Design Of Small Coring Bit Based On Deep-sea Vehicle And Study On Drilling Process Parameters

The deep sea contains abundant energy resources,which is an important region for human society to seek future survival and development.Before the development and utilization of marine resources,it is necessary to have a full understanding of the ocean.Deep-sea drilling and sampling technology is an important method for obtaining core samples from submarine formations.With the mature development of manned diving technology,small coring sampler relying on submersible has become a new research direction for the study of core sampling in shallow seabed seabed due to its more flexible and accurate drilling operation.Aiming at the difficulties in drilling technology of small deep-sea coring sampler and the characteristics of drilling rig that are concentrated on the core bit,this thesis studies the structure and drilling process parameters of the small core bit based on the carrier.According to rock mechanics and previous research results,the rock breaking mechanism of single cutter and combined cutter is expounded from the perspective of cutting force of PDC coring bit.Through the mechanical analysis of cutter rock breaking process,it is concluded that the main influencing factors of drilling rate are rock properties,cutter structure parameters and drilling process parameters.Through the mechanical analysis of the Jiaolong manned submersible under different working conditions,the theoretical limit load that the submersible can withstand in the drilling process is obtained: the drilling pressure is about 166 N when the manned submersible is sitting down,the drilling pressure is about 500 N when the ballast system works and the drilling pressure is 830 N when the push-down propeller is added.Based on the finite element analysis,the nonlinear dynamic simulation model of rock breaking with single cutter of PDC coring bit is established.By analyzing the influence of cutter shape,roll angle,backward angle and combined deflection angle on rock breaking efficiency,it is concluded that the non-shaping cutter(3/4 circle)with backward angle of 20° and roll angle of 10° has good rock breaking performance for harder rock.Based on the finite element analysis,the nonlinear dynamic simulation model of PDC coring bit torsional drilling and rock breaking is established.By analyzing the influence of the installation position of the non-shaping part of the cutter and the number of cutter on the rock breaking efficiency,it is concluded that the rock breaking effect is the best when the non-shaping part is all located inside the bit.Under higher drilling pressure,smaller teeth spacing plays a major role in the influence of bit performance,and the footage displacement increases with the increase of the number of cutter.Under lower drilling pressure,the drilling pressure on single cutter plays a major role,and the footage displacement decreases with the increase of the number of cutter.Under the condition of satisfying the operation safety of Jiaolong manned submersible,the influence of different drilling pressure and bit speed on the average reverse torque and drilling acceleration of the bit is analyzed.It is concluded that under the condition of constant bit speed,the average reverse torque and drilling acceleration increase with the increase of drilling pressure.Under certain drilling pressure,with the increase of bit speed,the average reverse torque decreases and the drilling acceleration increases.