PRISM :: Browsing by Author "Wong, Ron Chik-Kwong"

Browsing by Author "Wong, Ron Chik-Kwong"

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Embargo
A Multi-Scale Progressive Damage Model to Estimate the Fatigue Life of Wind Turbine Blades
(2024-06-18) Gunness, Neysa Meagan; Sun, Qiao; Singh, Meera Nand Kaur; Wong, Ron Chik-Kwong
Wind turbine blades experience fatigue loads resulting from cyclic loading conditions during its operation. Damage caused by fatigue loads poses a threat to the integrity of the wind turbine structure thus, it is critical to accurately predict the effect of damage progression on the remaining life of the blade. As it is the case with most composite material structures, a multiscale modelling approach is required when designing a fatigue methodology for wind turbines. Coupled models at different geometric scales have been used to understand how the operational response of the entire wind turbine system is affected by damage in the composite blades. However these methodologies employ high-fidelity damage models that are time and computationally intensive. Furthermore, most models that predict the blade’s lifetime rely on macroscopic damage models that do not consider the physical damage mechanisms. The macroscopic models produce a very conservative estimate of the fatigue life of the blades. Damage mechanics models which capture the stiffness degradation of the damaged blade in terms of a physical damage parameter such as matrix cracking can be incorporated within a multiscale framework. This type of model can capture the effects of the damaged blade on the entire wind turbine system to estimate the fatigue life with increased accuracy. This study aims to improve the current multiscale methodology by incorporating a damage mechanics model which accounts for matrix crack evolution under cyclic loading. The damage mechanics model implemented and presented in this thesis, is implemented based on a 2D finite element cross-section analysis in which the entire blade is modelled as a beam composed of several cross-sections. The material response and the structural response was analysed as damage progresses. This multiscale methodology which includes coupling with an aeroelastic analysis software, HAWC2, can be used to predict the structural response of the blades subjected to damage. The proposed method can also reduce the reliance on high-fidelity damage models to calculate the fatigue life due to damage, thus resulting in a more efficient approach.
Open Access
Advanced Failure Analysis in Geomaterials: Application to Reservoir Geomechanics
(2017) Gong, Xu; Wan, Richard; Hicher, Pierre-Yves; Coombe, Dennis; Sudak, Les Jozef; Priest, Jeffrey; Wong, Ron Chik-Kwong
The manifestation of failure in geomaterials and its proper analysis are constitutive aspects that geotechnical engineers are faced with routinely in design. In most instances, geostructures are examined at the ultimate plastic state where failure is deemed to occur along a slip surface where plastic deformations localize. This plasticity condition is classically analyzed with the Mohr-Coulomb failure criterion. However, other forms of failure also exist where the localization of deformations is totally absent such as in the case of static liquefaction. This distinct mode has been coined as ‘diffuse failure’ which has the peculiarity of occurring at stress levels well below the plastic limit, thus rendering a classic Mohr-Coulomb analysis insufficient. Hence, the signature of failure in geomaterials seems to be directly related to two principal modes by which it is manifested: one with localized slips, and another variant where deformations are diffused without any localization phenomena. In order to address the many subtle features of failure, a clear mathematical representation of the underlying physical phenomena is needed. In this thesis, failure is considered as an instability of homogeneous deformations, and as such the observed failuremode is a direct result of the underlying constitutive equations admitting bifurcations in solutions for the material response. Different failure criteria are derived, serving as failure indicators which signal the various modes that emerge during loading history following a certain hierarchy. To translate theory into engineering practice, the thesis endeavors to apply the above mathematical aspects of failure in the study of geomaterials undergoing multiphasic flow and thermal transport such as in the extraction of heavy oil from an oilsand reservoir in Alberta, Canada. Governing equations describing the physics of all phases (solid, water, gas and oil) involved are formulated within mixture theory using continuum mechanics principles. A special computational strategy is adopted to solve efficiently the coupled system of equations using both finite elements and finite differences. Finally, the developed computational model is tested in the context of an actual oil field case study implicating steam injection and oil production in an oilsand reservoir in Alberta, Canada. To close the loop, attention is obviously focused on material failure concepts developed in the first part of the thesis. Geomechanical properties that enter the computational model are obtained from a separate comprehensive laboratory testing of shales and oilsands at high temperature and pressure.
