MacCormack, K.E., Rokosh, D., and Branscombe, P. 2019. The Alberta Geological Survey 3D geological modelling program; Chapter 5 in 2019 Synopsis of Current Three-Dimensional Geological Mapping and Modelling in Geological Survey Organizations, K.E. MacCormack, R.C. Berg, H. Kessler, H.A.J. Russell, and L.H. Thorleifson (ed.), Alberta Energy Regulator / Alberta Geological Survey, AER/AGS Special Report 112, p. 24–38.

Regional scale 3D models provide insight into general unit geometries and stratigraphic relationships; however, potentially significant local scale data and unit geometries are rarely preserved. Accurate modeling of local scale unit geometries and stratigraphic relationships is important for understanding aquifer-aquitard connectivity, estimation of aquifer volume, and prediction of contaminant migration pathways; this is particularly important in previously glaciated areas because of the high degree of lithological heterogeneity and stratigraphic variation in glaciogenic deposits. This study presents a case study (Ontario, Canada) that explores the impacts of an optimized model (in which high-resolution data are preserved in local scale models as 'golden blocks') and non-optimized regional scale 3D models on the predicted geometries and stratigraphic relationships of coarse- and fine-grained units (lithofacies associations) within a Quaternary stratigraphy. Each of the regional scale models include high quality data (outcrop and cored borehole logs) and low quality data (water well lithology logs); however, the optimized model was constructed by seamlessly integrating the golden blocks into the regional scale model using an algorithm (producing a 'nested' model), whereas the non-optimized model was built using a global modeling approach. By way of comparison to unit geometries previously delineated in outcrops and surficial geology maps and hydraulic responses from pumping tests, the results of this study indicate that coarse-grained units, which host significant municipal aquifers, and fine-grained units were more realistically and accurately represented in the optimized model as a result of the nested 3D modeling approach. This case study demonstrates a relatively simple and effective method for preserving high quality data in a regional scale 3D model without sacrificing model accuracy in key areas of interest (e.g. aquifer well fields).

As the field of three-dimensional (3D) subsurface geological modeling develops at an increasingly rapid rate, so too does the number of available software programs catering to these applications, most of which offer very similar ensembles of algorithms for interpolating data. A few studies have analyzed the effect of algorithm selection on the accuracy and uncertainty of subsurface geologic models, but little consideration has been given to the uncertainty and variability introduced into the model by software program selection. In this study, inverse distance weighting (IDW) and ordinary kriging (OK) algorithms are used to interpolate identical data sets by three different software programs (ArcGIS, ROCKWORKS 2006, and VIEWLOG). The results indicate that the output of the IDW and OK interpolation algorithms are inconsistent between programs and that this variability should be considered when assessing the uncertainty associated with subsurface model results. Program selection appears to have a significant influence on model output results when modeling complex subsurface geological environments, particularly when interpolating clustered data, which are most commonly used in geological and environmental applications.

Testing the accuracy of 3D modelling algorithms used for geological applications is extremely difficult as model results cannot be easily validated. This paper presents a new approach to evaluate the effectiveness of common interpolation algorithms used in 3D subsurface modelling, utilizing four synthetic grids to represent subsurface environments of varying geological complexity. The four grids are modelled with Inverse Distance Weighting and Ordinary Kriging, using data extracted from the synthetic grids in different spatial distribution patterns (regular, random, clustered and sparse), and with different numbers of data points (100, 256, 676 and 1,600). Utilizing synthetic grids for this evaluation allows quantitative statistical assessment of the accuracy of both interpolation algorithms in a variety of sampling conditions. Data distribution proved to be an important factor; as in many geological situations, relatively small numbers of randomly distributed data points can generate more accurate 3D models than larger amounts of clustered data. This study provides insight for optimizing the quantity and distribution of data required to accurately and cost-effectively interpolate subsurface units of varying complexity.

One of the first stages of the three-dimensional (3D) subsurface modeling process involves collation and analysis of available borehole and/or outcrop data to identify individual subsurface units, usually distinguished by the grain size of the sediment, and the elevation of their bounding contacts. Input data can come from a variety of sources and may be categorized according to their reliability and/or quality. The output from the 3D model is a prediction of subsurface conditions based on these data and the reliability of the output model is highly dependent on both the quality of input data and the types of interpolation methods used. This article presents a new quality weighting methodology that allows the user to assign a differential weighting factor to data points of variable quality in the modeling process. Input data are categorized into high and low quality datasets which are then recombined using a grid math process in which a differential "weighting" factor is applied. This allows the 3D modeling program to maximize the use and effectiveness of data from all available sources while giving high quality data greater influence on the final model output, and will result in the generation of more accurate and reliable 3D subsurface models.

