GEOL . C ROAT. 49/2 329 ZAGREB 1996 

Ahsrract - Note 

Geological, Geophysical and Geochemical Data in the Oil 
Exploration of Central Adriatic Area 

Danko DRECHSLER ', Edita BALAZ-BOROMISA', Mario SUSTERCU: ' 

and Anda ALAJBEG2 

The Dinaricles Mesozoic carbonate platfo rm consti ­
tutes an ex tensive palaeogeographic un it of the Nco­
Tethys p lat form system. T he large sedimentary CO Ill ­

plex wi thin the p la tform di sp lays good hydrocarbon 
potent ial. /\ de tailed s tudy of the lates t geological data 
from the Ka mali block and other relevant areas is based 
on the follow ing e lements: 

- slnHig raphi c evolution linked to structural history; 

- definiti on of potential source rocks , their stratigraphic 
and geographic exten t; 

- palac: ol cc lon ic contro l of variolls depositional envi ­
ronm ent s . These range from extremely res tri c ted 
(anox ic) conditions, to high energy zones on the plat ­
form marg ins and the edges of intraplatform basins 
and lagoons; 

- difTerent ial platform subsidence and burial of poten­
ti a l source rocks during ptmform evolution and post 
p[a tfol1n fl ysch and mol asse sed imcntation; 

- the d is tribution of reservoirs and sea ls; 

the locati on of traps and the timing o f thei r develop­
ment in re lation to the liming of hydrocarbon gene ra­
tion and migration. 

The complex geological sett ing or the area required 
detailed struc tural ana lysi s, to provide the base ror con­
stru c ti o n or balanced geological cros s sec tion s. The 
genc ra l na ture or geo logical maps , the scal e and Ihe 
data qu oted the rein , were insufficient for that purpose. 
To enable beller understanding of the struc tural concept 
o f the mea, sa tellite data were introduced. 

Landsa t scannograms at scale I :50.000 cove ring the 
Central Adriatic and adjaccnt areas wcre anal ysed . The 
da ta were recorded by LA iOSAT-5 sate llite, using the 
Thematic Mapper technique (Ti\1 ). The TM scanne r 
reco rds a wide spectre of visible and nca r infrared 
wavelengths, on 7 spectral channels (16 de tec tors e3ch) 
at an e levation of 700 km. The data arc di gitally trans­
millcd to Earth and processed by computer. 

Struc tura l interprctation or the area based on Land­
sat TM analys is inc luded all available data; the base 

I INA-N;dbplin, SUbiccva 29, HR- [0000 Zagreb. Croali a. 

PROCEEDINGS 

geological map, wel l elata, published art ic les and fie ld 
e1arirication of several details. The s truc tura l e lements 
were out lined and by observing the nature or the ir con­
tacl s, it was possible to antic ipa te the pos ition o r th rust 
faulls and the direction of the ir strike. The inte rp re tation 
e nab led us to follo w the regional s truc tu ra l pattc rn , 
dctermine changes in struc tu ral trends, to rank structura l 
e lcmcnts regarding the ir length , and de fine changcs in 
the sense of structural deformati on. Land sat T M inte r­
pre tation of the area on-shore, toge ther with the inte r­
pre tation of off-shore seism ic data , resul ted in the con­
struc tion of new structural map of the exploration area. 

Geochemistry confirmed or deni ed the prediction s 
of source availability, of the ir depositional environment , 
whether tlley were oil prone and the ir maturity. It eluc i­
dated the genc ti c re lationsh ip be tween the ke roge ns, 
bitumens, oils and oi l seeps in the expl orati on area as 
we ll as explaining the consequences o r biodegradatio n. 

Organi c geochemi stry enablcd the identification o r 
Triassic , Jurassic and Cre taceous source rocks. Sterane 
aromatizal ion and porphyrine matu rity parame te rs 
offe red re liable indicati ons of the reac hed ma turit y 
rank. Hopancs distribution were used to de te rmine thc 
Ell and gammacerane for the hype rsa line depos itional 
environment. 

Accord ing to [he s tearans and MAS di stributions , 
8,ecompani ed by BC isotope data , the explored hydro ­
carbon s were posi ti ve ly di stin guished and asc ribed to 
the relevant sourcc rock. 

The low molecular hydrocarbons in well s, as we ll as 
tile bitumen in cores and outc rops, were fo und to cxhi ­
bit littl e e ffect of biodegradati o n. Oil seeps suffe red 
severe biodegradation. The re lation of s te ranc aromati ­
zat ion to ArlO allowed the de te rminat io n o r viscos ity 
which the biodeg radcd hydrocarbons would have had if 
they were preserved. 

The in te rp re tcd data , especially whe n integrated , 
present a reliable basis 1'01' the prediction o f explorati on 
risk and potential in the studied o il gene rati ve basin. 

~ INA Research & Development Savska 41 /1 0, HR- [()(X)O Zagreb, Croal ia. 



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