Sliding Steerable Drilling PDC Bit Drilling Mechanics Research

Slide-steering drilling of polycrystalline diamond compact(PDC)drill bit,mainly including whipstocking and compound drilling,is a typical complex drilling method in oil and gas drilling engineering,which is utilized in well trajectory control and improve rock-breaking efficiency effectively."Digital drilling simulation technology of PDC drill bit"is advanced technology focuses on drilling mechanical behavior in formation of the bit developed in recent years,which simulates the process of interaction between the bit and rock under the condition of complex movement.PDC drill bit is restricted by hole structure,formation conditions and bottom hole assembly during the process of compound drilling,which leads to serious failure mode like "heart tunneling ","ring groove" and so on.On the basis of studying the failure mechanism of PDC bit in slide-steering drilling,This paper mainly carried out the following work:(1)By studying the mechanics behavior of drill string at the direction well or horizontal well,The flexible bending angle and deflection of the screw bending arm were obtained under the condition of different stabilizers.On this basis,a kinematics model of PDC drill bit under slide-steering drilling was established(including whipstocking and compound drilling).(2)The effects of the factors such as the cutters layout,the angle of the well,the position and number of the stabilizer,the structural parameters of screw(including the flexible bending angle and the length of screw arm)and the transmission ratio were analyzed.By means of the orthogonal experiment with four factors and four levels,the range analysis and variance analysis of the radial coverage of the cutters and the "convolution" distance generated by the heart were discussed.(3)The suitable for Nanchong sandstone,Wusheng sandstone and limestone of the CD2 value was obtained.(4)On the basis of a new mechanical model,digital drilling simulation technology of PDC drill bit had been developed and enhanced to study on eccentric drilling for the PDC drill bit,and the error analysis was carried out by comparing with the laboratory eccentric test results of 6 "full-size PDC drill bit,the analysis results verified the reliability of the simulation system.(5)The working mechanics for the homogeneous rock(Wusheng sandstone)of two kinds of different working modes of PDC were analyzed.The law of interaction between bit and rock was studied.Then the bottom hole pattern,PDC cutters cutting output,cutting force,and the guiding force variation for the different conditions of the external diameter of the screw motor,the flexible bending angle of the screw motor,and the outer diameter,length and position of the stabilizer,and the bottom hole pattern,unbalanced contact state of PDC cutters,cutters invasion characteristics,cutting output,cutting force and the selection of the transmission ratio and the flexible bending angle in different formation conditions were obtained respectively under the condition of whipstocking and compound drilling.(6)According to the drilling mechanical behavior and failure mechanism of PDC bit under the condition of slide-steering drilling,the technical idea and implementation method of the PDC drill bit's individual design of the whipstocking and compound drilling had been discussed.The research results improve the understanding of the rock-breaking mechanism of the PDC drill bit in slide-steering drilling,including whipstocking and compound drilling,and the new understanding can provide a reasonable explanation for the performance of the drill bit,hich offers a reference for the work performance analysis and the individual design of drill bit.