Table of Content

    25 October 2017, Volume 4 Issue 5 Previous Issue    Next Issue
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    Research Development of Large Separation Devices in LNG Pretreatment for FLNG
    LI Yan, YU Xi-chong, WANG Chun-sheng, WANG Qing, HAN Xu-liang
    2017, 4 (5):  249-254. 
    Abstract ( 139 )   PDF (7137KB) ( 47 )  
    Separation devices are the key equipment in the liquefied natural gas (LNG) pretreatment process of the offshore floating production system, and the distributions in the devices could make large impacts on the separation efficiency, especially under the specific conditions in the offshore oil/gas field, which will decrease the efficiency of the pretreatment processes. We review the overseas and domestic research status about the gas-liquid flow and mass transfer performances under sloshing conditions, analyze the characteristics of the gas-liquid separator, packed column and the purification process, and provide some research approaches for improving the separation efficiency of the floating equipment. According to the practical project, the current problems and the future research emphases of the offshore separation equipment are pointed out, which could offer advices for the offshore separator selection and optimization.
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    Analysis and Research of New Technology on Feed Water Treatment Process for Boiler Used in Offshore Heavy Oil Thermal Recovery
    WANG Hai-yan, WANG Chun-sheng, ZHENG Xiao-peng, ZHANG Ming, SHANG Chao, WANG Guo-dong
    2017, 4 (5):  255-259. 
    Abstract ( 71 )   PDF (3528KB) ( 61 )  
    A new kind of technology called mechanical vapour compression (MVC) is proposed for the feed water treatment process for boiler used in offshore heavy oil thermal recovery. The characteristics of this new technology are analyzed, such as treated water quality, energy consumption, maintenance cost and area covered, also, the new technology is compared with reverse osmosis (RO) technology. From the analysis results, compared with RO technology, the new technology can tolerate feed water of worse quality, total dissolved solid (TDS) of its treated water is less than 5 mg/L, and the area covered of new technology can reduce by more than 20% with less maintenance cost. However, the cost of MVC itself and energy consumption of this technology are high, and need to be localized. Through analysis, it is proved that MVC technology can be used in oilfield produced water recycling process for boiler used in offshore heavy oil thermal recovery. In conclusion, in the situation of offshore heavy oil thermal recovery, MVC can be used in feed water treatment process for boiler, and its application prospect is very broad.
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    Study of the Technology for Crude Oil Dehydration by Electrostatic Coalescence
    SHANG Chao, WANG Chun-sheng, ZHENG Xiao-peng, ZHANG Ming, SUN Jing, WANG Hai-yan
    2017, 4 (5):  260-265. 
    Abstract ( 119 )   PDF (4365KB) ( 49 )  
    We introduce a new and efficient technology for crude oil dehydration by electrostatic coalescence. This technology accelerates the separation of oil and water by electric field. The experimental results show that this technology can greatly reduce the size and weight of treatment facilities and adapt to the working conditions of water content of crude oil up to 95%. It can also be used as an effective means of heavy oil dehydration.
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    Calculation and Application of Reverse Circulation Well Killing Method in Offshore TCP Perforation
    WANG Yun-hai, HE Peng-fei, LI Jun-bao, WAN Xiang, YUAN Ze-ming
    2017, 4 (5):  266-270. 
    Abstract ( 220 )   PDF (2879KB) ( 47 )  
    Reverse circulation well killing method is commonly used in offshore tubing conveyed perforating (TCP). With this method, the lag time is short, so that the time for killing well can be saved; the formation fluid does not pollute the casing annulus, so that the wellbore can be kept clean. According to the characteristics of offshore perforating string, we deduce the formula for calculating the densities of overflow and well killing fluid, as well as the calculation formula of shut-in pressure and circulating pressure in the well killing process. Calculation is carried out for a reverse circulation killing example. The results show that the casing pressure is the highest at the beginning, and after the overflow all goes into the drilling tool, the initial circulating pressure is lowered to the stable circulating pressure. When the well killing fluid enters the annular vacuum and reaches the negative pressure valve, the casing pressure drops to the terminal circulating pressure. During the rising and discharging of the overflow or the well killing fluid, the casing pressure remains unchanged.
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    Feasibility Analysis of Surface Casing Depth Optimization in Deepwater Drilling
    HAO Xi-ning, SUN Li-li, YIN Zhi-ming, WANG Yu
    2017, 4 (5):  271-275. 
    Abstract ( 273 )   PDF (3671KB) ( 53 )  
    The strength of casing shoe and the drilling window of next section depend on the depth of shallow casing running, which influences the wellbore structure and casing level. According to the features of formation in an oversea deepwater block, in order to increase the depth of shallow casing and simplify the wellbore structure, the weighted drilling fluid is used to replace sea water for pump & dump drilling. The pump & dump drilling program and critical parameters are analyzed, so as to provide a new idea and method for reducing cost and improving efficiency in deepwater drilling. As the study shows, pump & dump is a good technology to increase shallow casing depth and optimize wellbore structure, which can reduce about $10M for a deepwater well. It is suggested to apply this technology to the deepwater well of which the drillability is good and the increasing depth of shallow casing is no more than 300 m.
