GEOL. C ROAT. 49/2 259 ·263 3 Figs. I 1 Tab. ZAGREB 1996 

Scienr{ji't.: I/ofe 

How a Better Knowledge of the Basins Can Reduce the Risk of 
Exploration: Input of Basin Modelling 

A lan MASCLE' and Bernard DURAND' PROCEEDINGS 

Key words: Weste rn Alps, Basin mode llin g, Ri sk of 
ex ploration. 

Abstract 
Basin modelling so fhvarc has been wid ely developed in (lie BO's 

,'11(\ is still the subject of active Research and Development in the oil 
compan ies, con tractors ilnd consultant agencies, and al so in the uni ­
versi ti es . A complete range of so ft ware appliC<lblc to the basin level 
arc now available [0 cxpl oralioni sls, includi ng 1-0, 2-D and soon 3-D 
tools. Mosl of them arc devoted to the va lidation o f glruclUra] 
hypotheses, to the prediction of source rock maturil ics. or [0 a recon­
struc tion of petroleum formation and m igrati on in bas ins. Another 
class of so ftware, mostly developed in the un ivers ities, attempts to 
describe the th ermomechanical behaviour of th e lithosphere du ri ng 
bas in formation and subsequent inversion (DURAND cl nl., 1997). 

The question now i s: how can these tool s help explorationists in 
reducing the risks (and as a consequence the cos!.~) of exploration? 

In order to discuss and answer this question, we wil l present a 
case study in which IfoP sort ware has been used to reassess the petro­
leum potential of the Southeast Basin and Gul f of Lyon in SE France. 
These two area.~ have been the locus of aelive ex ploration from the 
60's to the ea rl y 80's, withou t commerc ial result s. The analys is and 
appraisal of failures have already been done and tile different poten­
tial petro leum systems recognized. Then l -D and 2-D modell ing was 
performed in order to selcct within thi s 50,000 km 2 area the few 
pl<lces where further exploration can be conducted wilh a minimum 
of technical and economic haz:trd s. 

1. REG IONAL SETTING 

The Southeast Bas in is thc thickes t onshore French 
sedimentary bas in w he re li p to 10 kill of Mesozoic­
Cenozoic sediments can be found loca lly ( Fig . I ). Basin 
dcve lopme nt occ urred in scvc ral stages be twee n lale 
Ca rbonirerous and lal e Crctaccous timcs. Partia l tccton­
ic invcrsion look place during I wo compressive even IS, 

in early and late Tertiary times. They were separated by 
an intervening stretc hing evcnt of Oli gocenc agc, whi ch 
led i'u nher south , to the o pening up of the wes te rn 
Medite rranean margins and ocean in Burd igal ian times 
(i ncluding the Gulf of Lyon located immediate ly sout h 

I InSlitul rran~ai s ell! PClrole, BP 311, 92506-Ruci l Malmaisol1, 
France. 

2 Ecolc Naliol1:llc Supcricurc du Pctrotc el dcs Motcurs, BP 311, 
92506-Rueil Malmaison. F"Ince. 

of the Southeas t Basin). In Neogene timcs the Pal aeo­

zo ic baseme nt of the Mass if Central was uplifted to 

about 2000 III as the result of an ascending aS lhe nos­

pheric plume. 

2. METHODOLOGY 

A large o il seep has been e xplo ited s ince a t least 

1608 in the vic inity of what wi ll la ter become the tiny 

Gabian o il field. Most of the explorat ion unde rtaken 

from 1955 (onshore) and 1975 (offshore) to the present 

has been d isappointing as no significant oil or gas fi e ld 

has cvcr been discove red, although about 150 wells 

have bee n d ri lled. A reasscssmc nt of the rc maining 

potential o f the Southeast Bas in and Gulf of Lyon bas in 

has been undertaken by lFP s ince 1991. T he main 

o bjecti ve was to se lect the few arcas where pot e ntial 

plays have not yct been tes ted, and where furt he r ex plo­

ra tion co uld be undc rtaken w ith a minimulll o f ri sks . 

The agenda of works has been as followed: 

a) synthes is of all avai lable geological data; 

b) e labora tion of the geochemical and geophys ica l clata 

base; 

c) ana lysis of failures in prev ious ex plo ration we lls; 

d) appra isal of the different pe troleum syste ms; 

e) J-D and 2-D nume rical modelling of selected s itcs or 
transects . 

Jtcms a-d are class ic works for a ny basin evaluat ion. 

Howcver, their importance should not be undercstima­

ted as the quality and thc con fid e ncc in the rnode ll ing 

wi ll direc tly be linked 10 the quality of the input data . 