Open Access
Age of Soils: A Measure of Creep History
(2017) Guo, Junwei; Wong, Ron Chik-Kwong; Wan, Richard; Priest, Jeffrey; Sudak, Les
Time-dependent behaviors of soils are critical for engineering design. Results of one-dimensional (1-D) constant rate of strain (CRS) tests on clays show that there is an existence of unique relationship between current stress and strain state for a given constant strain rate, irrespective to previous stress-strain-time history. In the present study, this relationship is employed to estimate the creep rate during the CRS test. It is found that the creep rate is consistently related to distance from current stress-strain state to the instant compression line, which is the creep void ratio or creep history, termed age of soils. Based on the creep rate as a function of creep strain or age of soils, the stress relaxation rate function is derived through the correspondence principle. Age contours are iso-creep rate lines defining the creep rate field in stress-strain space. Creep Balanced State equation states that CRS path will converge to a iso-creep rate line. This equation is used to determine the CRS path and quantify the rate effect on preconsolidation pressure. Age- and pressure-dependent secondary compression coefficients are incorporated in the above framework.
Open Access
A Comprehensive Study of Fluid Flow and Its Interactions within Porous Media in Steam-Assisted Gravity Drainage (SAGD) - Experimental and Simulation Studies
(2022-09) Kasraian, Ali; Bryant, Steven L.; Dong, Mingzhe; Maini, Brij; Sarma, Hemanta Kumar; Wong, Ron Chik-Kwong; Trivedi, Japan
Since the invention of steam assisted gravity drainage (SAGD), numerous efforts have been made to explore and enhance the process. This work studies three previously overlooked parameters and the noteworthy effect they have on reservoir pressure and saturation distributions: the shape of the steam chamber, the thermal expansion of the fluids, and the creation of a hydrocarbon bank. The results show that neglecting to consider these yields an inaccurate description of pressure and saturation distributions. Most notably, the pressure gradient is generally positive (dP/dx>0) from the chamber edge into the mobile region, contrary to an alleged monotonic pressure gradient horizontally (with dP/dx<0) from the chamber edge toward the cold part of the reservoir. Secondly, a hydrocarbon bank barrier limits the horizontal condensate flow from the chamber edge to the cold region, contrary to previous assertions of a horizontal flow path from the chamber edge into the cold region due to the initial water mobility in the reservoir. Consequently, neither the initial water mobility nor the difference between the injection pressure and the reservoir pressure result in a notable horizontal convective heat transfer from the chamber edge to the cold reservoir. A variety of SAGD studies have reported the production of water-in-oil emulsions. A key question is whether the emulsions are generated in situ. Exploring potential causes for in situ emulsification in SAGD has been limited to steam condensation. No rigorous investigation has been done on the possibility of in situ emulsification during commingling flow of the bitumen and condensed steam toward the production well. To this end, a detailed experimental study was performed, focusing on the role of four parameters: the viscosities of wetting and non-wetting phases, the wettability of porous media, the phase containing emulsifier, and the flow rate ratio. The in situ emulsification – for both non-wet in wet and wet in non-wet type of emulsions – only occurs if the capillary number of the non-wetting fluid is equal or larger than 0.000036. The capillary number analyses suggest that water-in-oil emulsions are unlikely to be generated in the mobile region in SAGD.
Open Access
Compression and Flow Behavior of Proppants in Hydraulically Induced Fracture
(2016) Man, Shuai; Wong, Ron Chik-Kwong; Wan, Richard; Priest, Jeffrey; Dong, Mingzhe
Short-term and long-term compression behavior of single proppant grains were thoroughly studied by diametrical compression tests and DEM/FEM simulations. Hydroprop showed the highest single grain crush-resistance while ceramic proppant grains with coarse surfaces were susceptible to creep behavior under load. One-dimensional compression tests under various stress levels and temporal conditions were systematically carried out to investigate the time-independent and time-dependent crushing behavior of proppant grain packs. Baylic Sand was the most crushing-prone whereas the OxSteel was the least. Most proppants showed creep behavior under long-term compression. Rock-proppant interaction tests were also performed which cast light on the proppant crushing and embedment under the field conditions. Pressure gradients of proppant-water slurries flowing through a small-diameter pipe were experimentally investigated and mimicked by DEM-CFD simulations. A generalized Darcy-Weisbach equation was proposed for the prediction of pressure gradients.
