aer/ags special report 112: chapter 6: three-dimensional

Chapter 6: Three-Dimensional Geological Modelling at theGeological Survey of Austria

Sebastian Pfleiderer1, Gregor Götzl

2, Clemens Porpaczy

2, Magdalena Bottig

2, and

Andrea Steinbichler2

1Department of Mineral Resources, Geological Survey of Austria, Neulinggasse 38, 1030 Vienna, Austria

2Department of Hydrogeology and Geothermal Energy, Geological Survey of Austria, Neulinggasse 38, 1030 Vienna, Austria

Pfleiderer, S., Götzl, G., Porpaczy, C., Bottig, M., and Steinbichler, A. 2019. Three-dimensional geological modelling at the GeologicalSurvey of Austria; Chapter 6 in 2019 Synopsis of Current Three-Dimensional Geological Mapping and Modelling in Geological SurveyOrganizations, K.E. MacCormack, R.C. Berg, H. Kessler, H.A.J. Russell, and L.H. Thorleifson (ed.), Alberta Energy Regulator / AlbertaGeological Survey, AER/AGS Special Report 112, p. 39–47.

Introduction

This paper gives an overview of 3Dgeological modelling activities at theGeological Survey of Austria (GBA).Activities started as early as 1991,and for the following 16 years contin-ued in the form of small, isolatedstudies constructing surfaces – so-called “flying carpets” – in GIS. Dueto the project-based nature of thesestudies, irregular funding and highfluctuation of staff, modelling exper-tise did not increase significantly until2010, when a modelling team was es-tablished and professional 3D model-ling software acquired. Regular fund-ing was secured in 2015.

The focus then shifted from model-ling for a specific, appliedgeoscientific purpose to modelling asa geological exercise in its own right.In cooperation with field geologists,large sedimentary basins were mod-elled at first, as their horizontal, layercake structure is easy to map and datasuch as drillings and seismic sectionsare abundant. In the central Alps,geological modelling started only inrecent years and follows a more con-ceptual approach, as the tectonic set-ting is complex and subsurface datascarce. Geological models in bothsedimentary basins and Alpine tec-tonic units are now often used for nu-merical models to study e.g. ground-water flow or geothermal heatdistribution.

Today, the modelling team consists ofexperts from the Applied GeosciencesDepartment but is closely linked tofield geologists and data managers. Inthe Geological Mapping Department,3D modelling has yet to be estab-lished as a regular tool to map and vi-sualize geology in three dimensions.While other Geological Survey Orga-nizations already deliver 3D modelsin conjunction with 2D maps, theGeological Mapping Department atGBA still restricts itself to publishingmaps, accompanied by a verticalcross-section constructed outside any3D modelling software. 3D data suchas strike and dip measurements ofstructural surfaces, borehole logs, aswell as derived products such ascross-sections and structural maps, donot find their way into a common datastorage system. Current plans strivefor the establishment of an integralworkflow and data management sys-tem, which would facilitate the mod-elling.

Organizational Structureand Business Model

The Geological Survey of Austria is afederal institution under the Ministryof Education, Science and Researchand is organized in three main depart-ments – Geological Mapping, AppliedGeosciences and Central Services.Geological Mapping comprises theDepartments of Hard Rock Geology,Sedimentary Geology and Paleontol-ogy & Stratigraphy, while Applied

Geosciences consists of the Depart-ments of Mineral Resources,Engineering Geology, Hydrogeology& Geothermal Energy, Geochemistryand Geophysics. Central Services in-clude Administration, Geoinfor-mation, IT & GIS, Public Relationsand the Library, Archive and Publish-ing Unit. Approximately 135 personsare employed at GBA, 85 of them asgeoscientists.

The geological mapping at GBAforms the basis for the applied geo-logical research on mineral deposits,groundwater, natural hazards and geo-thermal energy. All activities aregrouped into either basic research, ap-plied projects or methodological andexperimental development. Data,maps and reports on all aspects ofAustrian geology are provided to pub-lic administrations, universities, re-search centers, industry and to thewider public through a geological in-formation service.

The geological modelling team cur-rently consists of five scientists in theDepartments of Mineral Resourcesand Hydrogeology & Geothermal En-ergy. The team cooperates closelywith colleagues performing numericalmodelling (groundwater flow, heatflow, geochemical interpolation,geohazard modelling and geophysicalinversion) as well as with field geolo-gists and experts on data definitionand management.

