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为了改善脉动水力压裂钻孔密封性能,选择膨胀水泥冻复合材料(简称PD复合材料)作为密封材料,采用具有典型代表性的管径为95mm和108mm的内壁粗糙的无缝钢管作为模拟钻孔,在不同封孔长度条件下,对压裂密封参数进行实验测定分析.结合Lagrange插值法,计算在所需压力条件下,钻孔密封合理长度.结果表明:PD复合材料承压能力与封孔长度成正比,与钻孔直径成反比.当钻孔直径较小时,钻孔密封段内裂隙扩展的困难程度随封孔长度的增加而增加;反之,随封孔长度的增加而减小.脉动频率越高,对钻孔密封的承压性能要求越高,且高频的脉动压力更有利于脉动压裂过程中钻孔密封段内裂隙的产生与扩展.当脉动水力压力为16MPa时,脉动水力压裂过程中合理的封孔长度为13m.
In order to improve the sealing performance of pulsed hydraulic fracturing, the porous cementitious composite (PD composite) was chosen as the sealing material. The typical representative seamless steel tubes with inner wall roughness of 95mm and 108mm , Under different sealing length conditions, the fracturing sealing parameters were experimentally measured and analyzed.The Lagrange interpolation method was used to calculate the reasonable length of the drilling seal under the required pressure.The results show that the pressure-bearing capacity of the PD composite and the sealing Is proportional to the length and is inversely proportional to the borehole diameter.When the diameter of the boreholes is small, the difficulty of the crack propagation in the borehole sealing section increases with the length of the seal borehole; on the contrary, it decreases with the increase of the seal borehole length. The higher the frequency, the higher the pressure bearing performance of the borehole seal, and the high frequency pulsating pressure is more conducive to the occurrence and expansion of cracks in the drilling seal section during the pulsating fracturing.When the pulsating hydraulic pressure is 16MPa, the pulsation Reasonable sealing length during hydraulic fracturing is 13m.