POTENTIALUL INFORMATIV AL METODEI REZISTIVITATII APARENTE A APELOR DE STRAT IN EVALUAREA FORMATIUNILOR DE INTERES PENTRU HIDROCARBURI CU APLICATII PE SELFUL ROMANESC AL MARII NEGRE

ALEXANDRU GHEORGHE, AURELIAN NEGUT, DANIEL SCRADEANU
Facultatea de Geologie si Geofizica, Universitatea Bucuresti

THE INFORMATIVE POTENTIAL OF WATER APPARENT RESISTIVITY
METHOD IN ASSESSING HYDROCARBON INTREST FORMATIONS WITH
APPLICATIONS ON THE ROMANIAN SHELF OF THE BLACK SEA
(Abstract)

The main theoretical elements and application of formation water apparent resistivity method (Rwa) as indirect, geophysical method, for formation water resistivity determination (Rw) and, on this base, total dissolved solids (total mineralization) evaluation of waters, are presented in the paper.
The applications have been done using the primary observation data from exploration wells drilled on the Romanian shelf of the Black Sea.
The comparison of total mineralization obtained by laboratory analyses with well logs calculated ones shows that total underground water mineralization evaluation methodology by geophysical logs is adequate.
The total dissolved solid changes from 6 to 30 grams/litre, with an average of 14 grams/litre for Lebada structures and from 2 to 22 grams/litre, with an average of 11.7 grams/litre for the other structures.
Generally, the analysed waters have a moderate mineralization, with values placed, practically, outside hydrocarbon fields water range values (usually these waters show mineralizations greater than 34 grams/litre).
The remarkable informative potential of formation water apparent resistivity method are emphasized, as follows:
(1) Formation water resistivity (Rw) and total mineralization determination for:
– quantitative formation evaluation by geophysical logs, particularly, fluid content (water and hydrocarbon) determination;
– concrete conditions definition for hydrocarbon migration and conservation, by including total mineralization among indices and hydrogeological criteria used in the hydrocarbon research strategy.
(2) Quick hydrocarbon formation identification with direct implications in well further program decision (well completion) or correct selection of perforation depth intervals. For analysed wells it has been shown that, in all cases, when Rwa >1 m, usually values included in the 1 – 5 m range, the identified formations are hydrocarbon bearing ones.
Key words: formation water resistivity, apparent formation water resistivity, apparent water resistivity method, water total dissolved solids (total mineralization), geophysical logs.