Study On Oxidation Characteristics Of Shale And Tight Sandstone

The unconventional energy,such as shale gas and tight sandstone gas,is rich in China and has high exploration potential.But because of the extremely low permeability of shale and tight sandstone reservoirs,it is particularly difficult to exploit shale gas and tight sandstone gas.In order to improve the permeability of reservoirs and enhance the flowing capacity of gas in the rock,this paper mainly used the method of oxidation to transform the physical properties of shale and tight sandstone,and studied the oxidation characteristics.The main content of this paper was using the low-temperature oxidation of hydrogen peroxide solution?H₂O₂?and high-temperature oxidation?combustion and pyrolysis?to oxidize the organic matters in shale,thus enlarged the average pore diameter of shale and improved the percolation conditions of reservoirs.After comparing the effects of the two oxidation methods on the pore structure of shale,it was found that both low-temperature oxidation and high-temperature oxidation could remove the organic matter in shale and improve the average pore diameter of shale.High-temperature oxidation could not only remove the organic matters more thoroughly than low-temperature oxidation,but also decompose the part of minerals,and its oxidation effect was better.With the increase of reaction time between the organic matters and hydrogen peroxide,the organic matters were gradually removed.After 48 hours low temperature oxidation,the average pore diameter eventually increased by about 44%.After high temperature oxidation of shale at different atmospheres?Air,N₂,CO₂,and Ar?,its average pore size had a following approximate rule:d_Air>d_N2>d_CO2>d_Ar.Similar to low-temperature oxidation of shale,high-temperature oxidation made the average pore diameter of shale increase with the heating time.Unlike shale,the content of organic matters in tight sandstone was much lower.The low-temperature oxidation of hydrogen peroxide could not effectively remove the organic matters in tight sandstone.However,high-temperature combustion could significantly improve the porosity of tight sandstone.As the combustion temperature increased,the organic matters and minerals in the tight sandstone gradually decomposed,and more pores and fractures appeared on the tight sandstone surface.The average pore diameter increased from 8.0 nm to 22.6 nm,increasd about 182%,which was beneficial to improving the flow capacity of gas in the reservoirs.The study on the oxidation mechanism of shale and tight sandstone organic matters has important theoretical reference and practical application value for the exploitation and application of shale gas and tight sandstone gas.