Impact of Salinity and Mineralogy on Slick Water Spontaneous Imbibition and Formation Strength in Shale

Mingzhao Chen, Jun Wang, Die Liu, Zhilong Jiang, Qianqian Liu, Tun Wu, Haisheng Liu, Weidong Yu, Jun Yan, Pingshan Wang

Index: 10.1021/acs.energyfuels.7b03516

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Abstract

Spontaneous imbibition is one of the mechanisms proposed to reveal the fate of fluids used during fracturing operations in shale reservoirs. However, the influence of salinity and mineralogy on the imbibition kinetics is not yet well understood. We performed imbibition experiments on samples collected from Woodford and Caney shale outcrops with slick water having salinities up to 15 wt % KCl. The impact of salinity on the imbibition rate and capacity shows a different trend for samples of varying mineralogy. A correlation between the carbonate/clay ratio and the imbibition rate is observed. This ratio and the illite content were linked to be factors affecting the impact of salinity on imbibition. This correlation suggests a maximum volume of imbibition at a ratio of 1.5. The impact of salinity on the formation strength seems to correlate with the amount of siderite and anhydrite present in the rock. It is worth noting that the swelling of the expansive clay minerals could mask the imbibition signature of the samples, where the apparent weight is used to estimate the liquid uptake. This is mainly apparent in the later stages when the bulk volume expansion can outweigh the liquid uptake; however, this effect does not reach the level of impacting the trends and correlations observed in this study.