Abstract: Study of Thermal Maturity in the Thrust-Belt Area of the Kutai Basin

Andang Bachtiar

Comparisons have been made between thermal maturity of wells and stratigraphically correlatable surface sections in the Buat and Saka Kanan synclines in the thrust-belt area of the Sanga-Sanga block in the Kutai Basin. The study shows that the rocks in the synclinal axis (represented by well maturity trends) have a different burial history from the rocks in the flank sections (represented by surface maturity trend). The synclinal axis rocks are more mature than the time-equivalent flank's sections, which indicate that the synclinal axis rocks have been buried deeper than the synclinal-flank rocks. This phenomenon supports the theory that in the Kutai Basin thrust-belt area, the synclinal axes are paleodepocenters, which were subsided deeper than the synclinal flanks.

The study also reveals that in Buat syncline, the west-flank section has been buried deeper than the east-flank section, implying that the structural inversion has uplifted the west-flank section higher than the east-flank section. Any migration or generated hydrocarbon prior to the uplift may have been preferentially from the "Hydrocarbon Kitchen" (paleodepocenter) toward the east flank of the syncline.

The relationships between synclinal axis and flank maturity established in this study may refine further prediction of subsurface thermal maturity using surface-section data in the thrust-belt area of the Kutai Basin.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994