Table of Content

    25 February 2019, Volume 6 Issue 1 Previous Issue    Next Issue
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    2019, 6 (1):  0-0. 
    Abstract ( 105 )   PDF (116250KB) ( 23 )  
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    2019, 6 (1):  0-0. 
    Abstract ( 37 )   PDF (143KB) ( 35 )  
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    Overview and Development Trend of Riserless Well Intervention Equipment
    LI Jun
    2019, 6 (1):  429-433.  DOI: 10.12087/oeet.2095-7297.2019.01.01
    Abstract ( 281 )   PDF (8227KB) ( 39 )  
    On the basis of the full investigation of oversea riserless intervention operation equipment, the history, the technology benefit and the operational capability of riserless intervention technology are introduced. Summary and comparative analysis are carried out for the existing riserless intervention techniques and equipment. The global riserless intervention service providers are summarized. Finally, the development trends of riserless intervention operations and equipment are concluded, and an outlook is presented for carrying out the riserless intervention study in China.
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     Power Calculation for the Selection of Screw Power Source for Subsea Control Module Running Tool
    WANG Hong-tao, SUN Qin, HAO Fu-qiang, XIE Cheng-lin, TANG Yi-chen
    2019, 6 (1):  434-437.  DOI: 10.12087/oeet.2095-7297.2019.01.02
    Abstract ( 199 )   PDF (1442KB) ( 48 )  
     Subsea control module (SCM) is the core unit of subsea production system. The realization of the control function of the SCM mainly relies on the hydraulic power to provide the driving force for the subsea valves. The running, installation and recovery of SCM is an important issue in the subsea production systems. Ordinary screw mainly works with sliding friction, for which the efficiency is usually 0.3~0.6. Compared with the ball screw, the drive efficiency and the drive speed are far less. Because of its self locking, ordinary screw is still widely used in the lifting mechanism. In this paper, according to the actual project case, through the mechanical analysis and calculation, for the power source of the screw drive mechanism, i. e., hydraulic motor, the power and the minimum output torque are obtained. The results can be used as the reference data of the type selection of hydraulic motor.
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     Interference Analysis for Vortex-Induced Vibration of Two Tandem Arranged Risers
    DUANMU Yu, CHEN Jian-ping, WAN De-cheng
    2019, 6 (1):  438-443.  DOI: 10.12087/oeet.2095-7297.2019.01.03
    Abstract ( 232 )   PDF (8346KB) ( 28 )  
     Risers are grouped in close proximity in engineering. The interference of two tandem arranged risers widely exists. The selfdeveloped solver viv-FOAM-SJTU is adopted for the prediction of the time-domain voxtex-induced vibration (VIV) response of deep-ocean risers. After the study of the benchmark case, the simulations of VIV of two tandem arranged risers with different spacings are carried out. The distance between two risers is changed from D to 4Dwhere D is the riser diameters. The results show that the distance between risers has little effect on the vibration mode. The VIV responses of the upstream riser with different spacing are fall dominated by the 4th mode, which is the same with the isolated riser. The VIV mode of the downstream riser is lower than the upstream one because of the interference between two risers. The responses of the downstream riser with different spacings are dominated by the 3rd mode. While, the distance between risers has a great impact on the trailing riser. With the increase of the distance, for the trailing riser, the weight of the 3rd mode decreases, and the weight of the 4th mode increases.
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      How to Improve the Bearing Capacity of Lifting Point for Jacket Removal
    HAN Jing-yan, ZHAO Qiang, WU Bin-bin, JIANG Yu-fei, YUAN Guo-dong
    2019, 6 (1):  444-449.  DOI: 10.12087/oeet.2095-7297.2019.01.04
    Abstract ( 232 )   PDF (17837KB) ( 25 )  
     The number of jacket removal projects is increasing in recent years. The bearing capacity of jacket lifting point is one of the most important factors to determine the removal method. We select a seven-year in-service jacket in Bohai Bay of China as an example. The marine growth thickness of the jacket is about 300 mm, which is about 10 times of normal marine growth thickness. The removal weight of the jacket is more than twice of the install weight of the jacket, and the trunnion (the lifting point type of the jacket) has already appeared pitting corrosion because it is in the tidal zone. So the trunnion needs to be strengthened. But the modification is difficult because the internal space of the trunnion is small. The thought and method of transformation of the trunnion are discussed detailedly. The way to improve the bearing capacity, which can effectively solve the defects of the original structure, is put forward. This research provides a design train of thought for the jacket removal projects in the future.