Embargo
Development of Advanced Rate-Dependent Analytical Model of Lead Rubber Bearing and Seismic Resilience Assessment of a Highway Bridge Network
(2024-08-22) Aghaei Doost, Vahid; Billah, AHM Muntasir; El-Badry, Mamdouh; Wong, Ron Chik-Kwong
Bridges serve as integral components of the transportation infrastructure, providing ongoing mobility and essential support to society. Within the realm of bridge engineering, a primary focus lies in the development of resilient bridges capable of withstanding multiple hazard events. Natural disasters can significantly impede transportation and emergency response efforts when bridges sustain damage. Recent events have demonstrated that highway bridges are highly susceptible components within transportation networks during various catastrophic events. In bridge construction, isolation bearings play a pivotal role by supporting the bridge superstructure and facilitating the transfer of forces to the substructure. Seismic isolation bearings exhibit the capacity to withstand substantial lateral displacements and effectively support axial loads induced by both gravity and earthquakes. Among various types of isolation bearings, lead rubber bearings (LRBs) have emerged as the prevailing choice for applications in both buildings and bridges. While several analytical models for LRBs have been developed to date, it is imperative to acknowledge that these existing modeling techniques do not encompass the loadings from various earthquake scenarios that represent a wide range of strain levels and rates. Therefore, it becomes imperative to ensure that LRB isolation systems exhibit predictable behavior under all possible loading conditions, coupled with the capability to maintain functionality even when subjected to hazards exceeding the design-level magnitude. The overarching objective of this research is to develop an advanced analytical model of LRB that can capture different characteristics of LRB nonlinear response that are currently not available in existing LRB models. To achieve this, a sensitivity analysis is conducted, employing different existing LRB analytical models to elucidate the critical features that significantly influence the seismic response of LRB-isolated bridges. Furthermore, this research embarks on the development of a high-fidelity advanced rate-dependent analytical model for LRBs that can account for rate-dependency, low-to-large strain levels, strength degradation of the lead core due to heating, rubber hardening, initial lead hardening, scragging, and Mullins damage parameters, and the influence of vertical loads within isolation systems. In addition, by implementing the developed LRB analytical model, a comprehensive evaluation of bridge seismic performance over the bridge life-cycle is conducted. The transportation network resiliency is crucial for ensuring the smooth functioning of a region, especially during and after a seismic event. Lastly, this research extends its scope to encompass seismic vulnerability and resilience assessment of a regional bridge network featuring LRB-isolated bridges. Comprehending the potential damages that may occur during seismic events enables engineers and policymakers to allocate resources strategically for retrofitting, maintenance, and disaster preparedness initiatives. By leveraging the Artificial Neural Network algorithm, finally, a framework for predicting the resilience and reliability indices of the regional bridge network is proposed. Through a comprehensive sensitivity analysis, the development of an advanced analytical model, and an evaluation of life-cycle resilience, this study contributes to the evolving field of bridge engineering and resilience assessment. Moreover, the exploration of multi-hazard vulnerability and resilience assessment extends the practical implications of this research, aiding in the creation of safer and more resilient transportation networks. In conclusion, this research provides an effective framework for vulnerability and resilience assessment that can be applied in both theoretical and practical applications.
Open Access
Direct simulation of stably stratified wall-bounded turbulence using the lattice Boltzmann method
(2023-04-27) Guo, Junwei; Zhou, Qi; Wong, Ron Chik-Kwong
The lattice Boltzmann method (LBM) is employed to simulate stratified plane Couette (SPC) flows in their statistically stationary turbulent state. The aim is to assess the suitability of the LBM for direct simulation of wall-bounded, sheared turbulence under the influence of stable stratification. The SPC flow is generated by two parallel plates moving in opposite directions with velocities ± U w, and the buoyancy is fixed at ± b w at the upper and lower plates, respectively. The Reynolds number Re = U w h / ν, where h is the half-gap height, and ν is the kinematic viscosity, varies from 1000 to 3000. The Richardson number Ri = b w h / U w 2 is set to 0 or 0.01. The LBM results are compared to direct numerical simulations using the conventional pseudo-spectral method, and good agreement is found in various turbulence statistics, such as mean and fluctuation velocity and buoyancy, Reynolds stress, turbulent heat flux, dissipation rate, wall fluxes of momentum and heat, and longitudinal and transverse turbulence spectra. The results from grid-sensitivity tests indicate that the uniform isotropic grid spacing Δ x in LBM needs to be no greater than approximately the near-wall viscous length scale δ ν to achieve adequate resolution of stratified wall-bounded turbulence.
