The pressure data is acquired on the ground in the traditional hydraulic fracturing in-situ stress measurement method. The data from the pressure sensor is the water pressure of the pipeline on the ground. Because of the pipeline parameters, flow change and test depth, the pressure value showed by the pressure sensor will be different from the actual pressure value of the rock crack underground. So, the accuracy of in-situ stress measurement results will be reduced if fracturing pressure is simply added by ground pressure and water column pressure. In addition, the pressure data will be disturbed by the noise due to the reciprocate shock of the high pressure water pump.
The above problems will be well solved if a tiny collector can be placed close to the test section in the borehole. The length of the experimental circuit board is only 50mm and the width is only 24mm. The working range of the pressure is 0–40MPa. Trafag 8253 is used as the pressure sensor. The tiny collector can run for about 30 hours with just one AA battery. The tiny collector is placed in a protective tube and the tube is connected to the fracturing pipe which is used in the traditional method. The experiment discovers that the actual pressure value near the rock crack underground is not simply added by ground pressure and water column. Also, there is a big limitation with the empirical formula which is used to calculate the underground pressure in the past. In engineering measurement, it will be more accurate and reliable using the method of underground pressure gathering to calculate the in-situ stress.
