- Current Issue
- Accept
- Online First Archive
Volume 52,2025 Issue 1
-
Influence of Wear on Rock contact area of V-shaped Cutter PDC Bit
QI Renze, REN Lei, BU Changgen
Abstract:
With the increasing demand of deep-sea and deep-earth drilling, the wear of downhole drilling tools using traditional PDC bit is serious, which cannot fully meet the drilling requirements of deep wells in hard formation, so the special-shaped cutter PDC bit, especially the V-shaped cutter PDC bit, become the focus of research. At present, there are few studies on the influence of wear on rock contact area of V-shaped cutter PDC bit, so it is very important to study the influence of V-shaped cutter wear on its ROP. In order to calculate the contact area between the V-shaped cutter and the rock in the wear stage, by using the method of plane inclined intercepting the cylindrical surface where the composite piece is located, we deduce the expression of the contact area as a function of the wear height and the geometric parameters of the V-shaped cutter, such as chord length and tangent angle, and we analyze the influence of the geometric parameters of the V-shaped cutter and the wear height on the contact area and the contact pressure. The results show that: in the early stage of wear, the contact area of cylindrical cutter and V-shaped cutter is the same, when the composite piece wears to a certain stage, the contact area of V-shaped cutter is smaller, and the smaller the chord length and tangent angle are, the smaller the contact area is; under the same load, when the wear reaches to a certain stage, the contact pressure of the V-shaped cutter is larger compared to that of the cylindrical cutter, and it have the ability to cut deeper into the rock. When drilling rock formations, V-shaped teeth PDC drills can be used, by measuring the height of the cutting teeth wear and accurately calculating the contact area between the cutting teeth of the drill bit and the rock, it is convenient to adjust the drilling pressure in time to maintain a higher drilling speed; or optimize the geometric parameters of the V-shape teeth when designing, which is also conducive to improving the drilling efficiency.
- 1
-
Design and analysis of continuous circulation valve
CUI Shuying, CHEN Xiaojun, CHEN Genlong, ZHAO Ming, TIAN Yingying, ZHANG Xin, HAN Zelong
Abstract:
The continuous circulation valve can maintain the continuous circulation of drilling fluid when drilling is stopped, which can effectively solve the sediment at the bottom of the hole and the fluctuation of pressure at the bottom of the hole, especially for the horizontal drilling of oil and gas in the sea. In this paper, a continuous circulation valve is designed, the structure and working principle of the continuous circulation valve are introduced, the force analysis and structural optimization design are conducted on the strength of the body under extreme working conditions, and the side opening of the bypass valve with a safety factor greater than 1.5 times was selected; A finite element stress analysis is conducted on the bypass valve, which comprehensively analyzed the stress distribution and sealing pressure. The influence of changes in the half cone angle of the sealing pair and the thickness of the valve on the stress and sealing effect of the bypass valve is obtained. The half cone angle of the sealing pair and the thickness of the valve are selected, and the bypass valve sealing test and body strength test are conducted, proving that the strength and sealing performance of the continuous circulation valve meet the actual usage requirements.
- 1
-
Dynamic Characteristics Analysis of CDH-125 Valve-less Pneumatic Down-the-Hole Hammer Impact System
Guo Naiming, Wang Qingyan, Luo Chaochun, Zhong Weiling, Li Haoxuan
Abstract:
This paper studies the impact dynamics process of the CDH-125 pneumatic down-the-hole (DTH) hammer, accurately analyzing the force state during the motion of the valveless distribution piston. Subsequently, based on the finite difference method, the thermodynamic and dynamic differential equations of the DTH hammer during its working process are iteratively solved to obtain the dynamic working characteristics of the DTH hammer piston and air chambers. These characteristics include the relative relationship between piston displacement and velocity, and the pressure and temperature exchange relationships in the front and rear air chambers. The results obtained from the finite difference method were compared and validated using the multiphysics simulation software SimulationX, showing a maximum speed discrepancy of 3% for the piston stroke, 19% for the return stroke, and 5% for the working frequency. Based on these results, further calculations and analyses of the gas viscous friction force between the piston and the inner cylinder were conducted. The results indicate that, compared to the ideal situation with non-viscous fluid, the viscous friction force reduces the working frequency of the DTH hammer by 0.15% per working cycle and increases the maximum energy consumption of the piston stroke by 0.05-1.34J per cycle. The impact of viscous friction on the dynamic performance of the DTH hammer cannot be ignored.
- 1
-
Failure analysis of PDC spherical cutter for drill bit
Zhao Hongchen, Meng Dezhong, Xu Liang, Ye Hongyu, Yue Wen
Abstract:
As one of the key technologies in the exploration and development of geothermal resources, the efficiency and effect of DTH hammer drilling largely depend on the performance of the drill bit, especially the quality and life of PDC spherical cutters. In response to the current issues such as low drilling efficiency and short service life due to the breakage, detachment, and severe wear of cutter in air-assisted percussive drill bits. This paper conducts a macroscopic and microscopic analysis of the PDC spherical cutter, investigates the causes of failure and the failure mechanisms, and proposes targeted measures for improvement. The results show that the main failure modes of PDC spherical cutters are tooth fracture, wear and fall off. The main reason for the failure of the cutter is that the cutter is damaged by tangential impact compression and normal tensile stress at the same time, while the poor performance of the cutter material itself, and the combination strength of the diamond layer and the cemented carbide matrix are also important reasons for the failure. In order to improve the performance and service life of PDC spherical cutters, the stress burden of the cutters can be reduced by optimizing drilling parameters and adjusting external operating conditions. In addition, innovation and improvement of the material formulation, structural design and manufacturing process of PDC spherical cutters is also an effective way to improve its impact resistance and wear resistance. Through these comprehensive performance improvement methods, the reliability of PDC spherical cutters can be effectively improved, thus improving the operational efficiency of downhole drilling and the service life of the bit.
- 1
