Using continuous microseismic records for hydrofracture diagnostics and mechanics

Abstract

Using continuous microseismic records is a novel technique for better understanding the mechanics of the fracture network evolution during a hydrofracture treatment, and to provide a tool for diagnostic evaluation of recorded microseismic data. Hydrofracture stimulations are widely used during well completions to optimize production volumes and extraction rates in petroleum reservoirs, enhanced geothermal systems and block-caving mines. Microseismic monitoring is now becoming a standard tool for evaluating the position and evolution of a given treatment, principally by source locating microseismic hypocenters and visualizing these with respect to the treatment volume and infrastructure. The continuous microseismic amplitude record includes the full history of the seismic energy response of the rock mass recorded at a given geophone. We present case studies illustrating the use of this technique for supplementing microseismic locations to better understand the evolution of the fracture treatment, and to diagnose the condition of a given data set, so as to design criteria for more effective processing of the discrete microseismic events.

Interpretation of resonance frequencies recorded during hydraulic fracturing treatments

“…For example, Long‐Period and Long‐Duration events (LPLD) are detected after band passing the recorded data based on the frequency content of the different observed signals (microseismic events, ambient noise...) obtained using the Short‐Time Fourier Transform (STFT) [ Das and Zoback , ]. Likewise, Pettitt et al [] try to incorporate in a single framework the microseismicity, hydraulic treatment conditions, and data frequency content. They observe resonance frequencies during and between microseismic experiments with variations in amplitude.…”

Fracture network engineering for hydraulic fracturing

“…Stepwise relative location (Reyes-Montes et al, 2009a) allows a more accurate source location within the observed MS cluster (and thus a more accurate analysis of the fracture network itself), as the technique depends only on the seismic velocity in the im- Pettitt et al, 2009) F r a c t u r e s mediate volume of the cluster rather than the velocity structure through the geological formation to the receivers. The approach uses a lattice of well-located master events along a developing hydrofracture to relatively locate target events with lower signal-tonoise and that may consist of only S-wave arrivals.…”

“…Analysis of fracture network connectivity and structure uses interpretation of the location data combined with algorithms that utilize amplitude information and source parameters processed from the waveforms. Pettitt et al (2009) investigate this additional amplitude information through analysis of continuous microseismic records. The case studies presented utilized the continuous streams of MS amplitude data recorded during the hydraulic treatments of oilbearing reservoirs and illustrated that both P-and S-waves can only be identified for a small fraction of the seismic record, with most released seismic energy appearing as single phase triggers in the record (Figure 6).…”

Potential use of resonance frequencies in microseismic interpretation

“…On the other hand, continuous recordings and their timefrequency analysis also provide valuable information as illustrated by Das and Zoback (2011) and Pettitt et al (2009). Das and Zoback (2011) use the short-time Fourier transform (STFT) to design a band-pass filter in order to remove background noise and undesired signals.…”