Microfracture and Surfactant Impact on Linear Cocurrent Brine Imbibition in Gas-Saturated Shale

Abstract

During and after hydraulic fracturing, fluid–shale interaction has a prominent impact on liquid retention and thus on gas phase permeability and gas productivity. By providing a low surface tension or wettability alteration, surfactants are widely used to decrease liquid retention after fracturing. To evaluate the liquid intake of a rock sample, an imbibition experiment is commonly used, especially when it is treated by a surfactant. However, conventional imbibition experiments with gas shale could not quantitate the imbibition behaviors as it does with conventional rocks because of the low porosity and extremely low permeability of gas shale. In this paper, a comprehensive experimental method was successfully developed to study the liquid imbibition in shale samples. Bulk shale easily fell apart during imbibition experiments. However, samples prepared with the coating method decribed herein remained intact except for fractures generated in them during the first imbibition. On each imbibition curve with i...