Fatigue Analysis of Subsea Jumpers due to Slug Flow

2014 ◽  
Author(s):  
Bob (H. E. J. ) van der Heijden ◽  
Henk Smienk ◽  
Andrei V. Metrikine
Keyword(s):  
Pressure Drop ◽  
Static Analysis ◽  
Fatigue Damage ◽  
Slug Flow ◽  
Oil And Gas ◽  
Operating Conditions ◽  
Design Phase ◽  
Line System ◽  
Excitation Mechanisms ◽  
The Difference

Rigid steel jumpers are used in a subsea flow line system to connect subsea components. They provide a certain flexibility with respect to installation and operating conditions. This flexibility makes the jumper susceptible to slug flow induced vibrations. Slug flow can be described as an alternating flow of long oil and gas bubbles which flow at the gas velocity. The alternation between oil and gas density causes loads on the jumper which causes the jumper to vibrate. Two excitation mechanisms can be identified; 1) The variation in weight along the straight sections and 2) the difference in impact loads on the bends. Due to the cyclic nature of these loads fatigue can cause the jumper to fail. As a main contractor of SURF-projects (Subsea Umbilicals Risers and Flowlines) Heerema Marine Contractors (HMC) is responsible for the engineering, procurement, construction and installation (EPCI) of the entire project scope, including the design of the subsea jumpers. Hence this paper has been set up by HMC and the Delft University of Technology to study slug flow induced fatigue in subsea jumpers and in order to find new design considerations. In the early design phase of a subsea jumper the offshore industry commonly uses, to authors knowledge, a static analysis to predict the fatigue damage caused by slug flow. Since the vibrations caused by slug flow are not incorporated in a static analysis an accurate tradeoff between flexibility and fatigue lifetime cannot be made during the design phase. As this tradeoff during the design phase is desirable, a new dynamic and more accurate analysis method has been developed which takes these vibrations into account. A comparison between this new methodology and the common industry method is made in order to quantify the difference in analyzed fatigue damage due to slug flow induced vibration. Additionally the effects of a pressure drop over a passing slug is also investigated to determine if a pressure drop should be incorporated as a design factor for slug flow induced fatigue. The new dynamic method will also be used to investigate the relation between jumper configuration and high slug flow velocity. It will show what excitation mechanisms are dominant and how this affects the fatigue behavior. Since is be the first time, to authors knowledge, such an extensive analysis of geometries and velocities is undertaken it will provide new insights into slug flow induced fatigue in subsea jumpers in general. The newly found amplification and attenuation of the vibration by the successive impacts on the bends of a subsea jumper are investigated.

The Effect of Bow Shape on the Springing/Whipping Response of a Large Ocean-Going Vessel: Investigated by an Experimental Method

2007 ◽  
Author(s):  
Gaute Storhaug ◽  
Torgeir Moan
Keyword(s):  
Fatigue Damage ◽  
Transfer Functions ◽  
Vertical Vibration ◽  
Full Scale ◽  
Relative Importance ◽  
High Frequency Response ◽  
Bow Flare ◽  
Excitation Mechanisms ◽  
The Difference ◽  
Wave Induced

Wave induced vibrations often referred to as springing and/or whipping increase the fatigue and extreme loading in ship hull girders. Both effects are disregarded in current ship rules. Various numerical codes exist for predicting the wave induced vibrations, but so far they are not considered reliable. Another means to investigate the importance of the high frequency response, although more resource demanding, is to carry out full scale measurements and/or model tests. Recently, full scale measurements of blunt ships have been carried out by DNV, and in this paper one of these ships was considered and tested in a towing tank to evaluate the additional fatigue damage due to the wave induced vibrations. Different excitation sources may excite the 2-node vertical vibration mode depending on ship design, and it is not straight forward to determine which is more important. The relative importance of the excitation mechanisms are investigated by two approaches in this paper. The first approach separates the whipping from springing to illustrate their relative importance based on basic theory in combination with model test results. The linear and second order transfer functions are utilized in this procedure. The second approach deals with the effect of the bow design on the additional fatigue damage. Three different bows were tested. The first bow design is identical to the real ship. The second bow design is a simplified version of the first one, by removing the bulb and flare. The third bow is fundamentally different from the two former blunt bows. Bow three is sharp pointed with a vertical sharp stem and vertical ship sides. The results indicate that the importance of whipping depends on the sea state, but that it is of similar importance as springing for the sea states that contributes most to the fatigue damage. Moreover, the difference in the additional fatigue damage due to wave induced vibrations for different bow shapes is moderate. This indicates that vessels with pointed bows and without pronounced bow flare, such as LNG vessels, may have a similar contribution from wave induced vibrations. Modern container vessels, which are more slender, but with pronounced bow flares should be further investigated.

