| The fracturing fluid plays a vital role in hydraulic fracturing and its properties will directly influence the fracturing operations and stimulation effect.The current rheology research of fracturing fluid mainly forcus on the temperature and shear rate,does not consider the influence of high pressure on the rheology of fracturing fluid in actual fracturing conditions.Therefore,studying high pressure rheology of fracturing fluids will help us understand actual dynamic characteristics of fracturing fluids at fracturing conditions,provide technical support for fracturing scheme design,and improve the success rate and efficiency of frac job.HPHT rheometers were used to simulate the pressure and temperature in actual fracturing conditions,which used to test high pressure rheology of different water-based fracturing fluids,especially the high pressure rheology of guar gel crosslinked with boron,such as the effect of temperature and shear rate on high pressure rheology.The experiments explored the non-oxidative gel breaking performance of activated carbon,metal magnesium oxide,aluminum hydroxide,polyhydroxy amine MHN-1 and polyhydroxy resin IRA under high pressure conditions,optimized the gel breaker with non-oxidative gel breaking ability.Finally,taking the breaker resin IRA as an example,filtered and removed the resin particles,crosslinking the broken fluid,the mixture of fluid of base liquid and broken fluid in 1:1,2:1,1:2,observe the pick-up property of the gel,test the rheology of the broken fluid and the mixture fluid,and explore the feasibility of reuse guar.The results showed only the fluid of guar gel crosslinked with boron and PVA gel crosslinked with boron have a reversible"pressure thinning"rheology property under high pressure.The B-O-C bond at point of cross-linked gel is broken at high pressure,which shows the fracturing fluid viscosity reduced;when the pressure restored,the B-O-C bond is regenerated,which shows the fracturing fluid viscosity recovered;Based on the reversible"pressure thinning"rheology of the guar gel cross-linked with boron,a non-oxidative gel breaking method is posed,by adding some boron strong affinity substance change the reversibility of"pressure thinning".Experiments showed that substance containing polyhydroxyl functional groups can be used as non-oxidizing breaker,such as polyhydroxy amine MHN-1 and polyhydroxy resin IRA,the viscosity of gel can be reduced to base liquid14 m Pa·s,which provides basis for reuseing guar component.Broken fluid,the mixture of fluid of base liquid and broken fluid can recrosslinked,have good pick-up property and the viscosity stabilized at 170 mPa·s at 170 s-1. |
