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Spring Slider And Finite Element Modeling Of Microseismic Events And Fault Slip During Hydraulic Fracturing
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Book Synopsis Spring-slider and Finite Element Modeling of Microseismic Events and Fault Slip During Hydraulic Fracturing by : Ali Kashefi
Download or read book Spring-slider and Finite Element Modeling of Microseismic Events and Fault Slip During Hydraulic Fracturing written by Ali Kashefi and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydraulic fracturing increases reservoir permeability by opening fractures and triggering slip on natural fractures and faults. While seismic slip of small faults or fault patches is detectable as microseismic events, the role of aseismic slip is poorly understood. From a modeling standpoint, geomechanical analysis using the Coulomb criterion can determine if faults slip but not whether slip is seismic or aseismic. Here we propose a computational methodology to predict fault slip, and whether slip is seismic or aseismic, using rate-and-state friction. To avoid computational costs associated with resolving small faults, we use the spring-slider idealization that treats faults as points. Interaction between faults is neglected. The method is applied to study fault slip from a hydraulic fracture that grows past a fault, without intersecting it. We represent the hydraulic fracture stressing using an asymptotic expansion of stresses around the tip of a tensile crack. We investigate the effect of fault length, orientation, and distance from the hydraulic fracture. For velocity-weakening faults with stiffness smaller than a critical stiffness, slip is seismic, whereas faults with stiffness greater than the critical stiffness slip aseismically. Furthermore, we compare the spring-slider idealization with a finite element analysis that resolves spatially variable slip. The spring-slider idealization provides reasonably accurate predictions of moment and even moment-rate history, especially for faults having stiffness close to or larger than the critical stiffness. Differences appear for large faults where rupture propagation is important, though differences might still be negligible for many applications. The spring-slider methodology could be applied to model statistics of microseismicity and aseismic slip on a population of small faults in a reservoir by populating a stochastic fracture network with spring sliders having frictional properties drawn from a statistical characterization based on well logs and experimental correlations between friction and rock properties.
Book Synopsis Microseismic Imaging of Hydraulic Fracturing by : Shawn Mawell
Download or read book Microseismic Imaging of Hydraulic Fracturing written by Shawn Mawell and published by SEG Books. This book was released on 2014-01-01 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microseismic Imaging of Hydraulic Fracturing: Improved Engineering of Unconventional Shale Reservoirs (SEG Distinguished Instructor Series No. 17) covers the use of microseismic data to enhance engineering design of hydraulic fracturing and well completion. The book, which accompanies the 2014 SEG Distinguished Instructor Short Course, describes the design, acquisition, processing, and interpretation of an effective microseismic project. The text includes a tutorial of the basics of hydraulic fracturing, including the geologic and geomechanical factors that control fracture growth. In addition to practical issues associated with collecting and interpreting microseismic data, potential pitfalls and quality-control steps are discussed. Actual case studies are used to demonstrate engineering benefits and improved production through the use of microseismic monitoring. Providing a practical user guide for survey design, quality control, interpretation, and application of microseismic hydraulic fracture monitoring, this book will be of interest to geoscientists and engineers involved in development of unconventional reservoirs.
Book Synopsis Modeling of Fault Reactivation and Induced Seismicity During Hydraulic Fracturing of Shale-gas Reservoirs by :
Download or read book Modeling of Fault Reactivation and Induced Seismicity During Hydraulic Fracturing of Shale-gas Reservoirs written by and published by . This book was released on 2013 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have conducted numerical simulation studies to assess the potential for injection-induced fault reactivation and notable seismic events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned towards conditions usually encountered in the Marcellus shale play in the Northeastern US at an approximate depth of 1500 m (~;;4,500 feet). Our modeling simulations indicate that when faults are present, micro-seismic events are possible, the magnitude of which is somewhat larger than the one associated with micro-seismic events originating from regular hydraulic fracturing because of the larger surface area that is available for rupture. The results of our simulations indicated fault rupture lengths of about 10 to 20 m, which, in rare cases can extend to over 100 m, depending on the fault permeability, the in situ stress field, and the fault strength properties. In addition to a single event rupture length of 10 to 20 m, repeated events and aseismic slip amounted to a total rupture length of 50 m, along with a shear offset displacement of less than 0.01 m. This indicates that the possibility of hydraulically induced fractures at great depth (thousands of meters) causing activation of faults and creation of a new flow path that can reach shallow groundwater resources (or even the surface) is remote. The expected low permeability of faults in producible shale is clearly a limiting factor for the possible rupture length and seismic magnitude. In fact, for a fault that is initially nearly-impermeable, the only possibility of larger fault slip event would be opening by hydraulic fracturing; this would allow pressure to penetrate the matrix along the fault and to reduce the frictional strength over a sufficiently large fault surface patch. However, our simulation results show that if the fault is initially impermeable, hydraulic fracturing along the fault results in numerous small micro-seismic events along with the propagation, effectively preventing larger events from occurring. Nevertheless, care should be taken with continuous monitoring of induced seismicity during the entire injection process to detect any runaway fracturing along faults.
