Fold-thrust belts: overlooked provinces or justifiably avoided?

This presentation draws upon contributions to a conference entitled ‘Fold-Thrust Belt Exploration’ held at the Geological Society of London during 2008. The conference was intended to assess the current state of science and industry in respect of the exploration and exploitation primarily of onshore fold-thrust belts. Onshore fold-thrust belts have tended to be perceived as ‘difficult’ places to explore and as a consequence are often avoided by companies. However, fold-thrust belts can host very large oil and gas fields and technical and logistical barriers to effective exploration may mean that substantial resources remain to be found. The conference was intended to assess whether techniques and understanding have advanced to the point of overcoming the historic negative perceptions of fold-thrust belts in favour of pursing the perceived yet-to-find resource. The conference and a resulting Geological Society Special Publication demonstrate how techniques have developed over time. It is evidently possible in certain circumstances and with sufficient, iterative effort to achieve good 3D seismic data quality. Structural restoration techniques have moved into the 3D domain and there is recognition that simple thermal constraints based on maturity of organic matter can be enhanced by more sophisticated palaeo-thermal indicators to allow the burial and uplift evolution of source and reservoir to be more closely modelled. A number of examples of the progressive development of better constrained structural models with more well and seismic data were shown. These seem to be moving away from the simplistic thin-skinned fault bend and fault propagation models employed in the earlier stages of exploration, with greater awareness of the common influence of pre-thrust structure and stratigraphy and of hybrid thick and thin-skinned deformation styles. However, progress in exploration seems likely to be a slow and very expensive iterative process of maximising the lessons learned from outcrop and well penetrations, of slowly improving seismic data quality and of industry working closely with academia to develop and continually improve the required understanding of subsurface geometries, reservoir and charge evolution and timing.