Rend. Online Soc. Geol. It., Vol. 30 (2014), pp. 28-32, 3 figs. (doi: 10.3301/ROL.2014.07) © Società Geologica Italiana, Roma 2014
Integrating data sources for 3D modeling: the Italian activity in the GeoMol Project a
b
Francesco E. Maesano ( ) & The Italian GeoMol Team ( ) _____________________________________________________________________________________________________________________________________________________ (a) ISPRA – Servizio Geologico d’Italia, Via Vitaliano Brancati 48, Roma Email:
[email protected] (b) Alessandro Cagnoni (Regione Lombardia, Milano) Chiara D’Ambrogi (ISPRA – Servizio Geologico d’Italia); Fabio Carlo Molinari (Regione Emilia Romagna, Bologna) Edoardo Monesi (CNR IGAG, Roma) Andrea Piccin (Regione Lombardia, Milano) Giancarlo Scardia (CNR IGAG, Roma) Document type: Short note. Manuscript history: received 07/10/ 2013; accepted 04/12/ 2013; editorial responsibility and handling by Paola Reichenbach. _____________________________________________________________________________________________________________________________________________________
ABSTRACT The GeoMol Project focuses on the realization of 3D geological models of the Alpine Foreland Basins to support the assessment of subsurface potentials (geothermal energy, underground storage, groundwater, etc.). GeoMol will provide consistent 3-dimensional subsurface information based on a transnational workflow for 3D models production, coherent evaluation methods, and commonly developed criteria and guidelines. These data will be used to implement a 3D geological framework model and conceptual workflows for geo-potential assessment. The main challenge is to integrate data that come in a different domain of the vertical axis, specifically depth for well logs, time for seismic lines, isobaths and isopachs maps in both the domains. The approach proposed by the GeoMol Project will highlight the possible problems in the exploitation of the geopotential related to concurrent use of subsurface and to the presence of potential active faults. KEY WORDS: 3D modeling, foredeep basin, geopotentials, Po Plain.
INTRODUCTION The assessment of geopotentials (geothermal energy, underground storage, groundwater, etc.) of the Alpine Foreland Basins (Molasse Basin and Po Plain, see Diepolder et al., this volume) is the main strategic goal of the GeoMol Project, funded by Alpine Space Programme-European Territorial Cooperation. The project will provide consistent 3-dimensional subsurface information based on coherent evaluation methods, criteria and guidelines developed at transnational level. The novelty of the project is the application of a common approach at European scale not only with the aim to obtain homogeneous 3D models of the subsurface, but also to develop new methodologies that can be exported in other areas for similar purposes, especially where problems of concurrent use of geopotentials could arise between nations or regions. Moreover the assessment of subsurface geopotentials must take into account the constraints given by the geological phenomena, for example the seismicity that is particularly relevant in the Italian pilot area, where historical and instrumental earthquakes had a great impact on the human activities (e.g., the seismic sequence of the May 2012 in the
Emilia area) (Fig. 1). The Italian pilot area (3800 km2), located in the central part of the Po Plain, has an important peculiarity when compared with the other GeoMol pilot areas, distributed along the Molasse Basin (Diepolder et al., this volume): the occurrence of facing external thrust fronts of two chains, the Southern Alps and Northern Apennines (Carminati and Doglioni, 2012 and reference therein), buried under a thick Plio-Pleistocene clastic succession (maximum thickness 7000 meters). The pilot area (Fig. 1) runs NW-SE from Brescia to Mirandola crossing the Southern Alps thrust (turned from E-W toward NE in the Lake Garda area, along the Giudicarie belt) and the external front of the Northern Apennines along the Ferrara arc (Fig. 1). These two thrust fronts are separated by the south-dipping Mantova Monocline (Ghielmi et al. 2010). Due to this complex structural framework the sedimentary succession of the pilot area is characterized by a large variability of the stratigraphic units in terms of environment,
Fig. 1 –Structural and seismic framework of the Italian GeoMol pilot area Hystorical seismicity is from CPTI11 (Rovida et al. 2011). Instrumental seismicity with M>2 from 2003 to 2013 from ISIDE catalogue (ISIDe Working Group, INGV, 2010). Structural elements (NA: Northern Apennins and Alps: Southern Alps thrust fronts) after Bigi et al. (1992)
