Assessing the Impact of Shallow Gas Hydrate Dissociation on Structural Integrity in Deepwater Wells

2021 ◽  
Author(s):  
P. V. Suryanarayana ◽  
Miodrag Bogdanovic ◽  
Kuhanesapathy Thavaras Pathy ◽  
M. Razali Paimin
Keyword(s):  
Gas Hydrate ◽  
Structural Integrity ◽  
Mechanical Response ◽  
Preliminary Assessment ◽  
Shallow Gas ◽  
Hydrate Dissociation ◽  
Integrity Assessment ◽  
Well Integrity ◽  
Transient Thermal ◽  
The Impact

Abstract Shallow gas hydrate zones are present in some deepwater fields. During production, the shallow hydrates may dissociate due to heat-up of the near wellbore formation, which can extend radially to several meters from the wellbore. This can compromise structural integrity of the well (particularly structural strings), cause subsidence, and impact subsea equipment installations. This problem is well known, and has been addressed in the literature. An enthalpy-based transient thermal simulation is required to determine the dissociation front. Further, post-dissociation formation mechanics and well integrity assessment are complex, requiring numerical approaches such as Finite Element Analyses. In this paper, we present an approach that allows a preliminary assessment of the severity of the impact of dissociation on well integrity, so that a more complex assessment may be undertaken only for severe situations. The main objectives of the preliminary assessment are: to model hydrate dissociation front and the radial extent of dissociation as a function of depth; evaluate response of formation to this dissociation; analyze mechanical response of the well to the modified mechanical properties within dissociated zone; and confirm well integrity. The paper describes the approach, and introduces two thermal metrics to assess the likely severity of the integrity impact of hydrate dissociation. Using these metrics, the need for a more detailed analysis can be determined. Further, load analysis and integrity checks of the structural strings and the wellhead that can be performed as part of the preliminary assessment are discussed. An illustrative example is used to demonstrate the approach.

A novel 1D thermo-hydro-biogeochemical hydrate model to assess the full benthic environmental impact of methane gas hydrate dissociation

2021 ◽  
Author(s):  
Maria De La Fuente ◽  
Sandra Arndt ◽  
Tim Minshul ◽  
Héctor Marín-Moreno
Keyword(s):  
Environmental Impact ◽  
Gas Hydrate ◽  
Transport Processes ◽  
Anaerobic Oxidation Of Methane ◽  
Anaerobic Oxidation ◽  
Microbial Oxidation ◽  
Saturation State ◽  
Hydrate Dissociation ◽  
Oxidation Of Methane ◽  
The Impact

<p>Large quantities of methane (CH<sub>4</sub>) are stored in gas hydrates at shallow depths within marine sediments. These reservoirs are highly sensitive to ocean warming and if destabilized could lead to significant CH<sub>4</sub> release and global environmental impacts. However, the existence of such a positive feedback loop has recently been questioned as efficient CH<sub>4 </sub>sinks within the sediment-ocean continuum likely mitigate the impact of gas hydrate-derived CH<sub>4</sub> emissions on global climate. In particular, benthic anaerobic oxidation of methane (AOM) represents an important CH<sub>4 </sub>sink capable of completely consuming CH<sub>4</sub> fluxes before they reach the seafloor. However, the efficiency of this benthic biofilter is controlled by a complex interplay of multiphase methane transport and microbial oxidation processes and is thus highly variable (0-100%). In addition, AOM potentially enhances benthic alkalinity fluxes with important, yet largely overlooked implications for ocean pH, saturation state and CO<sub>2</sub> emissions. As a consequence, the full environmental impact of hydrate-derived CH<sub>4</sub> release to the ocean-atmosphere system and its feedbacks on global biogeochemical cycles and climate still remain poorly quantified. To the best our knowledge, currently available modelling tools to assess the benthic CH<sub>4</sub> sink and its environmental impact during hydrate dissociation do not account for the full complexity of the problem. Available codes generally do not explicitly resolve the dynamics of the microbial community and thus fail to represent transient changes in AOM biofilter efficiency and windows of opportunity for CH<sub>4</sub> escape. They also highly simplify the representation of  multiphase CH<sub>4 </sub>transport processes and gas hydrate dynamics and rarely assess the influence of hydrate-derived CH<sub>4</sub> fluxes on benthic-pelagic alkalinity and dissolved inorganic carbon fluxes. To overcome these limitations, we have developed a novel 1D thermo-hydro-biogeochemical hydrate model that improve the quantitative understanding of the benthic CH<sub>4</sub> sink and benthic carbon cycle-climate feedbacks in response to methane hydrate dissociation caused by temperature and sea-level perturbations. Our mathematical model builds on previous thermo-hydraulic hydrate simulators, expanding them to include the dominant microbial processes affecting CH<sub>4</sub> fluxes in a consistent and coupled mathematical formulation. The micro-biogeochemical reaction network accounts for the main redox reactions (i.e., aerobic degradation, organoclastic sulphate reduction (OSR), methanogenesis and aerobic-anaerobic oxidation of methane (AeOM-AOM)), carbonate dissolution/precipitation and equilibrium reactions that drive biogeochemical dynamics in marine hydrate-bearing sediments . In particular, the AOM rate is expressed as a bioenergetic rate law that explicitly accounts for biomass dynamics. Finally, the model allows tracking the carbon isotope signatures of all dissolved and solid carbon species. In this talk we will present the model structure for the multiphase-multicomponent hydrate system, describe the specific constitutive and reaction equations used in the formulation, discuss the numerical strategy implemented and illustrate the potential capabilities of the model.</p>

