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North America
Abstract Liuhua 19-5 gas field is a two subsea well head marginal field. The development is through subsea tie back technology. The field is located 240km to the south east of Hong Kong with 200m water depth. During the execution of the project, several challenges were met such as delayed delivery of long lead items resulted in re-alignment of most offshore installation activities. The topside modification to the existing platform also encounters problems, such as safety issues, late stage project scope changes. Quality issues for some local products stretched the pre-commissioning time, cracks on the slug catcher vessel after heat treatment etc. Various measures were taken to solve those difficulties. The project achieved its target startup date with overall effective control on schedule, cost, safety and quality. There are also four China first use technology been successfully implemented. Introduction Liuhua19-5 gas field development is located in South China Sea in water depth of 185m. The development plan is to use subsea wells heads tie back to the existing PY30-1 gas field central platform 11km to the south-west. The main scope including two subsea well head production system, one 11.4km long rigid flow line, one 11.4km composite electric-hydraulic control umbilical, one subsea pipeline end manifold, 5 pipeline expansion spools and two rigid jumpers, topside modification and installation of additional processing equipment on the existing platform (Fig.1). Sanctioned in June of 2011 with a target field startup end of 2013, the project is a schedule driven project. Start bidding process for long lead items right after project sanction established a good start. However unforeseeable delays of subsea production system happened at the later stage of the project which resulted in re-alignment of most offshore installation activities to accommodate this change (Yue, Liu and Mao, 2013). The topside modification to the existing platform also encountered problems, such as safety issues, late stage project scope changes. Quality issues for some local products stretched the pre-commissioning time, cracks on the slug catcher vessel after heat treatment etc. Various measures were taken to solve those difficulties.
- North America > United States > Montana > Roosevelt County (0.24)
- Asia > China > South China Sea (0.24)
- Asia > China > Hong Kong (0.24)
- Europe > United Kingdom > North Sea > Central North Sea > Central Graben > Greater Stella Area > Block 30/6a > Stella Field > Stella Ekofisk Formation > A2 Well (0.99)
- Europe > United Kingdom > North Sea > Central North Sea > Central Graben > Greater Stella Area > Block 30/6a > Stella Field > Stella Andrew Formation > A2 Well (0.99)
- Europe > United Kingdom > North Sea > Central North Sea > Central Graben > Greater Stella Area > Block 30/6-2 > Stella Field > Stella Ekofisk Formation > A2 Well (0.99)
- (3 more...)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Downhole and wellsite flow metering (0.96)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Subsea production equipment (0.95)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Offshore pipelines (0.91)
- (2 more...)
Abstract The dependence of wave damping below solid ice is investigated for the ice model with nonlinear visco-elastic rheology, taking into account existing data on the transient creep of ice. The nonlinear dispersion equation and modified nonlinear Schrodinger equation (NLS) are derived. The influence of the nonlinear visco-elastic rheology of ice and the eddy viscosity in the ice-adjacent water layer on wave damping and modulation instability are investigated and discussed in this paper. Introduction Surface waves can propagate below drift ice and create ice failure over large distances in a relatively short time. These effects are important for sea ice dynamics and energy exchange between the atmosphere and the ocean. According to the data of the USSR Register on the wave climate in Russian Arctic seas (Smirnov, 1987), the typical periods of wind waves and swells are in the range of 7.6 to 14 s. Experimental data on the spectral composition of flexural-gravity waves in the Arctic were analyzed by Nagurny et al. (1994) and Wadhams et al. (1995) to show that a major portion of the wave energy corresponds to waves with periods greater than 16 s. Wadhams et al. (1995) supposed that the most intensive vibrations of the ice cover are forced by the low-frequency portion of the swell spectrum, which propagates across long distances under the ice. The propagation of surface waves below drift ice is accompanied by additional processes of energy dissipation in comparison with surface waves propagating in the water with an ice-free surface. The difference is explained by the influence of friction at the ice-water interface on the energy dissipation, floes interaction and energy dissipation in the ice caused by its bending. The influence of the eddy viscosity on wave damping below a continuous ice cover was discussed by Liu and Mollo-Christinsen (1987). They derived the temporal decay and spatial rates of monochromatic plane waves propagating in water of infinite depth covered by an elastic ice sheet and demonstrated that the results of the damping rate compared reasonably well with observations in the marginal ice zone (Wadhams, 1978; Weber, 1987).
