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Collaborating Authors
Reservoir Characterization
Strain concentration is greater for pressurized pipe than for unpressurized pipe, both for girth welds with soft regions compared to the base metal and for girth welds with misalignment. Strain concentration increases with increasing internal pressure, although the increase is less than proportional to pressure. The amount of strain concentration is strongly dependent upon the configuration, with greater thickness limiting strain concentration. For pipes with planar flaws, it can be important to consider both the crack driving force and the constraint around the crack tip. Pressure can notably increase the crack driving force in crack-tip opening displacement (CTOD) or J. Yet the crack-tip constraint has not been observed to change much with pressure when the pressure is applied first. INTRODUCTION Strain-based design is used for many situations for pipelines where the loadings from forces other than the internal pressure can be the largest generators of stress and strain in the pipe wall. Such loadings can be generated by soil subsidence, frost heave, thermal expansion and contraction, landslides, pipe reeling, pipe laying, and several other types of environmental loading. Designing based on strain for these cases has an advantage over designing based on stress because these loadings tend to apply a given displacement rather than a given force to the pipe. This work has been designed to provide information to improve the general guidance particularly for pipelines with axial tensile loadings in combination with internal pressure. Softened heat-affected zone (HAZ) regions have been observed to concentrate strain, particularly under internal pressure as seen in Liu et al. (2005). It was recognized in Mohr (2003) that large strain concentrations could be created around girth welds where the axial strain was combined with a lower strength in the weld HAZ and with internal pressure in the pipe. This finding was dependent upon finite-element models and example tests where the applied displacement was in tension along the axis of the pipe.
- Europe (0.68)
- North America > United States (0.46)
- Well Completion > Hydraulic Fracturing (0.68)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers (0.68)
- Reservoir Description and Dynamics > Reservoir Characterization (0.48)
The problem of soil-pipe interaction along active faults is here numerically taken into consideration by following a displacement based approach. The interaction is analysed by means of lumped coupled elastoplastic springs, whose failure locus is piece-wise linearised and the equations governing their behaviour are set in a form such that a linear complementarity problem can be formulated. The numerical formulation is conceived for taking into account large displacements. The ground motion is controlled; the solution in terms of pipe displacements and internal pipe actions is presented and its dependency on geometrical parameters is discussed. The problem of the axial instability of the pipeline is also studied. INTRODUCTION The mechanical interaction between a buried pipeline and the surrounding soil is one of the most important factors that engineers have to account for in pipeline design. Relative soil-pipe displacements induce a change in actions on the external surface of the pipe (Fig. 1), thus resulting in a net additional load distributed along the buried structure. Fig. 1 Idealized normal stress distribution over the pipe at rest (a) and after a horizontal rightward pipe displacement (b). After Audibert & Nyman (1977). When increasing relative soil-pipe displacements, these additional loads modify the pipeline layout, thus increasing actions within the structure and eventually inducing the lost of the serviceability or even the failure of the pipe with consequent leakage of the internal fluid. It derives that the soil-pipeline interaction is a crucial problem from an economic, technical and also environmental point of view. Relative soil-pipe displacements can be due to several causes: the most common are related to landslides, where buried pipelines cross potentially unstable soil masses (either in mountain regions or in subaqueus environments) that can move several tens of centimetre per year. To these latter we must add relative soil-pipe displacements induced by seismic events.