Effect of Particle Size and Viscosity on Erosion in Annular and Slug Flow

2012 ◽  
Author(s):  
N. R. Kesana ◽  
J. M. Throneberry ◽  
B. S. McLaury ◽  
S. A. Shirazi ◽  
E. F. Rybicki
Keyword(s):  
Multiphase Flow ◽  
Electrical Resistance ◽  
Slug Flow ◽  
Annular Flow ◽  
Oil And Gas ◽  
Flow Regimes ◽  
Operating Conditions ◽  
Solid Particles ◽  
Metal Loss ◽  
Head Probe

Solid particle erosion is a mechanical process in which material is removed from a surface due to impacts of solid particles transported within a fluid. It is a common problem faced by the petroleum industry, as solid particles are also produced along with oil and gas. The erosion not only causes losses resulting from repairs and decreased production but also causes safety and environmental concerns. Therefore, the metal losses occurring in different multiphase flow patterns need to be studied and understood in order to develop protective guidelines for oil and gas production equipment. A large scale boom loop, which is capable of generating a wide variety of multiphase flow regimes was used for conducting experiments. Specifically, this work examines erosion measurements in multiphase slug and annular flow regimes. These flow regimes are selected since they produce higher metal losses than other flow regimes, and they also occur for a wide variety of operating conditions. Experiments are performed on a horizontal 0.0762 m (3-inch) diameter pipe, with superficial gas velocities ranging from 15.2 m/s (50 ft/s) to 45.7 m/s (150 ft/s) and superficial liquid velocities ranging from 0.46 m/s (1.5 ft/s) to 0.76 m/s (2.5 ft/s), for liquid viscosities of 1 cP and 10 cP. Carboxymethyl Cellulose (CMC) was used to increase the viscosity of the liquid without significantly altering the density of the liquid. Three different sand sizes (20, 150 and 300 micron sand) were used for performing tests. The shapes of the sand are also different with the 20 and 300 micron sand being sharper than the 150 micron sand. Erosion measurements are taken using Electrical Resistance (ER) probes which relate the change in electrical resistance to the change in the thickness of an exposed element resulting from erosion. Two probes are placed in a bend and another probe is placed in a straight section of pipe. The probes in the bend are flat-head probes, and they are placed flush with the outer wall in the 45 and 90 degree positions. The probe in the straight pipe is an angle-head probe which protrudes into the flow with the face placed in the center of the pipe. Under the flow conditions investigated, the angle-head probe measures the maximum erosion due to its placement. Results demonstrate a significant increase in the metal loss occurs when increasing the superficial gas velocity and decreasing the superficial liquid velocity. The effect of changing the viscosity of the liquid is not as clear. Results suggest a slight increase in metal loss by increasing the viscosity from 1cP to 10 cP in slug flow. However, for annular flow, higher erosion occurs for the lower liquid viscosity considered.

Influence of Ocean Transport on the Design of Onshore and Offshore Constructions, Modules, Topsides, Jackets and Towage on FPSO Design

2013 ◽  
Author(s):  
A. J. Bos ◽  
T. M. Ligterink
Keyword(s):  
Fatigue Damage ◽  
Proper Motion ◽  
Oil And Gas ◽  
Offshore Structures ◽  
General Purpose ◽  
Design Phase ◽  
Floating Structures ◽  
Final Destination ◽  
Rules Of Thumb ◽  
Negative Effect

Oil and gas installations both onshore as well as offshore are often built in modules and components on a different location than where those facilities are commissioned. Although stress and fatigue damage have proven to be significant on these structures during ocean transport, ocean transportation is often not adequately accounted for during design. Prior to arrival on its final destination, constructions are exposed to severe motions when carried on a modules carrier, a general purpose vessel or towed by 1 or more ocean tugs. The authors argue that calculations on the significance and effect of these motions should be based on proper motion response calculations instead of currently used ‘rules of thumb’. Especially regarding the continuing growth of the size of these carriers and the weight of the structures which both increase the negative effect of sea behavior and affects the loads on the constructions. This article aims to explain the importance of design for transport during the design-phase of these onshore and offshore structures. A distinction is made between structures transported aboard a barge, semi-submersible or general purpose vessel and floating structures transported through a ‘wet-tow’ operation.

