April 2011

The Boquillas Transgressive Systems Tract in Val Verde and Terrell Counties, Texas: Outcrop Analog for the Oil and Gas Productive Eagle Ford of South Texas

Nick Whitcomb, University of Louisiana at Lafayette

Abstract Summary

Unconventional reservoirs have recently been attracting more attention as viable prospects. The Boquillas (Eagle Ford) formation is one such package of rock offering hydrocarbons as both a source and reservoir. In order to exploit these shale formations, multilateral horizontal wells are drilled and then fractured which requires adequate knowledge of the formation.

The current study is concerned with outcrops in Val Verde and Terrell counties, where locally the Eagle Ford is called the Boquillas. Here the Eagle Ford can be divided into lower, middle, and upper members. This study focuses on middle member vertical variability, because it holds the anoxic organic shale targeted for production. The middle member consists of alternating sequences of thin limestone with carbonate-rich shale. To learn more about the variability and cause of these sequences, a measured section and stratigraphic column were constructed; thin sections were made from many of the limestone beds, and shale sampling for character analysis. It is thought that the limestone beds represent regressive episodes in which the basin’s up dip carbonate factory increased in size and produced more carbonate material. Diagenesis is believed to have also contributed to the limestone sequences by selective dissolution of carbonate material from the interbedded limey shale. Thin section analysis shows high organic content, concentrations of foraminifera and calcisphere rich zones, with a common neomorphic texture to the limestone beds. Shale sample analysis was done for TOC, permeability/porosity, biostratigraphy, and XRD for a holistic understanding of the Eagle Ford outcrop lithologies.

Biographical Sketch

Nick is 23 years old, and began collecting rocks at the young age of 4 and to this day still has the first rock he picked up! He was born in Buffalo, NY and moved shortly after to the area of northern Illinois where he grew up. He began his official geologic career August of 2005 at the University of Illinois where he eventually graduated with a B.S. in Geology. While there he accomplished a sedimentological study of the Pennsylvanian Walshville channel and Herrin coal depositional characteristics.

He came to Louisiana for graduate school to not only immerse himself in the petroleum industry, but also to pursue a thesis involving field study and carbonates to which Dr. Lock was a perfect fit! He also was a member of the 2011 IBA team that took 3rd in the Gulf Coast section. He plans on graduating in December, 2011.