Crustal-Scale Seismic Imaging in the Natuna Basin (Indonesia) and Its Impact on the Tectonic History of the Central Sunda Craton
Granath, James W.¹; Dinkelman, Menno G.²; Christ, Janice M.²; Emmet, Peter A.²
¹Granath & Assoc. Consulting Geology, Highlands Ranch, CO.
²ION/GXT, Houston, TX.
Acquired in 2008, the NatunaSPAN™ survey provides a regional crustal-scale framework of seismic data that give insight into the architecture and history of the hydrocarbon-bearing East and West Natuna Basins. The survey comprises over 2,500 line km of regional reconnaissance 2-D data acquired with a 50 m shot interval, 25 m group interval and maximum offset of 9130 m. The record length is 18 seconds. The data have been processed to PSTM images of 16 seconds and PSDM images to 40 km, and tie exploration wells for stratigraphic control. Modeling of available gravity and magnetic data is used to constrain seismic velocities of deeply buried sedimentary and non-sedimentary rocks that are critical to the PSDM imaging workflow. Well penetrations of the basement in the Natuna Basins suggest it is composed of Mesozoic forearc and arc-related lithologies, including metamorphic roof pendants of rocks possibly as old as Paleozoic. The survey results are compatible with the concept that the crust is an accretionary prism and arc, with a crust ranging from 25 km thick in the east to 35 km thick in the west and with compatible crustal fabrics. A westerly-dipping planar fabric underlies the East Natuna Basin as might be expected in a forearc that overlies an east-to-west dipping subduction zone, while interfering arcuate to parabolic reflectors under the West Natuna Basin ghost the shapes of multiple plutonic bodies that would comprise the core of the arc batholith. Oligo-Miocene extension in East Natuna roots in this fabric, forming the habitat of the East Natuna discoveries. Numerous mud diapiric bodies and gas chimneys are evident in the data. Miocene inversion affected the productive Paleogene rifts of the West Natuna Basin with even younger (transpressive?) positive flower structures developed along the Cumi Cumi and Kakap wrench zones within the inversion field. The data clearly show the evolutionary time-progression of distributed inversion of the rift basins to the more concentrated deformation along the flower structures. Those wrench zones correlate in time with one phase of major subsidence in the neighboring Malay Basin, and are on-trend with the strike of the Malay Basin boundaries, exemplifying a pattern of evolution of some of the deeper basins in South East Asia.
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012