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Characterizing the Creep Behavior of Eagle Ford Shale under Different Fluids and Stress States

Mouin Almasoodi, Abousleiman Younane, and Hoang Son
University Of Oklahoma

Some rocks display continuous increase in strain with time when subjected to constant load. This behavior is known as creep deformation. Creep deformation creates challenges in production from shale plays such as fracture closure, permeability reduction, and wellbore casing collapse.

The measurement and modeling of the creep behavior of Eagle Ford shale will be addressed in this study. Eagle Ford shale is a prolific unconventional oil and gas play, located in the Western Gulf Basin in South Texas. It was deposited as deepwater marine shale in the late Cretaceous. Creep experiments were conducted on rocks collected from an outcrop in Comstock, Texas. Three samples were cored and prepared. Each sample has one inch diameter, and a length of two inches. Also, X-Ray Diffraction analyses were performed to obtain mineral compositions.

To study the influence of shale-fluid interaction on the creep behavior, the first sample was saturated with water, the second one was saturated with a nonreactive fluid, and the third one was kept dry. These samples were subjected to multiple steps of incremental confining pressure and axial stress in a triaxial loading cell. Data were collected continuously in real-time via an acquisition system.

In conclusion, the theory of linear viscoelasticity was used to model the samples time-dependent deformation for both confining and deviatoric steps. The study provides two viscoelastic models through which the creep deformation can be predicted.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013