Petro Geotech (Canada)

Abstract δ 13 C in particulate organic carbon (POC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), carbon dioxide (CO 2(g) ) and methane (CH 4(g) ), together with geochemical modeling, were applied to describe carbon cycle evolution in 40 boreal lakes situated across a permafrost thaw gradient in northeastern Alberta, Canada, where hydrological and geochemical trends had previously been established in a multi‐decadal study. Progressive carbon cycle succession, characterized by enhanced allochthonous carbon loading, methanogenesis, methane oxidation, and alteration of in‐lake DIC regulation, is found to progress in response to periodic water input increases associated with permafrost thaw, and has resulted in modification of the carbon cycle processes in post‐thaw lakes. Hydrologic indicators, including water yield (WY), groundwater—surface water ratio (GW/SW), and tritium content appear to undergo evolution across the thaw gradient, and proceed consistently among softwater, circumneutral, and hardwater lakes, although site‐specific differences in underlying organic versus inorganic carbon source balances are apparent. Progressive CO 2 supersaturation and CH 4 increases generally accompany permafrost thawing. Isotopic signatures suggest mainly acetoclastic methane production, found in previous studies to be common for newly‐thawed peatlands, subsequently modified by methane oxidation in 50% of lakes. Alteration of hydrologic, geochemical and carbon cycling processes has important implications for understanding potential trajectories of climate‐driven changes near the southern margin of the zone of discontinuous permafrost.

Abstract Critical plastic strain and stress at a wellbore wall are identified and commonly utilized in sanding and wellbore collapsing pressure prediction. Extensive experimental testing results suggest that the critical pressures of wellbore collapsing and sanding onset calculated based on statically determined stresses, however, generate large margin when compared to the testing results. These existing models may suffer various shortcoming and an accurate prediction on sanding or wellbore collapsing pressure may require a model which reflects the fundamental behavior. An elasto-plastic model with non-associated plastic flow and stress or strain-dependent failure/sanding criteria are re-visited, simplified analytical solutions of stresses, strain and critical pressure, solution procedure for sanding by incorporating all these fundamental mechanical behavior are developed. A critical effective plastic strain model is utilized and CEPS subject to different external/internal loading are calculated and validated against hollow cylinder testing results. Analytical solutions with nonlinear and linear yielding criteria are applied. These simulating results are compared to those results of THC tests and a geomechanical model with consideration of stress-deformation rather than with stress only is recommended for wellbore collapse and sand predictions.

Summary To evaluate the effects of seasonal variation in the irregularly layered media due to the freezing in the cold region, we carried out continuous seismic observations, including a shallow borehole and weight-drop measurement at a site with a soft change of soil materials in Kitami City. In this paper, we reported the outline of the observations and measurements, and we showed the results of initial analysis by weight-drop excitation data in a linear array and borehole seismic observation data.

Wildlife population dynamics are modulated by abiotic and biotic factors, typically climate, resource availability, density‐dependent effects, and predator–prey interactions. Understanding whether and how human‐caused disturbances shape these ecological processes is helpful for the conservation and management of wildlife and their habitats within increasingly human‐dominated landscapes. However, many jurisdictions lack either long‐term longitudinal data on wildlife populations or measures of the interplay between human‐mediated disturbance, climate, and predator density. Here, we use a 50‐year time series (1962–2012) on mule deer (Odocoileus hemionus) demographics, seasonal weather, predator density, and oil and gas development patterns from the North Dakota Badlands, USA, to investigate long‐term effects of landscape‐level disturbance on mule deer fawn fall recruitment, which has declined precipitously over the last number of decades. Mule deer fawn fall recruitment in this study represents the number of fawns per female (fawn:female ratio) that survive through the summer to October. We used this fawn recruitment index to evaluate the composite effects of interannual extreme weather conditions, energy development, and predator density. We found that density‐dependent effects and harsh seasonal weather were the main drivers of fawn fall recruitment in the North Dakota Badlands. These effects were further shaped by the interaction between harsh seasonal weather and predator density (i.e., lower fawn fall recruitment when harsh weather was combined with higher predator density). Additionally, we found that fawn fall recruitment was modulated by interactions between seasonal weather and energy development (i.e., lower fawn fall recruitment when harsh weather was combined with higher density of active oil and gas wells). Interestingly, we found that the combined effect of predator density and energy development was not interactive but rather additive. Our analysis demonstrates how energy development may modulate fluctuations in mule deer fawn fall recruitment concurrent with biotic (density‐dependency, habitat, predation, woody vegetation encroachment) and abiotic (harsh seasonal weather) drivers. Density‐dependent patterns emerge, presumably due to limited quality habitat, being the primary factor influencing fall fawn recruitment in mule deer. Secondarily, stochastic weather events periodically cause dramatic declines in recruitment. And finally, the additive effects of human disturbance and predation can induce fluctuations in fawn fall recruitment. Here we make the case for using long‐term datasets for setting long‐term wildlife management goals that decision makers and the public can understand and support.

