Chaco basin has favorable geological conditions for tight oil and gas, including high quality source rocks and reservoirs. Undiscovered oil and gas reserves are large.
The Chaco Basin is a foreland basin with an approximate area of 284,000 sq km, lies on the eastern side of the Andes, in Bolivia, northern Paraguay, and northwestern Argentina. Three structural domains are recognized in the basin:
a thin-skinned, northeast to southeast-vergent fold-thrust belt, which has deformed the western fringe of the basin along the edge of the Eastern Cordillera;
a foothill belt where this deformation is attenuated or incipient; and
the Andean foreland.
Thus, on the basis of these features, the Chaco Basin is divided into four sub-provinces: the Chaco Sub-Andean Zone, the Chaco Foothill Belt, the Chaco Sub-basin, and the Izozog High. The Izozog High constitutes the southeastern, undeformed part of the basin. The Western part of basin was intensively affected by tectonic movements, anticlines are developed. The eastern part of basin mainly develop gentle structures, Cenozoic strata are exposed on surface. Tectonics are usually controlled by basement faults. Thickness of sedimentary rocks are over 6000 meters, strata include Devonian, Carboniferous, Permian, Triassic, Cretaceous and Cenozoic. Discovered oil and gas are mainly concentrated in the Chaco Sub-Andean Zone and the Chaco Foothill Belt, in the western part of the Basin. The approximate remaining recoverable (proven and probable) reserves of the basin are 1,100 MMbo and 62,300 Bscfg, which categorize the basin as extremely prospective. Total reserve distribution is as follows: 80% in Bolivia, 20% in Argentina and less than 1% in Paraguay.
