A critical review of water uptake by shales

• Published in: Journal of natural gas science and engineering Vol. 34; no. C; pp. 751 - 766
• Main Author: Singh, Harpreet
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2016; Elsevier
• Subjects: Capillary; Electro-chemical forces; Review; Shale flowback recovery; Spontaneous imbibition; Shale flowback recovery; Spontaneous imbibition; Electro-chemical forces; Review; Capillary
• ISSN: 1875-5100
• DOI: 10.1016/j.jngse.2016.07.003

The shale boom in North America started more than a decade ago, however, the issue of substantial fracturing fluid loss inside shale did not draw much attention for a decade. In the past few years, many researchers conducted laboratory experiments to 1) observe various processes by which water imbibes into shale rocks, and 2) understand the mechanisms behind each process that contributes to fluid uptake in shale. Although there is consistency in most of the observations that control the liquid filling in shales, some issues remain in regards to wettability. Many mechanisms seem to be contributing to liquid filling in the laboratory experiments, but there is no consensus on the dominant mechanisms. Even though some observations from field provide consistent signatures, we do not yet have a verified answer for the geo-mechanisms behind those observations. This paper provides a critical review of the observations (laboratory and field), the mechanisms behind those observations, and the models to mimic the imbibition behavior of shales. In this regard, following contents are critically reviewed: 1) history of imbibition in shales, 2) laboratory observations, 3) field observations, 4) mechanisms of water imbibition in shales, and 5) simulation models. We also discuss evaporation of water in shale as an additional mechanism that has not been proposed before, but may be contributing to the loss of water in shale formations. •We provide a critical review of spontaneous liquid uptake by shales.•Following contents are reviewed: 1) laboratory and field observations, 2) mechanisms, and 3) simulation models.•We also propose and discuss evaporation as a mechanism that may be contributing to the loss of water in shale formations.