Browsing by Author "Riazi, Naimeh"

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    Anatomy of a buried thrust belt activated during hydraulic fracturing
    (2020-10-18) Riazi, Naimeh; Eaton, David W.
    Tectonically active fault networks are often inter-connected, but in the case of injection-induced seismicity, prior knowledge of fault architecture tends to be severely limited. In most cases, reactivated faults due to fluid injection are inferred, after-the-fact, by the spatial distribution of induced-seismicity hypocenters; such reliance on post-injection seismicity impedes any pre-operational risk analysis, as well as development of a more holistic understanding of fault-system models. By combining high-resolution, depth-migrated 3-D seismic data with a new focal-depth estimation method that reduces spatial uncertainty of hypocenters, this study pinpoints microearthquake fault activation within a buried thrust belt in the Montney Formation in western Canada (British Columbia). During hydraulic-fracturing operations, rupture nucleation occurred on seismically imaged thrust ramps that cut through the Debolt Formation, a massive carbonate layer that underlies the stimulated zone. High-resolution seismic images reveal transverse structures, interpreted as basement-controlled fold hinges or tear faults that transferred displacement between thrust faults during Late Cretaceous - Paleogene compressional shortening. The spatio-temporal pattern of induced seismicity suggests that these transverse structures provide permeable pathways for aseismic pore-pressure diffusion, thus connecting distinct thrust faults and enabling earthquake triggering on a timescale of days and at distances of up to 2 km from the injection wells. Inferred relationships highlight how the fault system is connected, including apparent stress concentrations at the intersections of transverse structures and orogen-parallel thrust ramps.
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    Application of Focal-Time Analysis for Improved Induced Seismicity Depth Control: A Case Study from the Montney Formation, British Columbia, Canada
    (2020-08-10) Riazi, Naimeh; Eaton, David W.; Aklilu, Alemayehu; Poulin, Andrew
    Characterization of induced seismicity and associated microseismicity is an important challenge for enhanced oil recovery and development of tight hydrocarbon reservoirs. In particular, accurately correlating hypocenters of induced events to stratigraphic layers plays an important role in understanding the mechanisms of fault activation. Existing methods for estimating focal depth, however, are prone to a high degree of uncertainty. A comprehensive analysis of inferred focal depths is applied to induced events that occurred during completions of horizontal wells targeting the Montney Formation in British Columbia, Canada. Our workflow includes a probabilistic, nonlinear global-search algorithm (NonLinLoc), a hierarchical clustering algorithm for relative relocation (GrowClust) and depth refinement using the recently developed focal-time method. The focal-time method leverages stratigraphic correlations between P-P and P-S reflections to eliminate the need for an explicit velocity model developed specifically for hypocenter depth estimation. We show that this approach is robust in the presence of noisy picks and location errors from epicenters obtained using a global-search algorithm, but it is limited to areas where multicomponent 3-D seismic data are available. A novel method to determine statics corrections is developed here, to ensure that both passive seismic observations and 3-D seismic data share a common datum in areas of moderate to high topography. Our results highlight the importance of transverse faults, which appear to provide permeable pathways for activation of other faults at distances of up to 2 km from hydraulic fracturing operations.
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    Monitoring Heavy Oil Recovery by Integrating Seismic Data with Reservoir Simulation
    (2015-03-16) Riazi, Naimeh; Lines, Larry
    The purpose of this research study was to monitor the recovery process of a heavy oil reservoir using the time-lapse seismic data in order to reduce the ambiguity of reservoir simulation. The sim2seis (simulation to seismic) procedure was applied in a cold heavy oil production with sand (CHOPS) reservoir located in western Saskatchewan, Canada to convert the pressure and saturation results to seismic attributes as a function of time. Qualitative and quantitative analysis of time-lapse seismic data was also performed to determine the changes in the elastic properties that occurred in the reservoir during hydrocarbon production. In the studied heavy oilfield, operated by Husky Energy Ltd, time-lapse seismic Amplitude versus Offset (AVO) analysis and inversion were also applied to detect the production related changes in the reservoir between the wells. Different time-lapse seismic techniques were applied to maximize the information taken from the seismic data and to increase the reliability of the seismic analysis. Although time-lapse seismic results were successful in identifying the anomalous zones, time-lapse seismic attributes were also extracted to highlight the changes observed in the reservoir and to better confirm and describe the physical properties of the anomalous zones. In addition, forward seismic modeling was applied to derive the AVO responses which should be expected in a typical CHOPS reservoir. The minimum thickness of the reservoir layer which can be resolved by the time-lapse seismic data was also determined by the forward modeling. To compare quantitatively the sim2seis results with the time-lapse seismic results, a rock physics model was also applied to link the reservoir simulation results to the seismic elastic properties and vice versa. This model attempted to mimic the conditions observed in the unconsolidated heavy oil reservoirs. In summary, this research study confirmed that the application of the sim2seis process can improve the characterization of a heavy oil reservoir in four dimensions in a quantitative sense. Different time-lapse seismic analyses were applied to extract the maximum information from the time-lapse seismic data and to identify the foamy oil zones and production footprints. This procedure leads to the improvement in the forecasting of the future reservoir performance.