- Europe (1.00)
- North America > United States > California (0.28)
- Geology > Structural Geology > Fault (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.71)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Piping design and simulation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (0.65)
Exploration of new energy resources located in areas of complex ground and ambient climate imposes strict requirements on pipeline material and design. One of the major research issues in such areas is differential ground movement, which, possibly, is associated with large longitudinal straining in addition to plastic circumferential elongation. Hence, common design principles need thorough re-consideration, notably with respect to strain hardening properties of both base metal and girth welds. This paper summarizes results of a research, which was conducted within Europipe GmbH and supported by Salzgitter Mannesmann Forschung GmbH. Central to the discussion is the numerical representation of strain hardening behavior of pipeline steels, which mainly was focused on base metal. In particular, the discussion comprises stress-strain behavior in transverse as well as in longitudinal direction, the effect of material ageing and the significance of uniform elongation. INTRODUCTION With the sustained rise in both oil and gas price to record levels, hydrocarbon reserves that were considered too expensive to justify production only a few years ago are now being considered as attractive. Fortunately, advances in technologies for exploration and production do allow uneconomic reserves to be accessed (Martin, 2006). These "new" reserves tend to be in regions where difficult ground prevails. That is to say, more and more pipelines will be prone to large differential ground movements. Differential ground movements may have many reasons such as soil subsidence, frost heave, thaw settlement and landslides, to name a few. A phenomenon, which is common to such load scenarios, is that they may evoke large longitudinal strains in addition to plastic circumferential elongation. This is very much different to the case of bare pressure containment where, mainly, circumferential and radial components of strain tensor undergo plastic deformation. Since longitudinal strains may be tensile or compressive complex multi-axial stress states accrue with plastic deformation developing in more than two co-ordinate directions, which, within a cross section, are not uniform any more.
- Materials > Metals & Mining (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (0.86)
- Well Drilling (0.68)
- Health, Safety, Environment & Sustainability (0.68)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Piping design and simulation (0.46)
Spudcan footprint left by former jack-up activity can be hazardous to new spudcan installation. A centrifuge model study was carried out to investigate the changes in the shear strength profiles within a footprint at two different times after its formation. By attaching a T-bar on a moving platform, the shear strength profiles at different locations within a footprint can be determined. The test results reveal that the interaction between a new spudcan installation and an existing footprint interaction is a time dependent problem. INTRODUCTION Mobile jack-up rigs are commonly deployed for offshore oil and gas explorations. In some instances, a jack-up rig may return to an old site to drill additional wells or maintain old wells. The existence of old footprints due to former jack-up activities may be hazardous for the new installation as an existing footprint can exceed 10 m in width and depth in soft soil (Stewart & Finnie, 2001). The new installation of jack-up spudcan foundation at a certain distance from the footprint center may induce excessive stress on the jack-up legs or slewing of the rig into the old footprint. The uneven soil bearing resistance at and around a footprint during a new spudcan installation is believed to be a significant factor for the problem of interaction between the spudcan and an existing footprint. Knowledge on the pre and post shear strength profiles within a footprint would certainly be useful to offshore engineers for the assessment of the footprint interaction problem. In view of this, a centrifuge model study has been initiated at the National University of Singapore to investigate the shear strength changes within a spudcan footprint. Details of the study are presented in this paper. EXPERIMENTAL SET-UP AND PROCEDURE Centrifuge Model Set-up Fig. 1a shows a photograph of the centrifuge model set-up for the present study.
High Performance Concrete (HPC) is a composite mixture containing cementitious material and aggregate. The cementitious material is blended with Pozzolans such as silica fume particles and fly ash to enhance its binding and durability properties. This paper studies the effect of pozzolanic materials on the compressive strength and modulus of elasticity of HPC. An experimental program is conducted to evaluate the effect of silica fume, fly ash, and combination of the two used as cement supplemental materials on the modulus of elasticity. Results show that adding silica fume to HPC increases both the compressive strength and the modulus of elasticity at early ages. However, the increase subsides at later ages (< 28 days). New equation is proposed to accurately predict the modulus of elasticity of HPC. INTRODUCTION As higher emphasis is made on long-term durability, high-performance concrete (HPC) is becoming a standard for transportation structures in the United States of America (USA) [1-8]. HPC is created to reduce the porosity by adding pozzolanic materials (i.e., silica fume and fly ash) that with the presence of water react with the calcium hydroxide released by Portland cement hydration to form a cementitious compound. As a result, HPC becomes denser with lower capillary pores and prevent chloride ion penetration reducing the corrosion potential of the steel reinforcement. The addition of pozzolanic materials does not only affect the HPC durability but also the mechanical properties, namely the compressive strength and modulus of elasticity. Both the compressive strength and modulus of elasticity are very important properties for structural engineers to design and evaluate the structure, especially for deflection and creep calculations [9, 10]. Thus, the effect of pozzolanic materials on modulus of elasticity needs to be investigated. The objective of this paper is to evaluate the effect of pozzolanic materials, namely silica fume particles and fly ash, on the modulus of elasticity of HPC.