Book Synopsis Modeling Hydraulic Fractures Using Microseismic Events by : Mohammed Zaki AlQassab
Download or read book Modeling Hydraulic Fractures Using Microseismic Events written by Mohammed Zaki AlQassab and published by . This book was released on 2020 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advancements in hydraulic fracturing technology have enabled the development of unconventional reservoirs. Hydraulic fractures increase the total surface area of the wellbore, which leads to an increase in production rate. One way to evaluate the success of hydraulic fracturing jobs is to detect microseismic events during fracturing. Mapping microseismic events help engineers identify the areal extent of the fractures. However, estimating the actual size, shape, and orientation of hydraulic fractures from microseismic events is challenging because microseismic events are week signals and include noise (Warpinski 2009). Here we propose a novel workflow that builds a discrete fracture model directly from microseismic events. We use several techniques such as density-based spatial clustering of applications with noise (DBSCAN), surface fitting, embedded discrete fracture model (EDFM), and proxy-based assisted history matching (AHM). We first define the region for each stage using the perforation intervals. Then, we use DBSCAN to reduce noise and identify clusters in each stage. Next, we choose the main cluster in each stage to fit a fracture plane to the microseismic events. The last step is to calibrate the fracture model using two scaling factors: one reduces the fracture height and the other reduces the fracture half-length. We determine the appropriate scaling factors using AHM. Therefore, the final calibrated fracture model would match field production data. We found that preliminary fracture model overestimates the size of the fractures. Hence, calibrating the fracture model with production data is important. There are several field applications that can benefit from our workflow. For example, we can compare the fracture models for several offset wells in a reservoir and make some correlations with their fracturing strategies. The best fracturing strategy can then be implemented for future wells. We also introduce a new approach that estimates bottom hole pressure from static wellhead pressure in wellbores filled with gas and water. We divide the gas column into (n) small segments. Then, we evaluate the pressure in each segment along with the depth of the gas-water interface by numerically solving (n+1) equations. This approach is useful in history matching since obtaining bottom hole pressure is challenging and expensive
Book Synopsis An Integrated Geomechanical, Microseismic, and Laboratory Study of the Bakken Formation by : Yi Yang
Download or read book An Integrated Geomechanical, Microseismic, and Laboratory Study of the Bakken Formation written by Yi Yang and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis integrates geomechanics, microseismic, and laboratory studies to investigate the role of preexisting fractures and faults in development of unconventional reservoirs. This study provides a new method for delineation of reservoir structure using microseismic data with support from geomechanics and laboratory measurement. The interpretation from this study can be applied to address some of the practical questions in highly fractured reservoirs, including, but not limited to, well design and hydraulic fracture design. The implication provides insights for future strategic development of fractured and faulted unconventional reservoirs. The first part of this thesis focuses on the production of shale oil from the Bakken Formation and consists of three approaches (Chapters 2-5). A geomechanical model shows the current stress state to be characterized by a NF/SS regime, with SHmax orientation ~N45°E. The microseismic events were recorded in six vertical observation wells during hydraulic fracturing of parallel wells X and Z, and are independently processed by two contractors. Both sets of event locations show three characteristics: First, rather than occurring in proximity to the stages being pressurized, many of the events occur along the length