Design optimization based on genetic algorithm for full-sized counter-type fracturing sleeve

Proper design of structural parameters of internal sleeve to promote structural strength and higher pressure required for the fracturing ball to drive the internal sleeve is one of key factors in design of full-sized counter-type fracturing sleeve. To minimize time and cost required for design, Plackett-Burman design is used to identify major factors that may affect the required pressure for the fracturing ball to drive the internal sleeve. In addition, the response surface method was used to construct the regression equation among outstanding factors and multiple responses and to determine the validity of the equation obtained. In this way, optimization with multiple targets can be simplified into optimization of singular target. In addition, desirable objective function can be established and optimal structural parameters can be identified on the base of genetic algorithm. Ls-dyna simulation processes were followed to simulate the driving of the fracturing ball on internal sleeve. Research results show that upon completion of optimization processes, pressure required for the fracturing ball to drive the internal sleeve has increased from 4.8 MPa to 7.2 MPa, while the maximum stress during the course increased from 992 MPa to 1 036 MPa, which is still less than allowable stress of relevant materials. Indoor simulation tests have been performed on the prototype of the internal sleeve. Upon completion of optimization, the pressure required for the fracturing ball to drive the internal sleeve increased from 5.1 MPa to 7.6 MPa. It can be seen that combination of Plackett-Burman design, the response surface method and the genetic algorithm can effective optimize structural parameters of the internal sleeve.