scholarly journals Effects of Asperity Distribution on Fluid Flow and Induced Seismicity During Deep Geothermal Exploitation

2016 ◽  
Vol 97 ◽  
pp. 470-477
Author(s):  
Antonio P. Rinaldi ◽  
Luca Urpi ◽  
Dimitrios Karvounis
Keyword(s):  
Fluid Flow ◽  
Induced Seismicity ◽  
Asperity Distribution

Lithology and reservoir properties of the Delaware Mountain Group of the Delaware Basin and implications for saltwater disposal and induced seismicity

2021 ◽  
Vol 91 (11) ◽  
pp. 1113-1132
Author(s):  
Katie Smye ◽  
D. Amy Banerji ◽  
Ray Eastwood ◽  
Guin McDaid ◽  
Peter Hennings
Keyword(s):  
Fluid Flow ◽  
Induced Seismicity ◽  
Gamma Ray ◽  
Produced Water ◽  
Storage Capacity ◽  
Reservoir Properties ◽  
Flow Models ◽  
Delaware Basin ◽  
Development Scenarios ◽  
Porosity And Permeability

ABSTRACT Deepwater siliciclastic deposits of the Delaware Mountain Group (DMG) in the Delaware Basin (DB) are the primary interval for disposal of hydraulic fracturing flowback and produced water from unconventional oil production. Understanding the storage capacity of the DMG is critical in mitigating potential risks such as induced seismicity, water encroachment on production, and drilling hazards, particularly with likely development scenarios and expected volumes of produced water. Here we present a basin-wide geologic characterization of the DMG of the Delaware Basin. The stratigraphic architecture, lithology, and fluid-flow properties including porosity, permeability, amalgamation ratios, and pore volumes, are interpreted and mapped. Lithologies are predicted using gamma-ray and resistivity log responses calibrated to basinal DMG cores and outcrop models. Sandstones exhibit the highest porosity and permeability, and sand depocenters migrate clockwise and prograde basinward throughout Guadalupian time. Permeability is highest at the top of the Cherry and Bell Canyon formations of the DMG, reaching tens to hundreds of millidarcies in porous sandstones. Porous and permeable sandstones are fully amalgamated at the bed scale, but at the channel scale, most sandstones are separated by low-permeability siltstones or carbonates where net sandstone is less than 30%. This geologic characterization can be used to assess the regional storage capacity of the DMG and as input for dynamic fluid-flow models to address pore-pressure evolution, zonal containment, and induced seismicity.

Multi-phase hydromechanical modeling of induced seismicity: general insights and the case study of the deep geothermal project in St. Gallen, Switzerland

2020 ◽  
Author(s):  
Dominik Zbinden ◽  
Antonio Pio Rinaldi ◽  
Tobias Diehl ◽  
Stefan Wiemer
Keyword(s):  
Fluid Flow ◽  
Induced Seismicity ◽  
Gas Flow ◽  
Fluid Injection ◽  
Induced Earthquakes ◽  
Stress Changes ◽  
Reservoir Conditions ◽  
Multi Phase ◽  
Phase Fluid

<p>Industrial projects that involve fluid injection into the deep underground (e.g., geothermal energy, wastewater disposal) can induce seismicity, which may jeopardize the acceptance of such geo-energy projects and, in the case of larger induced earthquakes, damage infrastructure and pose a threat to the population. Such earthquakes can occur because fluid injection yields pressure and stress changes in the subsurface, which can reactivate pre-existing faults. Many studies have so far focused on injection into undisturbed reservoir conditions (i.e., hydrostatic pressure and single-phase flow), while only very few studies consider disturbed <em>in-situ</em> conditions including multi-phase fluid flow (i.e., gas and water). Gas flow has been suggested as a trigger mechanism of aftershocks in natural seismic sequences and can play an important role at volcanic sites. In addition, the deep geothermal project in St. Gallen, Switzerland, is a unique case study where an induced seismic sequence occurred almost simultaneously with a gas kick, suggesting that the gas may have affected the induced seismicity.</p><p>Here, we focus on the hydro-mechanical modeling of fluid injection into disturbed reservoir conditions considering multi-phase fluid flow. We couple the fluid flow simulator TOUGH2 with different geomechanical codes to study the effect of gas on induced seismicity in general and in the case of St. Gallen. The results show that overpressurized gas can affect the size and timing of induced earthquakes and that it may have contributed to enhance the induced seismicity in St. Gallen. Our findings can lead to a more detailed understanding of the influence of a gas phase on the induced seismicity.</p>

