Evaluation of the Wettability of Carbonate Rock Condensate Gas Reservoirs Modified by Nanoparticles
In order to change the wettability of near-well reservoirs in condensate gas reservoirs and effectively re-lieve condensate gas retrograde condensation damage,the structural characteristics of fluorinated SiO2 nanoparticles were investigated by using X-ray diffraction,low-temperature N2 adsorption,and scanning electron microscope ob-servation to evaluate the adsorption degree of fluorinated SiO2 nanoparticles on carbonate rock cores with different mineral contents;and the changes in the wettability of the rocks,the efficiency of spontaneous permeation,the pressure difference of the single-phase seepage,the oil-gas phase relative permeability curves,and the changes in the condensate recovery before and after the adsorption of the nanoparticles were investigated by carrying out the contact angle measurements,the spontaneous permeation,and the single-phase and two-phase seepage experi-ments for the core displacement.The results show that The shape of fluorinated SiO2 nanoparticles is similar to a u-niform sphere,the average particle size is 30.34 nm,and the average pore size is 20.00 nm;the adsorption a-mount of fluorinated SiO2 nanoparticles on the surface of carbonate rock increases with the increase of porosity,but in the low-permeability rock cores,the change of adsorption amount and the wetting contact angle increases with the increase of calcite content;the oil and gas two-phase co-seepage zone of the rock after nanoparticle adsorption,the oil-gas two-phase co-seepage zone of the rock widens,the isotropic point moves to the upper left,the maxi-mum oil-gas relative permeability increases greatly,and the irreducible water saturation and remaining oil satura-tion decrease significantly;the fluorinated SiO2 nanoparticles can be adsorbed on the surface of the rock in about 10 min,transforming the liquid-wetted rock,which is strongly oleophilic and hydrophilic,into an intermediate(gas)-wetted rock,lowering the capillary pressure in pores and the resistance to the seepage of condensate,and raising the relative permeability of gas and oil phases to achieve the goal of blocking removal and increase of production and efficiency.The research results have great value for field application and promotion.
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