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    Strength Assessment on Corroded Subsea Pipeline Based on the Code of DNV-RP-F101
    WANG Meng, ZHAO Dong-yan
    2017, 4 (5):  276-280. 
    Abstract ( 335 )   PDF (3626KB) ( 109 )  
    The failure of submarine pipelines due to corrosion defects has an increasing tendency in recent years. In order to assess the failure risk when corrosion occurs, we present a review of the strength assessment procedure of DNV-RP-F101. The parameters which will impact on burst pressure are studied. And the relation between DNV-RP-F101 and DNV-OS-F101 is discussed. Based on the calculation results, the following conclusion can be made. Among the key parameters, the inspection accuracy has the greatest influence on the strength assessment results. When certain condition is satisfied, the ratio of yield to tensile is negligible.
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    Development in Deepwater Pipe Laying
    HUANG Yu, BAO Jia
    2017, 4 (5):  281-286. 
    Abstract ( 323 )   PDF (3555KB) ( 79 )  
    We introduce the pipe laying development in the world from the aspects of technology and equipment. For pipe laying technology, the main pipe laying methods are introduced according to the technology advantages and disadvantages. The key requirement for pipe laying capacity is also described. For pipe laying equipment, the most advanced pipelay vessels are introduced with their laying capacity, engineering achievements, vessel parameters, etc. The importance and developing trend for deepwater pipelay vessel are described.
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    Numerical Simulation and Model Test of the Motion Responses of Multi-Body Floating Operation System at Sea
    HAN Xu-liang, XIE Bin, WANG Shi-sheng, YU Xi-chong, LI Yan
    2017, 4 (5):  287-292. 
    Abstract ( 166 )   PDF (5496KB) ( 113 )  
    In order to ensure the safety and reliability of multi-body floating operation system at sea, we present the retardation function approach based on the three-dimensional (3D) potential flow theory. The mathematical model of the coupled motion responses of multi-body floating operation system is established. The effect of hydrodynamic interaction of multi-body floating system is fully taken into account, and the motion responses of multi-body floating system are tested comprehensively under different wave headings. The motion performance of transport ship in close proximity to spar platform is investigated for offshore installation operation under different wave headings. Then the numerical simulation results are presented and compared with the model test results. Satisfactory agreements are achieved, proving the validity of the mathematical model. From the results, it is found that the local wave may generate an amplification or shadowing effect for multi-body system in close proximity offshore operation.
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    Influence of Current Speed on Dynamic Amplification Factor of Jack-Up Units
    MA Wang-kou, YUAN Fei-hui
    2017, 4 (5):  293-299. 
    Abstract ( 273 )   PDF (6068KB) ( 73 )  
    Random wave dynamic response analysis method is studied and used to analyze a sample drilling jack-up unit. The result shows that current suppression on the dynamic and static responses of the unit increases as the current speed increases, but the dynamic amplification factor decreases meanwhile. The result also shows that the inertial force computed by random wave dynamic response analysis method increases relatively slowly since this method can take account of current effect. So random wave dynamic response analysis method should be selected to calculate dynamic amplification factor and inertial force under large current speed for optimizing structure design of legs and increasing variable deck load of jack-up units.
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    Stability Analysis and Wet-Towing Resistance of a Tension Leg Platform
    YANG Xu, CHEN Guo-long, FAN Mo, TAN Yue
    2017, 4 (5):  300-306. 
    Abstract ( 238 )   PDF (4606KB) ( 48 )  
    Tension leg platform (TLP) is an important type of deepwater floating platform which has not been applied in the South China Sea. We analyze buoyancy and stability performance of a TLP with MOSES software, estimate towing resistance and check the results according to the related rules. The results can give reference to the design of TLP.
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    Comparative Analysis of Calculation Methods for Axial and Torsional Stiffness of Unbonded Flexible Riser
    PEI Xiao-mei, ZHANG En-yong, LI Li-wei, ZHOU Wei-wei, CAO Jing
    2017, 4 (5):  307-314. 
    Abstract ( 302 )   PDF (7380KB) ( 22 )  
    We present the study of unbonded flexible pipe and provide a case of 8 inch unbonded flexible riser at the water depth of 300 m. Firstly, the theoretical calculation formulae are introduced for the analysis of axial and torsional stiffness of the unbonded flexible riser. On the basis of the theoretical calculation, finite element analysis is carried out by modelling all layers separately to reflect the mechanical behavior of each layer. The numerical results are compared with the theoretical results for tensile load and torsion. The different contributions of each layer are discussed. Under the axial load or torque, the theoretical results are consistent with the numerical results, and the theoretical results of torsional stiffness are more conservative. During the actual engineering design, the appropriate calculation method can be chosen according to the design stage.
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     Contents of Vol.4, No.5, 2017
    OEET Editorial Office
    2017, 4 (5):  5001. 
    Abstract ( 116 )   PDF (722KB) ( 38 )  
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