Improvement of the Impact-Echo Method for the Higher Reliability in the Structural Integrity Assessment

2006 ◽  
Vol 321-323 ◽  
pp. 336-339 ◽  
Author(s):  
Mi Ra Cho ◽  
Ki Bong Kim ◽  
Sung Ho Joh ◽  
Tae Ho Kang
Keyword(s):  
Structural Integrity ◽  
Stress Wave Propagation ◽  
Layered Systems ◽  
Impact Echo ◽  
Practical Applications ◽  
Integrity Assessment ◽  
Excellent Method ◽  
The Impact ◽  
Impact Echo Method

The impact-echo method, which is to evaluate the integrity of concrete and masonry structures nondestructively, is an excellent method in practical applications, and provides a high quality of structural integrity assessment. However, in the case of multi-layered systems in which each layer has different stiffness, the impact-echo method may lack reliability in thickness evaluation, which demands improvement of the impact-echo method. This study was first dedicated to the understanding of stress-wave propagation in the impact-echo test, and secondly, the reliability of the impact-echo method was investigated through the numerical simulation of the impact-echo test. The investigation included the research on influencing factors such as stiffness contrast between layers and receiver location. Finally, the research in this paper led to the development of the phase-difference response (PDR) method, based on the frequency response between two receivers deployed in a line with an impact source.

scholarly journals Recent Developments of the Linear Matching Method Framework for Structural Integrity Assessment

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Daniele Barbera ◽  
Haofeng Chen ◽  
Yinghua Liu ◽  
Fuzhen Xuan
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Structural Integrity ◽  
Direct Methods ◽  
Matching Method ◽  
Integrity Assessment ◽  
Wide Range ◽  
The Impact ◽  
Linear Matching Method

The linear matching method (LMM) subroutines and plug-in tools for structural integrity assessment are now in extensive use in industries for the design and routine assessment of power plant components. This paper presents a detailed review and case study of the current state-of-the art LMM direct methods applied to the structural integrity assessment. The focus is on the development and use of the linear matching method framework (LMMF) on a wide range of crucial aspects for the power industry. The LMMF is reviewed to show a wide range of capabilities of the direct methods under this framework, and the basic theory background is also presented. Different structural integrity aspects are covered including the calculation of shakedown, ratchet, and creep rupture limits. Furthermore, the crack initiation assessments of an un-cracked body by the LMM are shown for cases both with and without the presence of a creep dwell during the cyclic loading history. Finally, an overview of the in house developed LMM plug-in is given, presenting the intuitive graphical user interface (GUI) developed. The efficiency and robustness of these direct methods in calculating the aforementioned quantities are confirmed through a numerical case study, which is a semicircular notched (Bridgman notch) bar. A two-dimensional axisymmetric finite element model is adopted, and the notched bar is subjected to both cyclic and constant axial mechanical loads. For the crack initiation assessment, different cyclic loading conditions are evaluated to demonstrate the impact of the different load types on the structural response. The impact of creep dwell is also investigated to show how this parameter is capable of causing in some cases a dangerous phenomenon known as creep ratcheting. All the results in the case study demonstrate the level of simplicity of the LMMs but at the same time accuracy, efficiency, and robustness over the more complicated and inefficient incremental finite element analyses.

Weld Residual Stress Activities Within the ATLAS+ Project

2018 ◽  
Author(s):  
Mike C. Smith
Keyword(s):  
Residual Stress ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Integrity Assessment ◽  
Weld Residual Stress ◽  
Stress Profiles ◽  
Assessment Procedures ◽  
Design And Manufacture ◽  
The Impact

Weld residual stresses can have significant effects on the service performance and structural integrity of pressure-retaining components in nuclear power plants. Reliable prediction and measurement of residual stress in plant-representative components can be challenging. The impact of residual stress on structural integrity can also be difficult to predict reliably. This paper describes the residual stress activities taking place within ATLAS+, and covers welded mock-up design and manufacture, residual stress measurements and simulation, the development of residual stress profiles for structural integrity assessment, and their incorporation into assessment procedures.

