Tecnologie GIS nella scelta dei dati di input per modellazioni numeriche 3D dello stato di fratturazione.

Transcription

1 GIT - Geology and Information Technology Group Sezione di Geologia Informatica della Società Geologica Italiana SECONDA RIUNIONE NAZIONALE 4-6 giugno 2007 Bevagna (PG) Tecnologie GIS nella scelta dei dati di input per modellazioni numeriche 3D dello stato di fratturazione Gianni Balestro*, Fabrizio Piana*, Masantonio Cravero**, Silvia Ponti*, Sergio Tallone* * CNR - Istituto di Geoscienze e Georisorse - Torino ** CNR - Istituto di Geologia Ambientale e Geoingegneria- Torino

2 Which knowledge behind geological modelling? ICT for geomodelling ICT - GIS technologies for knowledge management

3 Conceptual map: work flow, objects, concepts and logical relations

4 Geological approach for 3D fracture simulation the observations come frome several sites and different geological objects to achieve a fracture model of a large area we have to simplify the geological framework and reduce number and kinds of elements we individuated some conceptual geological objects that could represent the main geological features 12 C. Abergo m c.g. objects are: C. Bozzella 20 C B F C B F T. Visone macrostructures tectonic domains diffused fracture networks lithostratigraphic units 13 C. Bazzana ϕ2a Grognardo 18 ϕ2a' GRF ϕ2b B D Z

5 Geological model (Alto Monferrato available and enough detailed (Alto Monferrato domain): Formazione di Cessole (Langhiano) ALTO MONFERRATO (AM) Regional unconformities Tectonic events 2 1 a Formazione di Cortemilia (Burd.sup. p.p. - Langh. inf.) Formazione di Visone (Burdigaliano) 2 superficie di discontinuità regionale Formazione di Rocchetta (Olig. inf. p.p. - Olig.sup.) a) Arenarie di Cassinelle 1 superficie di discontinuità locale Ma M I O C E N E MIOCEN M T S L E B A Sediment deposition Subsidence Formazione di Molare (Olig. inf. p.p. ) Substrato metamorfico 50 m 25 m 0 m 30 OLIGOCENE OLIGO C CENE R NORD GVII veins and FBC GVII, GVIII veins Listwaenites GV rocks 5000 m GVI rocks GIII veins GII, GIII rocks GI rocks R3 rocks GIII veins semi-brittle shear zone (top to North mov.) GIV FBC GII and GIII veins GII rocks 500 m 100 m GV rocks GII veins Ciglione thrust Val Gorrini thrust 500 m Methanebearing fluids a b Alto Monferrato a F. Visone b Methane-derived carbonates VOLTRI GROUP VALOSIO CRYSTALLINE LIGURIAN UNITS

6 Conceptual geological objects Grognardo thrust zone (GTZ), well exposed along the Visone river, south of Acqui Terme. Equal Area N=45

7 Hypothesis Fracture Ensembles for FracMan 3D simulation The conceptual geological objects used for simplified representation of structural setting are thought to control the fracture state of the rock domains they bound If more than one object have controlled the development of the fracture network, then more than one geological object should be distinguished in a same outcrop So, distinct fracture ensemble can be recognized even in a single outcrop, each one referred to a distinct conceptual geological object fracture ensembles are analyzed and simulated separately

8 Fracture ensembles Different fracture ensembles are observed in a single outcrop normal faults reverse faults normal faults and often at different scales reverse faults Scaling properties can thus be studied to enhance the suitability of 3D stochastic simulations

9 3D model of Fracture ensembles FracMan codes Golder - Dershowitz, 1999 Fracture Set separation Equal Angle y Fracture Trace Length analysis Survey site µ l /σ l [m] (obs) µ r /σ r [m] Fracsize µ r /σ r [m] Warburto n 1 FN 0.89/ / / FN 0.94/ / /0.27 x 8 FN Observed Fracture trace length 0.74/ / /0.19 Fracture radius evaluation

10 Geological approach for 3D fracture simulation Fracture Data capture Fracture analysis Fracture Stochastic Simulation by FracMan code (Dershowitz, 1999) were thus performed separately for each geological object Aggregation of simulated data performed at the scale of the entire domain (i.e aggregation constrained by the deterministic assumption of the actual elements of the geological model)

11 FracMan 3D simulation Fracture traces - site 1 All fracture ensembles 20 m Single fracture ensemble (RF) Single fracture ensemble (NF) Observed data Simulated data

12 FracMan 3D simulation Peculiar c.g. objects: Strain localization zones (FracMan War Zone) Site 8

13 Conceptual Map FracMan 3D simulation

14 FracMan 3D simulation Generation volumes Simulation is done within generation volumes derived from geological knowledge base (deterministic constraints to modelling)

15 FracMan 3D simulation Fracture generation Fractures are stochastically generated using statistical modules derived from: knowledge of actual fracture distribution laws knowledge of scaling laws (similarity of fractures at different scales)

16 Geological knowledge for definition of 3D simulation regions FracMan 3D simulation GEOLOGICAL MODEL GEOMETRICAL MODEL (simulation regions)

17 determ.constraints GEOMETRICAL MODEL (simulation regions) FE stochastically generated both from geological knowledge base FE

18 determ.constraints GEOMETRICAL MODEL (simulation regions) FE stochastically generated both from geological knowledge base FE

19 GEOMETRICAL MODEL (simulation regions) FE

20 Exploration Traceplane Analysis GEOMETRICAL MODEL (simulation regions)

21 GIS project CARG database sheet n.194 Acqui Terme INFORMATIVE LAYERS FRACTURE NETWORK KNOWLEDGE BASE DESCRIPTIVE TABLES METADATA SHEETS geological features compound-conceptual geological object () geological interpretation

22 INFORMATIVE LAYERS related to DESCRIPTIVE TABLES LAYER GEOLOGY (coverage of geological units) LAYER FEATURES AGGREGATION ID NAME TYPE ANNOTATION 1 2 Sr6 Sr4 Valosio slice Voltri metaophiolites SIMULATION REGIONS (geological generation volume) STRUCTURES (fault segments) FEATURES AGGREGATION MACROSCALE FAULTS ID NAME TYPE ANNOTATION 1 Grognardo thrust zone fault-bounded domains

23 INFORMATIVE LAYERS related to DESCRIPTIVE TABLES LAYER SAMPLING WINDOWS FRACTURE ENSEMBLE ID NAME TYPE ID_FAULT 1 Fe1 reverse faults 2 Fe2 normal faults 1 ID_SIMULATION REGION 2 SPATIAL / CONCEPTUAL RELATIONSHIPS OF INPUT DATA WITH CONCEPTUAL OBJECTS

24 Quesito finale:?? L uso crescente di tecnologie digitali dell informazione e comunicazione per la modellazione semi-automatica di oggetti geologici pone il problema della predisposizione e utilizzazione di strumenti logici e pratici atti a descrivere e rappresentare l incertezza dei dati e delle interpretazioni di partenza (input l.s.) e di riformulare il modello geologico concettuale in corso d opera??