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The most important mechanical properties of casing and tubing are burst strength, collapse resistance and tensile strength. These properties are necessary to determine the strength of the pipe and to design a casing string. If casing is subjected to internal pressure higher than external, it is said that casing is exposed to burst pressure loading. Burst pressure loading conditions occur during well control operations, casing pressure integrity tests, pumping operations, and production operations. The MIYP of the pipe body is determined by the internal yield pressure formula found in API Bull. This equation, commonly known as the Barlow equation, calculates the internal pressure at which the tangential (or hoop) stress at the inner wall of the pipe reaches the yield strength (YS) of the material.
The most fundamental idea in thermodynamics is the conservation of total energy, which is termed the "first law" of thermodynamics. The first law is based on our every day observation that for any change of thermodynamic properties, total energy, which includes internal, potential, kinetic, heat, and work, is conserved. We begin with the first law of thermodynamics applied to an open thermodynamic system. As illustrated in Figure 1, an open system allows mass and energy to flow into or out of the system. M indicates mass, and Q indicates heat.
Abstract This paper proposes a new analytical derivation to incorporate bending and torsion into collapse calculation, further pushing the already existing approach of combined loading equivalent grade proposed in API TR 5C3 (2019) Clause 8.4.6 Eq. (42) for axial stress and internal pressure (identical to ISO TR 10400 Clause 8.4.7) used to calculate a differential collapse pressure. This new derivation is also based on Hencky-von Mises maximum distortion criterion. The interest of developing such combined loading equivalent grade is to enable the use of the four collapse types described in Clause 8 i.e., Yield Strength, Plastic, Transition and Elastic. The formulae are adapted to a closed-form equation similar to current Eq. (42), enabling pipe collapse performance calculation. Newly derived formulae are checked against a size governed by yield strength collapse to verify consistency. The restrictions regarding collapse performance under compression are discussed.
Validation testing of subsea equipment designed for high pressure/high temperature (HP/HT) applications is necessary but can be extremely expensive and infeasible. The complete paper presents a practical approach for validating design-verification analysis for subsea equipment, using a representative pressure valve block to correlate finite-element analysis (FEA) predictions for strain changes with actual measured changes. The design methods use the guidelines in technical report API 17TR8, and load cases per API 17TR12. Current editions of API standards covered in API Subcommittee 17 (API SC 17) for subsea production equipment are geared toward designing the equipment for its absolute internal working pressures. Also, on the basis of previous regulatory requirements for the offshore industry, until 2014 it was not advised to take advantage of the external seawater hydrostatic head and other external pressures to design certain types of subsea equipment covered under API SC 17.
A 2-year comprehensive effort to design, test, manufacture, and deploy a new high-pressure completion tubular (CT) for Chevron's deepwater Gulf of Mexico (GOM) operations is presented. The completion application expected harsh, aggressive loading modes and high pressures to be encountered. The major challenge was to design, test, and manufacture a subsea-completion string that would provide efficient hydraulics during fracturing operations while ensuring mechanical and pressure integrity. In 2004, the first built-for-purpose CT incorporating a gas-tight, rotary-shouldered connection was developed and deployed in the GOM. Since that time, rotary-shouldered connections have evolved (this evolution is described in detail in the complete paper).
This work is a study of collapse pressure of perforated pipes to evaluate the effect of lateral perforations on the radial resistance of pipes under external pressure. These types of pipes represent a simple and economical technology widely used as sand-control meshes or perforated liners. One of the most common challenges to high flow rates in mature fields is the migration of sand to the well. High rates of oil production together with maximum sand retention is the optimal result. In accomplishing this complex goal, perforated pipes play a vital role because they are a simple and inexpensive application, and they are widely used in the industry.
Kuang, Wenyu (National University of Singapore) | Ong, Paul, Pang Awn (National University of Singapore) | Quek, Ser Tong (National University of Singapore) | Kuang, Kevin, Sze Chiang (National University of Singapore)
Pipelines are critical for transportation of oil and gas. A Steel Strip Reinforced Thermoplastic Pipe (SSRTP) is applied in the offshore environment because of its superior mechanical performance. Due to the complex subsea conditions, SSRTP is subject to severe loading and may be damaged during its design life. The failure modes of SSRTP, related to four principle loading cases, are investigated in the FE models. The preliminary results will reveal the mechanical behavior of the critical layer of SSRTP prior to damage. An optical fiber sensor is then introduced within the SSRTP as a novel system to monitor the strain of the critical layer.
