| Gas drilling technology accounts for about 30%of the world's onshore drilling.It has been widely accepted by technology personnel in the oil drilling industry and it is increasingly used in major oil fields.Gas drilling technology uses gas as circulating medium,which has significant advantages in improving drilling speed,overcoming malignant engineering accidents such as lost circulation,sticky cards,and protecting oil and gas reservoirs.At present,the state's scientific research on gas drilling mainly focuses on improving drilling speed,protecting reservoirs,preventing leakage,wellhead safety,and researching new equipment.The corrosion erosion characteristics and hazards appearing in gas drilling are less considered.In this paper,the ground sand discharge pipeline is taken as the research object,and the hard stratum of the Sichuan Basin is taken as the engineering research background.The erosion wear characteristics of the sand discharge pipeline are studied from various angles and the corresponding structural optimization design scheme is proposed.The following research is made specifically:(1)It is clear that the position of the pipe section where the sand discharge line is most severely damaged,and it is found that the pipeline leakage caused by erosion wear is induced by the vulnerable pipe section.The application status of gas drilling sand pipelines and the investigation of gas drilling safety accidents were investigated,and the research status of erosion wear and sand drainage pipelines at home and abroad was compiled.Determine the main influencing factors of erosion wear of sand discharge pipelines.(2)Based on the display dynamics theory,LS-DYNA was used to establish a multi-particle erosion model to simulate the erosion damage evolution process of the vulnerable pipe section of the sand-discharge pipeline in gas drilling,and to explore the impact of erosion mechanism and engineering parameters on erosion results.The design choice of pipe provides a theoretical basis.Taking the whole section of the vulnerable pipe section as the research object,the internal mechanism of the erosion field of the pipe wall and the debris particle trajectory on the pipe wall is analyzed from the perspective of computational fluid dynamics,which provides a new idea for the structural optimization design of the transition joint.(3)Considering that the gas drilling in the different drilling formations during normal drilling is changed when the bottom hole returns to the mixed medium,the impact on the erosion and wear of the vulnerable pipe section of the sand discharging pipeline is affected.When the gas layer is drilled,the total gas flow in the well is increased,and the high-speed rock is poured into the sand discharge line.When the drilling encounters the water layer,the bottom of the well returns the gas-liquid-solid three-phase mixture,and the flow law in the sand discharging pipeline is more complicated,and the erosion wear is difficult to predict.Considering the special case of rockburst occurring in the well during drilling,the mass flow of the returning cuttings is increased and the shape of the particles is irregular,and the erosion degree of the sand discharging pipeline is studied.(4)Considering the geographical constraints and the layout of the field pipe network,it is possible to encounter curved joints of different structures for use as a connection transition.The erosion wear characteristics of different structural bent joints under normal gas drilling conditions were studied respectively,and the advantages and disadvantages of each joint structure were analyzed.(5)According to the previous research content,combined with the advantages and disadvantages of the curved joint and the T-joint,the joint of the optimized structural design is proposed as the transition joint of the vulnerable pipe section of the sand discharging pipeline.The erosion wear characteristics and debris particle aggregation of the joint under various working conditions were verified,and the results were good. |
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