Utilizing High-Resolution LiDAR Data to Improve Surface Geological Maps and Structural Interpretations in the Western Highlands of Papua New Guinea

Abstract

Tectonic scale collision at the northern margin of the Australian Plate has resulted in the formation of the Papuan Fold Belt (PFB), an archetypal fold-and-thrust belt located onshore within present day eastern Indonesia and Papua New Guinea (PNG). The PFB is highly prospective for hydrocarbon exploration, containing some of the preeminent oil and gas fields of the Asia-Pacific region. Throughout most of the PFB the surface geology is covered with thick vegetation and dense jungle canopy, making geological mapping and the construction of structural interpretations integrating the surface trends difficult. In some regions, these two tasks are further hindered by stratigraphic repeats and thickness anomalies, potentially created by multiple levels of differential detachment throughout the fold-belt. In order to better constrain the surface geology and regional hydrocarbon systems, approaches to oil and gas exploration have traditionally incorporated remotely sensed topographic datasets, such as Synthetic Aperture RADAR (e.g. GeoSAR) and NASA’s Shuttle Radar Topography Mission (SRTM). The effectiveness of these datasets is often impeded by their ability to penetrate through the dense foliage, and provide an accurate and consistent return of the surface geology. In comparison to these traditional approaches, the use of high-resolution (1-5m) Light Detection and Ranging (LiDAR) data, provides a significant improvement in the quality of surface geological imaging. Interpretation of this style of data presents a new opportunity to deliver original insights into the surface geology and structural architecture of the PFB. Early surface geological maps across the Donaldson Range in the western highlands of PNG outline a ~NW-SE striking anticline within the Miocene-Oligocene Darai Limestone, underpinned by a shallow ~NE dipping thrust fault. High-resolution LiDAR data acquired across the range has allowed for the remote sensing of structural data, including the identification and three-dimensional measurement of bedding and fault planes at the surface. Structural interpretation of the data reveals the Donaldson Range may be broadly comprised of two components: A southern section comprising a tightly folded ~NW-SE striking, SE plunging anticline, and a northern section composed of a detached gravitational thrust sheet abutting the southern anticline along the northern margin of the ranges. Remotely sensed bedding measurements from LiDAR data across the range were also used to review and, if needed, recalibrate geometrical projections from strontium isotope ratios taken from legacy and proprietary surface traverses. In combination with two-dimensional seismic datasets, this process assisted in remapping sections of the Base Darai Limestone, further supporting the structural interpretation of the LiDAR dataset. To the east in the Blucher Range near Devils Race, the remote sensing of geological data provided a similar degree of insight. In this case, current surface geological maps outline a generally conformable stratigraphic section dipping ~30◦ towards the south. High-resolution LiDAR data acquired over the region assisted in refining surface stratigraphic boundaries between different geological units, and revealed a complex, tightly folded ~NW-SE trending section within the Ieru and Toro units. This insight suggests that the frontal region of the PFB in the vicinity of the Blucher Range may be more highly deformed and structurally complex than the current model and surface maps suggest. This potentially opens up new hydrocarbon exploration opportunities within the region. Using two case studies from the western highlands of PNG, this study demonstrates the applicability and effectiveness of high-resolution LiDAR data towards improving geological surface maps and structural interpretations. The authors would like to thank ExxonMobil Corp. for the use of the data and software packages, along with joint venture partners Santos Ltd. and Oil Search Ltd.

AAPG Datapages/Search and Discovery Article #90371 © 2020 AAPG Asia Pacific Region, The 1st AAPG/EAGE PNG Geosciences Conference, PNG’s Oil and Gas Industry: Maturing Through Exploration and Production, Port Moresby, Papua New Guinea, February 25-27, 2020