水力压裂物理实验模拟初探

Preliminary study on physical experimental simulation of hydraulic fracturing

为了研究水力压裂中岩石的破裂及裂缝延展规律,开展水力压裂实验模拟.采用大型真三轴压裂设备对花岗岩岩样(300 mm×300 mm×300 mm)进行水力压裂,16道检波器接收,在识别的声发射信号上拾取初至走时,Geiger定位结果表明,压裂中声发射事件位置与压裂示踪剂显示相一致,CT扫描制作的数字岩心准确反映实际的破裂面.从压裂曲线上提取的破裂压力,结合围压分析表明,整个破裂面与初始破裂相一致,岩石破裂后沿该破裂面延展,直至结束.实验分析表明,裂缝发育由裂缝方向和裂缝类型共同决定,遵循裂缝发育能量消耗最小原则,合理解释了本次实验压裂现象;针对实验中单一破裂现象,提出了改进水力压裂设计的建议.

In order to study the rule of rock fracture and extension in hydraulic fracturing, hydraulic fracturing experiment simulation was carried out. The granite samples(300 mm×300 mm×300 mm×300 mm) were hydraulic fractured with large-scale true triaxial fracturing equipment. Sixteen geophones were received and the first arrival travel time was picked up on the identified acoustic emission signals. Geiger positioning results show that the location of acoustic emission events in fracturing is consistent with the display of fracturing tracer. The digital image data produced by CT scanning is accurate. It really reflects the actual fracture surface. The fracture pressure extracted from the fracturing curve and the analysis of confining pressure show that the direction of the whole fracture surface is basically the same as the initial fracture direction, and the rock extends along the fracture surface until the end of the fracture.The experimental analysis shows that the fracture development is determined by the direction and type of the fracture, and the experimental phenomenon is reasonably explained according to the principle of minimum energy consumption of the fracturepropagation. In view of the single fracture phenomenon in the experiment, some suggestions are put forward to improve the hydraulic design.