The Evolution of the Eagle Ford Play: A Petrophysical Viewpoint

Since 2008, the Eagle Ford has evolved from a rank wildcat concept into one of the most prolific unconventional plays seen to date. Although this formation has been proven to be productive throughout much of its areal extent, results have shown that significant economic variability exists. The reason for this variability is linked closely to the heterogeneity of its key petrophysical properties.

Using a consistent petrophysical evaluation methodology, we have been able to evaluate and quantify the Eagle Ford reservoir throughout this trend as well as determine areas of optimum reservoir development and associated hydrocarbon storage capacity. Conversely, it is also possible to identify areas that should be avoided based on present day economics. This presentation will present snapshots in time of the Eagle Ford as it evolved from its origins in the South Texas downdip gas trend in 2008 through the identification of its prolific updip oil trend over the past 3+ years. Within this evolutionary discussion, both positive as well as negative areas will be discussed. Critical early concerns about the reservoir will be addressed as well as the attempts to extend this play into areas of both thinner reservoir as well as non-comparable depositional conditions.

There is a direct relationship between reservoir quality and economics within the trend. However, drilling and completion practices play an important part in the effective monetization of this play. Lateral placement and length as well as fracture stimulation efficiency all play a part in dictating the economic viability of the Eagle Ford in any one area. Geomechanical variability also plays an important part in the exploitation of this play. Faulting and fracturing intersected by a horizontal wellbore can create situations where stimulations fail to effectively treat the untapped Eagle Ford reserves due to communication with shallower and depleted intervals.

As will be the case in many unconventional plays, there will be multiple phases of development in the Eagle Ford as operators re-visit areas of early drilling to further exploit the Eagle Ford where it has been ineffectively evaluated. The key to these secondary and tertiary phases of exploitation will be tied directly to the link between reservoir quality and heterogeneity as it impacts the effective fracture stimulation and associated drainage from this complex reservoir system.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California