ABSTRACT: Wellbore integrity in a gas hydrate bearing formation during drilling remains great challenge as a complex solid-fluid and decomposed hydrate process interaction is involved. A wellbore temperature increase and/or depressurization processes my induce additional stresses and extra fluid flow, which in turn may trigger wellbore instability and unexpected fracturing. In order to understand and quantify the thermal-hydraulic-mechanical behavior with hydrate decomposition (THMD) process and the wellbore responses to the pressure and temperature variation under a given in-situ stress regime, a fully coupled THMD model is proposed and developed in this paper. A simplified semi-analytical solution for the induced stresses, pore pressure, and temperature change at the wellbore and inside the formation is presented. A linear Mohr-Coulomb criterion is utilized to define the onset of the wellbore instability in which a hydrate saturation depending cohesion is also incorporated. Laplace transformation is applied and a numerical method is used to solve the transformed homogeneous PDE. We conclude that thermally and hydration induced stresses may affect wellbore integrity during hydrate gas production due to wellbore pressure reduction and temperature increase. Unlike those stress perturbation in the conventional gas reservoir, critical temperature and pressure must be surpassed and additional incremental stresses may be induced due to the hydrate hydrate decomposition. Also additional fluid mass and energy transfer may take place by which both temperature and pore pressure may be induced due to the hydrate decomposition/recomposition. In additional the hydrate saturation change due to the typical drilling strategy applied may reduce the hydrate formation significantly,and this may also affect the production pressure control and management. Thus managing pressure for both maximum production and wellbore integrity must be optimized accordingly. 1. INTRODUCTION Wellbore stability has been a long-observed and widely studied problem during drilling and production in petroleum industries. Stresses around a created borehole due to primarily the in-situ stress from the far-field may increased during drilling and production when the wellbore pressure is reduced. Once such an induced stress state exceeds a strength, measured or estimated, a borehole stability issue, i.e. the borehole lost its integrity, will be brought up. Other than affected by the intact formation strength and initial in-situ stresses, wellbore orientation, formation hydraulic and thermal conditions, and drilling mud chemistry are all critical factors in stability analysis [Bradley, 1979; Santarilli et al., 1986, Detournay and Cheng, 1988; Ewy and Cook, 1990; Wang et al., 1996; Gassemi and Liu, 2005; Neyan, 2010]. Producing hydrate gas either by depressurization or/and increasing wellbore temperature has been proposed for gas exploitation in gas hydrate-bearing sediments (GHBS)[Masuda et al., 1997; Moridis, 2003; Moridis et al., 2007]. Wellbore stability has been reported due to a much more complex mechanical responses maybe provoked near a borehole to the exploiting procedure mentioned [Hyoto et al., 2002; 2008; 2013; 2014; Li et al., 2019,Wang, 2019]. The most economical approach in producing hydrate gas is to change the ice-like hydrate into fluid by reducing the pressure or increase the temperature so that a critical equilibrium condition is exceeded [Kim, 1987; Holder and Hand; 1982]. Such a procedure on the other hand will dissociate the hydrate so that newly created fluid (water and /or gas) mass may alter the conventional equilibrium condition. The new dynamic equilibrium system due the hydrate phase change may affect the mechanical response of the entire formation and particularly in the vicinity of the borehole, where phase change shall take place first and persist until the solid hydrate is decomposed completely. Furthermore the formation strength may be reduced significantly after hydrate dissociation [Masui et al., 2005; 2008; Hyoto et al., 2002; 2008; 2013, 2014; Li et al., 2019; Priest et al.; 2019]. A coupled thermal-hydraulic-mechanical model with hydrate dissociation (THMD) is proposed and numerical methods are typically utilized, i.e. Uchida et al., [2013]; Freij-Ayoub et al., 2017]. Although analytical solutions are convenient and a tool easy to use, but difficult to be tractable, a semi-analytical solution is developed in this paper for borehole mechanical responses under depressurization. A analytical solution and fully coupled THMD model are required for drilling and well integrity design during drilling and production; A semi-analytical solution is developed by incorporating THMD model including phase change and hydrate saturation-dependent cohesion. Specifically the solution is applicable specifically for the situations when the critical temperature/pressure are surpassed, i.e. the solid hydrate dissociation initiates and is decomposed into water and gas phase. Unlike those in the conventional reservoirs, the cohesion in GHBS is weakened significantly with hydrate saturation reduction [Koyno et al.,2002; 2008; 2013; 2014; Li et al., 2019]. gas and water saturation are balanced between fluid extraction at a producing well and supply from either the adjacent formation and those decomposed in each pore volume. The porosities based on the pore volume in the solid phase from the porous skeleton and combined solid hydrate+skeleton should be defined, as