- North America > Canada > Quebec > Arctic Platform (0.98)
- North America > Canada > Nunavut > Arctic Platform (0.98)
Identification of Flapper Fin Oscillations for Active Flow Control Applications in Improved Watercraft Propulsion
Belibassakis, Kostas A. (National Technical University of Athens) | Xiros, Nikolaos I. (University of New Orleans) | Politis, Gerassimos K. (National Technical University of Athens) | Filippas, Evangelos (National Technical University of Athens) | Aktosun, Erdem (University of New Orleans) | Tsarsitalidis, Vasileios (National Technical University of Athens)
Abstract In this study, the data analysis of an oscillating flapping wing is conducted for the development of a describing function model especially for heave force data series obtained using a Boundary Element Method (BEM) for different geometrical kinds of flapping wings. The wing experiences a combination of vertical and angular oscillatory motion, while travelling at constant forward speed. The vertical motion is induced by the random motion of the ship in waves, essentially due to ship heave and pitch, while the wing pitching motion is selected as a proper function of wing vertical motion and it is imposed by an external mechanism. The data series obtained by simulation of the unsteady lifting flow around the system was applied to develop a closed-form lumped phenomenological model for fin motion control synthesis. Using this model a state-space controller for thrust augmentation flappers will be later developed. Our study concerning post-processing data series of thrust-producing flapping foils can in effect be a useful application for feedback control law design. Introduction Biomimetic propulsors is the subject of intensive investigation, since they are ideally suited for converting environmental (sea wave) energy to useful thrust. Recent research and development results concerning flapping foils and wings, supported also by extensive experimental evidence and theoretical analysis, have shown that such systems at optimum conditions could achieve high thrust levels; see, e.g., (Triantafyllou et al., 2000; Triantafyllou et al., 2004). A main difference between a biomimetic propulsor and a conventional propeller is that the former absorbs its energy by two independent motions: the heaving motion and the pitching (wing) motion, while for the propeller there is only rotational power feeding. In real sea conditions, the ship undergoes a moderate or higher-amplitude oscillatory motion due to waves, and the vertical ship motion could be exploited for providing one of the modes of combined/complex oscillatory motion of a biomimetic propulsion system (Triantafyllou et al., 2000; Triantafyllou et al., 2004). At the same time, due to waves, wind and other reasons, ship propulsion energy demand in rough sea is usually increased well above the corresponding value in calm water for the same speed, especially in the case of bow/quartering seas.
Abstract Single Edge Notched Tension (SENT) fracture toughness test specimens are being used for a wide range of applications due to the higher fracture toughness that is measured by SENT specimens compared to an equivalent specimen under bending (SENB). The testing of SENT specimens is now standardized in BS 8571:2014 (BSI, 2014) and there is potential to use SENTs for high and low temperature tests, in a wider range of material thickness, and for different applications. This paper describes the validation of a method for carrying out SENT tests at very low temperatures, using threaded ends to allow testing inside a temperature controlled test chamber, while preventing the specimen from yielding at locations away from the intended notch tip. Two designs of threaded-end specimens were assessed for their feasibility; directly machining a round threaded portion onto a square section specimen is the simpler approach, while the alternative is attaching to the square section specimen (in this case by friction welding), a wider diameter round bar for threading. Numerical models of the notch location and of the threads under load were compared for their respective strain capacity. A successful SENT specimen design has greater strain capacity in the threaded end than around the notch. The results of the numerical models were compared to experimental tests on both designs with different notch depths. Machined threads were shown to be limited to applications with low weld strength over-match, deeper notch depths and single point fracture toughness testing (including multi-specimen R-curve testing). Friction welding the threaded portion allowed threaded-end SENT specimens to be successfully used for unloading compliance tests R-curve tests, shallower notched specimens and where there is weld strength over-matching. Introduction Single Edge Notched Tension (SENT) fracture toughness test specimens (Fig.1) are now being used for a wider range of applications. The test specimen became established for use with fitness-for-service assessments of flaws in pipeline girth welds under high strain conditions during installation, as described in DNV-RP-F108:2008 (DNV, 2008), and were later further established for all subsea pipelines in DNV-OS-F101:2013 (DNV, 2013). The lower constraint of the SENT specimen, compared to the historically more common Single Edge Notched Bend (SENB) specimen, results in higher values of fracture toughness being measured in SENTs at ambient temperature.