The selec tion of the mode lli ng lools will also be depen­

dent on the availability of quality data. 1-D modelling is 

easy to operate and the result s are very rapidly obtained. 

Numerous hypotheses can thus be tes ted for a low cos t, 

and these tools wi ll be used when only a limited amount 

of data is ava il ab le. Conve rsc ly, 2-D mode llin g tool s 

are more diffic ult to operate and are time consu ming 

(for bo th people and computers). Only a few geolog ical 

hypotheses can be tes ted, a nd the use of suc h 100ls 

should be restric ted to are as whe re a complc te se t of 

good quality data can be obtained . 



260 

SOUTH·EAST 
BASIN 

o km 

PO PLAIN 

'00 

3. A V AILABLE BASIN MODELLING 
SOFTWARE 

Software developed at I[<P cover a wiele range of 

geological processes. \-D software sllch as "Genex" 
will be lIsed to model the subsidence, thermal and 

source rock maturity histories of selected sites in sedi­

mentary basins (sec one application in the Gulf of 

Lyon; Fig. 2). Such processes within basins can also be 

investigated with 2-D software such as "Thcmispack" 

or "Thcmiscomp", with the benefit that fluid pressures 

and nows can also be investigated. \Vc arc now develo­

ping a s imilar tool , "Thruslpack", devoted 10 the study 

of thrust belts anclthcir foreland; an application on the 

Chartreuse Massif or the western Alps, once part of the 

Southeast Basin, before tectonic inversion in Tertiary 

limes (Z IEGLER & TIORVATH. 1997). is shown on 

Fig. 3. or equal importance, the variety of data needed 

for proper usc of the software is listed in Table I. 

8 ___ 

Geologia Cronlic,! 49/2 

Fig. I Slrucluralmap of the Southcast13asin, Wcstern 
Alps. Lcgend: 1) Palaeozoic basemcnt: 2) internal 
Alps; 3) externa l Alps and Jura Thrust belt: 4) 
Western Alps foreland: Southcast Hdsin, Pro­
vence Plalform; 5) stable Europcan craton; 6) 
Tcrtiary Basins: Po Plain. Molassc and Valence 
Basin, Bressc unci Rhinc Graben: 7) main alpine 
thrust fronts; 8) main Early Mcsozoic normal 
fclllits. 

4. CONCLUDING REMARKS 

I-D and 2-D modelling have been performed across 
a continental margin (the Gulf or Lyon) and the 
foothills of a thrust belt (the western Alps), i.c. in areas 
where exploration is expensive. The benefit or such 
modclling work is three fold: 

a) to unite thc work or a multidisciplinary team and to 
make an atlcmpt to quantify geological data; 

b)as some important input data arc often not available 
(the thermal history for instance) it is possible to test 
several geological hypotheses (either st ructural , geo­
chem ical, thermal, ... ) and to appreciate the range of 
uncertainties resulting from this lack or data; 

c) to promote the most appropriate studies to gather the 
geological data that appear to be of crucial impor­
tance for the petroleum evaluation of the object area. 

Acknowledgements 

Some of thi s work was supported by the IBS project 
(Integrated Basin Studies), part of the Joule Research 
Programme funded by the Commission of the European 
Communilies (conlract n' JOU2-CT-92-01 10). 



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iVlasck: & Du r;llld: ! Iowa Beller Knowledge of the 13a~ in s Can Rcducc the Risk of Exploration .. . 263 

1. GEOLOGIC DATA 

a. Stratigraphic data: well constrained litholog ies and well dated formations (especially syntectonic deposits). 

b. Structural data: well balanced cross-section with the restoration before deformation. 

c. Kinematics data: timing of deformation and displacement rates on faults. 

d. Vertical displacements: erosion and subsidence history. 

2. THERMAL DATA 

a. Heat flow history (may be estimated from geochemical data) . 

b. Density, thermal conductivity, heat capacity, radiogenic heat and specific area of sediments (avai lable stan­
dard default values vs. lithologies). 

3. GEOCHEMfCAL DATA 

a. Local cal ibrat ion of source rocks maturity. 

b. Kinetic parameters of sou rce rocks (available standard default values for 4 types of source rocks). 

T,lblc I Rcq llired data for 'Thrllstpack" modelling. 

5. REFERENCES 

DU RAN D, B. cl a l. (eds.) (1 997) : Extension· in·colli ­
sian basins.- Geological Society special publicat ion, 
in preparation. 

Z IEG LER, P.A. & HORVATH, F. (eds.) (1997): Struc­
lure and Prospeels of the Alpine Basins and Forc­
land.- Peri-Tethys Memoir, 2, in press. 



264 Geologia Croatica 49/2