Shallow Gas and Shallow Water Flow Induced by Natural Gas Hydrate Dissociation in Deep Water Sediments

2017 ◽  
Author(s):  
Zhiwu Gong ◽  
Shaoran Ren ◽  
Liang Zhang ◽  
Guodong Cui ◽  
Yanmin Liu ◽  
...  
Keyword(s):  
Natural Gas ◽  
Shallow Water ◽  
Water Flow ◽  
Deep Water ◽  
Gas Hydrate ◽  
Natural Gas Hydrate ◽  
Shallow Water Flow ◽  
Shallow Gas ◽  
Hydrate Dissociation

Numerical Investigation of Thermo-Mechanical Behaviour of Ball Grid Array Solder Joint at High Temperature Excursion

2011 ◽  
Vol 367 ◽  
pp. 287-292 ◽  
Author(s):  
E.H. Amalu ◽  
N.N. Ekere ◽  
R.S. Bhatti ◽  
S. Mallik ◽  
G. Takyi ◽  
...  
Keyword(s):  
High Temperature ◽  
Solder Joint ◽  
Numerical Investigation ◽  
High Temperatures ◽  
Structural Integrity ◽  
Mechanical Response ◽  
Coefficient Of Thermal Expansion ◽  
Electronic Systems ◽  
Bonded Materials ◽  
Transient Thermal

The solder joints of surface mount components (SMCs) experience thermal degradation culminating in creep and plastic shear strain deformation when subjected to cyclic temperature load over time. Degradation at the joints is due to thermal stress induced by the incompatible, differential and nonlinear expansion mismatch of the different bonded materials in the assembly. The stress magnitude influences the strain behaviour. Plastic strain response of solder joint is critical at the materials interface at the lower part of the joint due to the occurrence of wider variation in the coefficient of thermal expansion of the bonded materials and this may lead to static structural failure. The life expectancy of electronic components reduces exponentially as the operating temperature increases thus making reliability a key concern for electronic systems operating at high temperatures and in harsh environments. This paper reports on the numerical investigation of thermo-mechanical response of a critical BGA joint especially the character of plastic deformation of SnPb solder used in forming the joint as well as the joint’s high temperature reliability. The analysis uses a 3-D models to predict the effect of the transient thermal load on the static structural integrity of a single BGA joint. In this study, the base diameter of solder ball (interface between the PCB, copper pad and the solder) experienced higher damage than the top diameter interconnects. The paper provides a simplified methodology to study the reliability of BGA solder joint at high temperatures excursion.

Structural Integrity of a Spar in Collision With a Large Supply Vessel

2013 ◽  
Author(s):  
Xinguo Ning ◽  
Bob L. Zhang ◽  
Sudhakar Tallavajhula
Keyword(s):  
Kinetic Energy ◽  
Structural Integrity ◽  
Impact Force ◽  
High Energy ◽  
Progressive Damage ◽  
Element Analysis ◽  
Impact Speed ◽  
Integrity Assessment ◽  
Damage Models ◽  
The Impact

The objectives of this study are to establish numerical approaches to evaluate the structural integrity of a generic Spar hull in collision with a large supply vessel and to reveal its progressive collision damage characteristics. Dynamic and nonlinear finite element analysis is implemented using ABAQUS/Explicit module [1] respectively for two collision scenarios. One is a realistic simulation where the impact kinetic energy governed by an initial impact speed and total mass of a ship is gradually depleted during the collision. The other is a simplified analytical method where the impact speed of a ship bow throughout the collision is constant or the total impact energy is unlimited. With a combination of calibrated material progressive damage models and Mises plasticity, progressive collision damages of the hull structures are accurately captured for structural integrity assessment. The collision energy absorption characteristics, the impact force-deformation curves, the progressive damage modes and the correlation between the impact force, kinetic energy and damages are revealed. Based on numerical investigation, the two analytical scenarios are compared and the implication for the design analysis is elucidated. As a complementary to the ABS code [2], the alternative collision damage criterion in ABS MODU [3] applicable to column-stabilized units is justified to be applicable to a Spar subjected to high-energy impact.

Modeling of pollution from the wastewater discharge of the city of Limassol

1995 ◽  
Vol 32 (9-10) ◽  
pp. 197-204
Author(s):  
G. C. Christodoulou ◽  
I. Ioakeim ◽  
K. Ioannou
Keyword(s):  
Field Observations ◽  
Wastewater Discharge ◽  
Dispersion Models ◽  
Preliminary Assessment ◽  
Westerly Winds ◽  
Dimensional Finite Element ◽  
The Impact ◽  
The City ◽  
Oceanographic Conditions ◽  
Continuous Loading

The paper presents a numerical modeling study aimed at a preliminary assessment of the impact of the planned sea outfall of the city of Limassol, Cyprus, on the waters of Akrotiri bay. First the local meteorological and oceanographic conditions as well as the loading characteristics are briefly reviewed. Two-dimensional finite element hydrodynamic and dispersion models are subsequently applied to the study area. The results of the former show an eastbound flow pattern under the prevailing westerly winds, in general agreement with available field observations. The spread of BOD and N under continuous loading is then examined for eastward as well as for westward flow as an indicator for the extent of pollution to be expected. The computed concentrations are generally low and confined to the shallower parts of the bay.

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