API and ISO models, which will make great improvements in the casing design of deep and ultra-deep wells on the basis of HCC material safety. [ABSTRACT FROM AUTHOR]

Failure data from oilfield showed that casings which were designed according to API standards were deformed and collapsed in salt formations. The main reason for decrease in strength may be caused by non-uniform loading (NUL) that was not considered in traditional casing collapsing strength design or that the designing method should be improved and developed. Obviously, the calculation of casing collapse strength is one of the key factors in casing design. However, the effect of NUL on casing collapse strength was generally neglected in the present computational methods. Therefore, a mechanical model which can calculate casing collapse strength under NUL was established based on the curved beam theory of the elasticity and was solved using displacement method. Simultaneously, three anti-collapse experiments were performed on C110 casing under NUL, and the strain and deformation laws of three casings in the process of collapse were obtained by the electrical method. Yield limit of every casing was obtained by analyzing those data. Experimental results are consistent with the results of calculation of new model. It indicates that the model can be used to calculate yield limit loading of casings under NUL. [ABSTRACT FROM AUTHOR]

Highlights: [•] We take into account the yield strength degradation for defective casing. [•] We obtain the collapse strength equation with defective casing. [•] This equation with defective casing presented is simple and practical. [Copyright &y& Elsevier]

The behaviors of corrosion and galvanic nickel based alloy couple of sulfur-resistant casing P110SS in the high sulfide gas well annulus protection fluid were studied. This study was conducted in a high temperature/pressure reactor which simulated the operating environment of oil ring annulus in Puguang Gas Field well. In addition, P110SS sulfur-resistant casing overall performance such as collapse strength, pipe body yield strength and internal pressure strength was also analyzed. Without the presence of hyperbaric H2S/CO2, the annulus protection fluid protected the casing excellently and the galvanic accelerated couple corrosion on P110SS casing was not significant. Thus, the collapse strength, pipe body yield strength and internal pressure strength of P110SS casing were reduced slightly. However, in the hyperbaric environment of H2S 5. 0MPa , CO2 3. 0MPa, the annulus protection fluid did not protect the casing properly and he corrosion rate was increased by around 100 times. Additionally, the galvanic accelerated couple corrosion on P110SS casing was significant. As a consequence, the performance of P110SS casing including the collapse strength, pipe body yield strength and internal pressure strength was decreased considerably. [ABSTRACT FROM AUTHOR]

In performance based earthquake engineering, it is important to accurately predict the seismic demand and capacities of structures. One recent estimation method is incremental dynamic analysis (IDA), which requires a series of nonlinear response history analyses (RHA) of the structure under various ground motions, each scaled to multiple levels of intensity, selected to cover entire range of structural response from elasticity, to yield and finally global dynamic instability. The implementation of IDA requires intensive computation and detailed knowledge of the nonlinear RHA of structures. In response to the complexity of IDA, an approximate method based on modal pushover analysis (MPA-based IDA) was developed. In MPA-based IDA, seismic demands are computed using the nonlinear RHA of the equivalent SDF systems instead of using nonlinear RHA of MDF systems. The objective of this study is to develop a simpler MPA-based IDA procedure that can avoid nonlinear RHA of equivalent SDF systems. For this purpose, MPA-based IDA employs the empirical equation of the inelastic displacement ratio ( C), defined as the ratio of peak displacement of the inelastic SDF system to that of the corresponding elastic SDF system given the strength ratio R, and that of the collapse strength ratio ( R), which is the ratio of collapse intensity to yield strength. The proposed procedure is verified by comparing the seismic demands and capacities of 6-, 9-, and 20-story steel moment frames as determined by the proposed method and exact IDA. [ABSTRACT FROM AUTHOR]

Few industries and undoubtedly no other resources have played such a significant role in modern world development as petroleum. Nowadays, access to geological formations bearing petroleum is slightly difficult due to most shallow reservoirs being close to the end of their economic life. Meanwhile, drilling operations have to get access to deeper reservoirs with more harsh conditions, leading to a considerable rise in instability potential. The consequences of failure are severe, and even simple bore hole instability may lead to the loss of millions of dollars in equipment and natural resources. The bore hole instabilities are not particular, and can happen in simple and very sophisticated drilling operations. In addition, these instabilities are not restricted to the drilling operation, and maybe happen even after many years that the completed well is subjected to the production. The authors intended to develop a new model for the collapse strength analysis of the casing design based on the geomechanical model and heaviest fluid used to drill the well and set the casing. This is based on the hypothesis that indeed the geomechanical in situ stresses and drilling fluid (used to drill the well and set the casing) in the annulus between the drilled well and casing exert radial stresses to the outside of the casing that may collapse the well. This survey leads to the easily computed equation to design the casing collapse strength based on the reality of the well and casing characteristics. This research is used and verified against a numerical model and field data in the South Pars gas field (Phases 6, 7, and 8 and well number SPDG-8) in the Persian Gulf and Cheshmeh Khosh oilfield in southwest of Iran. The results indicate that the proposed model is optimum and possesses satisfactory accuracy and precision. [ABSTRACT FROM AUTHOR]

Abstract: Probabilistic assessment of post-buckling strength of thin plate is a difficult problem because of computational effort needed to evaluate single collapse load. The difficulties arise from the nonlinear behaviour of an in-plane loaded plate showing up multiple equilibrium states with possible bifurcations, snap-through or smooth transitions of states. The plate strength depends heavily on the shape of geometrical imperfection of the plate mid-surface. In this paper, an artificial neural network (ANN) is employed to approximate the collapse strength of plates as a function of the geometrical imperfections. For the training set, mainly theoretical imperfections with the corresponding collapse loads of plate calculated by FEM are considered. The ANN validation is based on the measured imperfections of ship plating and FEM strength. [Copyright &y& Elsevier]

