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裂缝宽度及其变化规律对验证水力压裂模型及指导压裂施工设计具有重要意义。由于水力裂缝宽度比其长度和高度小3~4个量级,且储层埋藏较深,目前尚无法直接测量实际地层中的水力裂缝宽度,仅能大致通过模型估算或数值模拟获得。通过在室内压裂试件中布置单根或多根布拉格光纤光栅(FBG)应变传感器,对类混凝土材料的水力裂缝宽度进行多点同步动态监测,得到不同时刻多点水力裂缝宽度的变化,并依据裂缝宽度变化得到了裂缝扩展速度,从而对水力压裂裂缝扩展中的尺度变化进行了过程描述。实验研究表明,室内水力压裂模拟实验中水力裂缝的宽度为微米级别,裂缝扩展速度为0.1 mm/s量级;在水力压裂过程中,裂缝宽度随裂缝扩展呈现波动式变化,并非随着裂缝扩展单调增加。研究结果对认识水力压裂裂缝的扩展及提升压裂工艺技术具有重要参考价值。
The width of cracks and its variation are of great significance to verify the hydraulic fracturing model and guide the design of fracturing construction. Because the width of hydraulic fractures is 3 ~ 4 orders of magnitude shorter than its length and height, and the reservoir is deeply buried, the width of hydraulic fractures in the actual formation can not be directly measured at present, and can only be obtained by model estimation or numerical simulation. By arranging single or multiple FBG strain sensors in indoor fracturing test pieces, the hydraulic cracks width of concrete-like materials are dynamically monitored by multi-point synchronization, and the change of multi-point hydraulic fracture width at different times is obtained According to the change of crack width, the crack propagation speed is obtained, and the scale change in the expansion of hydraulic fracturing is described. Experimental results show that the width of hydraulic fractures in the laboratory hydraulic fracturing simulation experiment is on the order of micrometers, and the rate of fracture propagation is on the order of 0.1 mm / s. In the hydraulic fracturing process, the fracture width fluctuates with the crack propagation, Crack expansion monotonically increases. The results of the study have important reference value for understanding the expansion of hydraulic fracturing and improving fracturing technology.