压裂泵泵头体相贯线裂尖应力场及应力强度因子研究

Research on Stress Distribution and Stress Intensity Factor of Crack Tip on Interesting Line of Fracturing Pumphead

压裂泵泵头体作为油气压裂工艺的中的关键装备,直接决定了压裂技术的成败,影响油气开采效率和经济效益。针对现有泵头体相贯线处的疲劳开裂失效现状,建立了泵头体有限元分析模型和不同初始长度的圆形裂纹断裂模型,通过分析裂尖应力场和应力强度因子的分布规律。结果表明:内压作用下,泵头体整体仍处于弹性区,只有裂纹面前方两侧的45°~70°区域进入塑性区。相贯线处的裂纹类型虽然为Ⅰ-Ⅱ-Ⅲ复合裂纹,但是仍然是I型裂纹主导,裂纹的起始位置位于两个内腔表面。不同裂纹长度,其应力强度因子分布规律基本一致;但是初始裂纹越长,裂纹越容易发生扩展。裂尖附近区域应力分布是影响裂纹起裂的关键因素,但泵头体两个相贯内腔半径也会影响裂纹起裂。通过分析泵头体裂尖应力场和应力强度因子,可以更好了解泵头体疲劳开裂原因和裂纹起裂位置,为泵头体的工程应用提供理论依据。

Fracturing pump head as the key equipment of fracturing operation, the working performance ofwhich directly decides the fracturing effects and economic efficiency of oil and gas exploitation. Considering the fa-tigue cracking failure conditions of pump head, the finite element analysis modeles of pump head and facture mode of circular crack with different initial length are built. Based on the analysis of stress distribution around the crack tip and the change law of stress intensity factor, the results show that： under the effect of internal high pressure, the pump head is still in the elastic stage on the whole, only an extremely small area 45° -70°around the two sides of crack surface is in the plastic stage. The fracture mode of the crack at the intersecting line of pump head is a mixed I - II - III crack,but the I mode crack still plays an overwhelmingly dominant role. The location of fracture initiation is at the inner surfaces of piston chamber and suction chamber. For crack with different length, the varia-tion trend of stress intensity factor is almost the same, but longer crack is easier to be propagated. Stress Distribu-tion is the key factor of crack initiation, but the radiuses of two inner chamber also have an influence on the action of crack initiation. The analysis on stress distribution and stress intensity factor give a better insight into the initia-tion reason and I nitiation position, which can provide a theoretical foundation for the practical application of pump head.