Downhole fracturing microseismic event identification method

Abstract

The invention relates to a downhole fracturing microseismic event identification method applied to hydraulic-fracturing microseismic monitoring. Downhole geophones are utilized to collect records during hydraulic fracturing, three-component data are subjected to polarization rotation, an energy ratio between given front and back time windows is computed in a time domain, an energy ratio between a radial component and a vertical component in the time domain, an energy ratio between front and back time windows in a main frequency band of a frequency domain and a time difference evening and superposition curve of multiple perforation signals are integrated, and microseismic events with different energy levels generated during fracturing are identified. By the method, identification efficiency of one-site effective microseismic events is improved effectively, meanwhile failure in effective event identification due to the fact the microseismic events have no amplitude response on a single component is avoided, strong energy noise interference is removed effectively, and classification of the events of different levels and types is facilitated by setting of different threshold values.

Description

technical field [0001] The present invention relates to seismic data processing technology in geophysical prospecting, which utilizes the energy ratio of three-component microseismic records and performs space rotation by analyzing received perforation signals to determine the frequency and period of microseismic events. The threshold value and a variety of signal characteristic curves are used to identify and identify different types of microseismic signals, and to improve the efficiency and effect of microseismic event identification in the fracturing process. Background technique [0002] In order to improve the recovery rate of low-permeability and low-porosity formations, hydraulic fracturing operations are often used in the process of oil exploitation, and the micro-seismic monitoring technology in the well is used to diagnose the hydraulic fracturing stimulation technology and adjust the construction scale, design scheme and Fracture description, efficient use of frac...

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Problems solved by technology

[0004] In the process of natural earthquake location, the identification of microseismic events often adopts the method of STA / LTA time window energy ratio scanning before and after. Natural earthquake stations often use single-component geophones, so this method is very suitable. Due to the complexity of hydraulic fracturing The source mechanism and the randomness of the horizontal component direction of the three-component geophones in the well lead to inconsistent or no response in the amplitude response of the microseismic events generated during the hydraulic fracturing process on the different components of the geophones at all levels. Before and after STA / LTA time-window energy ratio scanning, microseismic events that have no amplitude response in some components may be missed, which will eventually affect the description of fracture orientation and fracture network shape generated by fracturing

[0005] When the monitoring distance is relatively long and the energy of the fracturing microseismic event is relatively weak, the energy of the fracturing microseismic event is similar to the background noise, and it is difficult to select a suitable energy ratio threshold to identify useful fracturing microseismic events from the background noise. For seismic events, how to amplify the difference in energy ratio between fracturing microseismic events and background noise, remove the interference of high and low frequency background noise, and highlight fracturing microseismic events, which is difficult to achieve with conventional microseismic event identification methods

[0006] Although various methods are used in the fracturing process to avoid various disturbances from the surface and the well, such as wellbore waves, gas and fluid flow around the well, and these disturbances are often very energetic, it is difficult to integrate them with the fracturing process by conventional methods. Fracturing microseismic events generated in

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