Sistema Petrolero Cacheuta-Barrancas De La Cuenca Cuyana, Provincia De Mendoza, Argentina

The Cuyo Basin extends through San Juan and Mendoza Provinces covering an area around 30,000 km2. However, commercial oil production is restricted only to the Tupungato and Rivadavia depocenters in the North of Mendoza province, with a EUR of 1.3 x 10~ bo. Petroleum accumulations in the basin are dominated by low-mature to moderately mature, viscous, high-wax and asphaltene-rich oils, sourced from the fresh-water lacustrine shales of the Triassic Cacheuta Fm. This unit is an extremely prolific, oil-prone source, that bears type I kerogen and displays high to very high organic contents (3-10% TOO) and elevated total generation potential (SPI: 8-10 tons HO/rn2). The Barrancas Formation (Jurassic) is the main reservoir of the basin, concentrating 58.7% of the produced oil, being the rest of the production located in different reservoir units from Devonian to Tertiary in age. The geographic extension of the Cacheuta-Barrancas (!) petroleum system (mature source rock and its related hydrocarbon accumulations) covers an approximate area of only 3,400 km2, hardly above 10% of the total basin area. Gas accumulations in the basin are volumetrically negligible. The processes of hydrocarbon generation, migration and accumulation were triggered and controlled by the development of a Tertiary foreland basin that overlapped the Cuyo Basin, providing the sedimentary column necessary for source rock maturation during the last 10 Ma up to present. Moderate mature oils (VRE.—0.7-0.9%) were sourced from the Tupungato-Tierras Blancas kitchen to typically feed the reservoirs of the Eje Oriental district, after southeastwards to eastwards long-distance lateral migration through the Barrancas carrier. The Punta de las Bardas Formation acted as an excellent quality regional seal. The contour area of Entre Ejes-Rio Hondo to the east sourced early oils (VRE—0.55-0.7%) that were mostly trapped locally. Pools in the western area close to the Tupungato pod only account for 12% of the oil production of the basin, contrasting with the 88% production computed for the Eje Oriental area, several tens of kilometers away from the kitchen, which points to the predominance of a lateral migration drainage style in the Cacheuta-Barrancas petroleum system. The Generation-Accumulation Efficiency (GAE) of the system is high, estimated around 14%. The good coupling of the charge process and the formation of structures, together with the quality of reservoirs, carriers and seals, are believed to be the reasons for this unusually high efficiency rate.