Open Access
Direct Simulations of Fluid-Particle Flow in Newtonian and non-Newtonian Fluids Using Coupled Lattice Boltzmann and Discrete Element Methods
(2021-09) Guo, Junwei; Wong, Ron Chik-Kwong; Zhou, Qi; Jasso, Martin; Wan, Richard G
Coupled lattice Boltzmann and discrete element methods are employed to investigate a suite of fluid-particle flow problems in both Newtonian and non-Newtonian fluids. First, the rheological properties of finer particle suspensions in a Newtonian fluid are investigated, as the particle shape and solid fraction vary. An increase of the relative viscosity is observed when the particles become more oblate, accompanied by an increase of particle contacts and contact distance. Particle reorientation is seen to occur systematically in denser oblate particle suspension subject to the shear flow. A connection between the micro-structure statistics and the suspension viscosity is proposed. Second, the shear rate effects on the finer oblate particle suspension viscosity are studied. The viscosity of the suspension is observed to decrease under a higher shearing rate due to the reduction of the inter-particle friction coefficient, resulting in the shear-thinning behavior of the suspension. Finally, the sedimentation of a granular particle cloud in shear-thinning suspensions is investigated, as the rheology of the suspension, Reynolds number, and particle cloud concentration vary. At higher Reynolds numbers, the particle cloud length grows in the direction of settling and reaches a quasi-steady state. The ratio of the particle cloud quasi-steady settling velocity to the single-particle terminal velocity in the same fluid, increases when the cloud settles in the shear-thinning suspensions. This velocity increase is more significant at a low Reynolds number. At even lower Reynolds numbers, the cloud loses its initial shape and disintegrates while settling, with particles escaping from the cloud due to differential particle settling velocities.
Open Access
Effect of Heating Rate on Thermally Induced Pore Water Pressure and Crack Evolution in Clay and Shales
(2024-01-19) Faghihinia, Masoomeh; Wong, Ron Chik-Kwong; Wan, Richard G.; Duncan, Neil Alexander
This thesis investigates the hydrothermal behavior of clay shale samples, with a specific emphasis on how heating rates influence temperature distribution and the evolution of pore pressure under elevated temperatures. Clay shales, characterized by their extensive geological presence and low hydraulic conductivity, carry immense importance across a wide array of applications, including their pivotal role as caprock in oil and gas reservoirs, geological storage of carbon dioxide, and nuclear waste storage. Ensuring the integrity of clay shale barriers is of paramount concern, as any compromise in their stability can lead to unintended releases of undesirable substances into potable water zones above or even onto the ground surface, potentially resulting in catastrophic consequences. The fundamental objective of this study revolves around gaining insights into clay shales response to heightened thermal loading and the potential excess pore fluid pressure generation. The research establishes a robust foundation by thoroughly investigating characteristics and material properties of clay shale and their dependencies on temperature. To achieve these objectives, the study employs FLAC3D software to conduct simulations on a three-dimensional cylindrical clay shale specimen utilizing an isotropic thermo-elastic model, subjecting it to temperatures of up to 600°C at varying heating rates. Additionally, the research explores the interacting coupled effect of hydraulic and thermal diffusion, employing a series of numerical simulations to shed light on this intricate relationship. Furthermore, this research investigates the integration of cutting-edge Machine Learning (ML) and Computer Vision (CV) techniques to enhance the precision, efficiency, and accuracy of thermal crack detection, localization, and segmentation. This innovative approach aims to overcome the challenges associated with visually identifying and analyzing thermal cracks, including the time-consuming nature of these endeavors and the potential for human errors.
