The Optimization Of Axial Length In Drill Pipe Upset Transition Area

As one of the most major components of oil drill stem, drill pipe plays a crucial role in oil industry. The data show that the geometry size of drill pipe upset transition area has a significant effect on drill pipe life. Therefore, making a further research on the geometry size of upset transition area has both theoretical and practical significance. This paper took Φ127mm API drill pipe as research object and has made the following studies:1. Study the wear effect caused by different axial lengths through gas blasting experiment. Keeping other dimensions constant,3groups of different axial lengths respectively90mm﹑135mmm﹑180mm are selected and testing samples at the ratio of1:3.175were manufactured. Then the wear situation of upset transition area was observed and measured through blasting experiment. The results show that changing axial lengths has little influence on pressure difference between the two ends of samples, the wear amount in upset transition area decreases obviously with the increase of axial lengths, wear amount of upset transition area which is near to pipe end is greater than that of upset transition area which is near to pipe body, and the wear amount reaches the maximum value at the intersection of upset transition area and pipe end.2. The numerical simulation of gas-liquid two phase flow in sample was carried out. By using the FLUENT software, the flow filed in sample was simulated. Based on simulation results and experimental results, the washout phenomenon in upset transition area and the wear situation of upset transition area with different axial lengths were analyzed. The data show that: the maximum pressure which is located at the upset transition area end is one of the main factors causing washout. Also, under the same working condition, increasing the axial length has no obvious effect on flow properties in drill pipe.3. The axial length of drill pipe upset transition area was optimized. Based on factors affecting wear and simulation results, the result that the impact angle is the main factor causing wear under the same working condition was obtained. After selecting proper wear model, calculate relative wear values of upset transition area of different axial lengths and obtain the optimal value for axial length. The results show that Finnie’s model is consistent with wear data and the optimal axial length is200mm.