Fold–thrust belts: overlooked provinces or justifiably avoided?

Abstract

This volume results from a conference intended to assess the exploration and exploitation primarily of onshore fold-thrust belts. These are commonly perceived as 'difficult' places to explore and therefore are often avoided by companies. However, fold-thrust belts host large oil and gas fields and barriers to effective exploration mean that substantial resources may remain.This volume shows how evaluation techniques have developed over time. It is possible in certain circumstances to achieve good 3D seismic data. Structural restoration techniques have moved into the 3D domain and simple thermal constraints can be enhanced by using more sophisticated palaeothermal indicators to more accurately model burial and uplift evolution of source and reservoirs. Awareness of the influence of pre-thrust structure and stratigraphy and of hybrid thick and thinskinned deformation styles is supplementing the simplistic thin-skinned fault-bend and fault propagation models employed in earlier exploration.The 'learning curve' in fold -thrust belt exploration has not been steep and further improvement seems likely to be a slow, expensive and iterative process with information from outcrop, well penetration and slowly improving seismic data. Industry and academia need together to develop and continually improve the necessary understanding of subsurface geometries, reservoir and charge evolution and timing.

Basement-involved reactivation in foreland fold-and-thrust belts: the Alpine–Carpathian Junction (Austria)

“…There is a growing body of literature recognizing that the commonly used transition from thick-skinned dominated regions in the orogenic hinterlands to purely thin-skinned dominated regions in adjacent forelands does not reflect the heterogeneous degree of crustal coupling observed in fold-and-thrust belts (FTB) worldwide (e.g. Cooper, 2007; Goofey et al 2010). Compelling evidence for mixed modes of deformation taking place at different places and times for one single FTB have been undoubtedly recognized (e.g.…”

Arc-parallel shears in collisional orogens: Global review and paleostress analyses from the NW Lesser Himalayan Sequence (Garhwal region, Uttarakhand, India)

“…Despite pessimist scientific views that fold and thrust belts/collisional orogens such as the Himalaya in general has a poor chance of hydrocarbon exploration (Goffey et al, 2010), or the postulation that some specific part of the LHS can be non-productive (Mishra and Mukhopadhyay 2012), ONGC has been targeting the Krol unit of rocks from the LHS, NW Himalaya, India (Bhattacharya, Internet Reference;Bose and Mukherjee 2020). The Krol and Tal units of the LHS are potential reservoir of moderate quality (reviewed in table 1 of Mishra and Mukhopadhyay, 2012).…”

Seismic Imaging of Salt-influenced Compressional Folds

“…The objective of seismic acquisition and processing is to reveal the subsurface geological structures. However, in difficult geological scenarios as FTB, seismic imaging often is a challenge, and seismic images are of low-quality, not allowing reliable interpretations (Goffey et al, 2010). This reduction in seismic quality is caused by the presence of complex structures in the FTB detaching on salt, such as steeply dipping beds, overturned beds, complex thrust fault geometries, symmetrical/asymmetrical tight folds, and detachment levels ( Figure 3).…”