Jean-François Ballard

Structure et contrôle paléogéographique de la zone subandine péruvienne

Abstract The north–south structural evolution in the Subandean zone (eastern side of the Central Andes) reflects the complexity of the orogenic front that propagates on an heterogeneous substratum inherited from pre-Andean palaeogeographies. The construction of balanced cross-sections shows that this north–south evolution corresponds to a progressive transformation from thick-skin transpressive deformation to thin-skin compressive deformation. The thrust front propagation is controlled, in the north, by NNE–SSW to north–south rift systems Permo-Triassic to Jurassic in age, oblique to the chain, and in the south, by the relatively isopach series of the preserved Palaeozoic silico-clastic platform.

Chapter 9: Discovery of a Bolivian Foothills Giant Gas Field: Incahuasi

Abstract This chapter will address the innovative and bold exploration approach that has led the French company Total and its Argentinean partner Tecpetrol to achieve what is one of the largest gas discoveries of the south Bolivian sub-Andean basin of the 2000–2010 decade. This discovery, named Incahuasi, is the result of multidisciplinary teamwork covering a period of 4 years from the initial geological concept definition to the drilling and testing of the discovery well Incahuasi-X1. The overall approach can be summarized as a combination of controlled risk decision making based on a regional geological knowledge and the development of new techniques such as the definition of dedicated biostratigraphy charts. This approach enabled the multi-disciplinary team to manage most of the uncertainties attached to this specific foothills context and define a workflow that led to success. The successful testing of the Incahuasi-X1 exploration well in 2004 led to a multi-tcf discovery currently under development. Located more than 120 km (75 mi) north of the existing Devonian gas fields, it opened a new exploration domain. It also highlights the benefit of a multidisciplinary and innovative approach in challenging areas such as the fold belts from prospect generation to discovery in a time constraint domain.

A Discovery in the Bolivian Fold-and-Thrust Belt: a Classical Integrated Approach is far more Important than Cutting-edge Methods, but…

An exploration case study in the Bolivian sub-andean FTB is shown as an example of an integrated geological approach from a regional study to block selection, exploration and successful drilling. In a tectonic wedge setting where in- and out-of-sequence folding and thrusting have shaped the Devonian Sandstone traps between several efficient detachment levels, structural geology is fundamental. Even more, as seismic data is of very poor quality. The multi-disciplinary regional approach involved a full review of the play (reservoir facies, age and paleogeography, petroleum system evaluation and post-mortem analysis) and cross-section building and balancing, based on a full dataset and revised geological maps (remote sensing and fieldwork data). Two extreme consistent structural hypotheses bearing strong implication on prospectivity have been tested as surface data don’t reflect the complexity at depth.