Abstract: Casing string is rotated by torque from wellhead during casing drilling. The method to determine casing torsion status under various torques in casing drilling was discussed. There are three different torsion statuses under different torques, including elastic torsion, elastoplastic torsion and plastic torsion. The residual stress distribution was also discussed under different torques. The average residual stress under elastoplastic and plastic torsion status was calculated respectively; The modified casing collapse strength formula was derived considering the effect of residual stress. The analysis of calculation results indicates that the residual stress caused the collapse strength to decrease 0.033% under elastoplastic torsion, and effects of residual stress on casing strength can be neglected when there is no geometry shape changes in the casing. [Copyright &y& Elsevier]

Abstract: The collapse strength is analyzed for typical periodic planar lattices under uniaxial compression. In this part, the quasi-static strengths of the lattices are predicted by limit analysis, with the consideration of the elastic effect and large deformation effect. The planar lattices are firstly classified into bending-dominated and membrane-dominated structures. Collapse strength of typical bending-dominated lattices, such as hexagonal and rhombus structures, has identical initial lower bound and upper bound, so that the equivalent stress–strain curve of a bending-dominated lattice possesses a plateau. On the contrary, the equivalent stress–strain curve of a membrane-dominated lattice, such as square, triangular or Kagome structure, usually contains a peak followed by a sharp drop without a plateau. Consequently, the energy absorption behavior of the bending-dominated lattices is similar to type I structure, while that of the membrane-dominated lattices is similar to type II structure. [Copyright &y& Elsevier]

• SET has different types of collapse and failure under different wall thicknesses. • The collapse strength of SET has a quadratic relationship with the expansion rate. • SET selection prediction formula based on FEM and experimental results is obtained. Excellent collapse strength of solid expandable tubular (SET) after plastic forming is an advantageous guarantee for casing repair, plugging, repeating fracturing and other processes. This performance indicator is not only relevant to factors such as expansion, residual stress, and material, but also closely to the SET selected in the initial design. At present, there are few related studies on the initial design and selection of SET. This paper uses the CAE software to establish SET expansion to collapse process three-dimensional kinetics finite element model, and analyzes the collapse strength of different specifications under different expansion ratios, from the perspective of theoretical and simulation, derives the prediction formula. The results illustrate that the finite element simulation result of this paper and the error of the experiment is below 2%, the form of collapse is consistent with the experiment, the reliability is good; the wall thickness and expansion ratio parameters of the pipe have a more important impact on the types of collapse. When the SET specification is confirmed, the greatest collapse strength is presented a secondary relationship with the expansion ratio. Each specification of SET has the maximum collapse strength, its maximum value is closely connected to the wall thickness and expansion ratio, etc. Combined with a large number of simulation data obtained a linear fitting formula between the original radius ratio D 0 /t and the optimum expansion ratio. This paper derives D 0 theoretical calculation formula based on maximum collapse strength by combination with the optimal expansion ratio, the nominal expansion ratio and geometric theoretical analysis. The results of this paper provide a certain theoretical guidance and research ideas for initial selection and design of SET. [ABSTRACT FROM AUTHOR]

This study considers the effects of dimple imperfections, i.e. imperfections caused by local accidents, on the ability of a plate assembly to resist compressive loads. Several different parameters for the plate were used, so that a relationship between these and the effect of the dimple imperfection could be developed. One such parameter was the position of the dimple imperfection on the plate. The study was based on finite element calculations. The results obtained were compared with the ones for the same panels without the dimple imperfections. It was found that the effect of the dimple imperfection is higher when positioned near the unloaded edge of the plate. It was also found that the effect on the collapse strength of this type of imperfection depends upon its amplitude and on the slenderness of the plate. [ABSTRACT FROM AUTHOR]

The effects of localized imperfections on the collapse strength of plates are studied by means of finite element analysis performed by different authors. First a benchmark study is performed to assess the accuracy of the results obtained using different codes on the same case study. Afterwards, a parametric study on the effect of the localized imperfections on the collapse strength is performed. Finally, the effect of combining local and global imperfections was studied. It is found that the addition of a localized imperfection changes the collapse strength of the plate, which depends on the amplitude and size of the localized imperfection change. [ABSTRACT FROM AUTHOR]

Abstract: The use of an integral measure of initial deflections of thin plates, based on the strain energy, has proved to be of importance in studying the influence of the imperfections on the strength of plates subjected to in-plane compression. The energy measure allows for a straightforward definition of compound modes and for a computational determination of the lower bound strength. The last quantity may be essential for assessment of plate design strength considering the imperfections as a random field. [Copyright &y& Elsevier]

Abstract: The influence of initial deflections on collapse strength of thin square plates in uniaxial in-plane compression is studied emphasising an integral energy measure of the imperfections. In calculations of the plate strength, measured data on distortions of stiffened plating in ships as well as buckling modes, compound and localised shapes are considered. The strength values are compared normalising the initial deflections by the energy measure or by the commonly employed amplitude to thickness ratio. The paper extends the previous study on strength of rectangular plates [Sadovský Z, Teixeira AP, Guedes Soares C. Degradation of the compression strength of rectangular plates due to initial deflection. Thin-Walled Structures 2005;43:65–82]. [Copyright &y& Elsevier]