压力波动对水力锚安全性能的影响

开发低渗难采油气藏的最好办法就是多层压裂技术，多层压裂具有针对性强、作业时间短、压裂效果好等特点，但在压裂过程中经常会出现压力波动，致使管柱上下蠕动从而导致关键工具水力锚和封隔器失效，严重影响施工安全，因此压力波动对水力锚安全性能影响的研究至关重要。针对水力锚锚定、封隔器全部失效这一危险情况，考虑了接触非线性以及压裂管柱的瞬态动力学特性，运用ANSYS软件，建立了上部压裂管柱和下部工具串的力学模型，对不同压力波动幅值下的压裂管柱进行瞬态动力学分析，分析结果表明水力锚最大轴向摩擦力值随波动幅值的增加而增大，同时计算出使水力锚滑脱失效的临界压力波动幅值。该研究结果不仅可以为水力锚的优化设计提供有效的理论依据，也为压裂施工提供合理参数。

Effect of pressure fluctuation on safety performance of hydraulic anchor

The multiple fracturing is the best technology to develop low-permeability oil and gas reservoirs whose exploitation is diffcult. It is advantageous with strong pertinence, simple process, short operation time, low cost and good fracturing effect. In the process of fracturing, however, pressure fuctuation occurs frequently, leading to up and down creeping of strings. As a result, key tools(hydraulic anchor and packer) are failed, and construction safety is seriously impacted. Therefore, it is crucial to study the effect of pressure fuctuation on the safety performance of key hydraulic fracturing tool, i.e., hydraulic anchor. As for the anchorage of hydraulic anchor, the complete failure of packer is the most dangerous scenario. To study this case, the contact nonlinearity and the transient dynamic characteristic of fracturing string were taken into consideration to establish the mechanical model for upper fracturing string and lower tool string by using software ANSYS. Based on this model, the transient dynamic analysis was carried out on fracturing strings under different pressure fuctuation amplitudes. And the critical amplitude of pressure fuctuation corresponding to the slippage failure of hydraulic anchor was obtained. It is shown that the maximum axial friction of hydraulic anchor increases with fuctuation amplitude.These data provide effectively the theoretical basis for the optimal design of hydraulic anchor, as well as the rational parameters for fracturing operation.