of well Y, a parallel well located between X and Z that had been in production for ~2.5 years at the time X and Z were stimulated. Second, relatively few fracturing stages are associated with an elongated cloud of events trending in the direction of SHmax as is commonly observed during hydraulic fracturing. Instead, the microseismic events in a number of stages appear to trend ~N75°E, about 30° from the direction of SHmax. Earthquake focal plane mechanisms confirm slip on faults with this orientation. Finally, the microseismic events are clustered at two distinct depths, one near the depth of the well being pressurized in the Middle Bakken Formation and the other ~800 ft above in the Mission Canyon Formation. Approximately 60% of the microseismic events from stage 2 exhibit similar waveforms that are occurring in adjacent multiplet clusters. Two multiplet clusters are relocated using the double-difference technique, and the relocated hypocenters are more clustered, delineating reservoir structures that are consistent with the focal plane mechanisms. We argue that all three of these patterns result from the hydraulic stimulation being dominated by flow channeling along preexisting faults. Combined analysis of hypocenter locations, focal plane mechanisms, fault slip, and 3D seismic data indicate that steeply-dipping N75°E striking faults with a combination of normal and strike-slip movement were being stimulated during hydraulic fracturing. A simple geomechanical analysis was carried out to illustrate how this occurred in the context of the current stress field, pore pressure and depletion in the vicinity of well Y during the 2.5 years of production prior to stimulation of wells X and Z. Laboratory measurements of 6 pairs of core samples from the reservoir suggest that the time dependent deformation of these rocks can be characterized by a power-law constitutive law. The constitutive parameters determined from 3-hour creep measurements follow a range and trend similar to those of samples from other shale gas reservoirs. By applying the viscous relaxation model, the differential horizontal stresses are estimated from geophysical logs. With the NF/SS faulting regime in the Bakken and an assumption of a constant faulting regime in sedimentary lithology, a continuous principal stress profile is estimated. The least horizontal stress magnitude suggests that the Lodgepole and Three Forks Formations adjacent to the Bakken Formation are not acting as frac barriers during hydraulic fracture. Thus, the asymmetric distribution of the microseismicity suggests the out-of-zone microseismic events are associated with preexisting fractures and faults rather than purely hydraulic fracturing growth. Moreover, the pore pressure perturbation required for slip is consistent with the occurrence of microseismicity, where events occur at depths that require less elevated pore pressure. Brittleness determined from elastic properties is considered, but it cannot explain the microseismicity. This is because brittleness is not an intrinsic rock property and cannot be characterized in a consistent way. Therefore, applying brittleness for locating the hydraulic fracturing sweet spot needs to be done cautiously. The second part of this thesis focuses on the feasibility of injecting CO2 to enhance coalbed methane production, as well as the capacity for long term CO2 storage in coalbeds of the Power River Basin, Wyoming. Laboratory measurements are performed to study the adsorption/desorption, mechanical, and transport properties of coal with gas saturation of He, N2, CH4 and CO2, at either increasing pore pressure or increasing effective stress. Results suggest that coal from the PRB has strong adsorption capacity for CO2, and this strong adsorption is stable unless the pore pressure drops below 2 MPa. Also, CO2-induced swelling will cause permeability loss, but the loss is less than one order of magnitude. Laboratory results indicate that the coal seam in the study area might be a good candidate for an ECBM and CO2 sequestration project. However, its feasibility still depends on future numerical modeling predictions, and the results reported in this study can be applied for further modeling work.
