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Summary A seismic monitoring case study is documented for stimulation of multiple wells completed in the Lower Montney Shale. A network of 4 broadband stations and 1 accelerometer were deployed and recorded numerous minor seismic events with moment magnitude between 0.5 and 2.8. Sequential hydraulic fracture stages progressively activated several parallel, critically-stressed faults, resulting in induced seismicity during the injection. The case study provides key insights about the spatial and temporal characteristics of the seismogenic faults, and the relationship to fracturing operations. Source mechanisms show a predominantly strike-slip mechanism consistent with lineaments apparent from the seismic locations. The case study highlights observations during multiple fault activation with progressive fault activation and the corresponding ground motion, and provides seismic observations conducive to effective mitigation following a traffic light protocol.
- North America > Canada > British Columbia (0.89)
- North America > Canada > Alberta (0.55)
ABSTRACT: A seismic monitoring case study is documented for stimulation of multiple wells completed in the Lower Montney Shale. A network of 4 broadband stations and 1 accelerometer were deployed and recorded numerous minor seismic events with moment magnitude between 0.5 and 2.8. Sequential hydraulic fracture stages progressively activated several parallel, critically- stressed faults, resulting in induced seismicity during the injection. The case study provides key insights about the spatial and temporal characteristics of the seismogenic faults, and the relationship to fracturing operations. Source mechanisms show a predominantly strike-slip mechanism consistent with lineaments apparent from the seismic locations. The case study highlights observations during multiple fault activation with progressive fault activation and the corresponding ground motion, and provides seismic observations conducive to effective mitigation following a traffic light protocol.
- North America > Canada > British Columbia (1.00)
- North America > Canada > Alberta (1.00)
- Geology > Structural Geology > Fault (0.88)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.62)
- Geology > Petroleum Play Type > Unconventional Play > Shale Play (0.62)
ABSTRACT: The initial state of pore pressure in the reservoir and the presence of permeable pathways are both likely to control stress perturbations during and after fluid injection. The pressure difference between reservoir compartments is usually caused by a barrier to fluid flow, such as an impermeable layer or fault. The objective of this study is to investigate the effects of pressure partitioning on induced seismicity in the vicinity of the Montney Septimus field near Fort St. John, British Columbia. A reservoir modeling approach is used to find the empirical relationships between petrophysical, geomechanical and hydrodynamic characteristics of the reservoir, and the regional induced seismicity. Preliminary results suggest that sealing faults act partially as pressure barrier, but seal preservation depends on depth and the reservoir pressure distribution. In general, areas with lateral gradients in pore pressure appear to mark the locations of faults that bound pressure compartments. In addition, regions with high fracture extension pressure gradient and low minimum horizontal stress show apparent correlation with induced seismicity. 1. Introduction The Montney tight gas play extends from central Alberta to northeast British Columbia (BC). The Septimus field is part of this unconventional play and is located centrally within the Kiskatinaw Seismic Monitoring and Mitigation Area (KSMMA), BC (Fig. 1). This area has experienced an increase in seismicity, including a total of > 200 cataloged events from 2013–2019 (Pena Castro et al., 2020). On November 30, 2018 an earthquake sequence initiated during hydraulic fracturing operations in the Septimus region of the Montney play. The ML 4.5 mainshock was followed by three significant aftershocks, measuring ML 4.3, ML 3.6, and ML 2.7 (Babaie Mahani et al., 2020; Pena Castro et al., 2020). In order to develop an optimal operational scenario for reservoir development that also minimizes the risk of induced seismicity, the role of pressure and stress partitioning on fault activation requires investigation. This study focuses on the fault and the structural model, petrophysical and geomechanical modeling, stress and pore-pressure analysis in the study area, and empirical relationships between these features and regional induced seismicity. The effect of pressure partitioning on induced seismicity will be discussed. The study area encompasses the Septimus field including the location of the November 2018 earthquakes, and covers a large part of the KSMMA area to ensure that the effects of far-field stress and regional tectonic setting are considered.
- Research Report > New Finding (0.50)
- Research Report > Experimental Study (0.34)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- North America > Canada > Saskatchewan > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- North America > Canada > Northwest Territories > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- North America > Canada > Manitoba > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- (10 more...)