ABSTRACT: A coupled formulation is developed, based on a dual-porosity model to simulate a naturally fractured aquifer under non-isothermal and two-phase fluid flow conditions. Two-phase flow coupled to the deformation in a dual-porosity type media, and local thermal non-equilibrium (LTNE) conditions are imposed for the energy transport between and among, respectively, two fluid and porous solid phases. Along and through them conductive and convective mechanisms may dominate. More importantly, different physical parameters reflect different rock types and fracture characteristics are defined and interpreted so that the corresponding rock behaviors may be represented. Models and physical interpretations developed and proposed by different researchers are reviewed and compared. The model is applicable in reservoir simulation of naturally fractured formations with two-phasefluidflow, such as safety design of CO2 injection and sequestration, oil/gas storage injectivity or capacity evaluation, and heat extraction design in geo-thermal reservoir. 1. INTRODUCTION The coupled thermo-hydro-mechanical (THM) response of a fluid-saturated naturally fractured medium is characterized by bulk skeleton deformation, fluid diffusion and heat transport processes via fluid flux through both matrix and fractures. The hydraulic process of the fluid flowing through the fissured porous skeleton and the mechanical responses to external loading may be calculated by poroelastic theory and the two processes are also coupled with each other simultaneously. When the saturated fissured porous block is heated, the pore pressure inside the porous may rise depending on the formation permeability, solid expands and these two processes shall be interacting with each other following the effective stress principle. Evaluations of THM responses under multiphase fluid flow via the entire porous formation subject to THM loading can be conducted based on their fundamental behaviors following an extended poroelastic constitutive laws with dual porosity and corresponding transport mechanisms in each fluid phase. Either drained moduli for the bulk porous skeleton and those for the matrix and fractured systems separately may be used. Accumulation and dissipation of the thermal potential on and through the fissured porous skeleton and fluid also follow energy conservation equilibrium condition. Separate non-equilibrium thermal energy transport processes may take place along or through the porous matrix and the fracture network, mainly by conduction within the solid matrix phase, depending on its permeability, and by conductive and convective heat transfer through the moving fluid in the fractures system. In an extreme scenario, perhaps typical of Granites and shales, through both the moving fluid and matrix heat flux is completely conductive, whereas in another extreme scenario, perhaps a naturally fractured sandstone, the heat flux along the solid phases (matrix and fracture) and fluid are conductive but a combined conductive and convective is dominating the fluid mass transport through the fracture. In addition, heat exchange between each adjacent system, i.e. between each fluid and solid system are transferable which are typically characterized by heat exchange coefficients assuming an instantaneous equilibrium condition may be reached at the contact areas. A convective components may also be incorporated depending on the hydraulic characteristics such as the fluid velocity between these systems. Simulating naturally fractured formation, early modeling work on the dual-porosity model initialized by Barentblatt et al, 1960 and Warren and Root 1963 assumed porous block is rigid. Studies on deformable skeleton were imposed later by Duguid and Lee, 1977 and a mixture theory is proposed by Aifantis [1977,1979,1980]. In these early work, the cross-coupling between the fracture and pore volume is ignored [Khalili and Valliappan, 1996; Khalili, 2003, 2008]. To improve Aifantis’s early work, improvement and extension of the dual-porosity formulations for single phase fluid flow are developed [Wilson and Aifantis, 1982; Khaled et al, 1984, Valliappan and Khalili-Naghadeh, 1990, Berryman and Wang, 1995; Berryman and Bridge, 2002; Berryman 2002, Khalili-Naghadeh and Valliappan 1991, Chen and Tuefel, 1997. Khalili and Valliappan, 1996, and Khalili and Selvadurai, 2003. The dual-porosity concept to include multiphase flow subject to a number of restrictions are also introduced [Lewis and Ghafouri, 1997; Bai et al., 1998; Pao and Lewis, 2002, and Nair et al. ,2005, Khalili, 2008].

