Sedimentological Characterization of the Eagle Ford Formation in the Southwest of the Maverick Basin, Coahuila, Mexico

Abstract

The Eagle Ford Formation (EF) in the Maverick Basin is the unconventional reservoir with the largest hydrocarbon production in southwest Texas, USA. This study presents the results of a detailed sedimentological characterization of the EF in the southwestern portion of the Maverick Basin located in Coahuila, Mexico. An integrated methodology was conducted using well information and two analogue outcrop cores of the complete EF including its lower and upper bounding units (Buda and Austin formations respectively).

The high-resolution stratigraphic and sedimentological study carried out consisted on sedimentary facies identification, biostratigraphy and chemostratigraphic analyses and logs and seismic interpretation. Five stratigraphic units were recognized in the EF in Mexico, correlated with the units proposed by Donovan et al. (2012) in West Texas. Units A and B (Lower EF), are characterized by organic matter-rich facies with high clay content and high gamma ray values. The main facies consist of argillaceous carbonate mudstone and planktonic foraminifera argillaceous wackestone. According to the high values of Mo, V, Ni and Cu elements, this stratigraphic package was deposited in anoxic conditions of a deep-marine basin. Lower EF age is middle to late Cenomanian, based on the presence of the Rotalipora cushmani and Whiteinella archaeocretacea biozones.

Units C, D and E (Upper EF) consist of homogeneous carbonate facies with lower organic matter and clay content. Their main facies are planktonic foraminifera wackestone and wackestone with packstone laminites. The low values of Mo, V, Ni and Cu elements suggest a more oxygenated depositional environment than the Lower EF, suggesting an outer platform environment. The Upper EF formation is recognized by the Helvetoglobotruncana helvetica, Marginotruncana sigali and Dicarinella concavata biozones, which allow to restrict its age from early Turonian to early Coniacian.

Unit B, in the lower EF, presents the best characteristics as an unconventional reservoir, given that it consists of argillaceous carbonate mudstone and wackestone facies, with the highest organic matter content. Analogue outcrop core data, along with well and seismic interpretations, allowed to establish the sedimentological distribution of the EF in the area.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018