Book Synopsis Finite Element Models of Earthquake Cycles in Mature Strike-slip Fault Zones by : John Charles Lynch
Download or read book Finite Element Models of Earthquake Cycles in Mature Strike-slip Fault Zones written by John Charles Lynch and published by . This book was released on 2002 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Study of Microseismic Events by : Yunhui Tan
Download or read book Study of Microseismic Events written by Yunhui Tan and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Microseismic is commonly used to monitor the hydraulic fracturing process. Seismic signals are recorded using either surface or downhole geophones to invert for hypocenters of rock movements (moment magnitude usually between -3 and 0) happened during hydraulic fracturing. The location of these microseismic events are used to estimate the stimulated reservoir volume. This thesis focuses on further understanding of microseismic events beyond the cloud of locations. To test whether the lineament of microseismic event cloud represent fluid filled open fractures, we looked at the change of S wave from perforations when it passes microseismic event cloud (Chapter 2). Strong attenuation of S wave suggests that the microseismic event cloud indicates fluid-filled open fractures.We also studied the evolution of medium velocity structure during hydraulic fracturing. By inverting the arrival time of perforation shots recorded by downhole geophones, we found that the velocity of stimulated region is higher than the unstimulated region (Chapter 3).A new model (Rutledge-Eisner model) is introduced to describe the mechanism of microseismic event generation. This model states that the microseismic events are a results of shearing on bedding planes caused by opening of hydraulic fractures. Moment tensor inversion results from surface microseismic monitoring of the Marcellus shale is presented to validate this model (Chapter 4).Based on this model, we explained some phenomena in the temporal and spatial distribution of microseismic events under different geological and geomechanical conditions (Chapter 5). We found that microseismic events concentrate behind the fracture tip in a single planar fracture propagation. Low in-situ stress environment leads to early microseismic events while high in-situ stress lead to late microseismic events during fracturing. Natural fracture networks show unique microseismic temporal patterns with the increased sand concentration. Higher in-situ stress variation between layers lead to more microseismic events and larger magnitude.In summary, microseismic monitoring is an effective method to reveal details about hydraulic fracturing.
Book Synopsis Hydraulic Fracturing and Induced Seismicity by : Mohammad Hossein Azad
Download or read book Hydraulic Fracturing and Induced Seismicity written by Mohammad Hossein Azad and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The injection of fluids into the ground is undertaken in a number of engineering practices including hydraulic fracturing, liquid waste disposal, CO2 sequestration and extraction of geothermal heat (EGS). Study of mechanisms for slip on faults/natural fractures due to hydraulic fracturing is of great interest for the energy resource industry in view of efficiency of hydraulic fracturing, seismic monitoring and seismicity related safety hazards. In this thesis, semi-analytical approaches are applied to investigate physical processes associated with hydraulic fracturing induced seismicity and to develop a deeper understanding of the problem. The primary focus is on the modeling of initiation and growth of slip on a pre-existing fault/fracture due to interaction with a single propagating hydraulic (tensile mode) fracture. The first part of the thesis is concerned with the relationship between hydraulic fracturing injection into a fault and the possibility of a seismic slip. The results show that the nucleation of dynamic slip on a fault with slip-weakening friction is only weakly dependent on the magnitude of the stress perturbation ahead of the propagating hydraulic fracture (HF), or the HF propagation regime, and is mainly controlled by the hydraulic fracture length (i.e., the size of the fully unloaded fault segment at a given time). The growth of the fault slipping patch remains stable when the background shear stress is smaller than the residual fault strength under ambient conditions. Otherwise, nucleation of dynamic slip takes place when the hydraulic fracture grows to the critical size, which is vanishingly small for critically-stressed faults (i.e., when the background stress approaches the fault peak strength) and is diverging when the stability boundary is approached. In addition, no dynamic slip transients are predicted when background shear stress is less than the residual fault strength. In the second part of the thesis we examine the possibility of a microseismic slip on a natural fracture as a result of poromechanical interactions with an advancing hydraulic fracture. Nucleation of slip on the frictional fracture approached by the hydraulic fracture depends on the state of in-situ stresses, hydraulic fracture pressure, angle of approach and friction of the fracture. Slip instability, consistent with field observations, occurs on the critically stressed and favorably oriented strike-slip fracture. Nucleation takes place as the slipping patch reaches the critical length. Finally, we have studied nucleation of slip on a natural fracture crossed by a propagating hydraulic fracture. Slip initiates along the edge crack as the frictional strength drops due to increase in pore pressure by diffusion of fluid from the hydraulic fracture.
