129 Presentaciones de Geociencias en Español: Continuamos con la experiencia en la GSA 2025/Geoscience Presentations in Spanish: Continuing the Experience at GSA 2025, Part II

This session invites Geosciences presentations in Spanish at all proficiency levels; abstracts can be submitted in English or Spanish and they do not count towards the GSA’s limit of one abstract oral presentation per person.

Monday, 20 October 2025
1:30 PM - 5:30 PM
HBGCC, 217B

Pore types and Pore size distribution of Late Mature Organic-rich Shales: La Peña and Eagle Ford Formations, NE Mexico

Paper number: 129-2
Program: Technical Sessions
Time: 1:50 PM – 2:05 PM

Authors

Abstract

La Peña and Eagle Ford Formations in the Sabinas Basin are significant organic-rich source rocks being assessed for unconventional hydrocarbons exploration in northeastern Mexico. However, the formation and evolution of shale pores in these source rocks are unclear. In this study, ten samples from four wells were used to characterize the pore structure by a combination of mineralogy, geochemistry, organic petrography, scanning electron microscopy (SEM), and low-pressure nitrogen adsorption techniques. Results indicate that the samples are rich in carbonates and primarily comprise calcite, which favors the formation of intergranular and dissolution pores. Meanwhile, the clay content is negatively correlated with the pore volume, which is not conducive to the development of larger pores. The more abundant pore types are constituted by intergranular, intragranular, intercrystalline and dissolution pores, while organic Matter (OM) pores were not found at the applied magnifications. Organic petrography reveals a post-oil and wet gas generation stage with vitrinite reflectance equivalent from 1.28% to 1.64%, and limited petroleum generation potential. In addition, micropores, mesopores and macropores are all present, with mesopores being the most dominant pore size (avg. 22.7 nm). However, we observe an anomalous sample with the highest maturity that exhibits the greatest relative proportion of micropores, accompanied by an increased adsorbed capacity.

We propose that these porosity attributes are related to the abundance and type of the organic matter, mineralogical composition and thermal maturity, being the latter the factor that exerts a dominant control over these characteristics.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413141

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