Research On Automatic Control Method Of Rotary Steering Drilling Tool Under Maintaning Drilling Mode

Rotary steerable drilling technology has more technical advantages,such as high trajectory control accuracy,high degree of automation,fast drilling speed,shortened drilling cycle,and saving drilling costs.Now,the static push-the-bit rotary steerable drilling system has been developed in China and put into large-scale field experiments and preliminary industrial applications.This article relies on the national “Thirteenth Five-Year Plan” major project “Research and development of rotary steerable drilling systems”.It mainly focuses on the issues of how to automatically,real-time,and accurately control the wellpath of the horizontal section under the automatic maintaning drilling mode of rotary steering drilling systems.Considering the change of the wellbore trajectory control instructions(the magnitude and direction of the steerable force),or other drilling parameters(weight-on-bit),new drilled wellbore has a transitional section where the curvature of the wellbore is constantly changing.To improve the prediction accuracy of wellbore parameters,the mechanical models of the static push-the-bit rotary steerable drilling assembly in actual wellpath with transitional wellbore section are established and solved by using the beam-column theory,and the matched method for predicting the build-up rate is optimized.Considering the ability of build-up rate and control modes of the rotary steerable tool,the boundary conditions of the target area,and other drilling requirements,a waiting-to-be-drilled wellpath design method,and its control instruction optimizing method and workflow are set up,which are matched to the automatic control mode of the horizontal section and helpful to improve the application levels of rotary steerable drilling technology.The results have shown that:(1)Taking the transition wellbore section into account and knowing how the build-up rate changes with the length of new drilled section have important guiding significance for the precision wellpath control of the horizontal section.(2)According to the simulation analysis results of steerable drilling and maintaining drilling,it can be seen that to improve the automatic regulation period of the horizontal section(maintaining section length + steerable section length)and reduce the times of manual intervention,it is necessary to appropriately reduce the steerable drilling build-up rate and select smaller steerable force under the steerable mode,as well as decrease the inclination change rate and azimuth change rate under the maintain mode.