H2O2-Enhanced Shale Gas Recovery under Different Thermal Conditions

Abstract

The permeability of tight shale formations varies from micro-Darcy to nano-Darcy. Recently, hydrogen peroxide (H2O2) was tested as an oxidizer to remove the organic matter in the rock in order to increase shale permeability. In this study, shale particles were reacted with hydrogen peroxide solutions under different temperature and pressure conditions in order to “mimic” underground geology conditions. Then, low-temperature nitrogen adsorption and desorption experiments were conducted to measure the pore diameters and porosity of raw and treated shale samples. Moreover, scanning electron microscopy (SEM) images of the samples were analyzed to observe pore structure changes on the surface of shale samples. From the experiments, it was found that the organic matter, including extractable and solid organic matter, could react with H2O2 under high temperature and pressure conditions. The original blocked pores and pore throats were reopened after removing organic matter. With the increase of reaction temperature and pressure, the mean pore diameters of the shale samples decreased first and then increased afterwards. However, the volume and Brunauer–Emmett–Teller (BET) surface areas of the shale particles kept increasing with increasing reaction temperature and pressure. In addition to the effect of reaction temperature and pressure, the pore diameter increased significantly with the increasing reaction duration. As a result, H2O2 could be used to improve the shale permeability.

Effects of Electro-Oxidation Process on Tight-Rock Wettability and Imbibition Oil Recovery

“…The previous investigations on oxidant–rock interactions have focused predominantly on permeability and pore connectivity improvement. − This is because oxidants can easily dissolve chemically unstable components including DOM, chlorite, and pyrite . For example, Yu et al found that H 2 O 2 can dissolve DOM in pores and pore throat under high temperature and pressure conditions, and the removal efficiency can be enahnced by increasing temperature, pressure, and reaction time. Chen et al found that NaOCl, Na 2 S 2 O, and H 2 O 2 can substantially dissolve carbonate, pyrite, chlorite, and organic matters, resulting in oxidation-induced fractures.…”

Evolution of Shale Microstructure under in Situ Heat Treatment: Synchrotron Small-Angle X-ray Scattering

“…1,10,15,16 Chem-ical stimulation refers to the transformation of the shale inorganic mineral matrix or OM by using acids, oxidants, or metabolites of microorganisms. 12,17 Heat treatment technology can be further categorized according to different methods into resistance heating, high-temperature steam injection, and electromagnetic heating. 13,18,19 Fracturing technology improves the connectivity of the reservoir by forming artificial fracture networks through mechanical stress.…”

“…For fracturing technology, the commonly used fracturing medium is water, although other fluids like liquefied petroleum gas (LPG), CO 2 , can also be used to help shale gas production to be more environmentally friendly and efficient. ,,, Chemical stimulation refers to the transformation of the shale inorganic mineral matrix or OM by using acids, oxidants, or metabolites of microorganisms. , Heat treatment technology can be further categorized according to different methods into resistance heating, high-temperature steam injection, and electromagnetic heating. ,, …”

Generation of oxidising fluids by comminution of fault rocks

“…For example, some lithologies such as shales have been shown to undergo a variety of degradation on interaction with H 2 O 2 (formation of cracks and voids, decomposition and dissolution of constituent materials, etc. ), which results in modification of their hydromechanical properties at varying rates depending on temperature (Chen et al, 2017;Zhou et al, 2018;Yu et al, 2019). Thus, the production and diffusion of oxidising compounds by a seismic event can potentially degrade surrounding fault zones and stimulate subsequent fault activity.…”