- Research Report > Experimental Study (0.68)
- Research Report > New Finding (0.49)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (1.00)
- Well Drilling > Casing and Cementing > Cement formulation (chemistry, properties) (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
This document discusses the development of a new UST inspection technique for UOE linepipe. There are two newly developed techniques, which are applied to inspect the submerged arc weld (SAW) seam of UOE linepipe for the first time. One technique is the phased array probe, which is designed and developed to have 16 angles in a probe and is used for inspection of longitudinal direction defect in the SAW seam. Another technique, is an exclusive probe to inspect concentrically the internal weld toe area. Using these probes, this document also discusses the In-line UST inspection system in the Sumitomo Metals Industries, Kashima UOE pipe mill. The requirements of Ultrasonic Testing for longitudinal SAW seam have become more severe in order to assure the quality of the weld. These requirements include, probe setting, signal evaluation and detection of various kinds of defects in the weld and HAZ area. The new inspection technique, mentioned above, is effective and useful not only to detect the natural defect present in the weld and Heat Affected Zone (HAZ) but also to satisfy all the requirements, which are specified in the international specification. INTRODUCTION High strength and heavy wall thickness steel pipes have been developed for high-pressure gas transmission system. The UOE pipes, which are essential to produce high strength such as X70 grade or higher, have been improved and successfully developed for application. Meanwhile, the requirements of Ultrasonic Testing, such as DNV, ISO specifications etc., for longitudinal SAW seam of UOE pipe have become more severe for inspection. These requirements include probe setting and signal evaluation. This means increasing the number of probes to detect the many reference standard defects, depending on the material wall thickness. as well as detecting various kinds of shape and direction of defects in the weld area, especially to the offshore heavy wall steel linepipe usage.
- Energy > Oil & Gas (0.93)
- Materials > Metals & Mining > Steel (0.48)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers (0.68)
- Reservoir Description and Dynamics > Reservoir Characterization (0.46)
To study the response of marine soil from Bohai bay in east coastline of China under wave loading, series of triaixal tests have been carried out on reconstituted marine clay samples under undrained condition. The test results indicate that the confining stress and the frequency of cyclic load have considerable effects on dynamic strength of the clay. Higher dynamic strength is corresponding to higher confining stress or higher loading frequency. The effect of loading cycles on equivalent shear modulus can not be neglected, and equivalent shear modulus decreases obviously with the loading cycles if the dynamic shear stress level is larger than 0.15. INTRODUCTION Engineering structures founded on any soil deposit are often designed to withstand both static and cyclic loads. In a marine environment, wave loading forms a significant proportion of the loads on offshore structures such as offshore petroleum platforms, offshore pipelines, storm surge barriers and harbor structures. The foundations of such structures transmit the dynamic loads to the marine soils below and it is quite likely that the engineering behavior of these soils get altered substantially under continuously cyclic loading. Marine soils near the shore and coastline in southeast china are mainly clayed soil. Research on the response of marine clay to cyclic loading is one of the key problems of Chinese marine engineering. Over the past decades, considerable advances in understanding the behavior of marine clay under cyclic loading have been made by researchers. Some early reported studies in the literature were conducted by Seed and Chan (1966) and Hardinand Drnevich (1972a, b). The behavior of marine clay samples were based on the results of cyclic triaxial tests or cyclic simple shear tests. Some other investigations in the literature were performed by Sangrey et al. (1969) and Vucetic (1988).