Book Synopsis The Role of Fluids in Faulting by : Yuyun Yang
Download or read book The Role of Fluids in Faulting written by Yuyun Yang and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid-rock interactions have long been recognized as crucial drivers in earthquakes and slow slip events. In the context of induced seismicity, the injection of high-pressure fluid underground during wastewater disposal, hydrothermal energy production or hydraulic fracturing operations have triggered earthquakes in geologically stable regions that previously had minimal detected seismicity. Many hypotheses about how these earthquakes were triggered have been proposed, including pore pressure diffusion, long-range poroelastic stressing, and fault loading and reactivation by aseismic slip. The injection of fluid into a fault not only alters pore pressure and triggers slip, but also changes properties of the fault zone that in turn impact fluid flow, pressure diffusion, and fault slip behavior. The most relevant properties here are porosity and permeability. Many experiments, in both the laboratory and in situ, show that dilatancy (the expansion of pores and the fluids within them) accompanies shear deformation of fault zone rocks. In the absence of fluid flow (i.e., undrained conditions), dilatancy reduces pore pressure, increasing the effective normal stress and strengthening the fault. Porosity changes also alter permeability. As pores dilate and more porous space becomes connected, permeability is enhanced. This facilitates fluid flow and enables pore pressure perturbations to reach greater distances along the fault in a shorter period of time. It is certainly evident that the evolution of porosity and permeability, while complex, can fundamentally influence fluid flow and fault slip behavior, and therefore needs to be taken into account in fault models with hydromechanical coupling. In the context of tectonic earthquakes and episodic slow slip events, rock porosity and permeability changes over the earthquake cycle also dictate the nature of the slip that occurs. During the coseismic period, rapid slip cracks open pore space and causes dilatancy, which strengthens the fault and prevents it from slipping further. Permeability is also enhanced as the porosity increases, which may act to weaken further parts of the fault as the fluid migrates. Over the interseismic period, the fault heals from mechanical compaction, and is also gradually sealed by ductile compaction mechanisms such as pressure solution, which involves dissolving minerals at stressed contact points and depositing them in pores. This closing of pores and permeability reduction increases the pore fluid pressure, which will weaken the fault and cause slip again, and this cycle continues. Understanding how the interplay of dilatancy, compaction produces and arrests fault slip is important in characterizing where and how slow slip events occur, and when that might give rise to earthquakes. In this thesis, I investigate the fault response to pore pressure changes coupled to porosity and permeability evolution using 2D numerical simulations of a strike-slip fault governed by rate-and-state friction. The first part of the thesis investigates aseismic slip triggered by fluid injection in the context of induced seismicity. The goal of this study is to evaluate the controlling factors for the initiation and propagation of aseismic slip, and to make testable predictions of potentially observable quantities like the migration rate of the aseismic slip front, as a function of prestress, permeability, injection rate, and frictional parameters. We showcase comparisons for different prestress conditions, permeability values, injection rates, initial state variables, and frictional properties, evaluating their relative importance in determining slip behavior. We also highlight how neglecting porosity and permeability evolution can drastically change the nature of fault slip, and connect our simulations with a limited set of observations to emphasize the important role of hydromechanical coupling in characterizing fault response to fluid injection. Furthermore, we calibrated our model and fit the results to InSAR observations of aseismic slip in the Delaware Basin that is caused by the injection of oilfield water. This shows the applicability of the numerical model to field data and potentially the monitoring of induced seismicity. The second part of the thesis focuses on earthquake cycle simulations in the tectonic context. We explore pore pressure, porosity and permeability evolution over the earthquake cycle and how they impact the occurrences of slow slip events and earthquake ruptures. The first model builds on the study of injection-induced aseismic slip and adds viscous compaction to porosity evolution to study slow slip events. We show that the slow slip events are driven by the interaction between pore compaction which raises fluid pressure and weakens the fault, as well as pore dilation which decreases fluid pressure and limits the slip instability. Cyclic behaviors of these events can range from long-term events lasting from a few months to years to very rapid short-term events lasting for only a few days. The accumulated slip for each event is on the order of centimeters, and the stress drop is generally less than 10 MPa. The second model ignores porosity evolution and only considers permeability evolution that is coupled to effective normal stress, fault slip and a characteristic healing time over which the fault heals interseismically. We demonstrate the viability of fault valving in an earthquake sequence model that accounts for permeability evolution and fault zone fluid transport. Predicted changes in fault strength from cyclic variations in pore pressure are substantial ($\sim$10-20 MPa) and perhaps even larger than those from changes in friction coefficient. We also show how fluids facilitate the propagation of aseismic slip fronts and transmission of pore pressure changes at relatively fast rates. The modeling framework we introduce here can be applied to a wide range of problems, including tectonic earthquake sequences, slow slip and creep transients, earthquake swarms, and induced seismicity.