Open Access
Effects of FRP Cross-wall Connectors in Multi-wythe Masonry Walls
(2016-01-13) Elrayes, Mahmoud; Shrive, Nigel Graham; Valluzzi, Maria Rosa; Nowicki, Edwin Peter; Wong, Ron Chik-Kwong; Lissel, Shelley Lynn; Shrive, Nigel Graham; Priest, Jeffrey Alan
The seismic performance of multi-wythe masonry walls is known to be generally poor, as they can exhibit local failure modes by wythe separation and collapse of the external wythes. For retrofitting them, it is widely acceptable to install transverse ties in combination with other intervention methods to provide proper connections between the wythes. The value of using transverse ties in heritage multi-wythe masonry walls has been questioned in recent research. Different finite element models were developed to simulate the behaviour of traditional transverse ties installed in multi-wythe walls. A simplified micro-model provided insight regarding stress transfer between the different elements of the system, and suggested that the traditional distribution of ties is inefficient. Macro-models were used to investigate the role of a single tie in resisting different loading conditions and found that the effect is minimal in most cases. The findings were in agreement with previous experimental research. An experimental program was performed to investigate non-traditional configurations and distributions of transverse ties. Large scale three-wythe walls were constructed and subjected to axial compression and lateral in-plane cyclic loads. Transverse ties made of FRP rebar were installed at different angles to the wall surface as opposed to the traditional leveled and perpendicular to the wall surface approach. Differences in the behaviour of the ties were observed including connection technique to the wall as well as the ability to transfer shear loads if placed in certain locations. Inclined transverse ties were grouped to form semi-continuous vertical, horizontal and diagonal elements to produce certain improvements in the structural performance of the wall in terms of lateral strength, stiffness degradation, energy dissipation, and post-peak behaviour.
Open Access
Effects of volume fraction and particle shape on the rheological properties of oblate spheroid suspensions
(AIP Publishing, 2021-08-06) Guo, Junwei; Zhou, Qi; Wong, Ron Chik-Kwong
Coupled lattice Boltzmann and discrete element methods were employed to investigate the rheological properties of oblate spheroid suspensions in a Newtonian fluid. The volume fraction of the particles is varied along with the particle aspect ratio. As the particle shape is varied from sphere to oblate, we observe an increase in the relative viscosity as well as an increase in the particle contacts and the contact distance. The more oblate particles in denser suspensions are observed to reorient systematically subject to the shear flow. We recast the viscosity data using the Krieger–Dougherty formula and report the modified Einstein coefficients.
Open Access
Experimental Investigation on the Shear Strength of Masonry Prisms
(2024-05-13) Farjad, Sahar; Shrive, Nigel; Sudak, Les Jozef; Wong, Ron Chik-Kwong
Masonry structures are used ubiquitisly all over the world from many years ago till today. However, there are still lots of unknowns in terms of their behavior. These ambiguities become even more significant when the structure is exposed to the shear loads. In addition, the Canadian masonry standard has been the focus of numerous studies, and it was shown that this standard might be improved in many aspects regarding the shear strength of masonry. In this study, first the variability of the mortar joint thickness in both brick and concrete block masonry was explored. Then, considering these variation, experimental tests were conducted to investigate the effect of mortar joint thickness on the shear strength of triplet masonry prisms made with concrete blocks. With regard to the conflict that exist in the literature about the effect of mortar type on the shear strength, it was another parameter investigated by a series of experiments. As evidenced by the results of this study, mortar type in fully grouted (FG) and partially grouted (PG) prisms was not an influencing parameter on the shear strength, as well as mortar joint thickness of fully-grouted prisms. It was shown that joint thickness did affect the shear stiffness though. In fact it was argued that mason experience and proficiency affect the shear stiffness and not the shear strength of FG prisms in this study. However, this study showed that mortar joint thickness does have some effect on the shear strength in hollow masonry prisms. According to the results the higher joint thickness showed less shear strength. Although to conclude this as a general rule, more experiments are required.
