Unconventional oil, gas, and geothermal resources play a key role in achieving a clean energy future. In recent few decades, hydraulic fracturing has substantially improved the extraction efficiency of these resources. Considering formation damage, environmental impact, and water consumption related to water-based fracturing, efforts have been made to develop non-aqueous fracturing technologies due to their potential to alleviate these problems and increase production. Currently, waterless fracturing technologies mainly include liquid/supercritical CO2 fracturing, liquid nitrogen fracturing, gas fracturing, CO2/N2 foam fracturing, gelled liquefied petroleum gas (LPG) fracturing, acid fracturing, microwave fracturing, and electric pulse fracturing.

The main concerns in developing non-aqueous fracturing technologies include environmental friendliness, feasibility, and effectiveness in stimulating reservoirs. Although multiple studies have reported that these waterless fracturing techniques are effective to some extent, these techniques may not work equally well for different reservoirs and the mechanics of their fracturing are still not fully understood. Therefore, there is an urgent need for comprehensive and comparative studies on the flow properties of these fluids in reservoirs, and the variation of physicochemical properties of reservoir rocks, fracturing behavior, and fracturing effects. Field trials should also be examined where applicable.

This Special Issue aims to present recent advances and challenges in non-aqueous fracturing for unconventional oil/gas and geothermal reservoirs. We encourage submissions focusing on mechanism analysis, laboratory experiments, numerical simulation, and field tests that can better understand the nature of non-aqueous fracturing technologies and are able to better evaluate these technologies for fracturing purposes. We welcome both original research and review articles.

Potential topics include but are not limited to the following:

• Liquid/supercritical CO2 fracturing
• Liquid nitrogen fracturing
• Gas fracturing with air, N2, and CO2
• Acid fracturing and stimulation of carbonatite geothermal reservoirs
• Microwave fracturing
• Electric pulse fracturing
• Foam fracturing
• Oil-based fracturing
• Fracturing behavior and mechanism analysis
• Characteristic and quantitative analysis of fracturing effect
• Waterless fracturing fluid flow properties in reservoirs
• Variation in physicochemical properties of reservoir rocks induced by waterless fracturing fluids
• Combination of multiple waterless fracturing methods