Study On The Rock Fragmentation Mechanism And The Optimization Design Of PDC Anchor Bit

PDC anchor bit has the very good rock fragmentation abilities with high penetration rate and long drilling time, which makes the drilling efficiency highly improved and the economic benefit remarkably increased. Now PDC anchor bit has been widely used in drilling field. But for the reason that it is sensitive to the formation characteristics and working conditions, it doesn’t achieve good performance in homogeneous formations such as conglomerate and interbeded sections. In order to reach the goal of enlarging the scope of PDC anchor bit application in oilfields, it is necessary to study the breakage mechanism in conglomerate formations and design the PDC anchor bit optimally.This article first reference the PDC bit of ancestor related theory, discussing the conditions needed for the rock fragmentation mechanism of PDC anchor bit, and thinking when the composite sheet rock drilling, the main influence factors of cutting into the rock have drill geometric parameters, different lithology and drilling parameters, etc. Among them, the mechanical properties of the rock makes rock shear broken are more likely to happen than rotary extrusion, especially for brittle rock that choosing to break rock in extrusion could save no consideration; Reference for the in situ observation of predecessors’ experience, the paper analyzes the failure forms in the process of PDC anchor bit drilling rock impact friction loss and damage, and the impact damage includes compact layer broken and peeling, also on the impact damage are discussed in this paper, the mechanism of the bit that compact performance defect oneself play an important role for damage; Of the above summary of mechanism of the impact of the proposed damage; And using SolidWorks Simulation3d Simulation software, and the Flow Simulation of fluid Simulation plug-in, establish finite element model of PDC anchor bit through the finite element static force analysis, get the equivalent stress and strain contours and the corresponding displacement nephogram, to analyze the maximum stress of anchor drill bit and the location of the maximum; For PDC anchor bit do buckling analysis, calculation of previous order modal and the corresponding critical load, to determine drill bit under different surrounding rock stress, the transition from stable to unstable, bit is in stable equilibrium state, or in buckling instability; Analysis of PDC anchor bit geometric parameters and the maximum stress history; Analysis of PDC anchor bit in drilling the different rocks such as sandstone and mudstone, the influence of geometrical parameters for chip removal; Analysis of PDC anchor bit pattern shape, and with different lengths of drill pipe as a whole mode, to ensure the safety of the drill bit does not produce resonance speed range. A dynamic model of PDC anchor bit vibration drilling. In the process of drilling, the bit and artifacts leave and periodically contact, analysis of the damping coefficient of the effect of PDC anchor bit drilling. Research main failure mode of the bit, analysis the PDC anchor bit rock fragmentation mechanism under different surrounding rock and the main factors that influence the bit damaged, puts forward improving design.In this paper, with theoretical analysis and numerical simulation, the main factors of affecting PDC anchor bit drilling efficiency were studied. The main factors have the geometric parameters of the tooth and side rake angle a angle β, and the purposes of analyzing parameters can improve PDC anchor bit better, so as to enhance its efficiency and service life and reduce its production difficult. Therefore, the study of rock breaking PDC anchor bit mechanism and optimal design of great significance.