Towards coupling fluid flow and rate-and-state friction in compacting visco-poro-elasto-plastic reservoirs

2020 ◽  
Author(s):  
Mohsen Goudarzi ◽  
Ylona van Dinther ◽  
Meng Li ◽  
René de Borst ◽  
Casper Pranger ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Induced Seismicity ◽  
Large Scale ◽  
Bulk Material ◽  
Frictional Heating ◽  
Fluid Pressure ◽  
Gas Production ◽  
Modeling Framework ◽  
Fully Coupled

<p>Induced seismicity as a result of natural gas production is a major challenge from both an industrial and a societal perspective. The compaction caused by gas production leads to changes of the effective pressure fields in the reservoir and stress redistributions occur particularly in the surrounding faults. In addition, the strong coupling between fluid flow and solid rock deformations and the role of fluid flow regarding the frictional properties of the faults necessitate a coupled and comprehensive modeling framework. A general and fully coupled thermo-hydro-mechanical finite difference formulation is developed herein and the results are verified against numerical benchmarks. A visco-elasto-plastic rheological behavior is assumed for the bulk material and a return-mapping algorithm is implemented for accurate simulation of the stress evolution. The geometrical features of the faults are incorporated into a regularized continuum framework, while the response of the fault zone is governed by a rate-and-state-dependent friction model. Numerical simulations are provided for large-scale problems and their efficiency is assured through the evaluation of the consistently linearized systems of equations along with the use of advanced numerical solvers and parallel computing. Although the proposed framework is a step towards the modeling of earthquake sequences for induced seismicity applications, the features of the numerical model are highlighted for other applications, including seismic events in subduction settings where the role of fluid flow inside the faults is considerable. Another application of the present, fully coupled hydro-thermo-mechanical formulation is the prediction of the fluid pressurization phenomena, where the frictional heating increases the magnitude of the pore fluid pressure inside the faults, and the resultant degradation of dynamic frictional strength is naturally captured. </p>

The influence of the heterogeneous asperity distribution on induced seismicity and permeability evolution during hydraulic fault zone stimulation

2020 ◽  
Author(s):  
Linus Villiger ◽  
Dominik Zbinden ◽  
Antonio Pio Rinaldi ◽  
Paul Antony Selvadurai ◽  
Hannes Krietsch ◽  
...  
Keyword(s):  
Shear Zone ◽  
Induced Seismicity ◽  
Shear Zones ◽  
Ductile Shear Zone ◽  
Permeability Evolution ◽  
Permeability Enhancement ◽  
Ductile Shear Zones ◽  
Injection Interval ◽  
Ductile Shear ◽  
Asperity Distribution

<p>Several decameter-scale in-situ stimulation experiments were conducted in crystalline rock at the Grimsel Test Site, Switzerland, with the aim to advance our understanding of the seismo-hydro-mechanical processes associated with deep geothermal reservoir stimulation. To allow comparability between the experiments, a standardized injection protocol was applied for all experiments. Induced seismicity was recorded using acoustic emission sensors and accelerometers, which were distributed along tunnel walls and within four boreholes. Hydro-mechanical responses of the fault zones were measured using grouted longitudinal fiberoptic strain sensors and open pressure monitoring borehole intervals. A total of four ductile shear zones (with brittle overprint) and two brittle-ductile shear zones have been stimulated during these experiments.</p><p>Here we present an analysis of heterogeneous permeability evolution within a target shear zone during ongoing stimulation. The shear zone in question is an originally ductile shear zone which contains a single fracture in the injection interval. The observed planar seismicity cloud indicates that most of the stimulation process was confined within the target shear zone. Hydraulic characterization of the injection interval before and after stimulation revealed an enhancement in interval transmissivity from 8.3<sup>-</sup>10<sup>-11</sup> m<sup>2</sup>/s to 1.5<sup>-7</sup> m<sup>2</sup>/s. Within the reservoir, the seismo-hydro-mechanical data (i.e. seismicity cloud, pressure peaks and local deformation) spatiotemporally coincide, suggesting that permeability enhancement along the shear zone is highly localized and heterogeneous. Thus, we argue that the permeability evolution is linked to asperity distribution and breakdown within the shear zone.</p><p>The conceptual model developed from the experimental analysis is implemented in a three-dimensional numerical model, with which we attempt to simulate the directional permeability creation observed in the experiment. The model accounts for a discrete planar fault zone of finite thickness with distributed low-permeability, brittle asperities embedded in a more permeable damage zone mimicking the ductile shear zone at Grimsel. The hydro-mechanical processes are modeled with the TOUGH-FLAC simulator, which sequentially couples fluid flow and poroelastic deformation within the fault and the surrounding medium. A Mohr-Coulomb failure criterion is used to simulate asperity reactivation, which can lead to permeability enhancement of the reactivated area.</p>

