The Research On The Formulation And Performance Of Foam Fracturing Fluid

With the development of low permeability reservoirs, fracturing has been a trend toenhance the oil production. Compare to conventional water-base fracturing fluid, foamfracturing fluid has the properties of low fluid loss, low residue content, and has few damageto core. And it is proper for low pressure, low permeability and water sensitive formation. Butwe have a late start of foam fracturing, it is not very well developed in our country, and it isnecessary for us to do some research on foam fracturing fluid.Firstly, we choose the formulation of foam fracturing fluid. We evaluate the properties ofnitrogen foam and carbon dioxide foam from three aspects: temperature, pressure and salinity.Nitrogen foam has better foam formation and stability. Compare five different kinds offoaming agent, we find that HY-2has good temperature resistance and salinity resistance. Asthe clay stabilizer, KCl can prevent clay swell by87.59%. Compare to other kind of claystabilizer, it has better properties of antiswelling. DL-1is a kind of cleanup additive, withDL-1in the foam fracturing fluid, the surface tension is21.98mN/m, and the interfacialtension with kerosene is just0.2008mN/m. It is helpful for the foam fracturing fluid to flowback.The formulation of foam fracturing fluid:①Base fluid:0.5%hydroxypropyl guar+0.5%YSJ bactericide+1%HY-2foaming agent+1%KCl clay stabilizer+0.3%DL-1cleanupadditive;②Crosslinked fluid:0.5%HTC-160cross linker;③Gel breaker:0.02%ammoniumpersulfate;④Gas：N2.We evaluate the performance of foam fracturing fluid. The viscosity can achieve178mPa.s, when the shear rate is170s-1at80℃. It has good temperature resistance. Theconcentration of sand carrying can get500kg/m3, and the settling velocity is very little, it isjust4%of conventional water-base fracturing fluid. It breaks completely after90min, and theviscosity of broken fluid is quite low, it is very helpful for the fluid to flow back. The residuecontent is176.5g/L, in a very low level, it accounts for35%of conventional water-basefracturing fluid. The fluid loss coefficient is4.26104m/min, accounting for78%ofconventional water-base fracturing fluid. The dynamic fluid loss is about30%of conventional water-base fracturing fluid. The damage to core is about60%.The tube rheometer is designed to measure the microstructure and rheology of foamfracturing fluid. We can get the size of bubble and the distribution of foam fracturing fluidwith different foam quality. The rheology model is corresponding to power law model.According to the experiment data, the rheology equation of foam fracturing fluid withdifferent quality is derived. And the effect of foam quality on the rheology and viscosity isobserved. We calculate the coefficient of friction resistance of foam fracturing fluid. Thetheoretical value coincides well with experimental value.