Fuxian Song

Detection and Enhancement of Microseismic Signals with Correlation Operators: "Cross Product and Master Event" Methods

A class of more general polarization filters, referred to as rectilinear motion detectors (REMODE), is being developed in which the filter functions are based on the correlation functions for two components. Sometimes the correlation function is used between a selected signal describing a target seismic event and seismic data (Gibson and Ringdal 2006). In this study, two ―linear motion detector‖ type operators were applied to enhance the signal/noise ratio of the microseismic signal.

Kinematics of Rupture Propagation During Hydraulic Fracturing

Summary The problem of hydraulic fracture propagation is of great interest for unconventional gas development because of wide use of fracturing treatment. In this paper, we analyzed a microseismic dataset from hydraulic fracture stimulation of a tight gas reservoir at Dowdy Ranch field, USA in order to determine the kinematics of fracture propagation. Evaluation of the spatial-temporal distribution of microseismic events reveals an asymmetric hydrofracture growth on two sides of the injection well; the east wing was almost three times longer than the west wing. The asymmetry was also reflected in the speed of growth and the number of microseismic events, with almost four times greater speed and ten times more events to the east than to the west. The east and west wings propagate at an average rate of 0.49 and 0.13 m/minute separately in a three-hour period. The average rupture size per event is around 0.58 m and 1.87 m for the east and west wings, respectively. Full waveform based complete moment tensor inversion indicates a dominant shearing mechanism of hydrofracture events. The derived source radius is similar to the average rupture size.

Improved Methods for Hydrofrac Event Detection and Phase Picking

The ability to detect small microseismic events and identify their P and S phase arrivals is a key issue in hydraulic fracture monitoring because of the low signal-to-noise ratios. We propose a array-based waveform correlation approach to detect small magnitude events with similar mechanisms and locations as a nearby master event. For the phase picking part, a transformed spectrogram method is used to identify the weak P arrivals. We have applied the technique to a downhole monitoring dataset of the microseismic events induced by hydraulic fracturing. The results show a better phase identification.