Dynamic monitoring of fracture extension in unconsolidated sand specimen by GPR

We conducted a GPR monitoring to observe the extension of fractures created by hydraulic fracturing. To achieve this monitoring, a measurement system with higher time accuracy and faster data acquisition rate are needed. We designed a VNA (Vector Network Analyzer) measurement system using a Vivaldi array antenna. The VNA measurement system has the time resolution of 1 ps/sample and the data acquisition rate of 0.78 sec/acquisition, where the system dynamic range is about 100 dB. The Vivaldi array antenna has a wide frequency bandwidth of 0.3 MHz~6 GHz. Comparing the actual formation of the fracture and the infiltrated region with the measurement result, we can verify the extension of the fracture indirectly. Also it may be possible to understand the relation between the pressure of the fracturing fluid and the formation of the fracture in real time.