Thermoporoelastic Analysis of Artificially Fractured Geothermal Reservoirs: A Multiphysics Problem

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Arash Dahi Taleghani ◽  
Milad Ahmadi
Keyword(s):  
Fluid Flow ◽  
Heat Generation ◽  
Induced Seismicity ◽  
Closed Loop ◽  
Thermal Power ◽  
Surface Subsidence ◽  
Electricity Production ◽  
Working Fluid ◽  
Hydraulic Fractures ◽  
Geothermal Systems

Abstract Geothermal systems are identified as either open-loop system (OLGS) or closed-loop systems (CLGS). In OLGS, fluid is produced from the subsurface, while there might be a concurrent fluid injection into the reservoir. The loss of working fluid, surface subsidence, formation compaction, and induced seismicity are major challenges in OLGS. To address the indicated challenges, closed-loop geothermal systems can be considered as an alternative option. In this method, a working fluid with low-boiling point is circulated through the coaxial sealed pipes to harvest heat from the formation of rock and fluid. Induced seismicity is essentially caused by the drastic quick changes in pore pressure. Thereafter, seismic risk assessment is expected for any new geothermal technology before starting the field implementation phase. To improve the heat recovery from closed-loop wells, we suggest highly conductive hydraulic fractures for CLGS to improve the heat generation rate. In conventional hydraulic fracturing treatments, fractures facilitate fluid flow; however, in the proposed configuration, induced fractures enhance heat flux into the wellbore. Considering the multiphysics nature of CLGS, a comprehensive analysis of this problem requires simultaneous modeling of fluid flow, energy transfer (heat), and rock deformation. A thermoporoelastic model is developed in finite element methods to simulate this problem. The numerical results suggest that fractures significantly improve thermal power and cumulatively produced heat in CLGS. The thermal conductivity of the proppants is the key parameter enhancing heat generation. The level of surface subsidence in the proposed technique is negligible due to the lack of geofluid production from the reservoir. Significant numbers of abandoned oil or gas wells exist around the globe which can be converted into the geothermal wells to produce electricity. This study shows the feasibility of electricity production from CLGS with minimum environmental hazards.

Investigation of injection-induced seismicity using a coupled fluid flow and rate/state friction model

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. WC181-WC198 ◽  
Author(s):  
Mark W. McClure ◽  
Roland N. Horne
Keyword(s):  
Fluid Flow ◽  
Induced Seismicity ◽  
Large Scale ◽  
Injection Pressure ◽  
Friction Model ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Isolated Fracture ◽  
Lower Magnitude ◽  
Event Magnitude

We describe a numerical investigation of seismicity induced by injection into a single isolated fracture. Injection into a single isolated fracture is a simple analog for shear stimulation in enhanced geothermal systems (EGS) during which water is injected into fractured, low permeability rock, triggering slip on preexisting large scale fracture zones. A model was developed and used that couples (1) fluid flow, (2) rate and state friction, and (3) mechanical stress interaction between fracture elements. Based on the results of this model, we propose a mechanism to describe the process by which the stimulated region grows during shear stimulation, which we refer to as the sequential stimulation (SS) mechanism. If the SS mechanism is realistic, it would undermine assumptions that are made for the estimation of the minimum principal stress and unstimulated hydraulic diffusivity. We investigated the effect of injection pressure on induced seismicity. For injection at constant pressure, there was not a significant dependence of maximum event magnitude on injection pressure, but there were more relatively large events for higher injection pressure. Decreasing injection pressure over time significantly reduced the maximum event magnitude. Significant seismicity occurred after shut-in, which was consistent with observations from EGS stimulations. Production of fluid from the well immediately after injection inhibited shut-in seismic events. The results of the model in this study were found to be broadly consistent with results from prior work using a simpler treatment of friction that we refer to as static/dynamic. We investigated the effect of shear-induced pore volume dilation and the rate and state characteristic length scale, [Formula: see text]. Shear-induced pore dilation resulted in a larger number of lower magnitude events. A larger value of [Formula: see text] caused slip to occur aseismically.

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