Shale under Pressure and Temperature

Texture, anisotropy, and fracturing of shale under pressure and temperature.

Lowell Miyagi, University of Utah and Waruntorn Kanitpanyacharoen, Stanford University used the multi-anvil press D-DIA assembly at 13 BMD, GSECARS, to deform shales to failure while collecting x-ray diffraction and radiography images. Diffraction images will be used to extract to texture and lattice strain evolution and radiography will be used to measure macrostrain and determine failure.

Shales are important to hydrocarbon exploration as cap rocks in conventional reservoirs. More recently shales are considered as source rocks due to the production of natural gas from shale unconventional reservoirs. Shales possess high intrinsic anisotropy due to texture (crystallographic preferred orientation) of their constituent clay minerals. Texturing in shales results in seismic anisotropy and a quantitative understanding of this anisotropy is important for accurate seismic exploration (Banik et al 1983). Texture is also known to cause fracture anisotropy which can affect both fracture toughness and fracture orientations (e.g. Lee et al 1993). However, the relationship between texture and fracture anisotropy has not been explored in shale. This is due to the fact that until recently volume averaged texture measurements in shales were exceptionally challenging.

 

A firm understanding of shale fracture properties at depth is important both to energy and the environment.