Abstract Casing collapse under external pressure is a complex phenomenon and is one of the governing factors in the tubular design of oil and gas wells. Collapse strength of a casing depends on its outer diameter to wall thickness ratio (i.e. D/t), material Young's modulus, yield stress, shape of stress-strain curve, temperature, ovality, wall eccentricity, circumferential residual stress, as well as combined loadings. This paper studies the quantitative effects of two geometric impefections, namely (i) wear on the inside diameter (ID) of casing and (ii) wall eccentricity angle; as well as two combined loading scenarios: (iii) dogleg bending and (iv) axial compression. Although these scenarios are not covered in the industry Standards, such as API TR 5C3 (June 2018 edition) , they are important factors that must be considered in the tubular design of oil and gas wells. In order to quantify the effects of the four scenarios listed above, nonlinear parametric collapse Finite Element Analysis (FEA) studies were performed. Modified Riks method was utilized to predict the casing on-site collapse pressure as well as the unstable post-collapse response. Both material and geometric nonlinearities were taken into account. Elastic-plastic material property with strain hardening was incorporated in the collapse FEA models. Based on the results of the parametric FEA simulations, some important observations and conclusions can be made: (i) for the scenario of casing ID wear, reduction in worn casing collapse resistance is nearly proportional to the reduction in minimum worn thickness regardless of the casing dimensiosns and material grade; (ii) for the case of wall eccentricity irregularity, as the circumferential location of maximum wall thickness moves closer to the minimum wall thickness location, the casing collapse resistance decreases; (iii) casing collapse resistance decreases as the dogleg severity (DLS) increases. Moreover, the effect of dogleg bending on collapse resistance has a strong dependence on casing dimensions and material grade; (iv) in contrast to the effect of axial tension, dependence of collapse resistance on axial compression is quite nonlinear and non-monotonic. In other words, as axial compression increases, collapse resistance increases until the axial compression reaches approximately 50% to 60% (primarily depending on D/t ratio) of yield strength, and then decreases as axial compression increases further.
ABSTRACT Market demand pushes subsea developments into ultra-deep water. Pipelines installed in such environment require very thick walls to cope with the extreme hydrostatic pressure. However, the design criteria for local buckling under combined loading in one of the prevailing submarine-pipeline design standards, DNVGL-ST-F101 (2017), are stated to be valid only for pipelines with a diameter-to-wall-thickness ratio (D/t) between 15 and 45. The European Pipeline Research Group (EPRG) evaluated whether the existing design equations can be used for very thick-walled pipelines with D/t below 15 that are subject to external pressure and bending, without affecting the level of conservatism underlying the code framework. The limit-state formulation for load-controlled behaviour is found to be increasingly conservative for thicker pipe walls. INTRODUCTION Background Intecsea reviewed the status of deep-water pipeline technology for the EPRG Design Committee as part of EPRG Project 178/2015. This study covers a gap analysis and was concluded in 2016. Areas that require further research were identified and subsequently included in EPRG's research roadmap. An important gap is the absence of a reliable and valid limit-state formulation for local buckling of thickwalled pipe when loaded by a combination of bending, axial force and pressure. The limit-state formulations for local buckling included in DNVGL-ST-F101, which is widely used for design of subsea pipelines, are stated not to be valid when D/t is less than 15. Deep-water pipelines installed to date require D/t in the order of 20 for external pressure design. This is the case in maximum water depths in the range of 2000–2500 m. When moving to ultra-deep water, the required D/t can be even lower than 15. This asks for technological advancements, which should also be sought in a fundamental review and a potential reformulation of the existing design equations. In addition to the lack of adequate design equations, manufacturability of line pipe with an extremely thick wall, meaning very low D/t, may be beyond the capabilities of the leading pipe mills. This depends on the selected manufacturing method; this paper considers seamless (SMLS) and longitudinally arc-welded (SAWL) pipe. The design of pipelines with D/t below 15 needs documented information on what can be produced, and according to which specification.
Wan, Feng (School of Mechanical Engineering, Yangtze University) | Huang, Peng (School of Mechanical Engineering, Yangtze University) | Liu, Yong-hui (School of Mechanical Engineering, Yangtze University) | Guan, Feng (School of Mechanical Engineering, Yangtze University)
ABSTRACT Engineering applications of such sandwich pipe structures in submarine pipelines requires further understanding on the structural resistance of these structures under accidental impact load. Finite element models are constructed and validated to analyze the full-range structural behaviors of CFDST composite pipelines under impact load combined with the internal and external pressures. The results show that composite pipelines possesses good structural resistance compared to single-wall steel pipes. Lifting the concrete strength and the steel grade for inner and outer tubes are helpful to strengthen the structural resistance of composite pipelines. During an impact process, most of the energy would be absorbed by the outer tube and a thicker concrete core can help to dissipate more energy. While the inner tube plays a minor role comparing with the outer tube and the concrete annular. The existing of internal pressure can enhance the load carrying capacity of composite pipelines, however it has no effect on the ratio of energy absorbed by each layer. INTRODUCTION As the oil industry shifts its attention to deepwater fields, submarine pipelines with reliable structural carrying capacity and thermal insulation performance are needed for oil and gas transportation. In recent year, due to the considerations of economic, installation and structural resistance, sandwich pipe structures infilled with polymeric or cement-based core have been proposed for deepwater application (Estefen, 2005), such as the concrete filled double steel tubular (CFDST) sandwich structure. In the design of deepwater pipeline, the external hydrostatic pressure and the bending load during the installation and operation are the main consideration. Therefore, extensive researches have been performed successfully in the past. For example, Fu (2014) et al. has investigated numerically the collapse, collapse propagation and bending of sandwich pipes with strain hardening cementitious composites. He (2015) studied the post-buckling responses and pressure capacity of steel-solid polypropylene–steel double skins sandwich pipes with different interlayer adhesion condition. Based on the FEA results, a simplified equation was developed to predict the collapse pressure of sandwich pipes with polypropylene annular. Gong (2018) investigated the buckle propagation of sandwich pipes filled with polypropylene core under external pressure. The results show that interface bonding conditions, core layer thickness and the ratio of wall thickness between inner and outer tubes have significant influence on the buckle propagation pressure of SPs.