A Mechanistic Model for Two-Phase Vertical Slug Flow in Pipes

1987 ◽  
Vol 109 (4) ◽  
pp. 206-213 ◽  
Author(s):  
N. D. Sylvester
Keyword(s):  
Pressure Drop ◽  
Slug Flow ◽  
Field Data ◽  
Oil And Gas ◽  
Mechanistic Model ◽  
Two Phase ◽  
Water Wells ◽  
Percent Difference ◽  
Average Percent Difference ◽  
Data Points

This paper presents the formulation of a mechanistic model for slug flow in vertical pipes. The equations required to determine holdup, the relevant velocities and pressure loss are presented. The model is fully deterministic and the pressure drop predictions of the model are compared to experimental field data for oil and gas and gas and water wells. For the 143 data points, the model shows an average percent difference of 4.83 percent, which is felt to be excellent.

Pressure drop and drag reduction in two-phase non-newtonian slug flow

1976 ◽  
Vol 54 (1-2) ◽  
pp. 111-114 ◽  
Author(s):  
Lambert Otten ◽  
Abdelrahman S. Fayed
Keyword(s):  
Pressure Drop ◽  
Drag Reduction ◽  
Slug Flow ◽  
Two Phase

Flow Coefficient Evaluation of Poppet Valves Used in Reciprocating Compressors for LDPE

2008 ◽  
Author(s):  
Enzo Giacomelli ◽  
Massimo Schiavone ◽  
Fabio Manfrone ◽  
Andrea Raggi
Keyword(s):  
Pressure Drop ◽  
Time Pressure ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Operating Life ◽  
High Fatigue ◽  
Strongly Connected ◽  
And Performance ◽  
Poppet Valves

Poppet valves have been used for a long time for very high pressure reciprocating compressors, as for example in the case of Low Density Polyethylene. These applications are very critical because the final pressure can reach 350 MPa and the evaluation of the performance of the machines is strongly connected to the proper operation and performance of the valve itself. The arrangement of cylinders requires generally a certain compactness of valve to withstand high fatigue stresses, but at the same time pressure drop and operating life are very important. In recent years the reliability of the machines has been improving over and over and the customers’ needs are very stringent. Therefore the use of poppet valves has been extended to other cases. In general the mentioned applications are heavy duty services and the simulation of the valves require some coefficients to be used in the differential equations, able to describe the movement of plate/disk or poppet and the flow and related pressure drop through the valves. Such coefficients are often determined in an experimental way in order to have a simulation closer to the real operating conditions. For the flow coefficients it is also possible today to use theoretical programs capable of determining the needed values in a quick and economical way. Some investigations have been carried out to determine the values for certain geometries of poppet valves. The results of the theory have been compared with some experimental tests. The good agreement between the various methods indicates the most suitable procedure to be applied in order to have reliable data. The advantage is evident as the time necessary for the theoretical procedure is faster and less expensive. This is of significant importance at the time of the design and also in case of a need to provide timely technical support for the operating behavior of the valves. Particularly for LDPE, the optimization of all the parameters is strongly necessary. The fatigue stresses of cylinder heads and valve bodies have to match in fact with gas passage turbulence and pressure drop, added to the mechanical behavior of the poppet valve components.