- Europe (0.68)
- North America (0.46)
Design and Experiment of An Abdominal Operation ROV
Wang, Guanxue (Huazhong University of Science and Technology) | Xu, Guohua (Huazhong University of Science and Technology) | Shen, Xiong (Wuhan Second Ship Design and Research Institute) | Xu, Han (Huazhong University of Science and Technology) | Liu, Chang (VTT Technical Research Centre of Finland) | Wang, Wenjin (Huazhong University of Science and Technology)
Abstract This paper focuses on design and experiment of an abdominal operation ROV. Firstly, overall design for system of abdominal operation ROV which consists of surface unit, power module, umbilical cable and ROV body is introduced. Secondly, the design of ROV body is described in detail to give a further study on body frame, buoyancy, thrusters, locking mechanism, underwater camera, lamps, navigation sensor and control cabin. Thirdly, research on control system which is the key part of ROV is presented. Finally, based on designed ROV a number of experiments are conducted to verify and test the functions and performances of abdominal operation ROV. Introduction With the increasing attention of human beings to marine resources, ROV has been growing as a major vehicle in ocean exploration. Due to the complex and uncertain underwater environment, ROV need to be equipped with operating system, power system, observation system and control system to complete a series of missions. It's significant to design and manufacture new type of ROV to adapt different working conditions while realizing various functions and high performances. The shape and the appearance of the ROV proposed in this paper is shown in Fig. 1. It weighs 52.25kg in air. Main dimensions are 700mm in length, 550mm in width and 425mm in height. The velocity is up to 4kn and it is capable of dividing to the depth of 300m under water. ROV is open frame equipped with thrusters, a linear actuator, an underwater camera, lamps and a navigation sensor. It is able to complete 3-DOF motion maneuvers: along axes X and Y, as well as rotate around Z by sending commands from the surface unit to the underwater main controller. To execute docking tasks, ROV will hover in order to search for the rod which is the object to be docked. When the rod came into the view of camera, ROV approaches to it and tilts its camera to identify the relative position between them. At the same time, ROV adjusts its attitude to let the rod insert into its abdominal operation mechanism with the help of the guidance conic. At last, the linear actuator extends out to lock the rod which means rigid connection between the ROV and the rod is completed, that is to say, docking tasks are achieved.
- Electrical Industrial Apparatus (1.00)
- Energy > Oil & Gas > Upstream (0.71)
- North America > United States (0.89)
- Europe > Sweden (0.89)
- Europe > Russia (0.89)
- (2 more...)
Abstract When analyzing the production data acquired from multiple shale gas wells, it is essential to remove pressure interference for obtaining correct reservoir characteristics. In this study, we employed deconvolution process to remove pressure interferences, however, it cannot be applied directly to shale gas data due to the nonlinearity occurred from desorption. Therefore, we propose new deconvolution method implemented by sorption-corrected pseudopressure to make linearization of pressure-rate relationship. With linearized production data, the results show that the proposed method enables to remove pressure interference effect of multiple fractured wells. Ultimately, one can analyze production data to obtain correct reservoir characteristics. Introduction Pad drilling which drills many wells by a single drilling rig has been widely used for developing shale gas reservoirs (Fig. 1). Pad drilling techniques allow rig operators to drill groups of wells more efficiently. The benefit of a drilling pad is that operators can drill multiple wells in a shorter time than they might with just one well per site. In the past, a drilling pad may have five to ten wells, which are horizontally drilled in different directions. Hydraulic fracturing is essential in developing of shale gas reservoirs because of the extremely low permeability of shale formations. Hydraulic fractures of each well may connect with adjacent hydraulic fractures from another well and it might occur pressure interference on each well (Kim, Chun, Jung, Park, and Sung, 2015). Pressure interference that is occurred by high permeability fractures would large affect results of production data analysis. Accordingly, remove of pressure interferences from an adjacent well is mightily necessary in shale gas pad drilling. Previous studies have used analytical solutions for removing pressure interference or multi-well type curve matching method. Especially, in shale gas reservoirs, the connected hydraulic fracture network created by adjacent multiple fractured horizontal wells has great effect on pressure interference in production data. However, due to heterogeneity and anisotropy yielded from hydraulic fracturing in shale formation, there is a limitation to implement previous method to remove pressure interference effect. In order to overcome this problem, deconvolution method is used. Deconvolution is a process to remove pressure interference; firstly, superposing the convolved result of production data acquired from multiple wells, and secondly, minimizing the error between the convolved result and the measured pressure data (Levitan, 2007; Cumming, Wooff, Whittle, Gringarten, 2014). This method has advantage for using in heterogeneity or anisotropy system because it does not employ analytical solution which assumes homogeneous and isotropic system. Nevertheless, deconvolution cannot be applied particularly in shale gas reservoirs, because as pressure declines desorption occurs, leading to nonlinearity due to large changes in compressibility which conflicts to the assumption of deconvolution (Kim, Jang, Ertekin, and Sung, 2015).
