LAUSR

Abstract Understanding clay hydration and swelling is crucial for designing drilling and fracturing fluids. Previous studies on water imbibition in gas shales indicate that clay hydration and swelling are partly responsible for strong water uptake of these rocks. However, measurements taken during these studies are not sufficient 1) to quantify imbibition-induced strain and stress caused by water imbibition, 2) to estimate porosity enhancement and excess water uptake due to clay swelling, and 3) to investigate the existence of possible correlations among clay content of gas shales, imbibed water mass, and imbibition-induced strain and stress. We measure strain and stress induced during imbibition of water, brine and oil into shale samples from the Horn River Basin. The results show a strong correlation among imbibed water mass, imbibition-induced strain and stress, and clay content of the shale samples. The strain and stress induced by water imbibition increase with clay content and imbibed water mass. For unconfined samples, water imbibition leads to pore volume enhancement of up to 0.8% of initial sample bulk volume. For partially confined samples, water imbibition induces a relatively-low expansive stress (