ABSTRACT: Structure and hydrocarbon potential of the Lengguru Fold Belt, Irian Jaya

Sutriyono, Edy¹ and Dr Kevin C. Hill²
(1) Fakultas Teknik Unsri, Universitas Sriwijaya, Palembang, Indonesia
(2) La Trobe University, Melbourne, Australia

The Bintuni Basin and Lengguru Fold Belt (LFB) include the ~30 tcf Tangguh gas discovery, sourced from Permian coal and/or Jurassic shale and hosted in Jurassic sandstone reservoirs. The LFB contains additional Cretaceous sandstone reservoirs. The LFB was formed by Late Miocene collision of an arc with the Birds Head microcontinent in what is now Cenderawasih Bay. This resulted in deformation with rapid uplift, erosion and cooling at ~5 Ma. Regional balanced cross sections of the LFB reveal Late Miocene to Pliocene thrusting responsible for km-scale shortening. The structural style was partly controlled by pre-existing structures in basement and associated changes in sedimentary facies. In the Late Miocene fault-propagation fold structures detached just above the basement and deformed the Mesozoic and Tertiary section, creating the Strongly Folded, Imbricate and Distal Facies zones of the LFB. Hydrocarbon traps formed at this time. Pliocene inversion of underlying extensional faults in basement elevated the LFB. During the Pleistocene, numerous extensional faults developed in the LFB as compression waned and the adjacent Mobile Belt collapsed into Cenderawasih Bay. This increases the risk that traps are breached. In addition, 4-5 km of burial of the Mesozoic reservoirs by Tertiary carbonates has destroyed much of the porosity. The areas with most potential are those are those in the northern LFB with a thinner Tertiary section and preserved highs that were not so deeply buried.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia