Applying seismic stratigraphy analysis for assessing upper Oligocene stratigraphic traps in Southeastern Cuu Long Basin

Abstract

As oil and gas production has been going on over a few decades, conventional plays such as pre-Tertiary fractured basement highs and Cenozoic structural traps become more and more exhausted, and the remaining targets of the same type do not have sufficient reserves for development and production. Exploration activities in Cuu Long basin, therefore, are shifting towards more complicating types of plays which are stratigraphic traps and combination traps. Several researches were conducted in southeastern marginal slope and indicated the possibility of stratigraphic pinch-out traps with insufficient petroleum system and low hydrocarbon potential. In spite of many researches, there are still difficulties in defining the distribution and in evaluating hydrocarbon potential of these traps, so seismic stratigraphy analysis in accompanied with interpretation of seismic attribute and well logs is very necessary to support this problem. Seismic stratigraphic analysis on seismic sections, in agreement with seismic attributes’ and log analysis’ findings, show that the stratigraphic/combination traps in Oligocene C and D were formed during lowstand system tract as sigmoid-oblique clinoforms downlapping onto underlying strata in distributary mouths/delta settings. The integration of seismic attribute analysis and well log interpretation has further defined the fan-shaped distribution of these traps. Thus, using various methods, the stratigraphic traps can be better revealed. Further studies, however, need to be carried out to fully evaluate hydrocarbon potential of these stratigraphic/ combination traps, and minimize risks in exploration drilling.