| Fractured oil reservoir,with largest oil reserves among unconventional reservoirs,is characterized by strong heterogeneity and developed fracture network.Thus,the profile control operation during water flooding is necessary.Foam and gel,as the most commonly used profile control agents,still have some defects:the difficult balance between foamability and foam stability and high friction resistance hindering in-depth profile control performance respectively.To solve these problems,a giant surfactant foam stabilizer and a new self-lubricating double network hydrogel plugging agent were successfully synthesized by one-pot method.Moreover,the performance of giant surfactant for foam stability and foamability was evaluated,and the foam plugging mechanism was studied in detail.Meanwhile,the influence rule of temperature and shear force on gel self-lubrication was investigated as well as relative profile control mechanism.Main research contents and conclusions are as follows:(1)Giant surfactant enhancing N2 foam stability,mechanical strength mechanism and its profile control performance researchA novel giant surfactant foam stabilizer APOSS-PS50 was synthesized by click linking hydrophilic modified polyhedral oligomeric silsesquioxane with hydrophobic long carbon chain.APOSS-PS50,with good surface activity,viscosifying and reinforcing properties,can effectively reduce foam surface energy,improve foam film viscosity and strength,so as to achieve foam reinforcement and stabilization without damaging foamability.With increased oscillation frequency,interfacial viscoelastic modulus and foam mechanical properties of APOSS-PS50/AOS foam all gradually enlarged.Compared with polymer stabilized foam(HPAM/AOS),the displacement differential pressure and oil recovery of APOSS-PS50/AOS foam increased by 23.5%and 23.2%,reaching to 2.68 MPa and 81.7%,respectively,indicating the largely improved profile control and oil displacement performance.(2)Shear-responsive self-lubricating double network hydrogel preparation and its profile control performance researchThe double network hydrogel profile control agent FPP,with shear-responsive self-lubricating property,was synthesized by introducing thixotropic N-fluorenylmethoxycarbonyl-L-tryptophan(FT)supramolecular network into PAM gel through one-pot method.Under shear force,FT network in FPP gel can disassemble,then,combine with water molecules to form lubricating fluid,which weep out on gel surface and endow its self-lubricating function.As FT addition increasing,FPP gel strength and surface friction coefficient first decrease and then remain unchanged.The optimal FT concentration was determine to be 0.5 wt%.In Comparison with traditional polymer hydrogel(PAM-PAANa),plugging rate,water flooding volumetric sweep efficiency and oil recovery of the best sample FPP-0.5 was increased by 83.1%,155.4%and 34.0%,up to 86.6%,83.5%and 71.3%separately,showing its better in-depth profile control ability.(3)Temperature-responsive self-lubricating double network hydrogel preparation and its profile control performance researchTemperature-responsive self-lubricating hydrogel PAFB,used in profile control,was synthesized by combining dynamic covalent network(FA-BGPP)based on Diels-Alder reaction with heat-resistant polymer network(PAM-HMTA-HQ).As temperature increases(80??140?):1)Reverse trend of DA reaction is strengthened,and FA-BGPP network gradually decomposes and produce lubricating fluid,which is squeezed out on gel surface to form a self-lubricating layer.2)PAFB gel strength and surface friction coefficient declined progressively,which is helpful to improve gel migration ability at deep formation with high temperature.At 120?,compared with PAHH,the plugging rate,subsequent water flooding differential pressure,low permeability layer fractional flow and oil recovery of PAFB gel were enlarged by 41.6%,57.3%,60%and 44.6%,up to 83.1%,118 KPa,80%and 75.6%respectively,indicating its good in-depth profile control performance from self-lubrication function. |
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