A Transient 3D CFD Model of a Progressive Cavity Pump

2016 ◽  
Author(s):  
K. R. Mrinal ◽  
Md. Hamid Siddique ◽  
Abdus Samad
Keyword(s):  
Oil And Gas ◽  
Complex Geometry ◽  
Transient Behavior ◽  
Oil And Gas Industry ◽  
High Viscosity ◽  
Solid Content ◽  
Operating Conditions ◽  
Cfd Model ◽  
Ansys Fluent ◽  
Flow Variables

A progressive cavity pump (PCP) is a positive displacement pump and has been used as an artificial lift method in the oil and gas industry for pumping fluid with solid content and high viscosity. In a PCP, a single-lobe rotor rotates inside a double-lobe stator. Articles on computational works for flows through a PCP are limited because of transient behavior of flow, complex geometry and moving boundaries. In this paper, a 3D CFD model has been developed to predict the flow variables at different operating conditions. The flow is considered as incompressible, single phase, transient, and turbulent. The dynamic mesh model in Ansys-Fluent for the rotor mesh movement is used, and a user defined function (UDF) written in C language defines the rotor’s hypocycloid path. The mesh deformation is done with spring based smoothing and local remeshing technique. The computational results are compared with the experiment results available in the literature. Thepump gives maximum flowrate at zero differential pressure.

Designing CO2 Transmission Pipelines Without Crack Arrestors

2010 ◽  
Author(s):  
Graeme G. King ◽  
Satish Kumar
Keyword(s):  
Wall Thickness ◽  
Carbon Capture ◽  
Power Plants ◽  
Oil And Gas ◽  
Cost Optimization ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Design Work ◽  
Industrial Facilities ◽  
Pipeline Network

Masdar is developing several carbon capture projects from power plants, smelters, steel works, industrial facilities and oil and gas processing plants in Abu Dhabi in a phased series of projects. Captured CO2 will be transported in a new national CO2 pipeline network with a nominal capacity of 20×106 T/y to oil reservoirs where it will be injected for reservoir management and sequestration. Design of the pipeline network considered three primary factors in the selection of wall thickness and toughness, (a) steady and transient operating conditions, (b) prevention of longitudinal ductile fractures and (c) optimization of total project owning and operating costs. The paper explains how the three factors affect wall thickness and toughness. It sets out code requirements that must be satisfied when choosing wall thickness and gives details of how to calculate toughness to prevent propagation of long ductile fracture in CO2 pipelines. It then uses cost optimization to resolve contention between the different requirements and arrive at a safe and economical pipeline design. The design work selected a design pressure of 24.5 MPa, well above the critical point for CO2 and much higher than is normally seen in conventional oil and gas pipelines. Despite its high operating pressure, the proposed network will be one of the safest pipeline systems in the world today.

Multiphase Transient Slugging Flow in Subsea Oil and Gas Production

2016 ◽  
Author(s):  
Zhenhua Zhang ◽  
Longbin Tao
Keyword(s):  
Data Analysis ◽  
Temperature Distribution ◽  
Numerical Model ◽  
Slug Flow ◽  
Field Data ◽  
Oil And Gas ◽  
Gas Production ◽  
Worst Case ◽  
Oil And Gas Production ◽  
Significant Difference

Slug flow in horizontal pipelines and riser systems in deep sea has been proved as one of the challenging flow assurance issues. Large and fluctuating gas/liquid rates can severely reduce production and, in the worst case, shut down, depressurization or damage topside equipment, such as separator, vessels and compressors. Previous studies are primarily based on experimental investigations of fluid properties with air/water as working media in considerably scaled down model pipes, and the results cannot be simply extrapolated to full scale due to the significant difference in Reynolds number and other fluid conditions. In this paper, the focus is on utilizing practical shape of pipe, working conditions and fluid data for simulation and data analysis. The study aims to investigate the transient multiphase slug flow in subsea oil and gas production based on the field data, using numerical model developed by simulator OLGA and data analysis. As the first step, cases with field data have been modelled using OLGA and validated by comparing with the results obtained using PIPESYS in steady state analysis. Then, a numerical model to predict slugging flow characteristics under transient state in pipeline and riser system was set up using multiphase flow simulator OLGA. One of the highlights of the present study is the new transient model developed by OLGA with an added capacity of newly developed thermal model programmed with MATLAB in order to represent the large variable temperature distribution of the riser in deep water condition. The slug characteristics in pipelines and temperature distribution of riser are analyzed under the different temperature gradients along the water depth. Finally, the depressurization during a shut-down and then restart procedure considering hydrate formation checking is simulated. Furthermore, slug length, pressure drop and liquid hold up in the riser are predicted under the realistic field development scenarios.

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