AER/AGS Special Report 112 • 39

Overview of 3DModelling Activities

3D geological modelling at GBAstarted with individual projects focus-ing on applied geoscientific topicssuch as the distribution of coal seams(Lipiarski and Heinrich, 1992), thethickness of groundwater protectinglayers (Moser and Reitner 1998), thestructure of Vienna’s building ground(Pfleiderer and Hofmann 2001) or thegeothermal potential of the EasternAlps (Götzl et al. 2007). The model-ling entailed the interpolation of for-mation tops from drill logs to createstructural maps and was performed inGIS (ArcInfo). Later projects, e.g. onthe geothermal use of tunnels(Rockenschaub et al. 2009), appliedprofessional software (GeoModeller)to aid the structural modelling.

In 2010, structural modelling startedto be recognized as a geological exer-cise in its own right, preceding ap-plied geoscientific studies, andGOCAD® was introduced as the mod-elling software of the Geological Sur-vey of Austria. Large sedimentarybasins outside the Alps were mod-elled, such as the Vienna basin (Götzlet al. 2012a), the Styrian basin (Götzlet al. 2012b) and the Molasse basin(Pfleiderer et al. 2016). Recently,work also started to focus on inner-al-pine sedimentary basins or valleys(Götzl et al. 2016) and on alpine re-gions or tectonic units such as theTauern window (Götzl et al. 2015),the Arzberg region (Götzl et al.2017), or the Dachstein region(Porpaczy et al. 2017).

In 2017, SKUA® was acquired and isnow gradually replacing GOCAD®.Ongoing modelling work centers ontwo themes. On one hand, bedrockstructures beneath sedimentary basinsare investigated, e.g. in the greater Vi-enna area and in the border region be-tween Austria and the Czech Repub-lic. On the other hand, a simplified,pan-Austrian framework model is be-ing developed, displaying major tec-tonic units down to the Mohorovièiæ

discontinuity (Pfleiderer et al. 2018).Altogether, 14 models have been fi-nalized and three are in progress as of2018.

Resources Allocated to3D Modelling Activities

3D geological modelling is partlysupported by federal funds, which arenot tied to any specific project andcurrently amount to 43,000 Euros peryear. These funds cover e.g. the workon the pan-Austrian framework modelas well as the development of web-based visualization tools and costsarising from data management or soft-ware licenses. Additional funds comefrom national and international pro-jects that include modelling activities.These projects are financed by Euro-pean and national funding agencies aswell as by government contracts.Summing up the budgets allocated tomodelling within these projects, thefunds amounted to 36,000 Euros in2018. In total, the modelling team hada budget of 79,000 Euros available in2018.

While the federal funds remainedconstant for the last few years, projectmoney varies from year to year. Nev-ertheless, the resources are sufficientto cover employment costs for ap-proximately 1.5 persons per year.Hardware costs are paid by in-housebudgets and do not impact on eitherof the two funding sources mentionedabove.

Overview of RegionalGeological Setting

Schuster et al. (2014) describe theAustrian geology in an easy-to-read,richly illustrated publication, whichcan also be viewed online (https://www.geologie.ac.at/rocky-austria).Figure 1 gives an overview of thegeological / tectonic setting.

The Variscan orogene in the North ofthe country is composed of graniticand gneissic rocks of theMoldanubian and Moravian

superunits, their Mesozoic cover,which is not exposed at ground level,and of Neogene sedimentary rocks ofthe Autochthonous Molasse.

South of the Alpine frontal thrust, theAlpine orogene is characterized bythrust-and-fold tectonics and includesthree superunits. These are (a) theSouth Alpine and Austro Alpinesuperunits, which are derived fromthe Adriatic continent, (b) thePenninic superunit, which representsremnants of the Penninic ocean andcontinental fragments, and (c) theSub-Penninic Superunit, which is de-rived from the European continentalmargin deformed during the Alpineorogeny. In the East, the Styrian andVienna basins cover the Alpineorogene with Neogene sediments.

The cross-section in Figure 2 illus-trates the tectonic structure along aNorth-South transect across Austria.Further details on the geology of theEastern Alps are given by Schmid etal. (2004), Froitzheim et al. (2008)and by Schuster and Fritz (2013).

Data Sources

Data used for 3D geological model-ling at the Geological Survey of Aus-tria are listed in Table 1. In Austriansedimentary basins, most of the datatypes listed in Table 1 exist with highdata densities due to extensive oil andgas exploration. In the central Alps,the only available data are commonlystrike and dip measurements as wellas outcrop boundaries and fault linesfrom geological maps. From these,cross-sections are constructed by fieldgeologists using their knowledgegained through mapping together withscarce borehole data.

