Development Of Self-crosslinking Foam Fracturing Fluid System

Compared with traditional water-based fracturing fluids,foam fracturing fluid has many advantages,such as high viscosity,low filtration loss,less damage,and rapid gel breaking,and hence is very effective in solving reservoirs with low permeability,low pressure,and water sensitivity.Therefore,this paper aims to develop a carbon dioxide foam fracturing fluid system with simple configuration and stable foam.First of all,the appropriate surfactant foaming agent with a suitable half-life is selected by group experiments.A hydrophobic associative polymer is designed as the foam stabilizer through molecular simulation,and the effectiveness of this design is proved by the simulation of the morphology,interactions of the foaming agent and the foam stabilizer.Then,the target polymer is synthesized and characterized.Octanol is selected as the synergist by experiment,and the influence of different proportion formula on the comprehensive performance of the system is studied.Finally,the performances of this foam system,including the rheological properties,viscoelastic properties,gel breaking properties and damage properties,are tested and evaluated experimentally.The result of the research shows that:(1)The hydrophobically associating polymer foam stabilizer and surfactant foaming agent have a good synergistic effect and play an effective role in increasing viscosity.(2)The foam stability of the synthesized polymer foam stabilizer is very outstanding.The volume of foam after stirring is very small but is still very stable after 7 days,with a long half-life.(3)Octanol has a very good synergistic effect on the system.The electron microscope experiment shows that octanol can make the cross-linking structure compact and orderly,and change the viscosity response into the elastic response.(4)The basic formula of foaming agent,stabilizing agent and synergist shows the lower performance loss in the salt environment than that in the alkali environment.When ammonium persulfate is used,it can break at 70℃ in the range of 0.3% ～ 0.5%,and it will not return to gel within 4 hours,and the average damage rate is 10.5%.Above all,the comprehensive performance of the system is good,and it has the potential application of field.