Book Synopsis Some Rock Mechanics Problems with Application for Hydraulic Fracturing by : Saied Mighani
Download or read book Some Rock Mechanics Problems with Application for Hydraulic Fracturing written by Saied Mighani and published by . This book was released on 2019 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydraulic fracturing is an essential tool used to enhance connectivity in shale gas reservoirs by maximizing the intersection between the hydraulic fracture (HF) and pre-existing natural fractures (NF) or faults. The technique is most effective when the hydraulic fracture crosses natural fractures rather than arresting on them. Experiments conducted to examine the interaction between HF and artificial pre-existing faults suggest that the coupling of diffusivity and fault slip is an important element of the HF-fault interaction problem. Fault slip, once activated is associated with an apparent increase in diffusivity. Whether the hydrofracture crosses or arrests on the pre-existing fault is also affected by surface roughness, differential stresses, and fault slip mode (i.e., stable or stick-slip sliding). Calibrated piezoelectric transducers were used to measure acoustic emissions (AE) generated during HF and fault slip. Moment tensor analysis of these events was used to distinguish pure tensile, shear, and possibly closure events during the experiments. Seismic moment magnitudes were approximately -7 for events during the initiation of the HF and about -5 for events during fault slip. Such a low ratio of seismic moments for tensile and slip events may explain the small numbers of tensile events recorded during reservoir stimulations. I also studied the time-dependent behavior in shales to gain insight into the post-stimulation efficiency of exploitations. Shale experiences strain hardening and compaction during loading by both isostatic (pressure-driven) and differential stress (shear-driven). Transient creep strain increased linearly with log(time), possibly transitioning to constant rate in timescale of several days. Motivated by the multi-scale nature of heterogeneities in shales, I examined the micromechanics of deformation using the nano-indentation technique. Elastic and creep moduli found in nano-indentation and triaxial tests agreed within a factor of 2, but within that factor, the creep strength may depend on spatial scale.
Book Synopsis The Physics of Friction and Fracture by : Elias Rafn Heimisson
Download or read book The Physics of Friction and Fracture written by Elias Rafn Heimisson and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Friction and fracture processes are ubiquitous in the brittle crust. Thus understanding the physics of these processes is of paramount importance to successfully model and interpret a wide variety of geological phenomena such as seismic and volcanic activity. In this dissertation, I develop theory and models based on the current understanding of the physics of friction and fracture. These physics-based models are then applied to a broad class of problems related to dike propagation, induced and triggered seismicity, and slow slip mechanics. In order to couple together the underlying physics of friction and fracture to data and observable characteristic of transient behavior in the crust we need models and constitutive relationships. This dissertation is mainly on making this connection, the challenges involved, and comparison with observations. The first challenge addressed in this dissertation is to connect fault friction and microseismicity (Chapter 2). I use the experimentally derived theory of rate-and-state friction to compute the time to instability for a spring slider under arbitrary stressing history. This analytical result is used to describe a population of spring-sliders, which represents a population of seismic sources with varying initial conditions. This theory results in a constitutive relationship that relates to seismicity production and stressing history. The theory is extended well beyond what has been previously explored, in particular, where I account for interactions between seismic sources (Chapter 3). This new interaction theory is applied to several practical problems such as fault slip models and earthquake migration through cascading. Further applications of the theory from Chapter 2 are explored in Chapter 4. Where a physics-based model of a dike intrusion is developed and deformation and seismicity are modeled in a fully consistent manner. The results suggest that dike induced earthquakes are triggered on preexisting faults. Furthermore, the results give insight into the frictional structure of the crust, which needs to be heterogeneous to satisfy the temporal and spatial distribution of the seismicity. The last two Chapters (5 and 6) explore in more details the mechanics of faults and dike intrusions respectively and are mostly independent of other chapters. In chapter 5, I account for poroelastic coupling the nucleation of frictional instabilities. This work leads to a new novel theory of slow slip, which demonstrates that slow slip nucleates spontaneously on mildly rate-strengthening faults under certain circumstances when slip couples to normal stress perturbation. In the final chapter, I show how the growth of dikes and depressurization of magma chambers are coupled through fully coupled simulations. The simulations provide new insight into how a dike lengthens with time before finally arresting.
