Explanation of High Water Uptake of Clay-Rich Shales by Quantifying the Effect of Capillary Pressure, Water Adsorption by Clay, and Clay Swelling

Advances in multi-lateral hydraulic fracturing have resulted in industrialhydrocarbon production from shale resources. One drawback of hydraulicfracturing technique is the high water retention in the clay-rich shales. Bycomparative water and kerosene imbibition studies and sample expansiontest, it was found that the effect of capillary pressure, water adsorption on claysurface, and clay swelling on water uptake is by two gas shale samples ofHorn River basin are in the range of ۵۷.۶%-۵۸.۵%, ۱۷.۱%-۲۴.۱%, and ۱۷.۳%-۲۵.۳%, respectively. The effective capillary pressure driven diffusivity ofwater for two samples are then estimated by mathematical and numericaltechniques. effective capillary pressure driven diffusivity of water in LKRand EV samples are ۱.۸۹۲۵×۱۰-۹ m۲/s and ۴.۱۲۵×۱۰-۹ m۲/s respectively. Thefaster water imbibition in EV sample compared to that of LKR sample ismainly attributed to its ۲.۲ times higher effective water diffusivity. The resultssuggest that water adsorption on clay surface and clay swelling occur in alonger time course compared to water uptake due to capillary pressure andthey are as important as capillary pressure in water uptake by clay-rich gases.

Keywords:

Clay-rich Shales , Capillary Pressure , Water retention , Water Adsorption of Clay Surface , Clay Swelling