The reliability evaluation on the offshore platform of an idealized three dimensional model subjected to wave and seismic force is carried out using the MCS approach in the present study. It is important to verify the response properties of the offshore structure with uncertainties to dynamic forces and structural properties. In order to enhance the performance based design of the offshore structure, it would be important to examine the uncertainty on the nonlinear response situation due to severe dynamic forces. It is suggested that the available estimation of performance based responses on the offshore structure can be carried out the reliability index evaluated with the MCS simulation to dynamic forces with considerably different characteristics. INTRODUCTION Damage evaluations of the structure subjected to severe wave forces and seismic forces give important roles on the reliable design of the structure. The strength demand spectrum is one of the most useful methods to be treated with the nonlinear response effects on the structure subjected to severe seismic motions. In order to implement the reliable design of the offshore structure, it is important to verify the effects on the uncertainties to the maximum response estimation as well as the nonlinear responses. For the offshore structure subjected to dynamic forces, the dynamic response is usually carried out with the time domain analysis and spectrum analysis. While the wave force should be most important dynamic force, it should be considered to clarify the combined contribution with the seismic force for the offshore structure located in seismic active area. For the structure subjected to severe seismic motions, it is very important to carry out the reliable evaluation with respect to damage situations. There are several available methods on the damage evaluations of the structure subjected to seismic motions.
- Reservoir Description and Dynamics > Reservoir Simulation > Evaluation of uncertainties (0.66)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (0.47)
The tsunami wave can be forced to break as a shock wave, annihilating her energy due to high intensity turbulence. This shockwave is created intentionally by a sea-bed sill, simulating an artificial steepening of the original sea-bed. The main advantage of the shock wave is that she conveys little water mass transport after breaking. Therefore, the sill functions not only as energy dissipater, but also as partly an imaginary opaque wall to arriving water mass. The unique energy matching between the tsunami wave and the marine quake power, make the tsunami wave inception predictable. INTRODUCTION Inviscid Tsunami Wave Inviscid tsunami wave propagation treated as shallow solitary water wave in the ocean is characterized by a constant wave shape while radiating from her birthplace. Physically constant wave shape is physically possible, if there is a very tight bound between all wave harmonics, unlike the oscillatory wave where each harmonic constituent is independent of each other and therefore tends to disperse. The physical mechanism of these binding of the harmonics is not yet known, but it may be attributed to the nonlinearities interactions resulting in reverse turbulence. When the wave enters the refraction zone, she starts to refract and her shape deform continuously, as she enters the continental shelf where the bottom starts sloping upward towards the land side. Internally this deformation of wave shape adsorbs wave energy since there will be spatial and temporal changes in the velocity distribution and therefore affect change in internal energy. But the energy loss due to the wave shape changes is small, and therefore we can neglect this loss until the wave breaks. These propositions were validated empirically by many research establishments. Therefore we can use inviscid model until the wave breaks, despite the tsunami wave propagating in shallow water where actually the bottom friction should be significant.
- Reservoir Description and Dynamics > Reservoir Characterization (0.69)
- Health, Safety, Environment & Sustainability > Sustainability/Social Responsibility > Sustainable development (0.49)
Cohesive soils by means of shear wave velocity from Bender Element (BE) test under unconfined stress conditions. Results from this evaluation are compared with those using suction (residual effective stress (p'r)) and deformation modulus (E50) obtained from UC test. It is revealed that p'r, E50 and Vs (G) values are closely correlated with each other and G value is mainly governed by p' value, provided that change in void ratio is small. INTRODUCTION Sample quality is a very important issue for obtaining reliable geotechnical parameters. Many researchers have tried to establish methods for evaluation of sample quality, in terms of, for example, strain at failure from the unconfined compression test, volume change caused by applying the in-situ effective overburden pressure (σ'v0) and so on. However, these traditional methods are mostly destructive tests: i.e., once these tests are performed, the sample cannot be used again. Instead of these tests, the shear wave velocity (Vs) from the Bender Element (BE) test has recently come to attention, because the test is relatively simple and time required for the Vs measurement is very short. In addition, the test is non-destructive so that the specimen after measuring Vs can be used for other mechanical tests to obtain geotechnical parameters. Authors have reported that Vs can be an index of sample disturbance (Nishida et al (2006)). However, geotechnical parameters of the Yuubari river clay layer tested in their research such as over consolidation ratio (OCR), grain composition vary drastically with depth. Therefore, these varieties may probably have influences on their tests results. In this study, relatively homogeneous clays are collected at the site of Mihara, Japan and UC tests as well as the above nondestructive tests are performed. This paper will examine a possibility in evaluating the sample disturbance, using Vs as well as the residual effective stress (suction (p'r)) and the deformation modulus (E50).
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (0.83)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.83)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)