Book Synopsis Geomechanical Analysis of Intraplate Earthquakes and Earthquakes Induced During Stimulation of Low Permeability Gas Reservoirs by : Owen Varnum Hurd
Download or read book Geomechanical Analysis of Intraplate Earthquakes and Earthquakes Induced During Stimulation of Low Permeability Gas Reservoirs written by Owen Varnum Hurd and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis applies the principals of geomechanics to address a breadth of fundamental scientific questions regarding rock properties near major active faults, physical mechanisms driving intraplate earthquake activity, and how induced earthquakes in low-permeability natural gas reservoirs provide insight into reservoir deformation during hydraulic fracture stimulations. The first part of this thesis applies a shear-wave splitting analysis to examine physical controls on crustal anisotropy mechanisms on and near the North Anatolian Fault in northwest Turkey. The analysis indicates that stress-controlled mechanisms appear to prevail at distances greater than 1 km from the main fault trace while structure-controlled mechanisms are observed within 1 km of the main fault trace, suggesting the existence of heterogeneous physical properties between the main fault zone and surrounding crust. The second part of this thesis applies fundamental geomechanical principals to examine the compatibility of shear slip on intraplate faults in the central and eastern United States and southeastern Canada with frictional faulting theory in the context of the regional tectonic stress field. The application demonstrates that maximum horizontal stress orientations consistently trend NE-SW across the study area, horizontal principal stress magnitudes become increasingly compressive with respect to the vertical stress moving from the central U.S. toward the northeastern U.S. and southeastern Canada, and shear slip on the vast majority of intraplate fault planes is well described by the Mohr-Coulomb failure criterion in the current stress field assuming hydrostatic pore pressure in the upper crust and laboratory-determined coefficients of fault friction. The final part of this thesis applies an integrated, geomechanical and seismological analysis to evaluate the response of low permeability natural gas reservoirs to hydraulic fracturing stimulations in two case studies in western Canada. Geomechanical, waveform similarity, and microseismic event magnitude scaling analyses indicate that the reservoir response to hydraulic fracturing is generally characterized by shear deformation occurring on small faults reactivated during hydraulic fracturing stimulations. The advanced double-difference earthquake relocation technique is applied to improve microseismic event hypocenter locations. While the technique reduces scatter in microseismic event hypocenter locations, it is susceptible to producing hypocenter location artifacts in limited (single or double) monitoring array configurations. However, synthetic test show the double-difference technique could be a viable tool in accurately relocating microseismic events provided a suitable monitoring array configuration (three arrays or more) exists.
Book Synopsis Modeling of Fault Activation and Seismicity by Injection Directly Into a Fault Zone Associated with Hydraulic Fracturing of Shale-gas Reservoirs by :
Download or read book Modeling of Fault Activation and Seismicity by Injection Directly Into a Fault Zone Associated with Hydraulic Fracturing of Shale-gas Reservoirs written by and published by . This book was released on 2015 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We conducted three-dimensional coupled fluid-flow and geomechanical modeling of fault activation and seismicity associated with hydraulic fracturing stimulation of a shale-gas reservoir. We simulated a case in which a horizontal injection well intersects a steeply dip- ping fault, with hydraulic fracturing channeled within the fault, during a 3-hour hydraulic fracturing stage. Consistent with field observations, the simulation results show that shale-gas hydraulic fracturing along faults does not likely induce seismic events that could be felt on the ground surface, but rather results in numerous small microseismic events, as well as aseismic deformations along with the fracture propagation. The calculated seismic moment magnitudes ranged from about -2.0 to 0.5, except for one case assuming a very brittle fault with low residual shear strength, for which the magnitude was 2.3, an event that would likely go unnoticed or might be barely felt by humans at its epicenter. The calculated moment magnitudes showed a dependency on injection depth and fault dip. We attribute such dependency to variation in shear stress on the fault plane and associated variation in stress drop upon reactivation. Our simulations showed that at the end of the 3-hour injection, the rupture zone associated with tensile and shear failure extended to a maximum radius of about 200 m from the injection well. The results of this modeling study for steeply dipping faults at 1000 to 2500 m depth is in agreement with earlier studies and field observations showing that it is very unlikely that activation of a fault by shale-gas hydraulic fracturing at great depth (thousands of meters) could cause felt seismicity or create a new flow path (through fault rupture) that could reach shallow groundwater resources.