Open Access
Experimental Studies on the Geomechanical Behavior and Heterogeneity in Laboratory Synthesized Hydrate-bearing Sands
(2023-09-21) Pandey, Mandeep Raj; Priest, Jeffrey Alan; Hayley, Jocelyn L.; Wan, Richard G; Wong, Ron Chik-Kwong; Bryant, Steven L.; Pinkert, Shmulik
Hydrate-bearing sands (HBS) store large volumes of methane gas, and along with their potential to be commercially exploited using current oil and gas production techniques, make them suitable as a future energy resource. When hydrates form in the pore space of a sediment, they significantly increase the strength and stiffness of the host sediment. The enhancement in mechanical properties is influenced by various factors, such as hydrate saturation, in-situ stress conditions, sediment type (fine-grained or coarse grained). Our current understanding of HBS behavior is based on studies of laboratory synthesized hydrate-bearing specimens, however significant variation in reported values exist that has been suggested to arise from differences in hydrate formation methods, test apparatus, test conditions. Results from testing natural HBS samples, obtained from offshore India, suggest that the particle size impacts geomechanical properties. However, laboratory studies on synthesized specimens are typically conducted on sand specimens with narrow particle size distributions (PSD) and exclude larger particles. As such, there is a lack of understanding of what may lead to variations in mechanical properties of HBS. This thesis reports on a comprehensive experimental program conducted on laboratory synthesized hydrate-bearing sands for two different PSDs, whose particle size was chosen to better represent the coarse fraction observed in natural cores. The laboratory study included detailed analyses of the shear modulus evolution during the formation of hydrates in the pore space of sands. The research also explored the effect that the initial water saturation had on the pressure and temperature conditions when hydrate formation was initiated, along with how it impacted the stress-strain response after hydrate formation. The results from the extensive testing highlighted an inherent heterogeneity in geomechanical behavior of HBS specimens formed and subjected to similar conditions. Conceptual models were developed to help visualize the experimental observations and gain better insights into the factors that led to differences in formation characteristics and resulting hydrate morphology that developed within different sands. The results of this study highlight that the variations in the geomechanical behavior of HBS reported in literature may arise due to the heterogenous distribution of hydrate within laboratory synthesized HBS studies, which is also likely to exist in natural hydrate bearing cores. Observations from the testing will help researchers better understand the behavior of HBS over a wide range of sediment types and formation conditions, like under permafrost, or within offshore seabed sediments.
Open Access
Field And Laboratory Study Of Infiltration Processes During Melt Events In Frozen Prairie Soils
(2021-08-10) Khawaja, Sama; Cey, Edwin; Hayashi, Masaki; Wong, Ron Chik-Kwong
In the northern hemisphere snowmelt infiltration into frozen ground can be dependent on preferential flow along larger pores called macropores which can play a critical role in directing snowmelt for groundwater storage. Areas like the Canadian Prairies can undergo two or more melt events in a year which can change the soil storage capacity and influence how snowmelt is partitioned between infiltration and runoff during spring. The effects of these ‘mid-winter’ melt events on soil pore networks are not well understood, making it difficult to incorporate them in hydrological models. This study investigated the infiltration processes during melt events by performing a series of tracer tests on a cropland and grassland site and a set of infiltration experiments on frozen soil columns. Results from the laboratory study show that macropore flow is the dominant transport mechanism during melt events leading to deep percolation and minimal interaction between infiltrating water and the soil matrix. Snowmelt that infiltrates during mid-winter melt events infiltrate and refreezes in air-filled soil matrix pores first which, along with the heat energy exchanged between the soil matrix and infiltrating water, can result in snowmelt from later melt events to refreeze in macropores as ice “plugs” rather than completely blocking a macropore network. This reduces infiltration in frozen soils during spring melt, encouraging more runoff and ponding. Macropore connectivity can affect infiltration rates as seen with the greater runoff ratios on the cropland site which was less macroporous than the grassland site. It can also influence refreezing dynamics in pores as runoff was not always necessarily higher on croplands during spring melt.
Open Access
Geomechanical Properties of the Montney and Sulphur Mountain Formations
(2017) McKean, Scott Harold; Priest, Jeffrey A.; Wong, Ron Chik-Kwong; Clarkson, Christopher R.
Accurate modelling of hydraulic fracturing is critical for improving the cost efficiency and societal acceptance of unconventional hydrocarbon exploitation. This thesis investigates the geomechanical inputs required to improve hydraulic fracturing using X-Ray fluorescence, helium pyncnometry, microhardness, point load strength testing, unconfined compressive strength testing, Brazilian testing, multi-stage triaxial testing, and ultrasonic pulse transmission. The Montney Formation and its outcrop equivalent, the Sulphur Mountain Formation, are studied. Static and dynamic experimental results are interpreted and compared using a transversely isotropic framework. The Sulphur Mountain samples were more brittle and heterogeneous than Montney samples, which were harder and failed in a more stable fashion. Heterogeneity was a stronger control on failure, strength, and elastic constants than anisotropy caused by layering. Complex failure mechanisms were observed in Brazilian and triaxial tests and yielded insights into fracture propagation processes, inhomogeneity, and stress concentrations.
