Research On Materials Optimization For Mono Hole Expandable Tubular

Mono hole drilling technology is able to optimize wellbore structure,both solve the problem that drilling in deep well in complicated stratum and changing of borehole diameter,in the meantime,it can save a great deal of drilling cost.According to the characteristics of mono hole drilling technology,this study optimize various materials which are different in mechanical properties and give out micro explanation on the mechanical behavior of materials,to find a pipe material that is suitable for large expansion rate drilling,and provide reference for material development.This research select from the expandable tubular which are commonly used in oil fields at present,both the J55 ERW welding pipe and austenitic stainless steel pipe with different specifications have been compared,meanwhile,University of Science and Technology Beijing has developed a new kind of expandable tubular.The expansion property has been analyzed from the viewpoint of composition and process and the tensile test has been made by 1000 KN microcomputer control electronic universal testing machine at the room temperature,then compared the different performance between tested materials before and after expansion.Metallographic microscope,Ultra-55 Zeiss scanning electron microscope,Oxford-EBSD and micro hardness tester were used to analyze the microstructure of the three kinds of different materials,and to explain the reason of the difference of the performance from the perspective of the material.Using ANSYS software to simulate the process of expansive,the TRIP steel tube expanded by the rate of 12%,and the results are compared with the field experiment of.The results show that the austenitic stainless steel pipe has lower yield strength before expansion,however,after taking expansion at the rate of 25%,austenitic stainless steel pipe reaching a high tensile strength and elongation,the microstructure is coarse austenite grain.,accompanied by deformation twins;TRIP pipe has a yield strength close to austenitic stainless steel before expansion,but after expanded at the rate of 10%,the yield strength and tensile strength is obviously increased,and the toughness of austenitic stainless steel is larger.Its microstructure is ferrite and residual austenite plus non tempered martensite,with expansion process going deeply,its unique TRIP effect makes the transformation of residual austenite into deformed martensite;J55ERW pipe has a high yield strength and toughness before expansion,but after expanded at the rate of 10%,the strength and toughness are decreased obviously,the microstructure is the mixture of ferrite and pearlite,and it has an obvious banded structure.The work hardening index of J55 ERW pipe,TRIP pipe and austenitic stainless steel pipe is increases in turn,the work hardening mechanism of J55 ERW pipe is mainly grain refinement.However,TRIP pipe has more than grain refinement.Its unique trip effect makes the transformation of residual austenite deformation into martensite,and that leads to a increase in the hardness and toughness.Austenitic stainless steel is due to the twinning deformation characteristics and high strength and high toughness can be ensured after expansion.Through the ANSYS simulation of expansive deformation process,the simulation result is obtained,which is close to the expansion force of the field experiment and the simulation results are effective.