A new scheme of shale wettability classification coupling contact angle and co-current spontaneous imbibition tests: An example of Haynesville Shale.

Abstract:

The fluid-rock interaction in shale controls hydraulic fluid leakage and hydrocarbon recovery. Wettability is one of the influential factors of fluid-rock interaction behavior. However, how to representatively determine wettability is still a debating issue. A systematical study of fluid-rock interaction by the contact angle, spontaneous imbibition, and fluid immersion porosimetry reflect wettability, wettability-related pore connectivity, and edge-accessible porosity. With a new scheme of wettability classification to couple the contact angle and the spontaneous imbibition tests, the wettability of mixed-wet shale can be presented in more detail. The advantages of the new classification are able to (1) provide more categories of wettability; (2) reveal a clearer difference of wetting characteristic; (3) quantitively show the preference to water to oil; and (4) consider the influence of directional fluid flow in the shale matrix. In this study, 10 samples of Haynesville Shale cored from San Augustine, TX were studied. Basic information such as mineral composition, organic richness, maturity, and pore structure is provided by various tests of petrographic microscopy, X-ray diffraction, TOC, pyrolysis, mercury intrusion porosimetry, and N₂ physisorption. According to the new wettability classification, these Haynesville Shale samples exhibit four types of wettability which are strongly water-wet, ultra-strongly oil-wet & strongly water-wet, strongly mixed-wet, and intermediately mixed-wet.

Acknowledgements: This project was completed with funding provided by the Nuclear Energy University Program of Office of Nuclear Energy at the U.S. Department of Energy (award number DE-NE0008797).