SummaryRecent advances in development of automated tools and machine learning algorithms based on artificial intelligence (AI) have revolutionized our interpretation approach of big data by making ...

We present inversion and interpretation results of helicopter-borne ZTEM and magnetic data acquired over the Canasil Resources Inc.’s La Esperanza project area, located along the western edge of the Mexican Silver Belt in Zacatecas and Durango States, Mexico. The La Esperanza property covers a number of low to intermediate-sulphidation silver-rich epithermal veins occurring as crustiform quartz-carbonate veins encompassed by sericite-argillic alteration. The 3D ZTEM inversion revealed that the La Esperanza vein mineralized zone in the southeast of the project area is associated with a narrow resistive zone near the surface and broader resistive zone at depth. The 3D magnetization vector inversion (MVI) suggests the presence of a deepseated magnetic structure below the mineralized vein, attributed to a mafic intrusive stockwork that is coincident with the resistive zone. The 3D ZTEM inversion and interpretation results of the data suggest the presence of at least two circular features with a resistive core and a more conductive ring consistent with porphyry-alteration systems, which merits further investigation. Presentation Date: Wednesday, September 18, 2019 Session Start Time: 8:30 AM Presentation Time: 11:25 AM Location: 301B Presentation Type: Oral

ABSTRACTZ‐axis tipper electromagnetic and broadband magnetotelluric data were used to determine three‐dimensional electrical resistivity models of the Morrison porphyry Cu–Au–Mo deposit in British Columbia. Z‐axis tipper electromagnetic data are collected with a helicopter, thus allowing rapid surveys with uniform spatial sampling. Ground‐based magnetotelluric surveys can achieve a greater exploration depth than Z‐axis tipper electromagnetic surveys, but data collection is slower and can be limited by difficult terrain. The airborne Z‐axis tipper electromagnetic tipper data and the ground magnetotelluric tipper data show good agreement at the Morrison deposit despite differences in the data collection method, spatial sampling, and collection date. Resistivity models derived from individual inversions of the Z‐axis tipper electromagnetic tipper data and magnetotelluric impedance data contain some similar features, but the Z‐axis tipper electromagnetic model appears to lack resolution below a depth of 1 km, and the magnetotelluric model suffers from non‐uniform and relatively sparse spatial sampling. The joint Z‐axis tipper electromagnetic inversion solves these issues by combining the dense spatial sampling of the airborne Z‐axis tipper electromagnetic technique and the deeper penetration of the lower frequency magnetotelluric data. The resulting joint resistivity model correlates well with the known geology and distribution of alteration at the Morrison deposit. Higher resistivity is associated with the potassic alteration zone and volcanic country rocks, whereas areas of lower resistivity agree with known faults and sedimentary units. The pyrite halo and ≥0.3% Cu zone have the moderate resistivity that is expected of disseminated sulphides. The joint Z‐axis tipper electromagnetic inversion provides an improved resistivity model by enhancing the lateral and depth resolution of resistivity features compared with the individual Z‐axis tipper electromagnetic and magnetotelluric inversions. This case study shows that a joint Z‐axis tipper electromagnetic–magnetotelluric approach effectively images the interpreted mineralised zone at the Morrison deposit and could be beneficial in exploration for disseminated sulphides at other porphyry deposits.