Eagle Ford and Pimienta Shales in Mexico: A Case Study

Abstract

Summary Our objective in this paper is to highlight the potential of the Eagle Ford (Cretaceous) and Pimienta (Upper Jurassic) shales in Burgos Basin (Mexico) through a comparison with the Eagle Ford Shale in Texas. The comparison is a case study focused on real data and their interpretation, north and south of the border, including geochemistry, geology, production, and reservoir–engineering data. Our overall approach includes the description of Eagle Ford data in Texas, as well as Eagle Ford and Pimienta data in the Burgos Basin. The geologic comparison is carried out using cross sections of the various formations and geophysical data. Geochemical and petrophysical data are compared using specialized crossplots. Production data are compared through rate transient analysis and by investigating the different flow periods observed in wells in both sides of the border. Reservoir–engineering aspects are compared using material–balance methods developed specifically for analyzing multipurpose shale petroleum reservoirs. Results indicate that there are many similarities but also some differences between the Eagle Ford Shale in Texas and shales in Mexico. The geologic and seismic cross sections show that there is continuity of the Eagle Ford on both sides of the border. However, structural geology in Mexico tends to be more complex than that in Texas. The geological and geochemical descriptions also show important similarities in the rock mineralogy, and the quantity, quality, and maturity of the organic matter. Well–log data show the same pattern of distribution on modified Pickett plots, developed originally for evaluation of the Eagle Ford Shale in Texas. Production data in the Burgos Basin shales are characterized by long periods (several months or even years) of transient linear flow, something that compares well with the Eagle Ford in Texas. Specialized material–balance calculations, which consider multiple porosities, have been used in the Eagle Ford Shale in Texas and are shown to have similar application in the Burgos Eagle Ford and Pimienta shales. On the basis of the Eagle Ford Shale performance in Texas, and the similarities with Burgos shales, the conclusion is reached that there is significant potential in the Mexican Eagle Ford and Pimienta shales. We present a comparison of the interpretation of real geoscience and engineering shale data collected on both sides of the border. The comparison is meaningful and suggests that the potential of shale reservoirs south of the border will be quite significant. Mexico should benefit from the lessons learned from the Texas Eagle Ford Shale.