Computer Aided Design Of High Speed PDC Coring Bit

With the development of China’s oil and gas resources gradually comes into the middle and later stage, people begin to drill and core for deeper and harder layers and the difficulty of the drilling operation coefficient also increases. As the key tool for drilling and coring in modern oil and gas well technology, the PDC coring bits have quick drilling speed, good stability, long life and other advantages,and has been widely used for many years. However,when the PDC coring bits are drilling in hard rock layers, there will be problems such as slow drilling rate, quick wear and so on. The drilling efficiency and service life of bits will severely reduce. Practical experience shows that the performance of bits is closely related with its structural design.The reasonable structure design can improve the bits’ drilling speed and reduce the wear to,achieve fast and efficient drilling. Therefore, with the continuous development of downliole drilling tools, it has important practical significance and academic value to research PDC coring bits using in high-speed environment.Firstly, the structure design of high-speed PDC coring bits was researched and analyzed in this paper. For the crown structure of high-speed PDC coring bits, three basic crown profile shape models were put forward and parametric design methods of each crown shape were summarized. Through comparing the advantages and disadvantages of three basic crown shapes, the crown shape for structure design of high-speed PDC coring bits was selected. According to the cutter arrangement theory of PDC coring bits, the cutters were arranged.Secondly, the force distribution of high-speed PDC coring bit was analyzed. The relationship between the force distribution of cutters with cutting parameters, caster angles of cutters and rock drillability grade was researched and analyzed. Mechanical calculation model of single cutter was established and the whole mechanics analysis model of the bit was established based on it. Finite Element Analysis was used to calculate the maximum stress and deformation of the high-speed PDC coring bit when it was in different cutting depth. And the bit’s strength was checked. The results show that the structure of the bit has sufficient strength and stability.Then, the FLUENT software was used to simulate and analyze the bottom-hole flow field of high-speed PDC coring bit. Describe the velocity and pressure distribution in the area of bit bottom,cutter and chip groove in detail. The velocity and pressure changes of the bottom-hole flow field when the bit in different flow, drilling rate and cutting depth conditions were simulated and calculated. Speed changes on the cutters’ surface were analyzed to check whether cleaning and cooling effect of the bit meet the design requirements and the bit structure design is reasonable.Lastly, write the structure design program software of high-speed PDC coring bit based on the theory of structure design. Use the Visual Basic 6.0 language to develop SolidWorks software’s econdly for structure design of high-speed PDC coring bit. It has very high practical value and development significance to design the high-speed PDC coring bit reasonably and scientifically.The computer aided design of high-speed PDC coring bit in this paper has certain guiding significance for drilling in hard rock layers.Through studying the bit structure design, simulating the bottom-hole flow field distribution and write a set of procedural design software for structural parameters, some results were achieved finally as follow.1. Through researching the crown profile shape and cutter arrangement theory of high-speed PDC coring bit, the advantages and disadvantages of three basic crown shapes were compared. It concluded that the high-speed PDC coring bits should be selected parabolic crown shape design and cutters arrange on straight blades. In order to achieve the goal of high speed drilling, the high-speed PDC coring bit has 8 blades and 48 cutters.2. The mechanical model between the force distribution of cutters with cutting parameters, caster angles of cutters and rock drillability grade was established, and the whole mechanics analysis model of the bit was established based on it. The maximum stress and deformation of the high-speed PDC coring bit when it was cutting the rock were calculated by Workbench software. When the cutting depth is 2 mm, the maximum stress is 18.22MPa and the maximum deformation is 0.0108 mm. When the cutting depth is 4 mm, the maximum stress is 56.331MPa and the maximum deformation is 0.0333 mm. When the cutting depth is 6 mm, the maximum stress is 117.48MPa and the maximum deformation is 0.0695 mm. The bit’s strength was checked to demonstrate that the structure strength and stability of the designed bit all meet the design requirements.3. The FLUENT software was used to simulate and calculate the velocity and pressure changes of the bottom-hole flow field when the bit in different flow, drilling rate and cutting depth conditions. The results prove that as the speed increases gradually, the pressure gradient and flow velocity in the bottom hole will increase, and the cleaning and cooling effect of the drill bit will be better. However, the increasing of cutting depth makes the pressure gradient and flow velocity in bottom hole decrease, which leads to debris piling up on the bit and impacts the cleaning and cooling effect of the bit. The rate of flow hardly affect the speed and pressure distribution of the bottom hole flow field.4. Write a set of structural parametric design software program for high-speed PDC coring bit. According to the structure characteristics of high-speed PDC coring bit, it can be divided into four structural unit. And set up unit databases respectively. Use the VB language to link the structural unit databases with the SolidWorks software. Call the programs to control the SolidWorks software drawing automatically. In this way, the structure design of high-speed PDC coring bit can be completed.In this article, the structure of high-speed PDC coring bit was design optimally,so as to achieve the purpose of the high speed for drilling. Use the numerical simulation method to simulate and calculate the bottom-hole flow field of the bit and write a set of structural parametric design software program for high-speed PDC coring bit. It provides a certain theoretical basis for the study of the structure design of high-speed PDC coring bit.