Structural Characterization of the Eagle Ford Formation, Val Verde County, Texas

Abstract

The Upper Cretaceous Eagle Ford formation has attracted considerable industry attention in recent years. It is one of the largest single economic developments in the history of the State of Texas and ranks as the largest oil and gas development in the world based on capital invested (according to eaglefordshale.com). High initial production rates are being reported. Both gas and oil are being produced from horizontally completed multilateral wells. Although the main targeted area of the play is located in South Texas and produces from various depths between 4000 and 14,000 feet), deep roadcuts through the Eagle Ford Formation along U.S. Highway 90 north of Del Rio (Val Verde County) provide an accessible window for improved understanding of the play.

The Eagle Ford Formation has been extensively studied through well logs and geophysical investigations. However, little is known about the structure and structural evolution of the play. The goal of this research project is to fill this gap by (1) measuring fracture systems orientation, frequency, spacing, and density, in relation to lithology variations, to reconstruct paleo- and contemporary stress fields; (2) recording fracture intensity to determine the number and nature of mechanical units present in order to establish a mechanical stratigraphy; and (3) characterizing calcite-filled veins in order to determine their origin, spatial distribution, and age relationship with the fracture systems.

The results of this project can be used to extrapolate new targets to investigate through hydraulic fracturing techniques, and will yield important information on hydrocarbon migration pathways. The data gathered will also provide information regarding the connectivity of the fractured beds. Cross-cutting relationships between joint systems and veins will reveal the chronologic history of fracture development, as well as joint relations to tectonic or neotectonic forces.

AAPG Datapages/Search and Discovery Article #90219 © 2015 GCAGS, Houston, Texas, September 20-22, 2015