Open Access
Hydro-Mechanical Coupling and Failure Behavior of Argillaceous Sedimentary Rocks: A Multi-Scale Approach
(2019-04-26) Eghbalian, Mahdad; Wan, Richard G.; Wong, Ron Chik-Kwong; Epstein, Marcelo; Priest, Jeffrey Alan; Regueiro, Richard A.; Shrive, Nigel Graham
This thesis aims at characterizing the hydro-mechanical behavior of argillaceous sedimentary rocks within a novel poro-elasto-plasticity framework that encompasses micro-mechanics and a multi-scale approach. The developed model considers argillaceous sedimentary rocks to be comprised of a mixture of clay aggregates and rock-type inclusions. The clay fraction has a dual porosity arising from micropores at the clay aggregate level and nanopores between the clay platelets that form the clay aggregates. The rock-type inclusions also have a dual porosity due to the presence of microcracks embedded into a nano-porous rock matrix. As such, the work develops multi-scale modeling techniques that elucidate the complex macroscopic characteristics observed in clay-rich rocks by advocating only the primitive physical laws at their fundamental scales. The outcome is an analytical constitutive law that transcends the various scales: from nano- to macro-scale. Therefore, the swelling stress originating in the nano-pores of clay particles and capillary stresses in the porous network, as well as micro-crack growth can be readily computed as a function of microstructure and physics across the various scales. The developed model is implemented within numerical modeling frameworks such as Finite Element Method (FEM) and eXtended FEM. Lab experimentally observed phenomena in argillaceous sedimentary rocks such as plastic/swelling deformations of clay aggregates and the failure of rock inclusions through micro-crack growth are successfully replicated.
Open Access
The Impact of Bedding Plane on Geotechnical Properties and Fractures Geometry of Montney Equivalent Outcrop Rocks
(2023-01-03) Tabatabaei Poudeh, Seyed Hossein; Priest, Jeffrey Alan; Pedersen, Per Kent; Wong, Ron Chik-Kwong
Hydraulic fracturing (HF) or fracking is extensively used to increase the permeability of unconventional source rocks, such as the Montney Formation which is a prolific producer of oil and gas in Western Canada. Optimizing the economic recovery of hydrocarbons in these reservoirs is dependent on understanding how the rocks fail. During HF, it is generally assumed that vertical fractures in the rock occur, since fracture propagate perpendicular to direction of minimum stress, which in the subsurface is typically in the horizontal direction. However, recent studies have shown that horizontal fractures are also formed as a part of the hydraulic fracture network (HFN), which is assumed to be related to weak bedding planes. To investigate the potential influence of weak bedding planes, a series of Brazilian tests were conducted on Montney equivalent outcrop rock samples. In these tests axial load is applied at different orientations to the bedding plane of the rock samples to evaluate the influence of bedding plane orientation on fracture behaviour, including Brazilian tensile strength, elastic properties and fracture propagation in micro and macro scale. The results of this study can lead to better understanding of the fracture behaviour of Montney siltstone and may help better predict HF fracture propagation and enhance hydrocarbon recovery.
Open Access
Improvement of Carbon Dioxide EOR in Water-Wet Reservoirs by Using Active Carbonated Water
(2016) Shu, Guanli; Dong, Mingzhe; Chen, Shengnan; Li, Huazhou; Hassanzadeh, Hassan; Mahinpey, Nader; Wong, Ron Chik-Kwong
CO2 injection for enhanced oil recovery has been widely and successfully used in many oil fields. The drawbacks of conventional CO2 injection are high mobility and gravity segregation, which lead to low sweep efficiency in the reservoir. Particularly in strongly water-wet reservoirs, a significant trapping of oil by water occurs after CO2 flood due to water blocking effect. To overcome the effect of water blocking, carbonated water flood is considered. In this thesis, a new injection strategy is proposed to recover the trapped residual oil in water-wet reservoirs. After waterflood, a slug of carbonated water is pre-flushed before CO2 flood, followed by an extended waterflood. A series of parallel tests are performed to compare the recovery efficiencies of tertiary floods. Additionally, the slug size of carbonated water is investigated and optimized to achieve the maximum economic value. In accordance with experimental results from parallel tests, it is recognized that molecular diffusion plays important role in recovering the trapped oil. In order to study the mass transfer process of dissolved CO2 from carbonated water into oil phases, a theoretical model is developed. The diffusion process is governed by diffusion coefficients of CO2 in water and oil phases. To determine these two diffusivities, an experimental method is proposed. In the experiment, two phases are placed in a closed diffusion cell immersed in a water bath at a constant temperature. To avoid natural convection, the water phase locates at the bottom and oil phase lies at the top. Combined with a developed theoretical model, pressure changes that occur in the cell are recorded and analyzed to investigate the mass transfer process. By means of the theoretical model and experimental method, effects of operational parameters on diffusion coefficients are studied. To explain the reasons for enhanced oil recovery by pre-flushing carbonated water before the CO2 flood, three types of experiments are involved in investigating the mechanisms. The derived theoretical model and experimental method can be applied to study the mass transfer process and to determine diffusion coefficients for any liquid-liquid system.
