Research On Impregnated Diamond Drill Bit With Friction Thermal Energy Generating Elements

Impregnated diamond drill bit is one of the most important rock-breaking tools in deep mineral resources and oil and gas resources exploration projects,but it has certain limitations when drilling special hard rock formations.For example,When drilling into a highly abrasive formation,the drill bit will wear excessively.When drilling into a weakly abrasive layer,the diamond will not be exposed in time due to slow carcass wear and the drill bit will slip.To avoid these phenomena,in addition to improving the material properties of the drill bit and optimizing the structure,the rock can be weakened by physical or chemical means to increase the drilling rate.At present,research focuses mainly on the use of thermal energy such as flame jets,lasers,etc.But these methods need a large of energy consumption,it is still in the laboratory development stage.In this paper,by inserting friction elements into the bit matrix,the drill bit will generate higher frictional heat at the bottom of the hole as the heat source to weaken the rock performance.Not only can energy consumption be reduced,the energy utilization rate at the bottom of the hole can be fully improved,but it can also drill faster in hard rock.This article first introduces and analyzes the process of impregnated diamond drill bit rock breaking and heat generation at the bottom of the hole.The mechanism of frictional thermal energy generated when the surface of the drill bit interacts with the rock is derived from the elastic and plastic deformation of the surface of the bit and the rock surface.Analysis of relevant data shows that when the heated surface of the rock is subjected to temperature fluctuations,the temperature fluctuation only appears in a depth range that is very close to the heated surface of the rock.The rock layer at this depth is defined as the rock temperature-sensitive layer.In the sensitive layer,severe cold and hot alternation will weaken the rock phenomenon and accelerate rock crack growth.Based on the study of the alternating weakening of the rock under cold and heat cycles,the key dimensions of a thermo-mechanical impregnated diamond drill bit with friction elements are calculated.Based on the theory of crack propagation minimum delay time,calculate the minimum waterways width required for the ?59mm and ?76mm drill bits to achieve the thermo-mechanical rock crushing effect under different drilling parameters.Taking a ?59mm drill bit as an example,the minimum area occupied by the friction element in each friction element layer(The part of the bit block that surrounds the friction element is called the friction element layer)is calculated by the maximum weight-on-bit that each diamond in the drill bit can bear.The matrix 64 # formula suitable for the thermo-mechanical rock crushing conditions was selected as the matrix material and silicon nitride was used as the friction element material.A ?59mm thermo-mechanical impregnated diamond bit was designed and prepared for laboratory drilling experiments.Drilling was performed using conventional bit,friction-free drill bit and thermo-mechanical bit.Measure the drilling speed and hole bottom temperature under the parameters of 10 kN drilling pressure,speed of 388 r / min,and flow rate of 10 ~ 30 L / min,and analyze the wear of the bit.The temperature at the bottom of the hole and the drilling speed of the bit generally increased with the decrease in flow rate.At a flow rate of 20 L / min,the temperature measured at the bottom of the thermo-mechanical bit exceeded the ?-quartz phase transition temperature.Compared with the wear of the friction-free bit and the thermo-mechanical bit,the surface of the friction-free drill bit is severely worn,there are deep grooves on the surface,the diamond falls off and the degree of oxidation is severity.The heat source is at the center of the matrix.The thermo-mechanical drill bit is less wear,and the high temperature region of the carcass is close to the friction element layer.That is,the addition of friction elements can not only improve the friction heat generation efficiency,improve the overall heating of the matrix,it can also improve the wear resistance of the matrix,making the soft 64 # formula suitable for drilling in hard rock.