Development and application of experimental apparatus of hydraulic sand fracturing

In order to study the transport rules of propping agent in unconventional gas exploration, an apparatus of hydraulic sand fracturing is developed. It is mainly composed of rock triaxial testing machines, servo control system of hydraulic fracturing pump and acoustic emission text system. The advantages of the apparatus are illustrated as follows: (1) Hydraulic sand fracturing tests are able to be implemented under different formation stresses and pump rates. (2) Fracturing fluid injection is controlled by means of the pump rate or pump pressure. (3) AE sensor is improved for pressure-resistance, which can be used in triaxial cell. A series of hydraulic fracturing tests are performed under a combination of different formation stresses, different pump rates and fracturing fluid with sand conditions by this apparatus. The results show that the larger the formation pressure and the higher the pump rate, the larger the initiation pressure in red sandstone. The further distance the hydraulic sand fracturing surface off the open hole, the lower the concentrations of agent. But the local part has no propping agent. AE cumulative hits linearly relate with the time at the initial stage and increase rapidly while the sandstone approaches failure.