Oxidative Dissolution Effects on Shale Pore Structure, Mechanical Properties, and Gel-Breaking Performance

Area of Science:

• Petroleum Engineering
• Geochemistry
• Materials Science

Background:

• Shale reservoirs face fluid-sensitivity damage, hindering hydraulic fracturing effectiveness.
• Conventional methods result in poor flowback and rapid production decline.
• Oxidative dissolution offers a novel approach to improve shale reservoir properties.

Purpose of the Study:

• To evaluate oxidative dissolution's impact on Wufeng Formation shale.
• To analyze changes in pore structure, wettability, and mechanical properties.
• To develop characterization models for oxidized shale.

Main Methods:

• Nuclear Magnetic Resonance (NMR) for pore structure analysis.
• Contact-angle measurements for wettability assessment.
• Triaxial compression tests for mechanical properties.
• Core-flooding experiments with NaClO solutions.

Main Results:

• Permeability increased by 66.67-266.67%; porosity rose by 1.79-9.58%.
• Hydrophilic surface fraction increased from 5.45% to 61.73%.
• Compressive strength decreased by up to 57.8%; elastic modulus showed non-monotonic changes.

Conclusions:

• Oxidative dissolution enlarges micropores, improves connectivity, and enhances water wetness.
• This process optimizes fracturing fluid performance and shale gas recovery.
• Provides a basis for oxidation-assisted stimulation in shale reservoirs.