- North America > United States > Colorado > Park Field (0.93)
- North America > Canada > Alberta > Kim Field > Co-Enerco Et Al Peigan 14-26-8-26 Well (0.93)
Abstract The recent application of the p-y method for foundations of offshore wind energy converters necessitates the verification of the p-y curves with regard to the diameter effect and the response to small loads. The paper therefore presents a comprehensive numerical study to evaluate the existing p-y approaches for piles in soft clay. The pile-soil interaction as well as the load-bearing behavior is compared to the well-known approach by Matlock for a wide range of pile dimensions. The study also includes the approximated Matlock curve as defined by the API guidelines and three approaches introduced in the literature to account for the effect of the pile diameter. Introduction The future expansion of the offshore wind energy will be strongly associated with the cost of energy. This economical pressure forces the installation of larger wind energy converters (OWEC) located in deeper waters in a more cost-effective manner. Due to its cost-effective and relative simple installation process, the monopile (cf. Fig. 1) is currently the preferred foundation concept for OWECs in water depths less than forty meters. The combination of large wind turbines installed in deep waters require for enormous monopile dimensions which are widely out of range with regard to common experience for pile foundations. Pile diameters up to 8 m are already installed and even larger diameters are currently planned. Concerning the geotechnical design of offshore foundation, the ultimate limit state (ULS) and the serviceability limit state (SLS) design proof have to be verified. The ULS design is carried out to guarantee sufficient soil resistance to ensure the structural safety of the OWEC. For the SLS proof, the deflections and rotations under the characteristic extreme loads have to stay below certain serviceability limits. The effects of cyclic degradation have to be accounted for within both design proofs, i.e. degradation of the ultimate resistance and accumulation of the deformations has to be considered (Achmus et al, 2008). Beside these geotechnical design proofs, the stiffness of the foundation due to relatively small loads, as occurring during operation of the turbine, has to be determined. Considering this stiffness in the dynamic analysis of the overall OWEC model, it has to be ensured that the structural eigenfrequencies of the turbine have a sufficient distance to the main excitation frequencies of the environmental and operational loads. In that, neither an underestimation nor an overestimation of foundation stiffness is in general conservative. An incorrect estimation of foundation stiffness and with that of the eigenfrequency will result in larger dynamic amplification of the loads and thus could negatively influence the structural lifetime of the OWEC.
- North America (0.70)
- Europe > Germany (0.68)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Mineral > Silicate > Phyllosilicate (0.68)
Study on Local Structure Strengthening Method for the Semi-Submersible Drilling Platform Column
Li, Yang (China National Offshore Oil Corporation) | Xie, Bin (China National Offshore Oil Corporation) | Xie, Wenhui (China National Offshore Oil Corporation) | Ni, Kankan (China National Offshore Oil Corporation)
Abstract During the operation period of the semi-submersible drilling platform, the floating status of the deep-water drilling platform have a great relationship with many factors, such as the waves, wave height, period, direction and wave phase angles, these factors combined different kinds of the sea states to affect the movement of the platform. According to the engineering experience and specification, dangerous wave condition of semi-submersible platform usually includes: sway, pitch, heave, yaw, roll, and surge. In addition, the semi-submersible drilling platform is a very complex structure which each component part and the local structure may emerge the maximum stress under different wave conditions and different phase angles. According to the calculation and experience, the local hot spot stress usually appears in the local connection structure and other important local components. Local crack occurred in these places will threat platform security if we do not take corresponding measures to strengthen these areas. In this paper, we focus on studying strengthening method for a crack area of the semi-submersible column, Strengthening method discussed including changing the T type beam dimensions, increase the toggle plate reinforced structure, through strengthening the toggle plate. The global strength of platform suffering from the critical wave load is analyzed after the critical wave load is calculated for the platform, so the load boundary of model for column and brace connection typical joint are calculated. The local strength of typical joint are calculated based on the load boundary and wave load, the results showed that structural strength of the typical joint. Based on the finite element method and according to the ABS and CCS specifications, analysis of semi-submersible drilling platform subjected to static strength in local office column crack load and environmental loading conditions. Comparative analysis of structural strength results of strengthened were concluded. It provides a theoretical basis and strengthening method feasible for strengthening the Deep-water semi-submersible drilling platform column key nodes.