The Dundas Valley is a bedrock valley infilled with up to 180 m of Quaternary sediment that underlies the Hamilton-Wentworth region of southern Ontario. Although the infill of the Dundas Valley contains a valuable record of past environmental change and controls groundwater and contaminant migration pathways in the region, the nature, origin, and spatial distribution of sedimentary units comprising the infill are poorly understood. This paper presents the initial results from the compilation and three-dimensional modeling of subsurface geological data obtained from water well and borehole records, and engineering and construction reports from the Hamilton region. RockWorks v. 2002 was used to model and create images describing the bedrock topography and valley infill stratigraphy. Analysis of cross sections and three-dimensional box models created by RockWorks v. 2002 allows five texturally distinct stratigraphic units to be identified within the valley infill. These units include bedrock (unit 1), draped by a discontinuous veneer of coarse sand and gravel (unit 2) interpreted as fluvial in origin, extensive silty clays and fine-grained diamicts (unit 3) that record either glaciolacustrine or sub-glacial conditions, coarse sands and gravels (unit 4) formed under high-energy shore-face conditions associated with postglacial Lake Iroquois, and silts and silty sands (unit 5) formed in lagoonal environments. The three-dimensional images showing subsurface sediment distributions and geometries for the Dundas Valley can be used not only to better constrain the late Quaternary depositional history of the region, but also to identify and delineate major aquifers and aquitards, essential for groundwater protection and remediation planning.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTVapor-Liquid Equilibria in Dilute Aqueous Solutions of Ethylene OxideK. E. MacCormack and J. H. B. ChenierCite this: Ind. Eng. Chem. 1955, 47, 7, 1454–1458Publication Date (Print):July 1, 1955Publication History Published online1 May 2002Published inissue 1 July 1955https://pubs.acs.org/doi/10.1021/ie50547a053https://doi.org/10.1021/ie50547a053research-articleACS PublicationsRequest reuse permissionsArticle Views285Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

In the silver catalyzed oxidation of ethylene or ethylene oxide (EtO), the silver catalyst activity measured under constant standard conditions in a flow system was found to be dependent on the conditions of previous catalyst treatment such as reaction temperature and reactant composition. The results are explained on the basis of slow establishment of equilibrium respecting fixation of stably sorbed oxygen atoms and surface products of oxidation. It is emphasized that in view of the slow processes observed, the kinetic measurements must be punctuated by frequent stabilizing check runs in order to maintain the catalyst in the same reference state.

A reaction mechanism for the silver catalyzed oxidation of C2H4 by oxygen has been formulated which is consistent with kinetic data for this system. It is suggested that both ethylene oxide and CO2 formation involve interaction of single gaseous C2H4 molecules with single oxygen adatoms. This may be a system of two parallel reactions of different activation energy requirements or a common initiation step to form adsorbed ethylene oxide which may then desorb immediately or isomerize to acetaldehyde followed by rapid oxidation to CO2 and H2O. Account is taken of the known adsorption characteristics of O2 on silver to deduce expressions for initial rates of ethylene oxide and CO2 formation as a function of reactant partial pressures. The generalized form of the equation is r = k(1 + a/pE + b/pO)−1, where k, a, and b are temperature dependent constants and pE and pO are partial pressures of ethylene and of oxygen respectively.A mechanism is also suggested for the heterogeneous oxidation of ethylene oxide which involves interaction between a gas phase ethylene oxide molecule and a single oxygen adatom to form an intermediate (probably formaldehyde) which is rapidly oxidized to CO2 and H2O. A similar expression to that above for the initial oxidation rate is deduced. These expressions have been fitted successfully to experimental data.

A flow type apparatus was used for kinetic studies of the silver catalyzed oxidation of ethylene oxide (EtO) by oxygen at 274 °C. Using N2 as diluent the concentrations of O2 and ethylene oxide were varied independently from 9.9 to 79% and 2.35 to 9.4% respectively while a total pressure of 1 atmosphere was maintained. Flow rates were varied to give a range of contact times varying from 0.06 to 0.25 sec. It was shown that EtO is oxidized without previous dissociation into C2H4 and O2. The dependence of the initial rate of oxidation of EtO on reactant concentrations excludes isomerization of EtO (to acetalde hyde) as a main step in its oxidation, and a direct oxidation mechanism is suggested. The results of a few experiments to determine the extent of isomerization of EtO to acetaldehyde in the absence of oxygen are presented. No steady state could be achieved but the results may be used semiquantitatively to support the belief that isomerization is not the rate determining step in the oxidation of ethylene oxide.

Experimental second virial coefficient data for carbon tetrafluoride, sulfur hexafluoride, and carbon dioxide have been used to investigate the intermolecular potentials of these molecules on the basis of a Lennard-Jones model. Force constants for the fluoride molecules can be fitted rather satisfactorily, but the constants so derived do not agree with those derived from other gaseous properties, e.g., the critical data. This result may be due to the assumption of central forces for the symmetrical fluoride molecules. For carbon dioxide it was found that the derived force constants varied with temperature, the high temperature data yielding lower values of the collision diameter r0. The results can be interpreted on the basis of a partial association. A likely configuration for the resulting dimer is suggested.

The gaseous compressibilities of carbon tetrafluoride in the temperature range 0–400°C, and sulfur hexafluoride in the temperature range 0–250°C have been measured at pressures up to 50 atmospheres by a method employing gas expansion. The data have been fitted to a series equation of the type, PV (Amagat units)=AT+BTP+CTP2+DTP4,and the virial coefficients are tabulated.

Measurements of the P-V isotherms for sulphur hexafluoride in a small temperature range of approximately 1.5°C. in the critical region have been made to determine the validity of some theoretical considerations recently proposed. No evidence has been found to support the postulates of Mayer with respect to anomalous second order transitions over a finite temperature range above the temperature of disappearance of a liquid meniscus designated Tm. All isotherms above the latter are found to have a finite slope and it is not possible to conclude that the Tm isotherm has a finite horizontal portion or "flat top". These conclusions are borne out by the nature of the isometrics which have been plotted and discussed qualitatively in relation to the existing theories.The temperature of meniscus disappearance Tm is estimated to be 45.547 ± 0.003°C. and at the previously determined critical density (1) of 0.7517 gm./cm.3 the corresponding pressure is found to be 37.113 ± 0.003 atm. The critical density was found to be approximately 0.73 gm./cm.3