Publications

The Tangguh gas fields in the Bird’s Head region of Papua, Indonesia, are 3-way and 4-way closures formed by strike-slip movement. The area has a long tectonic history - with Permian extension and Triassic inversion followed by a series of oblique compressional events, which modified and locally re-activated the older structures. Three main fault systems are present: Triassic thrusts (inverted Permian structures), Oligocene strike-slip faults and Plio-Pleistocene strike-slip faults. Permian extension generated NW-SE oriented grabens, which were variably inverted in the Triassic, and locally re-activated in the Jurassic. Following a long passive-margin sequence, a prolonged oblique collisional event is recorded by left-lateral strike-slip faults in the Eocene-Oligocene – culminating with folding, uplift and truncation at the Base Oligocene Unconformity. This Oligocene folding amplified the pre-existing Triassic inversion structures forming the basic outlines of the Tangguh fields. Following Miocene tilting (due to flexural loading by the evolving Lengguru fold belt to the east), a new set of strike-slip faults were generated in the Plio-Pleistocene. These young faults were heavily influenced by the location of pre-existing structures, and locally re-activate some of the fault planes. Although strike-slip faulting has long been recognized at Tangguh, the magnitude and impact of lateral movement has not previously been estimated. Recent re-evaluation of 3D seismic has identified several piercing points that can be used to measure lateral displacement, such as Miocene carbonate lineations, Eocene clinoforms and Paleocene anticline crests. Recognizing piercing points at several stratigraphic levels allows estimates to be made of the lateral movement during different tectonic events. Oligocene lateral displacements are thought to be several kilometers, whilst the recent Plio-Pleistocene reactivation can locally add several hundred meters. Understanding the amount of lateral offset is important for reservoir mapping and evaluating the potential for structural compartmentalization.