INTEGRATING DATA SOURCE FOR 3D MODELING. THE ITALIAN ACTIVITY IN THE GEOMODEL PROJECT
facies, and thickness (Fantoni et al. 2010; Ghielmi et al. 2013). Both the orogens are characterized by active seismicity; the historical catalogue (Rovida et al., 2011) shows a concentration of activity along the Ferrara and Emilia arcs, and in the Giudicarie belt area (Fig. 1). In addition the area covered by the available dataset includes the seismogenic sources of the May–June 2012 seismic sequence in Emilia and the epicentral area of the most destructive event of the Po Plain – the 1117 Verona earthquake (Basili et al., 2008; DISS Working Group, 2010) – , whose seismogenic source is still debated. METHODOLOGY The common workflow defined for the development of 3D models in the GeoMol Project is partly derived from the Georg Project (www.geopotenziale.org/home), but it underwent some modifications due to the specific characteristics of the available dataset (Fig. 2). The dataset for the Italian pilot area consists of published geological sections and maps (Pieri and Groppi, 1981; Bigi et al., 1992; Fantoni and Franciosi, 2010; R.E.R. and ENI-AGIP, 1998; R.L. and ENI-AGIP, 2002), 12000 km of seismic profiles and 133 deep-well logs (Fig. 3A) kindly provided by ENI or available in the Ministero dello Sviluppo Economico website (http://unmig.sviluppoeconomico.gov.it/). The main challenge of the GeoMol 3D modeling workflow is: i. to harmonize data in time and depth domain with
Fig. 2 – Methodological workflow for the GeoMol Project
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common criteria, in order to define a new stratigraphic vocabulary, which merges different original interpretations (Tab. 1); ii. to consistently integrate data that come in different domains of the vertical axes: time domain (seismic lines, velocity data, time-depth or time velocity curves of wells) and depth domain (published geological maps, cross sections, isobaths and isopachs maps). After the criteria definition, the workflow follows two parallel approaches (Fig. 2) by interpreting and managing separately time domain and depth domain dataset. However an iterative process occurs during seismic interpretation as well data are used to check the depth of the digitized key seismic reflectors. The further step is the construction of 3D models. This can be accomplished by following two approaches (Fig. 2): i. to build a "raw" 3D model using only the information in time domain, by interpolating the interpreted seismic horizons and faults. This "raw" 3D model in time (Fig. 3B) can be depth-converted as a whole to quickly test the velocity models; ii. to depth-convert the horizons and faults digitized in time domain and to integrate the objects with the depth domain dataset (Fig. 2). In this case the best velocity model available for the area is used to run the time-depth conversion. At this point it is crucial to check the consistency of the time-depth conversion results with the constraints in depth domain. If important misfits are observed, the process must be reiterated
F.E. MAESANO & THE ITALIAN GEOMOL TEAM
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changing the interpretation or the velocity model. The data can be then used to build surfaces and the depth 3D model. These objects can be populated with attributes previously stored (e.g., temperatures, lithological properties, etc.). Code
Type
Base/Top
PLS045
unconf
base
PLS065
unconf
base
PLS080
unconf
base
PLS114
unconf
base
Age (Myr)
Middle Pleistocene
Calabrian
Horizon 0.45
AES and “Yellow” surface
0.65
MIS16
0.8
AEI and “Red” surface
1.14
"near Jaramillo" reflector
1
Base marine quaternary 2
PLS125
unconf
base
PLS150
unconf
base
1.6
Base marine quaternary 1
PLS260
unconf
base
Gelasian
2.6
Base Gelasian
Pl
unconf
base
Lower Pliocene
5.3
base Pliocene
ME4s
unconf
base
ME4
unconf
base
ME3
unconf
base
ME2
unconf
base
ME1
unconf
base
Mup
unconf
base Ghiaie di Sergnano base ME4 unconformity Messinian
base ME3 unconformity base ME2 unconformity 7.3
base ME1 unconformity
base
upper Miocene
upper Miocene unconformity lower Miocene unconformity
Mlw
unconf
base
lower Miocene
Eom
strat
top
middle Eocene
top Scaglia
KAp
strat
top
lower Cretaceous
top Maiolica
top
lower Jurassic
top Calcari grigi
top
upper Triassic
top triassic evaporites
J Tr
strat strat
Tab. 1 – Stratigraphic horizons selected for the interpretation and the 3D modeling in the Italian pilot area. AES, AEI, Yellow and Red surfaces are referred to Emilia Romagna and Lombardia aquifers maps (RER&ENI-AGIP, 1998; RL & ENI-AGIP, 2002). Messinian unconformities are referred to Ghielmi et al. (2013).
PRELIMINARY APPLICATIONS The final use of GeoMol Project products is not restricted just to the geopotential assessment (e.g., 3D volume calculation of target units). As a matter of fact it also can be the base for other debated topics (e.g., relationship between Mesozoic extensional tectonic and Neogene compressional structures), as well as other applications (e.g., slip rates evaluation). Some preliminary examples are here briefly described. 3D VOLUME OF TARGET UNITS One of the main goal of the geopotential assessment, especially for underground storage and geothermal uses, is to reconstruct the 3D volume of the target units, also taking into account their attributes (porosity, permeability, temperature, etc.). The geocellular volume construction is performed by using the available mapped horizons as volume constraints,
which can be in turn formation tops or basal unconformities of sedimentary sequences (Tab. 1). The use of 3D modeling techniques allows quantifying the rock volume and the stochastic fractures network distribution, if enough data are available. RELATION BETWEEN MESOZOIC EXTENSIONAL TECTONIC AND NEOGENE COMPRESSION The mapping and 3D reconstruction of the structures related to the Mesozoic extensional tectonics in the foreland monocline is one of the topic of interest in the pilot area. The inherited structures in the Mantova Monocline could have a great influence in the propagation of the external front of the Northern Apennines. These extensional structures have been recognized under the external front of the Ferrara arc (Rogledi, 2013). During the first step of the seismic interpretation it has been observed that in correspondence of the main normal displacement in the carbonatic succession, the overlying Apenninic detachment surface passes into a steep ramp (e.g., the Viadana Horst, Fig. 3C and D, and the Piadena structure). This interpretation will be tested in more detail using all the available seismic profiles and the 3D models. SLIP RATE EVALUATION The slip rates evaluation is an application that can be developed by processing the GeoMol dataset according to the workflow already developed in previous studies (Cooke and Marshall, 2006; Maesano et al., 2013). In the proposed approach, the horizons deformed by potential active blind thrust are decompacted and restored with different algorithms on the base of the type of deformation observed (trishear, fault parallel flow, dislocation modeling). This methodology for the slip rate calculation can be further improved by the large amount of data collected in the framework of the GeoMol Project to obtain the lateral variability of the slip rates along a fault and a better estimation of the sediment compaction influence on slip rate measurements.
CRITICAL POINTS AND FURTHER DEVELOPMENTS Possible critical points are of geological and technical nature. Geological critical points are mainly related to the harmonization of data published over a long span of time and interpreted in different ways. Other problems can arise during the final elaboration of the 3D modeling and regard its geological and geometrical consistency. To test the structural admissibility of the model, restoration and balancing of the key structures must be performed. Technical problems are connected with the time-depth conversion and with the non-homogenous distribution of
INTEGRATING DATA SOURCE FOR 3D MODELING. THE ITALIAN ACTIVITY IN THE GEOMODEL PROJECT
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Fig. 3 – Dataset and preliminary applications for the GeoMol project. A) Dataset available for the Italian GeoMol pilot area, base geological map from the Structural Model of Italy (Bigi et al., 1992); B) Preliminary 3D model in time domain; C) Seismic section showing the relations between the inherited normal fault in the Mantova monocline (Viadana horst) and the geometry of the overlying Ferrara thrust front.; D) Map of the dataset and fault trace (in purple) in the Viadana area, recognized also under the Ferrara arc; the line highlighted in yellow is displayed in fig. 2C.
attribute data in the pilot area. For this reason different algorithms will be tested to find the best way to interpolate attributes (ordinary kriging, inverse weight distance, natural neighbors). The final product will be a multi-scale 3D model useful for management of shallow and deep underground resources, as water supply, geothermal energy and carbon and gas storage, respectively.
ACKNOWLEDGMENTS The project GeoMol is co-funded by the Alpine Space Program as part of the European Territorial Cooperation 2007-2013. The project integrates partners from Austria, France, Germany, Italy, Slovenia and Switzerland and runs from September 2012 to June 2015. Further information on www.geomol.eu Seismic data are kindly provided by ENI S.p.A. MOVE software suite (Midland Valley Ltd.) released under Academic Licence Agreement.