Borehole data in Austria are currentlycollected in databases of the federalstates and accessible via online webservices. Some states offer public,free-of-charge access, others havegranted GBA password-protected ac-cess. However, the services only pro-vide individual drill logs in image or



Figure 1: Geological overview based on the Multi-thematic Map of Austria 1:1,000,000 (Krenmayr, 2017; Hintersberger etal., 2018), modified after Froitzheim et al. (2008).

Figure 2: Cross-section through the Eastern Alps after Schuster and Fritz (2013) and Schmid et al. (2004) (for location ofcross-section see dotted line in Figure 1).

table format, and entire data sets can-not be imported directly for model-ling purposes. Only two of the ninefederal states share their entire bore-hole databases with GBA.

Data sharing practices of oil and gascompanies in Austria are restrictivewith respect to drill logs and seismicsections. Although federal laws pre-scribe that any exploration data arehanded to GBA, the data often remainwith the companies. However, agree-ments exist which allow GBA to ob-tain data for specific projects. Datacan then be used internally but publi-cation of raw data is prohibited with-out prior consent of the data owners,and derived information can only bepublished if the exact location of theunderlying data is concealed. For theinterpretation of seismic sections,GBA relies on subcontracted, externalconsultants, as no internal expertiseexists in-house.

Drill logs and cross-sections pub-lished in maps and journals of theGBA, are made accessible to the pub-lic through data viewers on thewebsite (https://gisgba.geologie.ac.at/gbaviewer/?url=https://gisgba.geologie.ac.at/ArcGIS/rest/ser-vices/AT_GBA_PROFILE/MapServer) and through OpenGIS®

web map services. These servicesshow the location of drill holes and

cross-sections, provide a preview, listmetadata on the title, scale and yearof publication, and offer a direct linkto the library catalogue.

A countrywide, digital elevationmodel of the ground surface, con-structed from airborne laser scan data

with a resolution of 10 × 10 m, isavailable as open government data(https://www.data.gv.at/katalog/dataset/dgm).

3D Modelling Approach

Currently, the 3D geological model-ling team of the Geological Survey ofAustria is in a transition phase be-tween explicit and implicit modelling.Some models are still being finalizedusing GOCAD®, constructing sur-faces explicitly through discretesmoothing interpolation betweenpoints and subsequent manual editingto achieve plausible results with re-spect to stratigraphic sequence, layerthickness and fault displacements(Pfleiderer et al., 2016). In 2017,SKUA® was acquired and the implicitmodelling approach adopted. Follow-ing the structure and stratigraphyworkflow, volumes are now con-structed by defining litho-strati-graphic sequences, building fault net-works, and then modelling horizons.

For further numerical modelling, re-sults from both modelling approachesare exported in the form of surfaces.The computation of geologic grids,the assignment of petro-physicalproperties to cells and the simulationof e.g. groundwater or heat flow areperformed by other software applica-tions such as FEFLOW or COMSOLMultiphysics®.

Clients

The Geological Survey of Austriadoes not operate commercially. Geo-logical modelling is carried out withinresearch projects and performed forstakeholders of these projects ratherthan for clients. Stakeholders includewater and mining authorities, engi-neering departments, spatial planninginstitutions and geothermal energyproviders. As these stakeholders rep-resent end-users of the models andusually have little geological exper-tise, there is no collaboration betweenthem and GBA as such when creatingthe models. The modelling teamtherefore rather seeks collaborationwith field geologists who can provideexpert knowledge in the area underinvestigation.

Modelling areas are most often de-fined by the respective funding bod-ies, e.g. cross-border model areas byEuropean Regional Programs or


Table 1: Data types and sources used for 3D geological modelling at the Geo-logical Survey of Austria.

model areas of inner-alpine valleys byprovincial governments. For Euro-pean research projects, stakeholders’interests are commonly collected atthe start of the project and regularstakeholder meetings organized to in-form about the projects’ progress. Forprojects commissioned by provincialgovernments, a much closer interac-tion exists. Before modelling, basedata are often provided by these gov-ernments, and regions (and layers) ofinterest are defined in cooperation.During modelling, feedback is givenregularly and any problems encoun-tered are discussed together to ensuresatisfactory results.

After project completion, and withoutremaining funds, there is no continu-ing support of end-users. Once themodel has been delivered, they are re-sponsible for storage, maintenanceand ongoing use. When new data be-come available or new interests of us-ers are expressed, updating or refin-ing of existing models is performedwithin new projects. These caseshowever have so far rarely occurred.

