Synergistic Effect Of Micro And Nano Materials On Conformance Control And Oil Displacement In Fractured Low-permeability Reservoirs

It is challenging to mitigate water channeling and drive remaining oil out of the matrix in naturally fractured low-permeability reservoirs.The commonly used technical solutions for a high-permeability reservoir might not be applicable to low-permeability reservoirs.Moreover,each technology has its demerits that can limit its scope of application.To address these problems,we propose a composite approach of injecting micro-and nano-scale particles to achieve conformance control and oil displacement in a dual-permeability porous media,which combines the advantages of both materials.Bilayer-coating microspheres(BCMS)of variant hydrogen-bond association temperatures ranging from 30?to 150?covered with double-layered coatings are fabricated for in-depth conformance control within heterogeneous reservoirs.The suspension stability and injectivity of the BCMS system are investigated.Static tests are employed to investigate the plugging behavior of BCMS at variant temperature and fluid salinity.A series of core floods are conducted to optimize injection parameters by changing the injection rate,particle concentration,particle injection volume,injection mode and permeability.An analytical model for the deep-bed filtration of BCMS in porous media is developed,accounting for the limited retention concentration and the velocity difference between the suspended particles and the carrier fluid.Modified hydrophobic nanosilica is produced by the in-situ modification process.The adsorption of the modified nanosilica onto the solid surface is studied.The oil displacement system of Nano-SiO₂ was constructed,and the effects of metal ion degree on the adsorption law of Nano-SiO₂ particles at the liquid-liquid interface are evaluated.The amount of nanosilica adsorbed on the solid-liquid and liquid-liquid interface is used as an indicator to unveil the rule of adsorption and desorption by changing temperature and particle concentration.The effect of silica nanofluids on wettability alteration of an oil-wet surface is investigated by measuring the three-phase contact angle.Three microfluidic chips are designed.A 2-D single-channel microfluidic chip is designed to study the dynamics of oil trapping at a pore throat.The remaining oil distribution after water flooding is analyzed by an irregularly etched 2-D grid-based microfluidic chip,which reveals the influence of nanofluids on the remaining oil of variant types.Moreover,the microscopic visualization tests performed on a 2.5-D micro-scale glass model with variant depths in a vertical dimension enable us to visualize and analyze the remaining oil distribution after water flooding,and unveil the influence of nanofluids on the remaining oil of variant types.Besides,two-dimensional visualization models of size-variant single,parallel,and curved channels are designed to study the microscopic filtration characteristics of BCMS and its sealing mechanism towards channels of different widths.We use a one-dimensional anisotropic physical model to study the major control and oil-displacement limitation of the BCMS system and to optimize the injection parameters of the nanosilica system as well as define its oil displacement limits.Meanwhile,cores of dual permeability are used to assess the synergistic effect of BCMS and nanosilica,revealing the oil-displacement mechanisms of the coinjection of micro-and nano-scale materials in low permeability fractured reservoirs.