Abstract
An investigation of the factors controlling the regional distribution of unconventional reservoirs - organic rich shales / carbonates - in Latin America, included the analysis and identification of the vertical relationship and characteristics between the reservoirs of different basins. The analysis provided evidence to understand why different formations in different basins have similar potential and supports a proposed interpretation.
The study is based on the analysis of the main source rocks which are being developed or targeted as unconventional reservoirs. These reservoirs grouped by basin, age, formation, and characteristics such as depositional environment, extension, lithology, thickness, depth, organic content, and kerogen type were analyzed. More than 20 basins in Latin America and 30 formations considered source rock, from Silurian to Cretaceous, have been evaluated (Figure 1). The paleogeography, in particular the distribution of the marine and terrestrial environments, at the moment of the deposition of these rocks was used to understand their presence and distribution in the subsurface.
Evaluated Basins, Organic Rich Shales and Age.
The distribution of relevant Latin America's unconventional resources is related to a sum of very well-known global factors closely associated with the extent of the Jurassic- Cretaceous seas in times of high eustatic levels, when most of the sediments generating unconventional resources were deposited. Proper interpretation and knowledge of the distribution of Mesozoic seas and their coeval events enables predicting the location of unconventional reservoirs, understanding the reason for their existence, and anticipating the main characteristics to be found in these rocks.
The geographical distribution of some of the most representative unconventional reservoirs in the main basins of Latin America relates to the regional event causing the deposition of these rocks during the Upper Cretaceous. Sediments of this age include formations in the north of South America, such as La Luna, Querecual, Naparima Hill and equivalents, which are synchronous with deposits such as Eagle Ford and Agua Nueva formations. The Upper Jurassic and Lower Cretaceous comprise a second group of unconventional reservoirs among which is the extended Vaca Muerta formation.
Understanding the relationship between occurrence, genesis and distribution of unconventional reservoirs in Latin America is fundamental to predicting the presence of these reservoirs, using global factors such as tectonic plate distribution and sea level. The summary with the characteristics of each of these reservoirs can be used as a guide to understand the magnitude of the hydrocarbon potential.
