Shale hydration damage captured by nuclear magnetic resonance

Abstract

Wellbore instability could restrict the efficient development of unconventional petroleum resources in shales as drilling fluids may influence the integrity of shales by causing hydration damage. In this work we study the impact of hydration on shale samples from Xi Feng formations using Nuclear Magnetic Resonance. Samples were saturated in distilled water for different durations and then samples’ T₂ relaxation time and the spectrum area were analyzed using NMR. Damage variable, which can not only interpret the hydration damage in shales quantitatively but has also a key importance to build the damage theory, was defined with NMR T₂ spectrum area, according to a relationship between the T₂ relaxation time and the size of damage. Accuracy of the defined damage variable was verified by NMR images.GRAPHICAL ABSTRACT

Keywords:

• Damage variable
• hydration damage
• NMR
• shale

Additional information

Funding

This work was supported by The Key Laboratory of well Stability and Fluid & Rock Mechanics in Oil and Gas Reservoir of Shaanxi Province; The National Natural Science Foundation of China under Grant 51174162; The National Natural Science Foundation of China under Grant 51674200; and Shaanxi Provincial Department of Education scientific research project under Grant 14JK1575.