Study On Optimization Of Hydraulic Structure Of PDC Bit Based On Numerical Simulation Of Downhole Two-phase Flow Field

PDC bit is one of the main rock-breaking tools in oil and gas exploration and development operations,and its performance directly affects the drilling efficiency and drilling cost.During the rock-breaking process of the bit,the high-speed jet generated by the nozzles can quickly cool the PDC cutters and transport the cuttings away from the bottom of the well.However,the high-speed jet carrying cuttings can also cause erosion damage to the bit body,resulting in premature failure of the bit.Aiming at the erosion problem of PDC bit,the erosion law of the PDC bit body is studied in this work by combining numerical simulation and field test,which can provide a certain basis for the optimization of the hydraulic structure of PDC bit.Based on CFD and erosion wear theory,a PDC bit erosion prediction model is established.The potential erosion area predicted by the simulation is compared with the actual erosion area of the drill bit,and the two have good consistency,which verifies the accuracy of the CFD prediction model.Based on the validated CFD model,the effects of seven factors,such as cutting size,drilling fluid flow rate,nozzle diameter,nozzle orientation,nozzle number,cuttings density and cuttings mass flow rate,on the average erosion rate of the bit body were studied in detail,and the erosion impact degree of each factor is evaluated and analyzed by using the fuzzy grey correlation analysis method.The numerical simulation and field test data show that the most vulnerable areas of the PDC bit body to erosion damage are the webbings between the PDC cutters and the blade front.Based on the research results,three anti-erosion hydraulic structures are proposed: optimization of nozzle orientation,multi-ridge guide structure,and directional extended curved nozzle.Numerical simulation analysis of the optimized PDC bit is carried out,and it is found that the erosion area and erosion strength of the bit are reduced,indicating that the three new hydraulic structure designs have great potential in improving the erosion resistance of the bit.