The principle of microseismic fracturing monitoring technology originated from the monitoring of natural earthquakes. In the hydraulic fracturing well, due to the change of pressure, the formation is forced to open a large fracture. Along this main fracture, the energy continuously radiates to the formation, forming the tension or dislocation of the formation around the main fracture. These tension and dislocation can radiate the seismic energy of elastic wave, including longitudinal wave and transverse wave, which is similar to the source in seismic exploration, but its frequency is quite high, and its frequency usually varies from 200 Hz to 2000 Hz.

(1)modelling

Based on the collected velocity logging data of fractured wells, as well as the data of seismic profile, velocity data, geological interpretation profile and lithology profile, the initial velocity model of reservoir section is established.

(2)Create ray tracing travel time files for each acquisition station   

In order to save the computing time of the computer in each spatial positioning, the ray travel time table from each point in the space defined by the P-wave velocity model to each ground acquisition station is first created and stored in a file.

(3)data pretreating

The time period of preprocessing microseismic continuous record data is selected, the velocity model of longitudinal wave or shear wave is used, and a certain filtering method is selected to calculate the energy distribution of longitudinal data volume and the depth comparison of production and construction target layer, and further correct the velocity model of longitudinal wave or shear wave.

(4)high precision positioning

The velocity model is verified and optimized according to the strong event records, and the model is further adjusted according to the travel time difference to optimize the velocity model and relocate all microseismic events.

(5)Positioning result analysis

According to the spatial distribution of events, the spatial distribution and distribution of fractures are determined.