Apart from the use by stakeholders,finalized models are stored on a GBAserver and made accessible to in-house staff. For public use, a web-based viewer was developed whichaccesses the models stored internallyand provides an interface for visualiz-ing 3D models, querying them withvirtual drill holes and slicing throughthem in any browser, without the needfor downloading any data or software.This viewer went online in 2016 andquickly became one of the most vis-ited pages of GBA’s website (https://gisgba.geologie.ac.at/3dviewer/). Cur-rently, it shows only one model, Vi-enna’s underground geology (see Fig-ure 3), but plans are well advancedfor a front page allowing the selectionof one of the 17 models, before view-ing (Figure 4).

To present 3D geological models tothe wider public, two types of physi-cal representations were realized, aglass block and a 3D print (Figure 5).

The former was produced by a laserengraving technique, etching 80 mil-lion points into a glass block to makesurfaces, fault planes and drill holesvisible in three dimensions (Schimpfand Wycisk, 2016). The latter wasmade by sending four simplified,closed surfaces to a 3D printer, whichproduced four plastic shapes whichcan be stacked upon each other.

Recent Jurisdictional-Scale Case StudyShowcasing Applicationof 3D Models

Information on this topic is currentlynot available.

Current Challenges

Approximately half of the funds for3D geological modelling constituteproject money. These projects typi-cally last one to three years. To securecontinuous funding, and to keep thestaff and their experience, new pro-jects have to be acquired constantly.As project money varies from year toyear, this can pose a financial chal-lenge. In addition, the modelling teamdepends to some degree on in-housedata managers and programmerswhose contribution, time and costshave to be planned well in advance.This sometimes adds an organiza-tional challenge.

Concerning the acquisition of basedata, the modelling team often facessignificant challenges as ownership ofseismic sections and most boreholedata lies outside GBA. Only if pro-jects are commissioned by institutionswhich hold and provide the necessarydata, or if data owners are part of theproject team, these problems aresolved easily.

On the data management side, GBA isstill lacking an integral workflow anddata management system for 3D mod-elling. Base data are currently storedin dispersed data bases and modellingproducts are filed individually. Thismakes maintenance and update of

data and models difficult. When newbase data are collected and previousmodelling results are refined in thecourse of new projects, it becomes achallenge to know which version wasbased on what subset of data andwhich layers represent the latest re-sult. Current plans at GBA strive forthe establishment of a central data ar-chiving system. Keeping a detailedlog file of modelling activities and re-sults in a central system would in-crease transparency and facilitatemodelling, especially for new staffjoining the team.

3D data collected by field geologists,such as strike and dip measurementsof structural surfaces, do not findtheir way into a common data storagesystem. Considerable time is spent togather and prepare base data beforemodelling. The Geological MappingDepartment has yet to recognize andembrace 3D modelling as regular toolto map and visualize geology. Thisdepartment’s main objective still is topublish 2D maps, accompanied byvertical cross-sections constructedoutside any 3D modelling software.The conceptual and organizationalchallenge here is to promote closercooperation and to make field geolo-gists and modellers “grow together”.

Lessons Learned

The adoption of an implicit modellingapproach with SKUA® proved apromising step to facilitate modellingand to introduce a transparent andverifiable workflow. Although intro-duction of the method and softwarerequires training (and time), the ap-proach will soon fully replace explicitmodelling at GBA.

To build bridges between the model-ling team and mapping geologists, thesoftware tool Subsurface Analyst(part of the ArcHydro Groundwatersuite by Aquaveo) was acquired toprepare and visualize 3D data (cross-sections, logs) in GIS as well as toderive cross-sections from finalized3D models in GIS. This has led to a



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situation profitable to both sides, asgeologists can make cross-sectionsdrawn on paper available to model-lers, and modellers can make theirmodels useful to colleagues whowork in 2D GIS.

The 3D viewer developed by in-houseprogrammers became a success storynot only by showing 3D geologicalmodels to the outside world andboosting the popularity of GBA’shomepage but also by sharing thesource code on GitHub (https://github.com/geolba/3dViewer). TheHungarian Geological Survey for ex-ample used the code and, with thehelp of GBA’s IT & GIS Department,further developed it to present theirgeological models.

Next Steps

With respect to model creation, cur-rent work will produce three newmodels. Two models focus on thebedrock structures beneath sedimen-tary basins to aid the use of thermalgroundwater and geothermal energy,while a third model will shed light on

Austria’s deep tectonic structures on apan-Austrian framework scale.

Concerning methodology, the explicitapproach will be phased out and fullyreplaced by implicit modelling. In ad-dition, planning and implementationof a central data storage and manage-ment system for 3D data and modelswill be carried out as a future step.

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Figure 4: Extents of 3D geological models constructed at the Geological Survey of Austria.


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