The Madre de Dios Basin, covering approximately 70,000 km2 in Bolivia, has remained unexplored in terms of its hydrocarbon resources. The primary objective of this study was to assess its unconventional hydrocarbon potential, specifically shale oil.
To facilitate the analysis and evaluation of the unconventional potential of the Madre de Dios Basin, information from well data and 2D seismic surveys has been employed and integrated to construct a geological model aimed at comprehending the Devonian basin's configuration, serving as the principal objective as an unconventional reservoir.
Furthermore, the new geochemical analyses revealed values for the entire section (180 m approx.), with Total Organic Carbon (TOC) values over 2%, Hydrogen Index (HI) between 400 and 600 mg HC/g TOC, and low Oxygen Index (rarely exceeding 50 mg CO2/g TOC). This is consistent with a high-quality, oil-prone, "rich" Type II kerogen. Furthermore, an exceptional basal section in the Lower Tomachi, informally referred to as "Tomachi Rich Net," exhibits TOC peak values up to 14%.
The assessment results that have followed a probabilistic analysis based on the Total Oil methodology of Jarvie (2012), have disclosed significant potential. This has successfully warranted a world-class consideration as an unconventional hydrocarbon source rock.
The Madre de Dios Basin is in the northwest of Bolivia and is shared with neighboring countries Brazil and Peru (Figure 1). It covers an area of approximately 315,000 km2, with roughly 35% situated within Bolivia (Beicip-Franlab, 2016). Morphologically, the region is densely covered with rainforest vegetation and traversed by various robust Amazonian-type rivers and swamps, which pose substantial challenges for any petroleum operations.
Geologically, the basin was once part of an intracratonic marine basin during the Paleozoic era before experiencing regional uplift during the Mesozoic. It possesses a stratigraphic record ranging from Precambrian to Cenozoic rocks.
Historically, the Upper Devonian, specifically the Tomachi Formation (Frasnian; Figure 2), has been cited as a potential source rock. Previously, Peters et al. (1997) and Bande et al. (2022) described Tomachi as a high-quality organic-rich rock with hydrocarbon-generating potential, deposited in a marine siliciclastic platform environment under suboxic to anoxic conditions. OBI (1991) also presented a valuable petroleum-source rock correlation between the oil produced from the Tomachi sandstone at 1266 m MD and three rock samples from well W-X1. The correlation is highly accurate with the sample at 1525 m MD, situated in the richest and closest section to the base of the Tomachi Rich. It was inferred that the produced oil was generated from this basal section.
