Long-Period, Long-Duration Seismic Events and Their Probable Role in Reservoir Stimulation and Stage Productivity
- AECOM, Morgantown, WV (United States); National Energy Technology Lab. (NETL), Morgantown, WV (United States)
- National Energy Technology Lab. (NETL), Morgantown, WV (United States)
- Univ. of Pittsburgh, PA (United States)
Hydraulic fracturing is a well-established technique to extract gas or liquid hydrocarbons from low-permeability formations like shale and tight gas reservoirs. Diffusion of hydrofracturing fluid outward from the stimulated fractures into the target formation produces slip across preexisting fractures and other discontinuities in the rock. Microseismic events recorded by downhole seismic monitoring arrays are a manifestation of associated deformation. Recent investigations suggest that the total cumulative seismic moment of microearthquakes during hydraulic fracturing is only a small portion of the total seismic energy release expected for the fluid volume injected into the formation. These observations suggest that other sources of energy release (such as inelastic deformation), contemporaneous with microseismicity, should be considered as relevant to the hydraulic fracturing process. Recent observations on long period, long duration (LPLD) seismic events suggest that slow slip emission along weaknesses that are misaligned with respect to the present-day stress field are likely an important mechanism of deformation and should be better understood and quantified in reservoir stimulations. In Morgantown, West Virginia, we carried out seismic monitoring of hydraulic fracturing activity using an array of five broadband, three-component surface seismometers. Using this network, we identified 89 high-amplitude, impulsive events and 436 long period, long duration (LPLD) events, with highly emergent waveform characteristics. In these interpreted LPLD events, we observed a significant concentration of energy in the 0.8-3 Hz frequency range. During hydraulic fracturing, LPLD events were found to occur most frequently when the pumping pressure and rate were at or near maximum values. As the main purpose of hydraulic fracturing is to stimulate oil and gas production from the less permeable reservoir, we compared the relative production contribution per stage to the frequency of occurrence of suspected LPLD events. We found positive correlation between the frequency of LPLD events and stage-by-stage gas production, highlighting the potential contribution of slow deformation processes and its effectiveness in the reservoir stimulation.
- Research Organization:
- National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)
- Sponsoring Organization:
- USDOE Office of Fossil Energy (FE)
- Grant/Contract Number:
- DE-FE0004000
- OSTI ID:
- 1569826
- Report Number(s):
- NETL-PUB-22084; 1094-6470
- Journal Information:
- SPE (Society of Petroleum Engineers) Reservoir Evaluation and Engineering, Vol. 22, Issue 2
- Publisher:
- Society of Petroleum EngineersCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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