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.
Highlights
There are tremendous shale gas resources in unconventional reservoirs, including tight gas shale and sandstone formations, these gas reservoirs have very low diffusivity and permeability, ranging from micro-Darcy to nano-Darcy [1,2,3]
The reactor was kept in steady state for a desired duration, during which the organic matter in the samples oxidized under high temperature and pressure conditions
Shale samples with particle sizes of 0.45-0.71 mm were treated with H2O2 solutions in a reactor under high temperature and pressure conditions in order to increase the shale permeability
Summary
There are tremendous shale gas resources in unconventional reservoirs, including tight gas shale and sandstone formations, these gas reservoirs have very low diffusivity and permeability, ranging from micro-Darcy to nano-Darcy [1,2,3]. Chen et al have used a high-temperature combustion method to remove organic matter in order to improve the shale matrix diffusivity [16,17]. In addition to high-temperature oxidation, low-temperature oxidation has been applied to improve shale effective porosity in experiments Oxidizers such as sodium hypochlorite (NaOCl), sodium peroxodisulfate (Na2 S2 O8 ), and hydrogen peroxide (H2 O2 ) have been widely used to remove organic matter from soil [17,18,19]. In order to increase the pore volume and porosity of shale, chloroform (CH3 Cl) was firstly used to remove extractable organic matter and hydrogen peroxide was used to remove solid organic matters [20]. The shale samples were heated in a reactor using H2 O2 as oxidative solution under different high temperature and pressure conditions. SEM images were employed to study pore structure changes on the surface of raw and treated samples
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