Abstract Flexible riser system has been developed for an FPSO in South China Sea in 300 m water depth under the typhoon condition. FPSO is moored by an internal turret mooring system. The riser system consists of three dynamic flexible risers, including two 8" ID dynamic insulated oil flexible risers, and one 8" ID dynamic water injection flexible riser. Lazy wave configuration with distributed buoyancy modules has been selected for the riser system. The riser system is designed in accordance with API RP 17B and API Specification 17J/17K, to ensure that the riser does not exceed maximum allowable tension and minimum allowable bend radius when subjected to specified extreme wave and current loadings. This paper presents the design and analysis of FPSO global motions and flexible riser global performance, including riser configuration, static analysis and dynamic analysis. The subject riser in this paper is an 8" ID production riser. Extensive sensitivity study has been performed for seabed stiffness, drag coefficient and loss of buoyancy. Introduction FPSOs have been widely used for oil and gas production, storage, and offloading in offshore China fields where lack pipeline infrastructure. Riser concept selection for these FPSOs has posed challenges due to harsh environmental conditions under which FPSO is subjected to large offsets and dynamics which are directly transferred from its hang-off structure along the riser length to its seabed connection. The strength and fatigue resistance of the riser system near the hang-off point and the touch down point (TDP) usually governs the riser concept selection. Free hanging flexible riser has been mostly used in moderate environments of offshore Brazil while concepts like Steel Catenary Riser (SCR) and Hybrid Riser Tower (HRT) are dominant in calm weather conditions of West of Africa. As a recent concept, a lazy wave SCR was first implemented of for Shell's BC-10 development offshore Brazil, where the riser was attached to a turret moored FPSO in 1500- 2000 m water. An FPSO deployed in harsh environmental conditions is subjected to large slow drift motions. The horizontal offset for a free hanging rigid or flexible riser design is usually limited within 10% of the water depth. This is a criterion very difficult to be achieved by a turret moored FPSO in 300 m water depth under typhoon conditions. Therefore, free hanging configuration, either SCR or flexible riser, is not a consideration.
- Asia > China (1.00)
- North America > United States > Louisiana (0.24)
Modeling of an Airplane Take-off and Landing on the Ice Cover in Variable Water Depth Conditions
Matiushina, Anna A. (Amur State University of Humanities and Pedagogy) | Pogorelova, Alexandra V. (Far Eastern Branch of the Russian Academy of Sciences) | Kozin, Victor M. (Amur State University of Humanities and Pedagogy) | Peregudova, Elizaveta D. (Far Eastern Branch of the Russian Academy of Sciences)
Abstract There are a number of investigations aimed to study the behavior of floating plates subjected to various types of loads. As a rule, when solving such problems it is assumed that the bottom of the basin is homogeneous. The paper presents a three-dimensional solution of the problem of an airplane take-off and landing on the floating ice in variable water depth conditions. Consider the motion of the airplane to the shore and away from it. The influences of the slope of the bottom, regimes of airplane movement on deflections of the ice cover are analyzed. Introduction In the future, the Arctic continental shelf will be the main source of energy resources, as it contains about 15% of offshore hydrocarbon reserves in the world. In this regard it is an actual problem for several countries to explore high latitudes. The development of the Polar Regions is impossible without permanent transport ways. Modern aviation is well adjusted to operation under conditions of the Arctic and the Antarctic. Choice of location of the runway on the ice cover is necessary to take into account different characteristics of the ice and the bottom surface topography. Over the past two decades, extensive studies were conducted of the impact on the ice cover various types of loads. The works of Kheisin (1967) and Squire et al (1996) are fundamental in this field. A number of works of Sturova (2008), Pogorelova (2012) and Pogorelova and Kozin (2014a) are devoted to research the effect of the variability of water depth on the propagation of flexural-gravity waves generated load movement in the floating ice cover. Sturova (2008) have considered in two-dimensional formulation influence of variable water depth at the unsteady load movement on the plate. For a small angle of the bottom surface in three-dimensional analysis in the work of Pogorelova (2012) investigated the effect of the angle of the bottom on the wave resistance of a load, moving on floating plate. It was shown that depending on the direction and angle of inclination of the bottom surface, the variability of the water depth can significantly increase wave resistance of a moving load. The solution of the three-dimensional problem of non-stationary load movement on the floating ice plate in variable depth of basin is represented in the work of Pogorelova and Kozin (2014a). The influence of the water depth, thickness of the plate, the size and intensity of the load, speed of uniform motion on the amplitude and the maximum deflection of the plate were analyzed.
- Transportation > Air (1.00)
- Energy > Oil & Gas > Upstream (0.34)