Book Synopsis Fault Evolution and Earthquakes by : Qingsong Li
Download or read book Fault Evolution and Earthquakes written by Qingsong Li and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The New Madrid Seismic Zone (NMSZ) in central United States is a good example of intraplate seismicity, which cannot be readily explained by the plate tectonics theory and remains poorly understood. I have developed a 3D FE model to simulate stress evolution in the NMSZ and surrounding regions. I find that, following a large earthquake, intraplate seismic zones tend to stay in a Coulomb stress shadow for thousands of years, while significant amount of stress and strain energy relieved from the large earthquakes may migrate to and remain within the surrounding crust. The results are consistent with seismicity in the NMSZ region following the 1811-1812 large events. To investigate fault evolution and seismicity in plate boundary zone, I have built a 3D dynamic model for the entire San Andreas Fault (SAF) system in California, with the first-order characters of its surface geometry. The results indicate that the geometry of the SAF may be the primary cause of the observed along-strike variation of slip rate, stress states, and seismicity. In particular, the Big Bend of the SAF causes the scattered seismicity in southern California and may have facilitated the development of the San Jacinto Fault (SJF) and other active faults there. I have explored the dynamic interactions between the SAF and SJF in the model and found that the initiation of the SJF tends to decrease fault slip rate on the southernmost SAF and focus strain energy in the Mojave Desert and along the East California Shear Zone. These results are consistent with the spatial distribution of earthquakes in southern California, and provide some insights into evolution of fault systems in the plate boundary zone as it continuously seeks the optimal way to accommodate the relative plate motion.
Book Synopsis A Study Of Microseismic Location Uncertainty by : Sirui Ma
Download or read book A Study Of Microseismic Location Uncertainty written by Sirui Ma and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Microseismic is an effective method of monitoring hydraulic fracture propagation in unconventional shale oil and gas field development. In this study, microseismic events are located by grid search method while location uncertainty is quantified in probability contours at the same time. We test the impact of different algorithm inputs on the location uncertainty. Variables include the choice(s) of velocity model, downhole array(s) geometry, seismic phase(s) (P-wave, SH-wave) and particle motion. We picked one perforation event recorded during the hydraulic fracturing of the Utica Shale in Ohio. By altering variables, we find out that S-wave arrival is better in constrain the uncertainty of location; whip array is better than single array; back-azimuth is not effective in downhole vertical array.
Book Synopsis Unconventional Reservoir Geomechanics by : Mark D. Zoback
Download or read book Unconventional Reservoir Geomechanics written by Mark D. Zoback and published by Cambridge University Press. This book was released on 2019-05-16 with total page 495 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive overview of the key geologic, geomechanical and engineering principles that govern the development of unconventional oil and gas reservoirs. Covering hydrocarbon-bearing formations, horizontal drilling, reservoir seismology and environmental impacts, this is an invaluable resource for geologists, geophysicists and reservoir engineers.
Book Synopsis Induced Seismicity Potential in Energy Technologies by : National Research Council
Download or read book Induced Seismicity Potential in Energy Technologies written by National Research Council and published by National Academies Press. This book was released on 2013-08-14 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past several years, some energy technologies that inject or extract fluid from the Earth, such as oil and gas development and geothermal energy development, have been found or suspected to cause seismic events, drawing heightened public attention. Although only a very small fraction of injection and extraction activities among the hundreds of thousands of energy development sites in the United States have induced seismicity at levels noticeable to the public, understanding the potential for inducing felt seismic events and for limiting their occurrence and impacts is desirable for state and federal agencies, industry, and the public at large. To better understand, limit, and respond to induced seismic events, work is needed to build robust prediction models, to assess potential hazards, and to help relevant agencies coordinate to address them. Induced Seismicity Potential in Energy Technologies identifies gaps in knowledge and research needed to advance the understanding of induced seismicity; identify gaps in induced seismic hazard assessment methodologies and the research to close those gaps; and assess options for steps toward best practices with regard to energy development and induced seismicity potential.