REFERENCES Bigi G., Cosentino D., Parotto M., Sartori R. & Scandone P. (Eds.) (1992) - Structural Model of Italy and Gravity Map, 1:500,000. Quad. Ric. Scientifica, 114, 3, S.EL.CA Florence. Basili R., Valensise G., Vannoli P., Burrato P., Fracassi U., Mariano S., Tiberti M.M., Boschi E. (2008) - The Database of Individual Seismogenic Sources (DISS), version 3: summarizing 20 years of research on Italy's earthquake geology, Tectonophysics, doi:10.1016/j.tecto.2007.04.014 Carminati E. & C. Doglioni (2012) - Alps vs. Apennines: The paradigm of a tectonically asymmetric Earth. Earth-Science Reviews, 112, 67-96 doi: 10.1016/j.earscirev.2012.02.004. Cooke M.L. & S.T. Marshall S. (2006) Fault slip rates from three-dimensional models of the Los Angeles metropolitan area, California, Geophys. Res. Lett., 33, L21313, doi:10.1029/2006GL027850, 2006. Diepolder G.W., R. Pamer & the GeoMol Team (2013) Transnational 3D modeling, geopotential evaluation and seismic risk assessment in the Alpine Foreland Basins – the project GeoMol. Rendiconti Online della Società Geologica Italiana, 30, 19-23.
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DISS Working Group (2010) - Database of Individual Seismogenic Sources (DISS), Version 3.1.1: A compilation of potential sources for earthquakes larger than M 5.5 in Italy and surrounding areas. http://diss.rm.ingv.it/diss/, © INGV 2010 - Istituto Nazionale di Geofisica e Vulcanologia - All rights reserved; DOI:10.6092/INGV.ITDISS3.1.1 ISIDe Working Group (INGV, 2010) - Italian Seismological Instrumental and parametric database: http://iside.rm.ingv.it Fantoni R. & Franciosi R. (2010) - Tectono-sedimentary setting of the Po Plain and Adriatic Foreland, Rend. Fis. Acc. Lincei, 21, 1, S197-S209, doi:10.1007/s12210-0100102-4. Ghielmi M., Minervini M., Nini C., Rogledi S., Rossi M. & Vignolo A. (2010) - Sedimentary and tectonic evolution in the eastern Po Plain and northern Adriatic Sea area from Messinian to Middle Pleistocene (Italy). Rend. Fis. Acc. Lincei, 21 (Suppl 1): S131–S166 DOI 10.1007/s12210-0100101-5. Ghielmi M., Minervini M., Nini C., Rogledi S. & Rossi M. (2013) - Late Miocene-Middle Pleistocene sequenze in the Po Plain – Northern Adriatic sea (Italy): the stratigraphic record of modification phases affecting a complex foreland
basin. J. Mar. Petr. Geol. 42, 50-81. Maesano F.E., Toscani G., Burrato P., Mirabella F., D’Ambrogi C. & Basili R. (2013) - Deriving thrust fault slip rates from geological modeling: examples from the Marche coastal and offshore contraction belt, Northern Apennines, Italy. Marine Petr. Geol., 42, 122-134, doi:10.1016/j.marpetgeo.2012.10.008. Pieri M. & Groppi G. (1981) - Subsurface geological structure of the Po Plain, Italy. In: Progetto Finalizzato Geodinamica, edited by C.N.R., Publ. n° 414. R.E.R and ENI-AGIP (1998) - Riserve idriche sotterranee nella Regione Emilia-Romagna Di Dio G. (Ed.), 119 pp., 9 sheets, S.EL.CA., Firenze. R.L. & ENI-AGIP (2002) - Geologia degli Acquiferi Padani della Regione Lombardia, Carcano, C. and A. Piccin (Eds.), 130 pp., 9 sheets, S.EL.CA., Firenze. Rogledi S. (2013) - Structural Setting of the Central Po Plain, International Journal of Earthquake Engineering. Rovida A., Camassi R., Gasperini P. & Stucchi M. (eds.), 2011. CPTI11, the 2011 version of the Parametric Catalogue of Italian Earthquakes. Milano, Bologna, http://emidius.mi.ingv.it/CPTI. DOI: 10.6092/INGV.ITCPTI11.
