Eagle Ford Solutions: Critical Log Data, Solutions and Conclusions
Halliburton Energy Services
The Eagle Ford formation presents a unique set of challenges to geologists and reservoir engineers when attempting to define the reservoir and understand the characteristics that contribute to production. From a conventional standpoint, the formation cannot be adequately described by traditional measurements of triple combo logs. General relationships can be established, but attempts to predict advanced reservoir properties, such as permeability, fluid type and the ability of the formation to accept effective fracture treatments do not conform well to correlations.
Nuclear magnetic resonance (NMR) logs added to logging suites provided a portion of the required solutions. Direct permeability transforms from relaxation, or T2, provided the first reservoir properties independent of any other log measurement. Permeability from well to well and even within a vertical section in a given well can now be established using the Bray-Smith permeability equation. In many cases, direct hydrocarbon identification can be established from the relaxation (T2) comparison or crossplot with polarization (T1). Combination with elemental capture logs can assist in kerogen identification.
Dipole sonic logs provided another important element of discovery. When these logs are run in vertical pilot holes, values for vertical and horizontal closure stress can be calculated. These, combined with permeability from NMR, allows the operator to precisely target the interval in the Eagle Ford that provides the best opportunity for enhanced production. When these are run in horizontal wells, anisotropy can be included to select intervals for fracture treatment that will have a greater ability to breakdown and retain the geometry of the fracture treatment.
In this study of enhanced logging techniques, the application of each of these devices will be considered in the Eagle Ford formation. NMR response for permeability and fluid type will be combined with data from dipole sonic logs to select the best landing horizon. Elemental capture data will be evaluated for kerogen content. Dipole sonic logs will be used to establish rock mechanical properties and anisotropy to determine the best fracture treatment locations and the best treatment designs. The combination possibilities of all of these devices will be explored as a recommended best practices review.
AAPG Search and Discovery Article #90202 © AAPG/STGS Geoscience Technology Workshop, Eagle Ford plus Adjacent Plays and Extensions Workshop, February 24-26, 2014, San Antonio, Texas