Basic Research On The Development And Application Of Viscoelastic Small Molecular Gel

Viscoelastic surfactants are also called "clean fracturing fluids".In view of the advantages of clean fracturing fluids with good rheological properties,thorough gel breaking,and increased fracturing scale,this paper determines the formula of the fracturing fluid system EOS,and at the same time examines its physical and chemical properties(viscoelasticity,temperature resistance,salt resistance,stability,suspended sand performance and breaking performance,etc.).In view of the treatment of fracturing fluid flowback fluids,on the basis of examining the fracturing fluid system EOS breaker fluid,the co-surfactants were screened by reducing the interfacial tension to construct a fracturing fluid EOS breaker fluid Oil displacement system as oil displacement agent.At the same time,the oil displacement performance was evaluated by reducing the interfacial tension of the oil-water surface,emulsification performance experiment and contact angle experiment.In addition,the formulation of the fracturing fluid system EOO was also investigated in this paper,and its physical and chemical properties of fracturing and its oil displacement performance after gel breaking were formulated and evaluated briefly.The EOS optimization results of the fracturing fluid system developed indoors are: 2% EAPB + 0.1% NaSal + 0.7% OAPB,the apparent viscosity changes with time is not obvious,the stability is good,and the formation and destruction of the network structure in the system also have reversible;good temperature resistance,salt resistance and shear resistance,the viscosity is higher than 30 mPa·s at 80 ℃,with the increase of the inorganic salt content,the apparent viscosity also increases accordingly,suitable for high salinity.The higher oil layer has a viscosity evaluation standard higher than 25 mPa·s after shearing at 80 ℃ for 1 h.The system shows a strong static sand carrying capacity when the sand ratio is 30%.An oil displacement system based on the system EOS breaker fluid was constructed.The system optimization results were: 0.1 ~ 0.2% breaker fluid + 0.04% LAP-9.The system lowered the surface tension to 27.92 mN/m;lowered the interfacial tension to 0.006 mN/m,the system can reverse the wettability of the surface of the lipophilic quartz plate,reduce the contact angle to 49.5 °,the static oil displacement effect is better,and the oil displacement rate can reach 17.5% at 60 ℃.The formula ratio of the EOO fracturing fluid system developed indoors is: 1.7% EAPB + 1.36% OAPB + 0.02% OHPSE,which has good high temperature resistance and can be applied to fracturing medium and high temperature reservoirs;salt resistance is good and suitable for medium and high fracturing of salt reservoirs;it has good rheology and shear resistance,meets the performance requirements of fracturing sand-carrying,and has good sand suspending properties;the crude oil is completely broken(diluted 4 times equivalent),low-content residue.The damage to oil and gas reservoirs is very small,and based on the system EOO breaker fluid as the oil displacement agent for simple evaluation,found that the system EOO breaker fluid has the potential for oil displacement.The system EOO breaker has a low surface tension;the static oil displacement effect of the system EOO breaker is good.At 80 ℃,the static flooding rate can reach 28 %,and as the concentration of the breaker fluid increases,the static flooding efficiency also increases.