Open Access
Integrated Geomechanics and Multiporosity Reservoir Simulation: Investigating Improved Oil Recovery by Huff-and-Puff Gas Injection in Shale Petroleum Reservoirs
(2023-08-30) Fragoso Amaya, Alfonso Rafael; Aguilera, Roberto; Moore, Robert Gordon; Mehta, Sudarshan A.; Wong, Ron Chik-Kwong; Camacho-Velazquez, Rodolfo
In shale formations, multiple stress-dependent porosity systems coexist, and fluid flow occurs through several processes that are also affected by rock deformation. This multiporosity, multitransport mechanisms and stress-dependent nature of shale reservoirs must be honored when modeling them. Thus, the objective of this dissertation is to develop an integrated numerical simulator of fluid flow and geomechanics that incorporates several storage and transport mechanisms of shale reservoirs and how they are affected by rock deformation. At the same time, this work investigates huff-and-puff gas injection to improve oil recoveries, which is one of the main challenges of shale play exploitation. This thesis attains these goals by: Introducing a methodology that integrates calculation of stresses and deformation of the fractured porous medium; changes in matrix (organic and inorganic) porosities and permeabilities, and fractures (natural and hydraulic) permeabilities; and their effect on production performance of shale reservoirs by primary recovery and huff-and-puff gas injection. Building a coupled geomechanics-fluid flow model that implements the methodology described above. History matching a huff-and-puff pilot well in the Eagle Ford Shale using multiporosity reservoir simulation and investigating the effect of adsorption and diffusion from solid kerogen. Carrying out a history match of data from a huff-and-puff pilot well in the Eagle Ford Shale using a commercial reservoir simulator and investigating several scenarios with the tuned model. Evaluating possible combinations of huff-and-puff gas injection and hydraulic refracturing to improve oil recoveries in shale reservoirs. It is concluded that the integrated multiporosity, multitransport mechanisms and stress-dependent model developed in this thesis properly evaluates changes that occur in the various porosities and permeabilities, and transport mechanisms in shales during primary production and huff-and-puff gas injection.
Open Access
Investigation of Initial Water Mobility and its Effects on SAGD Performance in Oil Sands
(2016) Zhou, Wei; Dong, Mingzhe; Chen, Shengnan; James, Lesley; Wong, Ron Chik-Kwong; Mahinpey, Nader; Hassanzadeh, Hassan
Steam-assisted gravity drainage (SAGD) has become a primary commercial in-situ thermal recovery method for oil sands in Alberta. Evidence of initial water mobility during the SAGD process has been observed by many previous field studies. However, no its effective determination method and little research about its effects on SAGD performance have been reported. In this thesis, a novel method is proposed to effectively determine the mobility of initial water existing as the continuous wetting phase in oil sands. More specifically, wax is used for the first time to simulate the immobile oil phase. Laboratory experiments are conducted to determine the initial water mobility with a stationary oil phase. To obtain a general correlation of initial water saturation and its mobility, a triangular tube bundle model is constructed to simulate the measured experimental data. A correlation of the initial water mobility is developed by matching the experimental results with the constructed triangular tube bundle model. To conduct a lab-scale study of initial water mobility, a new two-dimensional physical model with a water flowing boundary is proposed for the first time. The greatest novelty of the 2D model is that the capillary pressure generated from the very fine sands with very strong water wettability, can prevent the oil from flowing into the fine sands zone, but can allow the water flow into the fine sands zone. It is proved by the experiments for the first time that the mobile initial water can promote the vertical and lateral growth of the steam chamber. To investigate effects of initial water mobility on SAGD performance at the field-scale, an elaborated numerical simulation study, with the properties of a typical Athabasca oil sands, is conducted. Initial water mobility is firstly classified into two categories (low and high) based on their steam chamber shapes. The simulation results show that, for a single well pair, low initial water mobility can benefit the steam chamber growth, but high initial water mobility has a negative impact. For the adjacent steam chambers in the same pad, low initial water mobility case with the same injection pressure has the highest NPV.