The Principle of the Drilling by Impregnated Diamond Bits and the Classification of Rocks

Recently impregnated diamond bits have been widely applied in drilling hard and medium - hard formations in the world . It is quite necessary to study the fracturing mecha-nism of the impregnated diamond bit and the classification of rocks , which can realize optimum drilling . Using multi - parameter rotary test stand can monitor and print nine parameters . The diamond size and concentration for experiment are various and there are nearly 200 types of samples , numbering over 1000 pieces . The results of laboratory are the same as those in the field . Besides , this paper expresses that the diamond concentration of impregnated diamond bits effect the bonding strength of diamond imbedded in ma-trix . During drilling by impregnated diamond bits three ways are used to cool the bits . The contact area between impregnated diamond layer and flow , and the drilling flow through annulus carrying away heat with conduction form can be shown by equations . It is impossible to classify the rock drillability only by using single factor . The best method is to use main factors to analyse the drillability of rocks. Only in this way , the results can be applied to practice .

Research on Fe-based impregnated diamond drill bits strengthened by Nano-NbC and Nano-WC

In order to improve the matrix performance of impregnated diamond drill bit to better meet the drilling needs,the effects of the addition of nano-WC and nano-NbC particles on the matrix material together with the mechanical properties and microstructure of the diamond-matrix composite material of the Fe-based diamond drill bit were studied by using the method of uniform formula design,regression analysis and solution finding.An indoor drilling test was also carried out using the fabricated impregnated diamond drill bit.The results showed that after the addition of nano-NbC and nano-WC,the hardness and flexural strength of the matrix material got improved,as the flexural strength of the diamond composite material increased to 4.29%,the wear-resistance ratio increased to 8.75%,and the tighter the chemical bonding between the diamond and the matrix.This,indicates that the addition of nanoparticles has a positive significance in improving the performance of the diamond composite.The results of the drilling test showed that the mechanical drilling speed of the impregnated diamond drill bit after nanoparticle strengthening is 25.85%higher than that of the conventional drill bit,and the matrix wear was increased by 17.5%.It proves that nanoparticles can improve the drilling performance and efficiency of drill bit.

Effects of Bionic Units in Different Scales on the Wear Behavior of Bionic Impregnated Diamond Bits

Based on anti-wear theory of soil animals, the samples of impregnated diamond bit with bionic self-regenerated non-smooth surface were designed and fabricated. Such a bionic surface was characterized by concave-shape units of different scales that continuously maintained their shape and function during the whole working process. Abrasion tests were carried out to investigate the performance of samples. Results showed that the bionic samples exhibit excellent wear resistance and drilling performance under the action of bionic self-regenerated units, especially those with units of 2 mm - 3 mm diameter. The par- ticle-trapping mechanism coming from the self-regenerated concaves and the lubricating mechanism coming from the con- tinuously self-supplying of solid lubricant are important reasons for reducing or even avoiding the severe abrasions. The im- proved drilling performance of bionic samples derives from, on the one hand, the back edge of bionic unit that contributes to exposing new diamond and supplying additional shear stresses to increase the cutting ability, on the other hand, the enhanced load per unit area due to the decreased contact area at the frictional interface. The relationship between the wear behavior and the scale of bionic unit was revealed. The unit of smaller scale on the bionic samples can enhance the shear stress level. Further reducing the scale to a contain extent will diminish the wear resistance of sample. While increasing the scale can lead to the poor lubricating effect.

Discussion of reasonable drilling parameters in impregnated diamond bit drilling

The impregnated diamond(ID)bit drilling is one of the main rotary drilling methods in hard rock drilling and it is widely used in mineral exploration,oil and gas exploration,mining,and construction industries.In this study,the quadratic polynomial model in ID bit drilling process was proposed as a function of controllable mechanical operating parameters,such as weight on bit(WOB)and revolutions per minute(RPM).Also,artificial neural networks(ANN)model for predicting the rate of penetration(ROP)was developed using datasets acquired during the drilling operation.The relationships among mechanical operating parameters(WOB and RPM)and ROP in ID bit drilling were analyzed using estimated quadratic polynomial model and trained ANN model.The results show that ROP has an exponential relationship with WOB,whereas ROP has linear relationship with RPM.Finally,the optimal regime of mechanical drilling parameters to achieve high ROP was confirmed using proposed model in combination with rock breaking principal.

Three-dimensional Numerical Prediction of the Flow and Temperature Field at the Surface of a PDC Bit

This paper provides a mathematical model and numerical method for predicting the velocity and temperature fields in the mud flows at the surface of a PDC (Polycrystalline Diamond Compact) bit. A 81/2' ( 21 59cm ) crown type PDC R bit is used as an example. The complex configuration of the PDC bit surface is resolved numerically using body fitting coordinates and the cutters are simplified as drag elements in the momentum equations and as heat source in the energy equation. The finite volume method is used to discretize the momentum and energy equations for the non Newtonian flow. The numerical results effectively predict the flow structure and temperature field which can be used to design and optimize the PDC bit.