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     Research and Application of Drill String Torsional Vibration in Deepwater Drilling While Jetting the Conductor
    JIANG Wei
    2019, 6 (1):  450-456.  DOI: 10.12087/oeet.2095-7297.2019.01.05
    Abstract ( 222 )   PDF (4401KB) ( 42 )  
      In deepwater dislling, 36-inch conductors are set using the drill string with mud motor. For tihs case, the torsional energy equation and kinetic energy equation of the drill string are established, and the natural frequency equation of the drill string under this condition is solved according to the Rayleigh principle of the energy cnservation equation. The frequency equation takes into account the effect of nine geometric parameters, i.e., the length, the outer diameter and the inner diameter of the drill string, those of the dirll collar, and those of the conductor. Such an equation has strong practicabibty and make the theoretical analysis fit better with the actual situation. Therefore, the use of this set of analysis and calculation method is of great significance to guide the resonable determination of engineering parameters, the avoid ance of torsional vibration, jeopardize the ensurance of down-hole operation safety and the pervention of down-hole accidents.
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     Application of HPG Composite Impactor Speed up Tool in Bohai Oilfied
    SU Jian, YUAN Ze-ming, HE Peng-fei, SONG Rui, WU Yi-biao
    2019, 6 (1):  457-464.  DOI: 10.12087/oeet.2095-7297.2019.01.06
    Abstract ( 199 )   PDF (19097KB) ( 31 )  
    With the deep exploration and development of Bohai oil field, it has been gradually developed from the middle and shallow oil reservoir to the middle and deep oil reservoir. The deep strata in a block of Bohai sea are mainly breccia, breccia and fine sandstone. This kind of formation is compact, hard, high compressive strength, strong abrasion, and poor drillability. In order to increase the mechanical drilling speed, shorten the drilling cycle and save the drilling cost. For the first time, HPG composite impactor speed up tool was used in a well in Bohai Sea, which improved the mechanical drilling speed of the applied well section, shortened the drilling cycle, and achieved remarkable results. The practice shows that the speed-raising tool has a good prospect for application.
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      DF13-2 Subsea Pipeline-drying Process Design and Construction
    ZHENG Song-xian, LI You-xing, WANG Jun, LIU Bin, CAO Zhong-zheng
    2019, 6 (1):  465-469.  DOI: 10.12087/oeet.2095-7297.2019.01.07
    Abstract ( 207 )   PDF (8964KB) ( 27 )  
     The drying of natural gas pipelines before production can prevent hydrate formation, pipeline corrosion and the fluidity of natural gas in pipelines. DF 13-2 subsea 24″ pipeline is 195 kilometers long, and the vessels need to complete offshore construction during typhoon and monsoon seasons, and the weather window for continuous operation is short. In order to complete the drying operation of the sea pipe as soon as possible in the operating weather window, the dry train composed of dry air, Desiccant and Gel is adopted to complete the fresh water desalination, pipeline drainage, pipeline purging and drying and other operations of the sea pipe at one time, so as to improve the operating efficiency. The size of the pig and the hardness of polyurethane were optimized, and the pig train was successfully collected. The abrasion resistance and tightness of the pig were tested, which could meet the requirements of longdistance pipeline drying.
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     Research on Resistance Performance of Drillship with Different Recessing Type Moonpools
    YANG Yi-fan, LI Xin, WU Bo, LI Jian-xing, SHENG Nan
    2019, 6 (1):  470-477.  DOI: 10.12087/oeet. 2095-7297.2019.01.08
    Abstract ( 304 )   PDF (10747KB) ( 34 )  
     Based on a drilling vessel, a model test was carried out in the multifunctional towing tank of Shanghai Jiao Tong University, combined with CFD numerical simulation, in order to study the added resistance of recessing type moonpools. It is found that additional resistance of moonpool is significant and may exceed 50% at high speed. Comparing the resistance of different recessing moonpools of this drillship under the draft of 8.53m, it shows that moonpool with postposition recess has better drag performance than that with preposition recess. Besides, inclined fore wall and rear wall of moonpool can bring a certain amount of drag reduction. Water oscillation caused by periodic eddy during the navigation of drillship is the main cause of added drag. After having optimized the shape of the moonpool, the water oscillation inside the moonpool is more gentle, which reduces the drag increase of the moonpool. These conclusions can provide reference for the drag reduction design of moonpool.
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     Discussions on Some Issues in Life Extension Assessment of Deep Water Jacket Structures
    HU Yong-ming, OUYANG Xiong
    2019, 6 (1):  478-481.  DOI: 10.12087/oeet.2095-7297.2019.01.09
    Abstract ( 221 )   PDF (3718KB) ( 45 )  
     In the life extension assessment of a deep waterjacket structure in South China Sea, the selection of extreme environmental conditions, insufficient structural strength and renewal of fatigue life of the structure are discussed. Based on relevant codes and papers, the feasible solutions are put forward, which can be used for reference in the structural design of deepwater jacket platform and the integrity management during subsequent operation period.
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