Stability Mechanism And Preparation Of Micro-bubble Fracturing Fluid Based On Thermosensitive Foam-stabilizing System

Foam fracturing fluid is a kind of low damage fracturing fluid with gas as internal phase and liquid as external phase,which has the advantages of environment friendly property,low water consumption and low cost.Although the research and application of foam fracturing fluid have made great progress,to further improve the foam fracturing fluid stability at high temperature is still one of the core issues restricting its application scale.Aiming at the problem of poor stability of the current foam fracturing fluid,a micro-bubble fracturing fluid with high temperature stability based on the thermo-sensitive foam-stabilizing system was prepared,which has important practical significance for widening the field application scope of the foam fracturing fluid.Sodium Dodecyl Sulfate（SDS）was used as the foaming agent by means of a Warning-blender high-speed stirring method.The anionic surfactants FMES,MES,FMEE were used as the main agent respectively,zwitterionic surfactant BS-12 and NaCl were used as auxiliaries,and BaTiO₃ nanoparticles was used as pyroelectric materials.With the aid of orthogonal experiment,with the foaming ability,half-life of foam and the viscosity retention rate of the fracturing fluid as the index,a reasonable formulation of the thermosensitive foam-stabilizing system,the rational formulation of microfoam fracturing fluid and its preparation parameters were optimized.The basic formulation of micro-bubble fracturing fluid（WP-FMFF）and preparation process were:0.5wt%SDS+2.0wt%FMES+0.8wt%BS-12+2.7wt%NaCl+0.8wt%BaTiO₃,the stirring time is 2 min and the stirring rate is6000 rpm.The particle size distribution of micro-bubble fracturing fluid system was analyzed by laser particle size analyzer,the result showed that the foam particle size distribution is between 30μm to 100μm,which means it belongs to the micro-bubble fracturing fluid.The stability mechanism,rheological behavior and drainage behavior of WP-FMFF micro-bubble fracturing fluid were explored preliminarily from the microscopic and macroscopic aspects through optical microscopy and rheological testing,etc.The results showed that WP-FMFF micro-bubble fracturing fluid presents the plastic rheological model,and the discharge behavior conforms to the"two-stage"drainage mechanism.WP-FMFF mainly depends on the special micro-bubble structure and the synergistic effect of the thermo-sensitive foam-stabilizing system to achieve high temperature stability.The comprehensive performance evaluation of WP-FMFF micro-bubble fracturing fluid system shows that:WP-FMFF micro-bubble fracturing fluid system has excellent proppant carrying capacity,and the static settling velocity is only 0.083cm/min,which meets the requirement of fracturing fluid industry（less than 1.08cm/min）.The system has good temperature resistance,temperature resistance to shear resistance,when the temperature reaches 100℃,the viscosity of micro-bubble fracturing fluid system is 50mPa·s.Moreover,without adding any gel-breaker or antifoam agent,it can break the glue thoroughly,and the broken liquid is clear without residue,and its surface tension and interfacial tension are low,which conducive for broken liquid to flowback.On the other hand,WP-FMFF micro-bubble fracturing fluid has good fluid loss control ability,reducing the formation damage,which means a good application prospect.