Electrofacies, elemental composition, and source rock characteristics along seismic reflectors of the Vaca Muerta Formation in the Loma La Lata area, Neuquen Basin, Argentina

Abstract

The Vaca Muerta Formation is a fine-grained marine lithostratigraphic unit that was deposited during the Late Jurassic and Early Cretaceous in the Neuquén Basin of Argentina. Accommodation space was generated by back-arc subsidence of the crust as the Pacific Plate subducted beneath the South American Plate during and after the break-up of the Gondwana supercontinent. The Vaca Muerta was recognized and named in early stratigraphic studies of the basin in the 1930s. The production of hydrocarbons in the basin led to subsequent detailed studies of the formation, primarily as an important source rock. Currently, however, the mineralogy, thickness, organic content, and maturity of the Vaca Muerta have highlighted it as a prospective resource play, comparable to plays in the United States such as the Eagle Ford. This study integrated well log, cuttings, and seismic data in the Loma La Lata area of the basin. Electrofacies were generated using well log data, with five electrofacies defined. Cuttings were analyzed for elemental composition, mineralogical makeup, and source rock characteristics. Cuttings at the base of the section proved to be good source rock and enriched in trace metals, with declining quantities up-hole. Seismic data was interpreted to highlight three major clinoform surfaces, one progradational and two aggradational. Electrofacies were related to both the results from cuttings and seismic reflector patterns. A relationship exists between the well-log values, source rock characteristics, mineralogy, and seismic patterns. Facies can be shown to vary along seismic reflectors between wells. The methodology and results presented here could help in high-grading current and future data for exploring and exploiting the Vaca Muerta Formation.