Abstract A vast number of the reported cases of increased seismicity of moderate magnitude (Mw > 0) earthquakes seem to be tied to some form of fluid injection activitiy, being it wastewater disposal by injection into deep wells or high pressure fluid injection into oil and gas reservoirs to hydraulically fracture the rock and improve hydrocarbon recovery. Regulations have been proposed to implement traffic light systems to dictate the responses that the industry needs to take based on either the magnitudes or observed particle velocities or accelerations on the surface. In order to relate the seismic hazard potential in seismically active areas, empirical ground motion prediction equations (EGMPE) are used to relate event parameters like magnitude and location to site characteristics such as peak ground acceleration (PGA) or peak ground velocity (PGV) which tend to be how building codes are parametrized. Therefore, local hazard assessment near hydraulic fractures that generate relatively large magnitude events need to be estimated more precisely by developing and using local EGMPEs. Hybrid deployments combining 15Hz downhole and low frequency near-surface geophones can be used to accurately capture both the localized microseismic events and any large magnitude events associated with hydraulic fracture monitoring across North American basins – Horn River, Eagle Ford, Barnett, and Montney for example. In our studies events with M>0 are observed for completions in these formations. While in many cases the magnitude of these events is too small to be felt on the surface, there are reports of higher magnitude events which have been sensed by workers on site and the local population. The exact relationships between magnitudes and shaking are not necessarily one-to-one. Shaking also varies based on the stress release of the events. As summarized recently by Hough (2014) for other fluid-induced seismicity, the lower stress releases typical for these sequences results in on-average less shaking than is observed for equivalent magnitude tectonic events. In order to quantify shaking over a seismogenic volume, we show how to develop EGMPEs based on the North-American examples. The EGMPE methodology developed in this study can be extrapolated for similar earthquakes of larger magnitude and included into future probabilistic hazard and risk analysis for induced seismicity as related to hydraulic fracture stimulations.
- North America > United States (1.00)
- North America > Canada > British Columbia (0.47)
- North America > Canada > British Columbia > Western Canada Sedimentary Basin > Horn River Basin > Horn River Shale Formation (0.98)
- North America > Canada > British Columbia > Western Canada Sedimentary Basin > Horn River Basin > Otter Park Formation (0.94)
- North America > Canada > British Columbia > Western Canada Sedimentary Basin > Horn River Basin > Muskwa Field > Muskwa Formation (0.94)
- (2 more...)
A Novel Coupled Approach to Investigate the Spatiotemporal Evolution of Fracturing-Induced Seismicity: Case Study
Hui, Gang (University of Calgary, Alberta, Canada) | Chen, Shengnan (University of Calgary, Alberta, Canada) | Gu, Fei (PetroChina Research Institute of Petroleum Exploration and Development, Beijing, China)
Abstract The recent seismicity rate increase in Fox Creek is believed to be linked to the hydraulic fracturing operations near the region. However, the spatiotemporal evolution of hydraulic fracturing-induced seismicity is not well understood. Here, a coupled approach of geology, geomechanics, and hydrology is proposed to characterize the spatiotemporal evolution of hydraulic fracturing-induced seismicity. The seismogenic faults in the vicinity of stimulated wells are derived from the focal mechanisms of mainshock event and lineament features of induced events. In addition, the propagation of hydraulic fractures is simulated by using the PKN model, in combination with inferred fault, to characterize the possible well-fault hydrological communication. The original stress state of inferred fault is determined based on the geomechanics analysis. Based on the poroelasticity theory, the coupled flow-geomechanics simulation is finally conducted to quantitatively understand the fluid diffusion and poroelastic stress perturbation in response to hydraulic fracturing. A case study of a moment-magnitude-3.4 earthquake near Fox Creek is utilized to demonstrate the applicability of the coupled approach. It is shown that hydraulic fractures propagated along NE45° and connected with one North-south trending fault, causing the activation of fault and triggered the large magnitude event during fracturing operations. The barrier property of inferred fault under the strike-slip faulting regime constrains the nucleation position of induced seismicity within the injection layer. The combined changes of pore pressure and poroelastic stress caused the inferred fault to move towards the failure state and triggered the earthquake swarms. The associated spatiotemporal changes of Coulomb Failure Stress along the fault plane is well in line with the spatiotemporal pattern of induced seismicity in the studied case. Risks of seismic hazards could be reduced by decreasing fracturing job size during fracturing stimulations.
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (1.00)
- Geology > Structural Geology > Fault (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- North America > Canada > Saskatchewan > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- North America > Canada > Northwest Territories > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- North America > Canada > Manitoba > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- (2 more...)