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.